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WATER C O R P O R A T I O N

ECOLOGICAL WATER REQUIREMENTS OF BLACKWOOD RIVER AND TRIBUTARIES - NANNUP TO HUT POOL

CENRM REPORT 11/04 FEBRUARY 2005

3 Blackwood River Ecological Water Requirements

__________________________________________________________________________________________ Centre of Excellence in Natural Resource Management Report 11/04

© Centre of Excellence in Natural Resource Management, The University of Western Australia

TITLE Ecological Water Requirements of the Blackwood River and

tributaries– Nannup to Hut Pool. PRODUCED BY Centre of Excellence in Natural Resource Management

The University of Western Australia 444 Albany Hwy, Albany, 6330 Telephone: (08) 9892 8532 Fax: (08) 9892 8547

Email: [email protected] PRODUCED FOR WATER CORPORATION OF WESTERN AUSTRALIA CONTACT CHRIS HIGGS DATE FEBRUARY 2005 PUBLICATION DATA Centre of Excellence in Natural Resource Management

(2004). Ecological Water Requirements of the Blackwood River and tributaries – Nannup to Hut Pool. Report CENRM 11/04. Centre of Excellence in Natural Resource Management, the University of Western Australia. February 2005.

ACKNOWLEDGEMENTS

This project was commissioned by the Water Corporation of Western Australia and supported by Chris Higgs and Sarah Fisher. Thanks go to Susan Creagh, Jessica Lynas, Lisa Chandler, Andrew Tennyson and Glenn Shiell for conducting field work. Geraldine Janicke, Lisa Chandler and Jessica Lynas also performed macroinvertebrate and fish identifications and assisted with collation of the draft report. Rosemary Lerch (Water and Rivers Commission) supplied stream flow data and John Relf (Bureau of Meteorology) rainfall data. Thanks also to Jenny McGuire (Chemistry Centre, WA) for performing nutrient analyses and to Susan Creagh and Rebecca Dobbs for editing the draft report. The Bunbury Office of the DoE kindly supplied water quality and macroinvertebrate data. DISCLAIMER

This report has been prepared on behalf of and for the exclusive use of water Corporation of Western Australia (the Client), and is subject to and issued in accordance with the agreement between the client and the Centre of Excellence in Natural Resource Management (CENRM). CENRM accepts no liability or responsibility whatsoever for it in respect of any use of or reliance upon this report by any third party. In particular, it should be noted that this report is a professional assessment and opinion only, based on the scope of the services defined by the Client, budgetary and time constraints imposed by the Client, the information supplied by the Client (and its’ agents), and the method consistent with the preceding.

CENRM could not attempt to verify the accuracy or completeness of all information supplied. Copying of this report or parts of this report is not permitted without explicit authorization of the Client and CENRM. Cover photograph: Blackwood River Site 18, off Mas Road, July 2004.



SUMMARY

The Water Corporation of Western Australia has applied for a license to operate a 45GL/annum borefield, abstracting from the southwest Yarragadee aquifer, in the vicinity north of the Blackwood River adjacent to Rosa Brook in south-western Australia. The current study provides an increased understanding of ecological susceptibility to changes in water regime (both quality and quantity) associated with the defined operations of the proposed Yarragadee scheme. Associated with this proposal, ecological water requirements (EWRs) were assessed for the Blackwood River and major tributaries between the Nannup township and Hut Pool. Nineteen sites along the main channel and twelve tributary sites were assessed with an additional three focal sites on St Johns Brook. To determine EWRs, data were collected on hydrology, channel morphology, water quality and aquatic biota and used in a ‘building block’ approach. This ‘holistic’ methodology is currently considered ‘best practice’ for determining EWRs for Australian systems. During July (mid-winter) 2004, the aquatic fauna and a range of physical and chemical parameters were collected/surveyed at study sites within the Blackwood River catchment. Extensive field measurements of channel morphology, water level slope, resistance to flow and bankfull capacity were measured. Aquatic macroinvertebrates were collected using qualitative sweeps. Fish were sampled using a combination of methods; sweeps, Fyke nets, electrofishing, baited box traps and direct observation. Riparian vegetation condition was qualitatively assessed. The majority of surveyed sites were within State Forest and characterised by relatively pristine riparian vegetation (A1-A2). Sites with some form of degradation (weed infestation, erosion or sedimentation) were mostly associated with anthropogenic influences such as fords, road bridges, fishing sites, camp grounds and boat ramps. Flows were generally high during the sampling period, following recent winter rainfall. All sites had low to moderate turbidity (≤40 NTU), circum-neutral pH and moderate to high daytime dissolved oxygen (DO) concentrations (53 - 107%). Data-logging (later during October) showed very low levels of DO in pools (particularly at night) and the ability of “riffles” to re-aerate oxygen-depleted waters. Conductivities in the Blackwood River were typically high, ranging from brackish 6,495µs/cm to saline 9,100µs/cm. Tributary sites were generally fresh (~345 to 457µs/cm). The water quality of the Blackwood upstream of Nannup indicated degraded upstream conditions with the elevated salinities and nutrients. This is considered a consequence of wide-scale land clearing. Current modelling predicts a doubling (without any Yarragadee developments) of salinity over the next 50 years; which will limit the success of any river restoration programs. Sampling aquatic macroinvertebrates, as an indicator of system “health” was based on National protocols (AusRivAs). Macroinvertebrates sampled of note were native freshwater crayfish including marron (Cherax cainii), gilgies (Cherax quinquecarinatus) and koonacs (Cherax crassimanus) which were almost totally restricted to tributary sites. As tributaries contain five of the six species of Cherax endemic to the south-west, they can be defined as a “hotspot” of crayfish biodiversity. Multivariate analysis (PATN) of macroinvertebrate community structure highlighted fundamental differences between the main stem of the Blackwood River and the tributary systems. Despite tributaries having a lower species diversity, they were refugia for sensitive fauna including crayfish, Plecoptera (stoneflies) and a restricted species of native fish; the mud minnow (Galaxiella munda). Further analysis separated the temporary and permanent tributary systems.



Seven species of native fish were present in study sites; western minnows (Galaxias occidentalis), cobbler (Tandanus bostocki), nightfish (Bostockia porosa), Balston’s pygmy perch (Nannatherina bolstoni), western pygmy perch (Edelia vittata), south-western goby (Afurcagobius suppositus) and mud/blackstripe minnows (Galaxiella munda/nigrostriata). Introduced mosquitofish (Gambusia holbrooki) were only present in the Blackwood River. As part of the EWR assessment, key components of the riverine ecosystem were first identified and then their monthly water requirements determined for a specific ‘desired future state’. This was defined as being no further degradation of the existing condition. However, it should be noted that an incremental long-term increase in salinity is predicted for the Blackwood system (without the proposed Yarragadee operations). In initial surveys, key ecological values/components were identified as: channel morphology, riparian vegetation, aquatic macroinvertebrates, reproductive migration of fish, pool water quality, carbon/energy linkages and flow into the estuary. However, in previous interim assessments, there were no quantitative measurements of the flow requirements of these ecosystem components. In the present study, quantitative measurements were made of these ecological components. The building block approach was then used to calculate the instantaneous flow rates required to attain various stage heights to sustain these key components. Flow models were constructed for the main tributaries and sites in the main stem of the Blackwood (where there was an adequate flow record). These models showed EWRs as a comparison against current monthly median flows. Based on these models, the main stem of the river has a significant capacity to meet all outlined EWRs at a low level of ecological risk. Typically, about 30% of the existing median flows are necessary to meet the water requirements of water dependent ecosystems at the current ecological state. The EWRs of the tributaries required proportionally more water than that determined for the main stem of the Blackwood (e.g. late summer; usually February) when there would be a reduced capacity to meet EWRs if there is a significant reduction in flow. Detailed scenario testing, using a range of possible Yarragadee salinities (100-400mg/L) and differing groundwater inputs to surface flows showed, that only in extreme scenarios (low Yarragadee salinity and 0% flow inputs into the Blackwood), were the guideline 80th percentile (as per the ANZECCs, “low risk” trigger) exceeded (only during summer). More probable scenarios (i.e. Yarragadee salinity 200mg/L and a 20% reduction due to abstraction) showed only small changes over the current exceedance of the 80th salinity percentiles. Sensitivity analyses showed the potential reduction in flow volumes from Yarragadee had more influence over the final salinity in the Blackwood than groundwater salinity per se. Based on the above analysis, an ecological risk assessment highlighted an issue of “medium” ecological susceptibility: changes to the flow permanence of the currently-permanent tributaries. These tributaries are important refugia for fauna which could reinvade the Blackwood if/when harsh seasonal conditions (particularly high winter salinities) ameliorate. It was also identified that dissolved oxygen levels in riverine pools of the Blackwood, could also represent a medium risk during late summer (this season was not assessed during this survey). It is essential that the ecological impacts (if any) of any modified flow regime are fully monitored and evaluated and this conducted in an adaptive framework (i.e. AEAM). Recommendations include: re-sampling of the fresher, permanent tributaries during summer to further investigate their role as refugia; measurement of Blackwood River pool DO levels across various flow scenarios and; monitor key ecological components of the Blackwood in a broader catchment context.



TABLE OF CONTENTS SUMMARY.................................................................................................................................................4

LIST OF PLATES......................................................................................................................................8

1. INTRODUCTION ................................................................................................................................10 1.1 STATUTORY / LEGISLATIVE FRAMEWORK................................................................................10 1.2 RESEARCH FRAMEWORK..........................................................................................................11 1.3 STUDY APPROACH ...................................................................................................................12

2. STUDY AREA ......................................................................................................................................13 2.1 HYDROLOGY.....................................................................................................................................13 2.2 CLIMATE CHANGE.............................................................................................................................20 2.3 WATER QUALITY..............................................................................................................................20 2.4 GROUNDWATER................................................................................................................................23 2.5 SALINITY GUIDELINES ......................................................................................................................24 2.6 VEGETATION ....................................................................................................................................25 2.7 PREVIOUS ECOLOGICAL ASSESSMENT ...............................................................................................26 2.8 FRAMEWORK TO ECOLOGICAL WATER REQUIREMENTS...................................................................27

3. METHODS ...........................................................................................................................................31 3.1 TIMING OF THE SURVEY....................................................................................................................31 3.3 RIPARIAN VEGETATION ....................................................................................................................31 3.4 CHANNEL MORPHOLOGY..................................................................................................................32 3.5 CROSS SECTIONS ..............................................................................................................................32 3.6 WATER QUALITY..............................................................................................................................34 3.7 MACROINVERTEBRATES ...................................................................................................................34

3.7.1 Field sampling .........................................................................................................................34 3.7.2 Laboratory processing .............................................................................................................34

3.8 FISH..................................................................................................................................................35 4. RESULTS OF JULY 2004 FIELD SURVEYS ..................................................................................36

4.1 RIPARIAN VEGETATION AND FORESHORE CONDITION ASSESSMENT ................................................36 4.2 CHANNEL MORPHOLOGY AND CROSS SECTIONS ..............................................................................39 4.3 WATER QUALITY..............................................................................................................................49

4.3.1 Salinity .....................................................................................................................................49 4.3.2 Temperature and DO ...............................................................................................................49 4.3.4 Redox Potential........................................................................................................................53 4.3.5 Turbidity...................................................................................................................................54 4.3.6 Nutrients...................................................................................................................................54

4.4 FISH..................................................................................................................................................56 4.4.1. South-western goby (Afurcagobius suppositus Sauvage) .......................................................58 4.4.2 Nightfish (Bostockia porosa Castelnau) ..................................................................................58 4.4.3 Western pygmy perch (Edelia vittata Castelnau).....................................................................59 4.4.4 Western minnow (Galaxias occidentalis Ogilby) ....................................................................59 4.4.5 Freshwater cobbler (Tandanus bostocki Whitley)..................................................................60 4.4.6 Balston’s pygmy perch (Nannatherina balstoni Regan) ..........................................................60 4.4.7 Mud minnow (Galaxiella munda McDowall), black-stripe minnow (G. nigostriata Shipway) 61 4.4.8 Pouched Lamprey (Geotricha australis)...................................................................................61 4.4.9 Mosquitofish (Gambusia holbrooki Girard) ............................................................................62 4.4.11 Water requirements of fish....................................................................................................63

4.5 MACROINVERTEBRATES ...................................................................................................................64 4.5.1 Gondwanic (Relict) Fauna.......................................................................................................71 4.5.2 Community structure................................................................................................................73 4.5.3 Macroinvertebrate fauna: conclusions ...................................................................................75



5. ECOLOGICAL WATER REQUIREMENTS...................................................................................76 5.1 RECOMMENDED FLOW REQUIREMENTS............................................................................................76

5.1.1 EWRs for River Morphology....................................................................................................76 5.1.3 EWRs for Fish ..........................................................................................................................77 5.1.4 EWRs for Riparian Vegetation.................................................................................................77 5.1.5 EWRs for Energy Flows...........................................................................................................77 5.1.6 EWRs for Pool Water Quality ..................................................................................................77

5.2 CONSTRUCTING A FLOW MODEL .......................................................................................................77 6. SCENARIO TESTING ........................................................................................................................84

7. ECOLOGICAL RISK ASSESSMENT...............................................................................................89 7.1 POSSIBLE ECOLOGICAL CONSEQUENCES ..........................................................................................92

8. MONITORING AND ASSESSMENT................................................................................................93 8.1 Monitoring Program...................................................................................................................93

9. SUMMARY...........................................................................................................................................96

10. RECOMMENDATIONS ...................................................................................................................97

11. REFERENCES ...................................................................................................................................98

GLOSSARY............................................................................................................................................105

APPENDICES ........................................................................................................................................111 APPENDIX 1. RIPARIAN CATEGORIES...............................................................................................112 APPENDIX II. HYDROLOGY OF WRC GUAGING STATIONS ...............................................................113 APPENDIX III. SYTEMATIC LIST OF TAXA .........................................................................................115 APPENDIX IV. WATER CHEMISTRY PROFILES ....................................................................................116 APPENDIX V. DISSOLVED OXYGEN/ TEMPERATURE DYNAMICS.......................................................117 APPENDIX VI. PHOTOGRAPHS OF SAMPLING SITES.............................................................................122 APPENDIX VII. CHANNEL CROSS SECTIONS FOR TRIBUTARY SITES.....................................................126 APPENDIX VIII. FLOW REQUIREMENTS FOR THE BLACKWOOD RIVER .................................................133 APPENDIX IX. SCIENTIFIC UNCERTAINTIES REQUIRING FURTHER RESEARCH ...................................134



LIST OF TABLES TABLE 1. RESOURCE CATEGORIES ACCORDING TO LEVEL OF UTILIZATION. ...................................................................... 10 TABLE 2. JULY 2004 SURVEY SITES IN THE BLACKWOOD RIVER CATCHMENT.................................................................. 15 TABLE 3. COEFFICIENT OF VARIATION (%) OF MONTHLY FLOWS AT EACH OF THE GAUGING SITES .................................... 17 TABLE 4. MEAN LONG-TERM WATER QUALITY IN THE TRIBUTARIES AND THE BLACKWOOD RIVER................................... 21 TABLE 5. CLASSIFICATION OF RIPARIAN CONDITION OF THE BLACKWOOD RIVER CATCHMENT . ....................................... 25 TABLE 6. BOTANICAL SUBDIVISIONS OF THE BLACKWOOD CATCHMENT.......................................................................... 26 TABLE 7. MACROINVERTEBRATE O/E SCORES FOR THE BLACKWOOD RIVER AND ASSOCIATED TRIBUTARIES ................... 27 TABLE 8. AUSRIVAS CLASSIFICATION SYSTEM FOR O/E SCORES. .................................................................................... 27 TABLE 9. ASSESSMENT OF RIPARIAN VEGETATION CONDITION......................................................................................... 37 TABLE 10. FORESHORE ASSESSMENT. ............................................................................................................................. 38 TABLE 11. CHANNEL MORPHOLOGY MEASUREMENTS TAKEN IN JULY 2004 FOR AN AVERAGE REACH OF EACH SITE.......... 40 TABLE 12. RESULTS OF MEASUREMENTS OF WATER QUALITY IN THE BLACKWOOD RIVER DURING JULY 2004. ................ 50 TABLE 13. DEFAULT TRIGGER VALUES FOR NUTRIENTS, DISSOLVED OXYGEN AND PH...................................................... 55 TABLE 14. FISH SPECIES RECORDED FROM BLACKWOOD RIVER CATCHMENT SURVEY SITES DURING JULY 2004............... 57 TABLE 15. SUMMARY OF NATIVE FISH LIFE HISTORY CHARACTERISTICS IN RELATION TO REPRODUCTION. ....................... 64 TABLE 16. AQUATIC MACROINVERTEBRATES FROM THE BLACKWOOD RIVER AND TRIBUTARIES IN JULY 2004................... 66 TABLE 17. AQUATIC MACROINVERTEBRATE TAXA ‘UNIQUE’ TO EITHER THE MAIN CHANNEL OR TO TRIBUTARIES............. 70 TABLE 18 . EWRS FOR THE BLACKWOOD RIVER AT 609058 (NODE 1) ........................................................................... 79 TABLE 19. EWRS THE BLACKWOOD RIVER AT 609019 (HUT POOL) (NODE 2)................................................................ 80 TABLE 20. EWRS AT ROSA BROOK AT 609001 (CROUCH RD) (NODE 3) ......................................................................... 81 TABLE 21. EWRS THE ST JOHNS BROOK AT 609018 (BARRABUP POOL) (NODE 4).......................................................... 82 TABLE 22. GROUNDWATER DISCHARGE BETWEEN DARRADUP AND HUT POOL.. .............................................................. 86 TABLE 23. ECOLOGICAL RISKS OF PROPOSED GROUNDWATER ABSTRACTION. .................................................................. 91 TABLE 24. OVERALL ECOLOGICAL RISKS ON ISSUES ASSOCIATED WITH THE MODELLED ABSTRACTION RATES. ................. 91 TABLE 25. RECOMMENDED MONITORING REGIME FOR THE BLACKWOOD......................................................................... 95

LIST OF PLATES

PLATE 1. SURVEYING CROSS SECTIONS. ........................................................................................................................ 33 PLATE 2. WATER QUALITY MEASUREMENTS BEING TAKEN IN SITU. ................................................................................. 35 PLATE 3. SWEEPING UNDER VEGETATION FOR AQUATIC MACROINVERTEBRATES USING A 250µM MESH POND-NET. ......... 35 PLATE 4. (A) SETTING THE FYKE NET IN THE BLACKWOOD RIVER AT ST PATRICK’S ELBOW; (B) ELECTROFISHING. ........ 35 PLATE 5. BANK AT BLACKWOOD RIVER SITE 5 NEAR MILYEANNUP FORD ..................................................................... 36 PLATE 6. BANK AT BLACKWOOD SITE 3, NEAR LONGBOTTOM ROAD, SHOWING SLOPE STEEPNESS. ................................ 36 PLATE 7. FOAM ON THE SURFACE OF THE BLACKWOOD RIVER, JULY 2004. ................................................................... 55 PLATE 8. SOUTH-WESTERN GOBY (AFURCAGOBIUS SUPPOSITUS) COLLECTED FROM HUT POOL ....................................... 58 PLATE 9. NIGHTFISH (BOSTOCKIA POROSA) COLLECTED FROM ST PATRICK’S ELBOW...................................................... 58 PLATE 10. WESTERN PYGMY PERCH EDELIA VITTATA (PHOTO ALLEN ET AL, 2002)........................................................... 59 PLATE 11. WESTERN MINNOW (GALAXIAS OCCIDENTALIS) COLLECTED FROM TRIBUTARY SITE F..................................... 59 PLATE 12. FRESHWATER COBBLER (TANDANUS BOSTOCKI) COLLECTED FROM BLACKWOOD RIVER SITE 3....................... 60 PLATE 13. BALSTON’S PYGMY PERCH (NANNATHERINA BALSTONI) COLLECTED FROM BLACKWOOD RIVER SITE 8 ............ 61 PLATE 14. BLACK-STRIPE MINNOW (A) AND MUD MINNOW (B) COLLECTED FROM LAYMAN BROOK (SITE F). ................. 61 PLATE 15. POUCHED LAMPREY GEOTRICHA AUSTRALIS (PHOTO SHOWN IN ALLEN ET AL, 2002)........................................ 62 PLATE 16. MOSQUITOFISH GAMBUSIA HOLBROOKI (PHOTO SHOWN IN ALLEN ET AL, 2002).............................................. 62 PLATE 17. A SALMONID (RAINBOW TROUT) ONCORHYNCHUS MYKISS (PHOTO ALLEN ET AL, 2002)................................. 63 PLATE 18. GILGIE (CHERAX QUINQUECARINATUS)........................................................................................................... 65 PLATE 19. FRESHWATER CRAYFISH ............................................................................................................................... 71 PLATE 20. BLACKWOOD RIVER SITE 1. ........................................................................................................................ 122 PLATE 21. BLACKWOOD RIVER SITE 2 ......................................................................................................................... 122 PLATE 22. BLACKWOOD RIVER SITE 3. ........................................................................................................................ 122 PLATE 23.BLACKWOOD RIVER SITE 5. ......................................................................................................................... 123 PLATE 24. BLACKWOOD RIVER SITE 6. ........................................................................................................................ 123 PLATE 25. BLACKWOOD RIVER SITE 7. ........................................................................................................................ 123 PLATE 26.BLACKWOOD RIVER SITE 8. ......................................................................................................................... 124 PLATE 27. BLACKWOOD RIVER SITE 10. ...................................................................................................................... 124 PLATE 28. BLACKWOOD RIVER SITE 11. ...................................................................................................................... 124 PLATE 29.BLACKWOOD RIVER SITE 13. ....................................................................................................................... 125 PLATE 30. BLACKWOOD RIVER SITE 18. ...................................................................................................................... 125 PLATE 31. BLACKWOOD RIVER SITE 19.APPENDIX VII ................................................................................................ 125 PLATE 32. TRIBUTARY A, ‘BALLAN’ CREEK. ............................................................................................................... 126 PLATE 33. TRIBUTARY SITE B, ROSA BROOK (DOWNSTREAM)..................................................................................... 127



PLATE 34. TRIBUTARY SITE C, ROSA BROOK (UPSTREAM). ......................................................................................... 128 PLATE 35. TRIBUTARY SITE D, ADELAIDE CREEK. ..................................................................................................... 129 PLATE 36. TRIBUTARY SITE E, SPEARWOOD CREEK................................................................................................... 130 PLATE 37. TRIBUTARY SITE F, LAYMAN BROOK........................................................................................................ 131 PLATE 38. TRIBUTARY SITE G, MILYEANNUP BROOK. ............................................................................................... 132

LIST OF FIGURES

FIGURE 1 LOCATION OF STUDY AREA IN THE BLACKWOOD RIVER CATCHMENT.. ........................................................... 14 FIGURE 2. RAINFALL DATA FROM BUREAU OF METEOROLOGY (BOM) SITE 009585 BETWEEN 1983 AND 2003.............. 16 FIGURE 3. FLOWS RECORDED IN ROSA BROOK FROM STREAMFLOW MONITORING SITE 609001 ....................................... 16 FIGURE 4. FLOWS RECORDED IN THE CHAPMAN BROOK AT STREAMFLOW MONITORING SITE 609022. ............................. 17 FIGURE 5. FLOWS RECORDED IN ST JOHN BROOK FROM STREAMFLOW MONITORING SITE 609018 .................................. 17 FIGURE 6. 1998 – 2004 TOTAL MONTHLY STREAM DISCHARGE IN THE BLACKWOOD RIVER AT HUT POOL....................... 18 FIGURE 7. MEAN/MEDIAN ANNUAL FLOWS AT TWO SITES ON THE BLACKWOOD RIVER.................................................... 18 FIGURE 8. LONGER-TERM DISCHARGE AT HUT POOL (1983-2004) AND RAINFALL AT NANNUP FROM 1998-2004............ 19 FIGURE 9. RELATIVE FLOW CONTRIBUTIONS................................................................................................................... 19 FIGURE 10. SALINITY (TDS IN MG/L) OF THE BLACKWOOD RIVER (1965-2003) AT HUT POOL. ..................................... 21 FIGURE 11. (A) MEAN TOTAL ANNUAL DISCHARGE (ML), AND (B) MEAN “SUMMER” DISCHARGE FOR THE BLACKWOOD.22 FIGURE 12. FIVE YEAR MOVING AVERAGE SALINITY OF THE BLACKWOOD, WARREN AND DONNELLY RIVERS................ 23 FIGURE 13. ESTIMATED RELATIVE IMPORTANCE OF YARRAGADEE DISCHARGE TO SURFACE WATER FLOWS .................... 24 FIGURE 14. THE RIVER CONTINUUM CONCEPT............................................................................................................... 30 FIGURE 15. MEASUREMENTS OF CHANNEL MORPHOLOGY. ............................................................................................. 33 FIGURE 16. METHODOLOGY USED TO DETERMINE CROSS-SECTIONAL PROFILES............................................................... 33 FIGURE 17. GENERIC CROSS-SECTION OF THE BLACKWOOD RIVER (SEE APPENDIX VIII). ............................................... 41 FIGURE 18. GENERIC CHANNEL CROSS-SECTION OF THE TRIBUTARY SITES (SEE APPENDIX VII). ..................................... 41 FIGURE 19. LONGITUDINAL MODEL OF DEPTH OF THE BLACKWOOD FROM NANNUP TO HUT POOL ................................. 42 FIGURE 20. DEPTH CATEGORIES ALONG ONE STREAM REACH (I.E. ONE MEANDER OR RIFFLE-POOL SEQUENCE) ............... 43 FIGURE 21. MID-DEPTH MEASUREMENTS (AT 10-MINUTE INTERVALS) OF TEMPERATURE AND DISSOLVED OXYGEN. ........ 52 FIGURE 22. MACROINVERTEBRATE ‘SPECIES’ RICHNESS IN THE BLACKWOOD RIVER AND TRIBUTARIES .......................... 65 FIGURE 23. UPGMA CLASSIFICATION OF JULY 2004 PRESENCE/ABSENCE MACROINVERTEBRATE DATASET .................... 73 FIGURE 24. SSH (SEMI-STRONG HYBRID) ORDINATION OF JULY 2004 MACROINVERTEBRATE PRESENCE/ABSENCE DATA. 74 FIGURE 25. SSH (SEMI-STRONG HYBRID) ORDINATION OF JULY 2004 MACROINVERTEBRATE PRESENCE/ABSENCE DATA . 74 FIGURE 26. MULTIVARIATE ORDINATION (PATN) OF EACH SITE ON THE BASIS OF COMMUNITY STRUCTURE.................... 75 FIGURE 27. PROPOSED FLOOD HYDROGRAPH FOR CHANNEL MAINTENANCE FLOWS. ....................................................... 76 FIGURE 28. LONG-TERM AND MEAN RAINFALL AT NANNUP (IN MM) AT STATION 009585............................................... 84 FIGURE 29. LONG-TERM 80TH PERCENTILE SALINITY CONCENTRATION IN THE BLACKWOOD. ........................................ 87 FIGURE 30. LONG-TERM 80TH PERCENTILE SALINITY CO................................................................................................. 88 FIGURE 31. NUMBER OF DAYS THE 80TH PERCENTILE WILL BE EXCEEDED UNDER DIFFERENT MODELLED YARRAGADEE

INPUTS (GROUNDWATER SALINITY AT 200MG/L).................................................................................................. 88 FIGURE 32. CONCEPTUAL FRAMEWORK AND PROCESS FOR SETTING A MONITORING AND EVALUATION PROGRAM . .......... 93



1. INTRODUCTION

The Centre of Excellence in Natural Resource Management (CENRM) was commissioned by the Water Corporation (WC) of Western Australia to determine the ecological water requirements (EWRs) of the Blackwood River between Nannup township and Hut Pool with this assessment including the major tributaries. The WC has applied for a license to operate a 45GL/annum borefield, abstracting from the southwest Yarragadee aquifer, in the vicinity to the north of the Blackwood River adjacent to Rosa Brook in south-western Australia. The current study represents a component of a multi-disciplinary assessment of water-related issues associated with the operation of the proposed borefield. The study provides an increased understanding of ecological susceptibility to changes in water regime and supplements initial research on the Blackwood River, Chapman Brook, St John Brook and Rosa Brook conducted in 2003 (Stage 1 Report, CENRM Report 07/03, 2003). A Stage 2 investigation addressed water allocation issues for other aquifer systems in the region and included the Donnelly River, Barlee Brook, Scott River and Margaret River (Stage 2 Report, CENRM 11/03, 2003). 1.1 Statutory / Legislative Framework

Since 1996, the Water and Rivers Commission (WRC) has had the role of custodian, independent arbiter and regulator of the water industry of Western Australia. The WRC currently operates under the Water and Rivers Commission Act 1995. The Rights in Water and Irrigation Act 1914 was the major water legislation in Western Australia. Under the 1999 amendments to the Act and the Water and Irrigation Amendment Bill 1999, EWRs must be met and not endangered by other consumptive users (or a formal assessment process is initiated). EWRs are defined by the WRC as “the water regimes needed to maintain ecological values of water dependent ecosystems at a low level of risk.” (Water and Rivers Commission 2000). The determination of EWRs for water resources for Western Australian systems is an integral part of the water allocation decision-making process as a fundamental input into determining the sustainable yield1 of those resources. The WRC is undertaking a program of allocation-planning for priority water resources that will define sustainable yields that take appropriate account ecological water needs. The priority basis of this program has been largely based on the relative level of allocation (Table 1) and demand pressures on each resource as identified in the Western Australian component of the National Land and Water Resources Audit (Water and Rivers Commission 2000).

Table 1. Resource categories according to level of utilization.

Utilisation as % of Sustainable Yield (approx.)

0-30% 30-70% 70-100% >100%

Level of Use Category C1 C2 C3 C4 Corresponding Response Category R1 R2 R3 R4

1 Sustainable yield can be defined as: “The amount of water that can be taken from a water resource system (expressed as an extraction regime) without causing unacceptable impacts.” (Water & Rivers Commission 2000, 2000a).



Most of Western Australia’s surface water resources are currently being managed at the R1 level, which involves a rudimentary estimate of the EWRs. An R3 or R4 response requires EWRs to be determined with a high degree of rigour (i.e. holistic methodology). The approach developed in this study is intended to provide indication of the sustainable yield for application at the R2 level to C2 category surface water systems (and on appropriate occasions to C1 systems). It is also important that any approach has an inbuilt conservatism to avoid: the risk of consequential environmental damage through over-allocation; and the need to reduce already-issued allocations (clawback). Water allocation plans are developed by the WRC at the level of regional, sub-regional and local areas (Water & Rivers Commission 2001).

1.2 Research Framework

There are two major approaches for setting EWRs for river systems; ‘bottom-up’ and ‘top-down’ methodologies. Bottom-up methods rely on a starting point of zero flows to which important flows are added. This is achieved by breaking the system down into key flow dependent components, allocating flows for each of these and then a flow model is constructed where allocations are monthly ‘parcels’ of water. The holistic methodology (Davies et al. 1996, Arthington 1998, Arthington & Zalucki 1998) is a bottom-up process using a building block approach. The holistic methodology aims to provide an assessment of in-stream flow requirements, using information on the relationships of flow and various attributes of the river ecosystem, ranging from channel characteristics, water quality and biological communities, to the major underlying ecological processes driving lotic systems (Arthington 1998a,b). This method requires detailed on-site measurements of channel morphology (typically multiple cross sections) (Brizga 1998). In contrast, top-down approaches begin at a starting point of the entire natural flow regime. The underlying context of the method is the requirement that EWRs should enable fundamental biophysical features and basic ecological processes to be maintained (Arthington & Pusey 1993, Davies et al. 1996, Arthington 1998a, b, Water & Rivers Commission 1998). Basic steps in its application are the analysis of the natural (unregulated) flow data for the river under study and the definition of features of the flow regime to be retained in any modified flow regime (Blüdhorn & Arthington 1995, Arthington 1998a). Periods of no-flow may also be required in variable or ephemeral systems (Arthington et al. 1998a). Once the low flows have been defined for each month, additional higher flows are specified in some months (e.g. for riparian inundation). These flows are incorporated to achieve essential ecological and other objectives (e.g. flows to stimulate fish spawning and migration) (Tunbridge and Glencoe 1988, Pusey et al. 1989), channel maintenance flows, small floods that connect the floodplain to the main river channel (e.g. Newbury and Gaboury 1993), flows to attain water quality thresholds in pools (Davies et al. 1996). The annual water needs of the riverine ecosystem are calculated from the sum of the low flow requirements throughout the year and the additional small and medium-sized floods. However, it is critical that any EWRs are considered first estimates or essentially testable hypotheses that can be assessed and revised in an adaptive management process (e.g. AEAM; Adaptive Environmental Assessment and Management) (Pigram and Hooper 1992).



These ideas were focussed by the COAG water reform agenda which were based on the premise that the environment has a right to water; that is it has to be regarded as a legitimate “user”. Consistent with this approach, the terminology used in this report is based on the National Principles for the Provision of Water for Ecosystems (ANZECC/ARMCANZ 2000) where: • Ecological Water Requirements describe water regimes (spatial and temporal) needed to

sustain the ecological values of water dependent ecosystems at a low level of risk.

• Environmental Water Provisions are that part of the ecological water requirements that can actually be met after further consideration of social and economic factors.

The Environmental Water Provisions Policy of the WRC recommended the holistic approach be considered ‘best practice’ for Western Australian systems (Arthington et al. 1992). This methodology has already been used for many other systems in south-western Australia (Davies et al. 1998).

1.3 Study Approach The initial ecological water requirements for the Blackwood River associated with the proposed southwest Yarragadee development was based, in part, on three sets of ecological criteria (URS 2004). One of these related to required stage heights to meet specific ecological targets. However, this interim approach was limited to a single cross section (at Hut Pool). Given the limited scope of the initial study, an objective of this proposed study was to provide an increased understanding of ecological susceptibility to changes in water regime, both quality and quantity associated with the Yarragadee proposal (i.e. to refine the preliminary EWRs as outlined in URS 2004). From this initial work, the key ecological issues associated with the proposed project were to determine:

1. Flow depth in the Blackwood River & tributaries (especially over riffles); 2. Pool water quality; 3. Water quality in the Blackwood River, and the potential importance of fresher tributaries.

Specifically, the current study also entailed (as an important contextual framework):

1) Quantification of the existing hydrology at gauging sites. 2) Assessment of the variation in the hydrology. 3) Identification of important water-dependent ecosystems. 4) Water requirements of these ecosystems (where possible). 5) The ecological risk associated with these possible impacts. 6) The uncertainty of these predictions. 7) Important knowledge gaps/recommendations for research.



2. STUDY AREA

The Blackwood River catchment, located approximately 280km south east of Perth, is the largest catchment in south-west Western Australia, covering an area of over 21,930km2

(Department of Environment Water Publications 2000). The catchment extends about 330km inland to drain the Yilgarn Plateau ~380m above mean sea level. The Blackwood River is the union of two major tributaries; the Arthur and Beaufort rivers (Beard 1999) and flows through the Bannister Uplands and the Darling Plateau. Much of the catchment lies to the east of the Darling Scarp, with the remainder draining the Blackwood Plateau, Scott Coastal Plain and Leeuwin-Naturaliste Ridge (Department of Environment Water Publications 2000). The upper catchment is within the Zone of Ancient Drainage, east of the Meckering line, where the landscape is flat and often includes Tertiary paleochannel sediments and salt lake systems. Lake Dumbleyung is the largest of the inland lakes common along the Arthur and Beaufort River systems (Beard 1999). This is a permanent salt lake which may have been dry prior to land clearing. The upper catchment does not contribute to Blackwood River flows unless Lake Dumbleyung out-floods (Department of Environment Water Publications 2000). Below the confluence of the Blackwood-Arthur, the river exhibits high sinuosity down the Blackwood Plateau (Beard 1999). From this point, the Blackwood River is permanent, receiving groundwater from the Perth Basin and ultimately flows into the Hardy Inlet (Figure 1, Table 2). The lower river is influenced by tidal events, receiving estuarine water as far as 42km upstream from the river mouth. Mean annual discharge from the Blackwood River to the Hardy Inlet is about 940GL. An area of the Blackwood system considered specifically important for ecological values is located within the Blackwood Conservation Park, 30kms downstream from Nannup township. The main channel of the tributary in this area is contained within CALM-managed forest and probably represents the highest quality riparian zone on the main stem or main tributaries of the entire river system (WRC, 1997). Although this section of the Blackwood River is significant, it still drains a substantial area of cleared agricultural land. Rosa Brook is a 4th order brook wholly contained within State Forest. At a sub-regional scale, St Johns Brook is the least-altered (Category A2, Appendix I) of larger tributaries.

2.1 Hydrology

The climate of the region is Mediterranean with hot, dry summers and cool, wet winters (Seddon 1972). The Blackwood catchment receives, on average, about 600mm of rainfall per annum with the Nannup township averaging approximately 900mm (see Figure 2 for mean monthly values). Maximum rainfall occurs in winter between June and August with minimum rainfall occurring in January and February. Rainfall is both highly seasonal and predictable (Figure 2).



Figure 1 Study area in the Blackwood River catchment. Location of survey sites indicated in pink and green (macroinvertebrate and fish sites).

I

J

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SJ3

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Sturke CreekL

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Poison Gully



Table 2. Survey sites in the Blackwood River catchment. The “distance upstream” is from Molloy Island (to confluence) and “summer flow” is based on a series of surveys conducted by Water Corporation during late summer 2002-2004; these sites were typically well-upstream of the sampling site. Thalwegs (measured in the current survey) indicate critical cease to flow depths in the Blackwood (tributaries) where red<50cms, orange 50-100cms and green>100cms (see Section 4.2).

Site

System Code Latitude Longitude Thalweg (m) Description Distance Upstream (km)

Summer flow observation at site

Hut Pool Blackwood 19 34 05' 22.5"S 115 17' 31.5"E 2.3 Upstream of pool 38.7 flow Mas Road Blackwood 18 34 05' 35.2"S 115 20' 07.3"E 2.0 At end of Mas Road 45.8 flow Blackwood 17 34 05' 05.6"S 115 20' 20.5"E 1.9 At track 47.0 flow Possy Rd Blackwood 16 34 05' 06.2"S 115 21' 04.7"E 1.8 At crossing 48.3 flow Blackwood 15 34 04' 35.1"S 115 21' 41.2"E 1.6 At track 49.9 flow Dead Man’s Pool Blackwood 14 34 04' 20.2"S 115 22' 51.0"E 1.0 Upstream from pool 55.7 flow Sues Bridge Blackwood 13 34 04' 33.2"S 115 23' 41.4"E 1.4 At bridge 56.7 flow Chester Rd Blackwood 12 34 04' 21.7"S 115 24' 42.7"E 1.3 End of road 62.0 flow Denny Rd (W) Blackwood 11 34 03' 54.2"S 115 25' 27.5"E 0.8 Track off Denny Rd 66.4 flow Denny Rd (E) Blackwood 10 34 03' 39.5"S 115 26' 54.2"E 0.9 Watering point 67.4 flow Punch Rd Blackwood 9 34 04' 25.8"S 115 27' 46.1"E 1.2 Meander Punch Rd 69.5 flow Judy Rd Blackwood 8 34 04' 53.8"S 115 27' 43.4"E 1.1 Crossing 69.9 flow St Patrick’s Elbow Blackwood 7 34 04' 36.5"S 115 30' 28.2"E 1.0 Off Denny Rd 77.5 flow Blackwood Rd Blackwood 6 34 07' 09.9"S 115 31' 30.9"E 0.4 South meander 86.8 flow Brockman Hwy Blackwood 5 34 05'15.6" S 115 33' 35.2"E 1.2 At ford 94.1 flow Darradup Blackwood 4 34 05' 17.8" S 115 34' 13.1"E 1.6 End of track 101.6 flow Longbottom Rd Blackwood 3 34 04' 52.8" S 115 36' 05.2"E 0.9 At bridge 108.5 flow Brockman Highway Blackwood 2 34 03' 53.6"S 115 36' 46.3"E 0.8 At track 108.9 flow Off River Road Blackwood 1 34 01' 13.2"S 115 38' 19.5"E 1.4 At Powerlines 112.3 flow “Ballan” Creek South Trib A 34°06'00.4"S 115°27' 50.0"E 0.3 Judy Rd 69.6 dry Rosa Brook NE Trib. B 34°03'72.6"S 115°25.51.4"E 1.1 Denny Rd 62.3 low flows Rosa Brook (up) NE Trib. C 34°01'38.3"S 115°27' 58.6"E 1.0 At bridge Couch Rd 62.4 dry Adelaide Brook North Trib. D 34°04'20.7"S 115°20' 29.6"E 0.3 At road culvert (up) 47.0 dry Spearwood Creek North Trib. E 34°04'20.0"S 115°18' 64.1"E 0.2 At bridge Denny Rd 41.3 flow Layman Brook North Trib. F 34°05'37.8"S 115°23' 00.0"E 0.3 Denny Rd 77.4 dry Milyeannup Brook South Trib. G 34°07'99.7"S 115°24' 10.3"E 1.2 Blackwood Rd (up) 93.7 dry Poison Gully South Trib. H 34°07'47.6"S 115°34' 11.7"E 0.5 Brockman Hwy 88.8 dry Sollya Creek SE Trib. I 34°07'22.1"S 115°20' 18.1"E 0.4 Brockman Hwy 99.1 low flows Red Gully SE Trib. J 34°07'30.6"S 115°33' 09.8"E 0.3 Brockman Hwy 102.7 flow McAfee Brook North Trib. K

34°07'88.9"S 115°18' 99.2"E 0.4 Crouch Rd 107.6 flow (didn’t reach the

Blackwood River) Sturke Creek SE Trib. L 34°06'08.7"S 115°19' 90.2"E 0.5 Four Mile Gully 114.7 pools St Johns (up) North Trib. SJ1 34°07'00.7"S 115°32' 97.1"E 0.6 St Paul Brook 131.8 dry St Johns (mid) North Trib. SJ2 34°05'44.2"S 115°32' 99.8"E 0.8 Barrabup Pool 131.8 low flows St Johns B (low) North Trib. SJ3 34°04'74.5"S 115°32' 97.2"E 1.2 Mowen Rd 131.8 flow



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Figure 2. Rainfall data from Bureau of Meteorology (BOM) site 009585 between 1983 and 2003, located at Nannup (left) and BOM site 009613 from 1983 and 2003 (Warner Glen; right).

To determine the existing hydrological state of the catchment, streamflow and meteorological sites were chosen along the Blackwood River and major tributaries (Figure 1, Table 2) (WRC, 2003a). Long-term rainfall data for the study area were obtained from Climate Services, Bureau of Meteorology (Perth). Flow records were provided by the WRC for all commissioned gauging stations within the catchment. Observations of summer flow conditions were based on a series of surveys conducted by the Water Corporation during late summer 2002-2004. The condition of the Blackwood River sites during this time was one of continuous flow. A number of tributaries were recorded as dry or with low levels of flow (Table 2). Flows within the smaller tributaries such as Rosa Brook and Chapman Brook are very responsive to rainfall (i.e. tight linkage) (Figures 3 & 4) as there is very little lag between peak rainfall and onset of flows. The larger tributary, St John Brook, and the Blackwood River itself showed a lag in flow response to rainfall (Figures 5 & 6 respectively). Mean flows for two sites in the Blackwood (Hut Pool and Darradup) are shown in Figure 7. On a larger temporal scale, the influence of annual rainfall on mean annual discharge (at station 609019 on the Blackwood) is shown in Figure 8.

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Figure 3. Flows recorded in Rosa Brook from streamflow monitoring site 609001 between 1968 and 1979. The closest long-term rainfall site was Nannup (009585).



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Figure 4. Flows recorded in the Chapman Brook at streamflow monitoring site 609022 (left) between 1995 and 2003 and site 609023 (right) between 1995 and 2003. The closest long-term rainfall site was Forest

Grove (009547).

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Figure 5. Flows recorded in St John Brook from streamflow monitoring site 609018 between 1983 and

2003. The closest long-term rainfall site was Nannup (009585).

The largest variance in monthly flows is in the summer (Table 3). This is due to the unpredictable nature of “summer” storms that can produce unseasonally large flows. This variation was more pronounced in the tributaries compared to the main stem of the Blackwood (Table 3). Note, flow has never been recorded in Rosa Brook gauging site between February and April and consequently the CV values are zero (Table 3). Table 3. Coefficient of variation (%) (see Zar 1974) of monthly flows at each of the gauging sites (see Figure 1 for station locations). Highlighted months for each system represent CV values> 100% (i.e. highly variable).

Blackwood River Rosa Brook St Johns Brook Chapman Brook 609019 609025 609001 609018 609022 609023 January 48.4 83.1 331.7 83.6 125.9 207.8 February 59.7 30.6 0.0 51.9 174.1 249.2 March 165.0 244.2 0.0 55.9 190.3 175.6 April 102.7 160.0 0.0 97.7 142.5 164.2 May 53.0 50.4 225.1 253.1 90.1 87.3 June 104.0 53.5 86.4 146.0 93.2 82.9 July 65.9 75.5 93.1 63.8 77.0 75.5 August 64.8 57.5 79.3 52.4 45.3 48.3 September 79.1 52.1 63.0 69.2 49.9 59.9 October 70.7 66.4 63.6 100.5 79.7 63.1 November 44.7 46.5 84.5 69.1 103.0 42.1 December 57.8 66.6 120.1 130.2 100.8 110.6



(a) Blackw ood Riv er - Hutt Pool

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Figure 6. 1998 – 2004 total monthly stream discharge in the Blackwood River at Hut Pool, together with total monthly rainfall and long-term mean monthly rainfall at Nannup.

Stn 609025 - Blackwood River (Darradup)

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Figure 7. Mean/median annual flows at two sites on the Blackwood River (Hut Pool 609019 and Darradup

609025). Left monthly mean/median flows for Darradup and right, Hut Pool.



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Figure 8. Longer-term discharge at Hut Pool (1983-2004) and rainfall at Nannup from 1998-2004.

The absolute contribution of each tributary to the mean annual flow of the Blackwood River is shown in Figure 9. Chapman Brook and St Johns Brook both contribute about 10% to the flow of the Blackwood. Rosa Brook has a much-reduced importance to overall flow volumes. There is a large transmission gain in the Blackwood between Hut Pool (609019) prior to its ultimate discharge into Hardy Inlet near Augusta. This is considered to be due to fresher inputs from the Leederville and Yarragadee groundwater formations. The surface expression of the Yarragadee formation is upstream of Hut Pool, approximately half way to Darradup (609025).

43.8GL

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Figure 9. Absolute flow contributions of St John Brook (red), Rosa Brook (green) and Chapman Brook

(yellow) to flows within the Blackwood River (Blue).



2.2 Climate change

South-western Western Australia has experienced a significant decline in rainfall since the 1960s (CSIRO 2001). Based on current models for global warming, CSIRO (2001) has predicted (by 2030) an increase in temperature for the south-west and a decreasing trend (-20% to +5%) in winter and spring rainfall and a ±10% change in summer/autumn rainfall. While the intensity of specific winter rainfall events may increase, their duration is expected to decrease. Correspondingly, the duration of drought events and rates of evaporation is also predicted to increase. The 20% decrease in south-west rainfall over the last 30 - 40 years has resulted in a 40% decrease in annual streamflow (CSIRO 1996).

2.3 Water Quality

Currently, approximately 13% of the Blackwood catchment is adversely affected by secondary salinisation. This is a result of over-clearing in the upper catchment, and currently discharge is brackish to saline. The main Blackwood River was historically fresh but the present salinity levels are expected to double over the next 50 years (CSIRO 2001). It is only in the lower reaches, below Bridgetown, where rainfall is sufficiently high and evaporation relatively low, that the tributaries transmit fresh water. To describe water quality, data was obtained from WRC from monitoring sites on the Blackwood River and tributaries (see Figure 1 & Table 4). The main branch of the Blackwood River has relatively high salinity levels (also see Figure 10). The peak in salinity was evident during July (Figure 10). In comparison, the tributaries were very fresh, with average salinity well below 1000uS/cm (Table 4). The downstream locations on both St John Brook and Chapman Brook showed an increase in salinity levels compared to upstream sites. Rosa Brook was the freshest of the tributaries with salinity levels comparable to the upstream Chapman Brook (Table 4). An important issue within the Blackwood catchment, is therefore the relative lower salinities of the tributaries compared to the main stem of the Blackwood River (Table 4). This is shown graphically in Figure 11. Land-clearing and agriculture has also contributed to elevated nutrient and sediment levels in the Blackwood resulting in occasional blooms of blue-green algae (WRC, 2003b). In the higher rainfall areas of the lower Blackwood region, nutrient levels are generally low (TN: 0-0.75mg/L; TP: 0-0.02mg/L to slightly elevated near Nannup 0.03-0.08mg/L) (WRC, 2003b). Nutrient levels in the Blackwood have resulted in recurrent blooms of cyano-bacteria in some reaches (WRC 2003b). Fifteen phytoplankton samples collected annually along the length of the Blackwood River, (from upstream at Eulin Pool to downstream at Alexander Bridge) have shown, in the five years that data have been analysed, significant changes to water quality and flora. Most of these changes have been attributed to low rainfall in recent years, with a resulting increase in salinity (WRC 2003c). Turbidity is high in the Blackwood with levels ranging from 6 NTU, near the confluence with Rosa Brook, to >25NTU near Nannup (WRC, 2003b). Soil erosion and subsequent pool aggradation (filling with sediment) have exacerbated water quality problems, including increased likelihood of pool anoxia (oxygen depletion).



Table 4. Mean long-term water quality in the tributaries and the Blackwood River (minimum-maximum).

System Site Water Temperature (oC)

pH Conductivity (uS/cm)

Sampling Period

Tributaries St John Brook 6091002

15.1 (10-23)

6.9 (6.2-7.4)

952 (258-3,522) 3/1970 – 3/1984

St John Brook 609018

15.8 (7.2-29)

6.7 (5.2-8.5)

692 (230-1,900) 4/1983 –5/2003

Rosa Brook 6091061

12.9 (7.8-19.1)

6.2 (5.3-7.5)

379 (203-731) 5/1983 –10/2002

Chapman Brook 6091005

16.4 (10.0-30.8)

6.9 (5.4-7.8)

536 (281-939) 4/1970 –11/2002

Chapman Brook 609022

14.4 (10.1-19.7)

6.9 (6.3-7.7)

379 (278-945) 9/1995 – 11/2002

Blackwood Darradup 609025

20.3 (12-29.4)

7.2 (8.7-6.4)

25,300 (2,567-50,510) 11/1998 – 5/2003

Hut Pool 609019

16.8 (10.0-29.8)

7.3 (5.8-8.6)

3,450 (1,164-9,390) 4/1983 – 4/2003

Figure 10. Salinity (TDS in mg/L) of the Blackwood River (20th, 50th [median] and 80th percentiles) based

on longer-term data (1965-2003) at Hut Pool.

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Figure 11. A diagrammatic representation of; (A) mean total annual discharge (ML), and (B) mean “summer” (January – March) discharge for the Blackwood River and two tributaries. The intensity of

colours represents increasing salinity values. The sizes of the “rivers” indicate the relative flow contributions. Further hydrological analyses in Appendix II.

A

B



The vast majority (84%) of the Blackwood River catchment has undergone extensive clearing due to agriculture, notably in the upper reaches. Broad-acre cereal cropping and sheep grazing dominate in the east, with more intensive agriculture, such as horticultural cropping, viticulture, dairy and beef farming, in the western areas (Department of Environment Water Publications 2000). As a consequence of clearing, predominantly of native woody perennials, the salinity of the Blackwood is increasing over time (Figure 12). In contrast, the salinity of the Donnelly River was low (<500ppm) and due to the “protected” nature of the catchment, has stayed relatively constant over the 60-year time period of the record (Figure 12).

Figure 12. Five year moving average salinity (as TDS) of the Blackwood, Warren and Donnelly rivers. Based on long-term data 1939-1999.

2.4 Groundwater

It was estimated that Yarragadee aquifer contributes ~14% of the baseflows in the lower Blackwood River (URS 2003). As demonstrated in Figure 9, this annual contribution to flow in the Blackwood is less significant than the total contribution from the tributaries. However, the importance of this contribution will be increased during summer/autumn months and also during drier years. Assuming that the contribution of flow from Yarragadee remains relatively unchanged from year to year, during drier years the contribution to surface flows could be up to 30% (Figure 13). The relative contribution of Yarragadee to the flow in the tributaries of the Blackwood is yet to be accurately determined. The salinity of the Yarragadee aquifer varies between 100-400mg/L (Mauger, 2003). Therefore, it is potentially an important source of freshwater to the largely brackish Blackwood River.

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Figure 13. Estimated relative importance of Yarragadee discharge (as a %) to surface water flows in the

Blackwood River at streamflow site 609019 during wet (minimum), dry (maximum) and average years.

2.5 Salinity guidelines

As salinity of the Blackwood is the overriding determinant of ecological condition, threshold and guideline values need to be assessed in the context of existing (and proposed) national guidelines. It is now considered inappropriate to use salinity tolerances of a single species (e.g. native fish) to adequately represent an integrated ecosystem response. Typically fish are reasonably tolerant to elevated salinities in contrast to many macroinvertebrate taxa. In addition, tolerance in fish can vary greatly with life stage, larval stages being generally more sensitive. There is very little published data on the salinity tolerances of native freshwater fauna and flora of Western Australian systems. Reduced macroinvertebrate species richness and diversity has been attributed to salinisation in other south-west river systems (see Williams et al. 1991; Bunn & Davies 1992), however the degree to which community structure is altered appears to vary between systems. Many freshwater species (i.e. amphipods, cladocera, odonates, trichopterans, dipterans) are considered able to tolerate elevated salinity. In a range of systems studied, salinity is usually the major factor influencing community composition (Geddes et al. 1981, Williams 1981, Timms 1983, Edward, Gazey and Davies 1994, Bunn & Davies 1992, Davis et al. 1993, Creagh et al. 2004b). Generally, aquatic organisms are classified as stenohaline (able to adapt to only a narrow range of salinities) or euryhaline (able to adapt to a wide salinity range — up to ~15,000mg/L). In Australia, most organisms in riverine systems are stenohaline. Salinity levels may affect aquatic organisms in two ways: 1. direct toxicity through physiological changes (particularly osmoregulation) — both increases and

decreases in salinity can have adverse effects; 2. indirectly by modifying the species composition of the ecosystem and affecting species that provide food

and/or refuge.



In Australia, the development of standardised salinity guidelines for inland waters is complicated by the large number of naturally brackish or saline wetlands, rivers and streams (ANZECC/ARMCANZ 2000). For these systems, the recommended ANZECC (2000) “trigger” values for assessing potential adverse effects relate to situations where discharges of either highly saline water or freshwater are likely to substantially change the existing (or desired) salinity regime in that system. Increased freshwater inputs can impact on largely marine dominated processes in estuaries. In the case of the Blackwood, reduced freshwater inputs from Yarragadee could effectively increase salinity levels in the river. The ANZECC/ARMCANZ (2000) guidelines state that “for important ecosystems, where an appropriate reference system(s) is available, and there are sufficient resources to collect the necessary information for the reference system, the low-risk trigger concentrations for EC (or salinity) should be determined as <20th or >80th percentile of the reference system(s) distribution, depending upon whether low salinity or high salinity effects are being considered.” The reference condition for the Blackwood in the context of the Yarragadee proposal is the existing condition, with recognition of the long-term predicted increases in salinity as a consequence of catchment clearing. In the months when test values are less than trigger values, there is low risk that adverse biological effects will occur and ANZECC/ARMCANZ (2000) recommends “only regular monitoring of the key performance indicators and condition indicators is necessary”. In the months when the test values are higher than trigger values, there is an increased risk that adverse biological effects will occur, and ANZECC/ARMCANZ (2000) recommend management actions should be implemented.

2.6 Vegetation

The natural vegetation of the Blackwood Plateau consists of mainly eucalypts; jarrah and marri. The distribution of the karri forest occurs where rainfall exceeds 1000mm annually and, in these regions, is usually intermixed with extensive jarrah-banksia low woodland in sandy areas, and low woodland and thickets of paperbark sedgelands in more swampy areas. Much of the vegetation in the lower Blackwood area has been cleared and most of the vegetation of the Blackwood River catchment has been impacted by human activity (Table 5, Appendix I). A total of three botanical districts, two sub-districts and 16 vegetation systems are located within the catchment (Table 6).

Table 5. Classification of riparian condition of the Blackwood River catchment (see Appendix I for category description).

System Reach Land Use Category

Hardy Inlet to Warner Glen Bridge

Agricultural Land B2-C3

to 25km’s upstream State Forest B1

Blackwood River

to Nannup township Mostly farmland B2-C3 St Johns Brook

Whole system Farmland and pine plantation

A3-C3

Rosa Brook Whole system State Forest A3



Table 6. Botanical subdivisions of the Blackwood Catchment (source: Department of Environment, Water

Publications 2000).

Botanical district Botanical sub-district Vegetation system

Avon Wagin

Dumbleyung

Broomehill

Tambellup

Narrogin

Pingelly

Corrigin

Darling Menzies Beaufort

Williams

Jingalup

Bridgetown

Boranup

Scott River

Warren Nornalup

Roe Hyden

Ongerup

2.7 Previous ecological assessment

Previous assessments within the study region have used an AusRivAs (Australian River Assessment) protocol where macroinvertebrate community structure is compared between test and control sites (Table 7). This assessment showed, using the protocol, that all sites (Blackwood and tributaries) could be classified as “unimpaired” (Table 8). Given the extent of catchment clearing and the resultant salinity levels, sites are clearly degraded. The AusRivAs technique, as it uses Family-level identification, has been criticised for lacking sufficient resolution for detailed bio-monitoring programs and the choice of the reference condition also limits the ability of the model to detect change (Bunn & Davies 2000). In the AusRivAs assessment, the O/E index (observed/expected macroinvertebrate families) for samples in the Blackwood River appeared to be “closer” to the reference condition in the dry, but many of the macroinvertebrate families were absent in winter (Table 7). St John Brook and Rosa Brook were found to be closer to control sites (as an O/E banding category) than the Blackwood and other tributaries (Table 8), possibly a consequence of the more intact riparian zone of these sites. Chapman Brook had more macroinvertebrate families during the “wet”.



Table 7. Macroinvertebrate O/E scores for the Blackwood River and associated tributaries (CALM, 2003).

System Catchment Dry

Wet

Forested 1.13 0.57 Blackwood River Agriculture 1.09 0.70

St Johns Brook Conservation 1.21 0.72 Forested - 0.60 Chapman Brook Agriculture 0.89 1.16

Rosa Brook Forested 1.12 0.39 Macleod Creek Agriculture 1.09 - Spearwood Creek Forested 1.06 0.52

Table 8. AusRivAs classification system for O/E scores.

Site Status O/E

Unimpaired >0.89 Slightly impaired 0.7-0.89 Impaired 0.41-0.69 Severely impaired <0.41

2.8 Framework to Ecological Water Requirements

Typically EWRs are set for river systems below dams or sites of major flow regulation. Although this is clearly not the case in the Blackwood River, reduced water inputs to the main stem, due to abstraction from Yarragadee, would effectively reduce the water quantity (and often quality) of downstream reaches. Consequently, the Yarragadee proposal could be viewed, if enacted, as functioning as a “virtual” dam-site.

An initial survey of the Blackwood and associated tributaries identified several important water-dependent ecosystems and fundamental ecological processes (URS 2004). Consequently, interim EWRs were assessed on this basis:

1. Channel maintenance.

Flow requirement: Significant flows are required to maintain the active channel morphology and scour accumulated material from pools (e.g. sediment, detritus etc) and inhibit further weed incursion into channels. Underlying theory: In-stream flows influence channel form through physical processes such as pool scouring (Arthington et al. 1994). Elevated flows are often required to maintain existing (or active) channel dimensions, preventing the accumulation of sediment and organic debris in river pools and prevent encroachment by riparian vegetation and weeds. Disturbances from high-flow events can also be important in structuring benthic communities and may influence ecosystem function (see Resh et al. 1988). Scour of river-beds, and undercutting of banks, is often essential for producing diversity of habitat, particularly for native fish.



2. Maintenance of pool water quality (dissolved oxygen).

Flow requirement: Flows to maintain adequate dissolved oxygen levels in channel pools. The Blackwood catchment is still “generating” sediment, which has aggraded (see Glossary) pools and therefore reduced habitat area. Consequently, pool volumes may now be insufficient to ensure satisfactory water quality, particularly dissolved oxygen (DO). Underlying theory: Sufficient water volumes are required over summer to ensure sufficient water volumes and adequate dissolved oxygen of the pools. Generally, values of dissolved oxygen> 2mg/L are required for aerobic processes. Adequate water quantities buffer the effect of high benthic respiration and other processes which remove dissolved oxygen from pools.

3. Maintenance of water quality (salinity).

Flow requirement: Flows to maintain water quality less than threshold values for the maintenance of aquatic fauna and fundamental ecological processes. Underlying theory: As previously discussed, most of the aquatic fauna in streams of south-western Australia are termed “stenohaline” and, as such, intolerant to elevated salinities. Guideline values are discussed in Section 2.5.

4. Riparian/ floodplain vegetation. Flow requirement: Seasonal inundation. Sufficiently large river flows to flood the riparian zone and stimulate seed-set and enable subsequent recruitment of vegetation. Underlying theory: Riparian vegetation is defined as vegetation on any land which, adjoins or directly influences a body of water (see Glossary). Riparian land is usually the most fertile and productive part of the landscape. Riparian vegetation regulates in-stream primary productivity through shading (Bunn & Davies 2000) and supplies energy and nutrients (in the form of litter, fruits, organic matter) essential to aquatic organisms. It also provides essential aquatic habitat such as large woody debris (LWD). Much of the in-stream habitat available for fish and macroinvertebrates originates from the riparian zone (Davies & Storey 1998).

Removal of deep-rooted riparian vegetation can result in floodplain scour, bank erosion and consequent sedimentation of the river channel, which leads to increased erosion or flooding further downstream (Lovett & Price 1999). The reaches of the Blackwood River of particular interest for riparian condition are between Nannup and the Hardy Inlet; where the Blackwood passes through a combination of agricultural land and State Forest (WRC, 1997).



5. Riverine macroinvertebrates. Flow requirement: Flows which do not cause channel instability or bank erosion and also maintain a diversity of hydraulic habitats. Flows of sufficient depth to keep riffle zones (“hotspots” of macroinvertebrate biodiversity) inundated. Generally, minimum flows of 5cm over riffles are considered adequate to support riverine macroinvertebrates. Underlying theory: Aquatic invertebrates are a fundamental component of aquatic ecosystems as the energy base of the food web. There are two main features of flow regimes that influence aquatic invertebrate community structure in south-west rivers. These are (after Streamtec 2001): Seasonality - Life histories of aquatic species are intrinsically linked to flow regimes (Bunn 1988). The variation in the degree of seasonality can lead to changes in invertebrate community structure (Bunn & Davies 1990) and changes in life history patterns. Predictability/Persistence - A key feature of the stream fauna is the high degree of concordance; that is, that the flow regime is not only highly seasonal but also predictable year to year (McMahon 1989, Bunn & Davies 1990, Bunn 1995) to which the fauna responds. Species that are susceptible to high and variable flows can synchronise their life cycles so that the sensitive stages (e.g. the larvae of crustaceans or pupating stages of some insects) occur only during the dry season.

6. Riverine fish.

Flow requirements: Sufficient water to enable successful reproductive migration of native fish. Water levels sufficient to inundate trailing streamside vegetation (i.e. egg-attachment points) during spawning. Generally, flows of at least 20cm over riffles and other “control points” during September/October are considered adequate to enable the completion of successful reproductive migration of native fish (e.g. Galaxias occidentalis). Underlying theory: The south-west of Western Australia has what is considered a depauperate freshwater fish fauna, with a high degree of endemism (Pusey et al. 1989). Components of the biology of native species most likely to be affected by altered flow regimes are migration and reproduction. Retention of water levels that maintain deeper pools can also be important to maintain habitats. The fresh sub-catchments may be important refugia for native species which are intolerant of seasonally-elevated salinities in the main stem of the Blackwood River.

7. Energy flows. Flow requirements: An unregulated, constant flow from the forested regions to the lower reaches is necessary to maintain ecological connectivity. Underlying theory: River ecosystems are integral components of the landscape, where ecological boundaries are often the entire catchment (Bunn & Davies 2000). Maintenance of food webs requires a linkage between upstream and downstream reaches. Analyses in south-western river systems (Davies 1994, Davies et al. 1998) have shown upland reaches to be reliant on the input of terrestrial carbon from forested reaches. In this context, the River Continuum Concept (RCC) is considered the appropriate ecological model for the Blackwood River and tributaries (Vannote et al. 1980) (see Figure 14).



Figure 14. The River Continuum Concept of Vannote et al. (1980) emphasising the linkages between

ecological function and hydrology (figure modified after Bunn 1997). This model is considered appropriate to describe ecological processes in the Blackwood River.

8. Fresh sub-catchments. Flow requirement: Salinity concentrations in the main stem of the Blackwood during some occasions would exceed tolerance levels of some of the native aquatic fauna and inhibit basic ecological processes. Consequently, maintenance of the fresher tributaries may be important as refugia for a range of aquatic fauna. Underlying theory: See Section 2.3.

9. Estuarine linkages. Flow requirement: The estuary is highly tidal and therefore considered beyond the influence of any perceived impacts of the Yarragadee proposal. Underlying theory: Estuaries are highly productive often as fish nursery habitats. This productivity is maintained, in part, by flows from their river systems. For the Hardy Inlet, flows should be maintained such that this water quantity and material transfer are maintained. For some systems, including the Hardy Inlet, river flows the previous year are correlated with the following catch (as CPUE) of some fish, prawns and crabs (URS 2004).

10. Seasonal adjustment. Flow requirement: Flows (in some months) to mimic the natural hydrograph. Underlying theory: The “historic flow paradigm” is central to EWRs and states that ecological processes and aquatic species have evolved in response to historic flows, and often develop life history stages (i.e. pupation) in response to the seasonal flows.

In-stream productionTerrestrial carbon

River carbon

River Continuum Concept (RCC)

Turbidity (light) limited

Riparian inputs important

Downstream transport of carbon important

Shade (light) limited



3. METHODS

The aim of the study was to essentially refine the interim EWRs and focus of pivotal issues as outlined in URS (2004). A field survey was conducted during July (winter) 2004 to address these issues. A follow-up survey of dissolved oxygen and temperature dynamics in pools was conducted during October 2004. A total of 34 ‘focal’ study sites were selected to represent a range of habitat and channel morphology types; 19 in the main channel of the Blackwood River and twelve tributary sites (Figure 1) with three additional sites in St Johns Brook. All sites were located between Nannup township and Hut Pool, and the majority within State Forest. Photographs of site conditions, in July 2004, are presented in Appendix VI.

3.1 Timing of the Survey

Previous studies of the macroinvertebrate fauna of south-west streams have identified distinct seasonality in the fauna with discrete assemblages occurring in winter/spring and summer/autumn seasons (Bunn et al. 1986, Storey et al. 1990). Such changes in macroinvertebrate community structure and function have been attributed to the influence of a highly seasonal and predictable Mediterranean climate with high winter flows and low summer flows (ARL 1987b). Winter/spring months are also considered critical for reproduction and movement of many native fish in the Blackwood River catchment, based on known periods of spawning and dispersal. The current sampling represented a winter/high-flow survey.

3.2 Study parameters

In the study, a range of issues associated with the already-defined water-dependent ecosystems were sampled/measured:

• Riparian vegetation (zonation, health, position on bank). • Channel morphology (water level slope, cross sectional profiles, thalweg (deepest point), bed

materials). • Water quality (pH, dissolved oxygen (DO), temperature, salinity, conductivity, redox, total N,

total P, turbidity). • Water quality dynamics; 24-hour data-logging of DO and temperature in select riverine pools. • Aquatic macroinvertebrates (partly-based on AusRivAs protocols but with Species level

assessment). • Fish (presence, abundance).

3.3 Riparian Vegetation

On-site assessments of riparian condition were made on the basis of dominant plant species and relative degree of disturbance such as weed invasion, livestock access and fire etc (see Appendix I). Assessments followed the rapid assessment methodology of Pen and Scott (1995) and WRC (1999). Riparian vegetation (see Glossary) was defined as vegetation on any land which, adjoined or directly influenced the water body and included vegetation on:

• river banks and on land immediately adjacent to rivers/streams, • gullies and dips which may have been seasonally or periodically connected to the river/stream by

surface water and • river floodplains that were likely to be interconnected with the river during flood events.



3.4 Channel Morphology

Dominant habitat substrates were visually assessed (by surface area) for mineral (e.g. silt, sand, gravels, cobbles) or other (e.g. vegetation, organic detritus) material. Extent of bank erosion and channel down-cutting was qualitatively assessed. Sedimentation, as pool aggradation (in-filling), was assessed as the relative amount of fine inorganic material covering the more typical bed substrate. On tributaries, distance from source was estimated from maps, stream water level slope was determined using a staff and dumpy level. Descriptions of overall stream condition were based on categories as outlined in WRC (1999).

3.5 Cross Sections

Measurements of hydraulic geometry of the river channels (channel morphology; water level slope, cross-sectional area and Manning’s n) were made at all sites. Cross-sectional area was measured using a surveyors’ dumpy level, staff and measuring tape (Figure 15, Plate 1). Level readings were taken at the water’s edge (active channel), bankfull level and flood plain (see Figure 16). These points were taken at right angles to the centre line of the channel. Measurements of channel morphology were typically (depending on accessibility) carried out over a 100m reach. To measure discharge, a narrow segment (control point; usually at culverts or under bridges) of stream of uniform shape was selected and velocity measured at 0.6x depth using a field velocity meter (OTT meter). Discharge volume (Q) was calculated using the relationship:

Q = width × depth × average velocity.

Bankfull discharges were calculated using Manning’s Equation:

Qbf=R 2/3.S 1/2/nbf where R=A/p

A=cross section area P=wetted perimeter

mean depth, S = slope of the active channel, n = Manning’s roughness factor (Newbury and Gaboury 1993).



Bankfull height / stage

Present flow

Central channel

Bankfull width

Figure 15. Measurements of channel morphology. Plate 1. Surveying cross sections.

,

Figure 16. Methodology used to determine cross-sectional profiles. These cross sections enabled determination of the flow volumes required to attain required stage heights.



3.6 Water Quality

Measurements of water quality were made in conjunction with the fauna sampling (Plate 2). Measurements of temperature (accuracy 0.1oC), dissolved oxygen (0.1 mg/L), salinity (0.1 TDS), pH (0.05 unit), turbidity (0.5 NTU) and redox (1mV) were made in situ using a portable Yeo-Kal 611 Multi Water Quality Analyser (Plate 2). Undisturbed water samples were taken for analyses of total nitrogen (TN) and total phosphorus (TP). Nutrient analyses were conducted by the Natural Resources Chemistry Laboratory, Chemistry Centre, WA (NATA registered). The dynamics of dissolved oxygen and temperature were measured using specific sensors (YSI 5739) which were attached to data-loggers (TPS 601) programmed to record at 10minute intervals over at least 24hr. At this period, data were downloaded in the field via a RS232 port into a laptop computer. A series of sub-routines converted data into units of DO and temperature. At the beginning and end of each 24hr run, each sensor was calibrated. The accuracy of the sensor was 0.25mg/L for DO and 0.1oC for temperature.

3.7 Macroinvertebrates

3.7.1 Field sampling

Qualitative samples of aquatic macroinvertebrates were collected at all sites using a standard FBA (Freshwater Biological Association) pond-net (250µm mesh size) sampling over a 50 metre reach (Plate 3), in a method based on the AusRivAs protocol. Overall, diversity of aquatic habitats was high and included riffles, meanders, pools, in-stream rocks and logs and a variety of in-stream and bank vegetation types. Consequently, field sampling was designed to incorporate all aquatic habitats and ensure as many species as possible were represented. A single composite sample was collected from each site and immediately preserved in 70% ethanol. 3.7.2 Laboratory processing

In the laboratory, samples were washed and organic sediments, including macroinvertebrates, were separated from the inorganic material by water elutriation. The organic sediments were then washed through a series of 2mm, 500µm and 250µm mesh sieves to partition the sample into fractions. The 500µm and 250µm fractions were sorted under a binocular microscope and collected macroinvertebrates stored in 70% ethanol. For each sample, the entire 2mm and 50 µm fractions were sorted, while 250µm fractions were sub-sampled by one-fifth. Macroinvertebrates were identified to the lowest taxon possible either by use of keys or by matching specimens to a voucher collection at the School of Animal Biology, University of Western Australia. Species-level identifications were made to increase resolution and hence ability of the bio-monitoring program to detect small or subtle changes. An estimate of abundance for each species was made using (log10) categories where; 1 = 1 individual, 2 = 2-10 individuals, 3 = 11-100, 4 = 101-1000, 5 = >1000 (see Appendix III). The existence of rare, restricted or endemic species were determined by cross-referencing taxa lists for each site/habitat with an established database (the University of Western Australia) and with the Department of Conservation and Land Management (CALM) Wildlife Conservation (Specially Protected Fauna) Notice 2003 (Government Gazette 11 April 2003, pp. 1158-1167) and with the 2003 IUCN Red List of Threatened Species (IUCN 2003).



3.8 Fish

Fish were sampled using a combination of methods including 250µm dip nets (in areas of reed beds, bank undercuts and under logs), Fyke nets set across an area of the river (Plate 4A); baited collapsible box traps, Smith-Root Model 12B backpack electrofisher (Plate 4B) or by direct observation. Traps and Fyke nets were set in the late afternoon and cleared in the early morning. The electrofisher was used predominantly in tributary sites where sampling was not precluded by high salinities and conducted over a 50m reach. All collected fish were identified, enumerated and measured for standard length and all native fish were returned live to the water. Nomenclature followed Allen et al. (2002). Appropriate licences to collect fish were obtained through the Department of Fisheries (WA) and animal ethics approvals through the University of Western Australia.

Plate 2. Water quality measurements being taken in situ.

Plate 3. Sweeping under vegetation for aquatic macroinvertebrates using a 250µm mesh pond-net.

(a) (b)

Plate 4. (a) Setting the Fyke net in the Blackwood River at St Patrick’s Elbow; (b) electrofishing in Milyeannup Brook.



4. RESULTS OF JULY 2004 FIELD SURVEYS

4.1 Riparian Vegetation and Foreshore Condition Assessment

To give an indication of the conditions during sampling, photographs of survey sites taken during sampling are given in Appendix VI. The majority of sites along the main channel of the Blackwood River within State Forest had a dense canopy of native, woody perennials (trees and shrubs), dominated by flooded gums (Eucalyptus rudis) and swamp paperbarks (Melaleuca rhaphiopylla). Most sites were classified as pristine (A1-A2, see Appendix I) with few weeds (Table 9). Overstorey tree cover ranged from patchy (20-80%), to continuous (>80%). The Longbottom Road site (Site 3) was within rural/agricultural land and was relatively degraded due to past clearing of catchment vegetation and through current unrestricted livestock access. Along the northern bank, pasture species dominated the riparian understorey vegetation with few native species present. Site 5 was also located adjacent to private residential property and was lightly disturbed, with local weed infestations. All tributary sites were located within State Forest and were categorized either as pristine or near pristine (A1-A2; Table 9 & Appendix I). The overstorey tree cover ranged from 0% (absent) to >80% (continuous). The middle-storey layers were typically more dense (>80%; continuous) along tributary sites compared to main channel sites (Table 9). Local weed infestations of the bridal creeper (Asparagus asparagoides, Plate 5) were evident at Blackwood River sites 1 and 5 (Milyeannup Ford). This creeper has been classified a ‘Weed of National Significance’ owing to its invasiveness, potential for spread, and economic and environmental impacts. Originally introduced as a garden plant, bridal creeper is a now a major weed across southern Australia, where its climbing stems and foliage typically smother native plants. The thick mat of underground tubers produced by A. asparagoides impedes both root growth and seed establishment of native plants. The bridal creeper is considered the most pervasive weed threat to floral biodiversity in South Australia and south-west Western Australia.

Plate 5. Bank at Blackwood River Site 5 near

Milyeannup Ford, showing extent of bridal creeper Asparagus asparagoides.

Plate 6. Bank at Blackwood Site 3, near Longbottom Road, showing slope steepness.



In undisturbed systems, riparian land is usually the productive component of the landscape. Riparian vegetation regulates in-stream primary productivity through shading and supplies energy and nutrients (in the form of litter, fruits, organic matter) essential to aquatic organisms and provides essential aquatic habitat (Bunn & Davies 2002). All Blackwood River and tributary sites exhibited elevated in-stream habitat diversity, with leaf litter, detritus, fallen branches and/or vegetation, and including riffles, meanders, pools, in-stream logs and rocks, and a variety of in-stream and bank vegetation types. Bank slopes along Blackwood River and tributary sites ranged from moderate (10-45°) to steep (>60°) (Table 10 & Plate 6). Typically, erosion and slumping appeared to be associated with localised anthropogenic disturbances. For example, localised slumping was apparent along track washouts near Milyeannup Ford (refer Plate 5).

Table 9. Assessment of riparian vegetation condition.

Drainage Site code Riparian category* Riparian description Overstorey cover 1 B1 Weed infested (Asparagus asparagoides):

understorey mainly natives > 80% continuous

2 A2 Near pristine: some weeds 20-80% patchy 3 B1 Weed infested: understorey mainly natives 20-80% patchy 4 A2 Near pristine: some weeds > 80% continuous 5 A3 Slightly disturbed: local weed infestations 20-80% patchy 6 A2 Near pristine: some weeds > 80% continuous 7 A2 Near pristine: some weeds > 80% continuous 8 A2 Near pristine: some weeds > 80% continuous 9 A2 Near pristine: some weeds > 80% continuous

10 A2 Near pristine: some weeds > 80% continuous 11 A2 Near pristine: some weeds > 80% continuous 12 A2 Near pristine: some weeds > 80% continuous 13 A2 Near pristine: some weeds > 80% continuous 14 A2 Near pristine: some weeds > 80% continuous 15 A2 Near pristine: some weeds > 80% continuous 16 A1 Pristine: no weeds > 80% continuous 17 A2 Near pristine: some weeds > 80% continuous 18 A1 Pristine: no weeds > 80% continuous

Blackwood River

19 A2 Near pristine: some weeds < 20% sparse “Ballan” Creek A A1 Pristine: no weeds < 20% sparse

B A2 Near pristine: some weeds > 80% continuous Rosa Brook Rosa Brook (up) C A2 Near pristine: some weeds 20-80% patchy Adelaide Brook D A2 Near pristine: some weeds < 20% sparse Spearwood Creek E A2 Near pristine: some weeds 0 % absent Layman Brook F A1 Pristine: no weeds 20-80% patchy Milyeannup Brook G A2 Near pristine: some weeds 20-80% patchy Poison Gully H A2 Near pristine: some weeds > 80% continuous Sollya Creek I A3 Slightly disturbed: local weed infestations 20-80% patchy Red Gully J A2 Near pristine: some weeds > 80% continuous McAfee Brook K A2 Near pristine: some weeds > 80% continuous Sturke Creek L A3 Slightly disturbed: local weed infestations 20-80% patchy St Johns Brook SJ1 A2 Near pristine: some weeds > 80% continuous St Johns Brook SJ2 A2 Near pristine: some weeds > 80% continuous St Johns Brook SJ3 A2 Near pristine: some weeds > 80% continuous

*after Pen and Scott (1995) and WRC (1999).



Table 10. Foreshore assessment.

Drainage Site code

Bank slope

Erosion Slumping Sedimentation

Blackwood River 1 45-60° 0-5% 0-5% 0-5% 2 45-60° >50%; undercutting 20-50% 0-5% 3 45-60° 5-20% 0-5% 0-5% 4 45-60° 5-20% 0-5% 0-5% 5 45-60° 0-5% 5-20% 0-5%; to 5 cm 6 >60° 5-20% 0-5% 0-5% 7 10-45° 5-20% 0-5% 0-5% 8 10-45° 0-5% 0-5% 0-5% 9 45-60° 0-5% 5-20% 0-5%; to 5 cm 10 10-45° 5-20% 0-5% 0-5% 11 10-45° 0-5% 0-5% 5-20% 12 45-60° 5-20% 0-5% 0-5% 13 45-60° 5-20% 5-20% 0-5% 14 45-60° 5-20% 0-5% 0-5% 15 45-60° 5-20% 0-5% 0-5% 16 45-60° 0-5% 0-5% 0-5% 17 45-60° 0-5% 0-5% 0-5% 18 45-60° 5-20%; track washouts 0-5% 0-5% 19 45-60° 0-5% 0-5% 0-5% “Ballan” Creek A >60° 0-5% 0-5% 0-5% Rosa Brook B 45-60° 0-5% 0-5% 0-5% Rosa Brook (up) C 10-45° 0-5% 0-5% 5-20%; to 25 cm in pool Adelaide Brook D 45-60° 0-5% 0-5% 20-50%; to 20 cm Spearwood Creek E 10-45° 10-20% 0-5% 0-5% Layman Brook F 45-60° 0-5% 0-5% 0-5% Milyeannup Brook G 45-60° 0-5% 0-5% 0-5% Poison Gully H >60° 5-20%; undercutting 0-5% 0-5% Sollya Creek I 10-45° 5-20%; undercutting 0-5% 0-5% Red Gully J 10-45° 0-5% 0-5% 0-5% McAfee Brook K 45-60° 0-5% 0-5% 0-5% Sturke Creek L 45-60° 0-5% 0-5% 20-50%; to 20 cm St Johns Brook SJ1 45-60° 10-25%; undercutting 0-5% 0-5% St Johns Brook SJ2 10-45° 0-5% 0-5% 0-5% St Johns Brook SJ3 10-45° 10-25% 0-5% 0-5%



4.2 Channel Morphology and Cross Sections

Stylised channel cross-section diagrams were produced for the Blackwood (Figure 17) and tributary sites (see Figure 18 & Appendix VII). A summary of results of channel morphology measurements for the Blackwood and tributary sites is given in Table 11. The Blackwood River sites were characterised by steep banks (30 to 450), and turbid, fast flowing water. Streambed materials were homogenous along the length of the river (sand over gravel), producing similar estimates for Mannings n (Figure 18, Table 11). Tributary sites exhibited moderate bank angles, near pristine vegetation conditions with a wide range of overstorey coverage across sites. Discharge from these tributaries was low, and during the survey they provided relatively small contributions to the flow of the Blackwood (Table 11). The longitudinal model of the Blackwood (Figure 19) shows, that generally, water depths were relatively constant, possibly due to the unstable nature of river sediments. This being the case, a well-defined thalweg was not usually evident. However, several sites in the Blackwood (2, 3, 7, 10, 11, 14) had thalwegs <100cm (depth at the sampling date), with site 6 having a thalweg <50cm (see Table 2). These shallow sections within the river are important “control” points as they represent critical cease-to-flow levels which may be impacted by Yarragadee abstraction. Details of the cross sectional profiles of the Blackwood and tributary sites are also presented in Figure 20 and Appendix VI & VII. Discharge rates (Q) were calculated at each of the tributary sites. These estimated discharges are considered to be those required to attain specific stage heights to meet ecological objectives. Along the length of the Blackwood, transmission gains were low, with sites and discharge requirements remaining fairly homogenous (Figure 20).



Table 11. Channel morphology measurements taken in July 2004 for an average reach of each site. (Note, the accuracy of discharge measurements in the Blackwood have considerable errors inherent in the cross-section, “panel” methods used in large rivers.) Manning’s n was estimated, based on paving materials and

debris, in the main stem of the Blackwood and calculated in the tributaries based on transposition (i.e. slope, discharge and wetted perimeter measured on-site) of the Manning’s equation (see Section 3.5).

Site code

Discharge (m3/sec)

Bed paving material

Gradient (%)

Wetted perimeter

(m)

Bankfull perimeter

(m)

Manning’s n

Blackwood 1 30.2 Sand over gravel 0.02 18.3 27.8 0.04 (est) Blackwood 2 36.4 Sand over gravel 0.02 18.8 30.4 0.045 (est) Blackwood 3 32.5 Sand over gravel 0.03 21.4 29.8 0.04 (est) Blackwood 4 34.2 Sand over gravel 0.02 22.9 30.6 0.04 (est) Blackwood 5 46.0 Sand over gravel 0.02 19.0 31.7 0.04 (est) Blackwood 6 35.2 Sand over gravel 0.02 21.5 34.6 0.045 (est) Blackwood 7 36.7 Sand over gravel 0.03 34.5 32.5 0.04 (est) Blackwood 8 38.9 Sand over gravel 0.02 22.6 33.7 0.04 (est) Blackwood 9 43.2 Sand over gravel 0.03 27.5 34.0 0.045 (est) Blackwood 10 56.4 Sand over gravel 0.03 22.3 35.8 0.04 (est) Blackwood 11 54.3 Sand over gravel 0.01 27.8 36.7 0.04 (est) Blackwood 12 51.9 Sand over gravel 0.02 27.4 35.4 0.045 (est) Blackwood 13 56.4 Sand over gravel 0.02 30.6 36.7 0.04 (est) Blackwood 14 67.2 Sand over gravel 0.02 32.4 38.9 0.04 (est) Blackwood 15 63.8 Sand over gravel 0.01 22.4 38.9 0.045 (est) Blackwood 16 76.3 Sand over gravel 0.02 25.4 39.2 0.04 (est) Blackwood 17 92.8 Sand over gravel 0.02 23.7 42.3 0.04 (est) Blackwood 18 123.5 Sand over gravel 0.02 26.5 44.5 0.04 (est) Blackwood 19 104.3 Sand over gravel 0.02 37.9 54.8 0.04 (est) “Ballan” Crk. A 0 sand over clay 0.02 3.74 5.04 0.05 (est) Rosa Br. (up) B 0.22669 sand over clay 0.07 12.58 14.88 0.052 Rosa Brook C 0.19025 sand/gravel/ rocks 0.36 7.04 9.94 0.055 Adelaide D 0.02374 clay/loam 0.03 6.87 13.03 0.053 Spearwood E 0.00221 sand/detritus 0.04 3.40 12.30 0.047 Layman Br. F 0.02172 clay/loam 0.04 2.95 8.90 0.053 Milyeannup G 0.25689 sand/gravel/rocks 0.03 8.98 11.97 0.048 Poison Gully H 0.01679 sand/gravel/rocks 0.03 8.60 10.20 0.047 Sollya Creek I 0.00126 sand/gravel/rocks 0.02 4.32 8.06 0.057 Red Gully J 0.11299 sand/gravel/rocks 0.02 7.89 12.02 0.052 McAfee Br. K 0.1265 sand/gravel/rocks 0.02 3.90 8.74 0.048 Sturke Creek L 0.0871 sand/gravel/rocks 0.02 5.82 9.71 0.052 St Johns SJ1 0.00226 sand/gravel/rocks 0.05 10.01 15.98 0.061 St Johns SJ2 0.18756 sand over clay 0.04 11.29 16.54 0.053 St Johns SJ3 0.34522 sand/detritus 0.02 13.28 19.78 0.045



Figure 17. Generic cross-section of the Blackwood River (see Appendix VIII).

Figure 18. Generic channel cross-section of the tributary sites (see Appendix VII).

Typically steep bank angle: between 30

and 45°.

Typically turbid, fast flowing deep water; depth about 1-

2m.

Macroinvertebrate and fish sampling area. Maximum sampling depth

1.5m.

Abundant leaf litter visible at most sites.

Most sites characterised by abundant riparian vegetation. Much of this vegetation was

submerged due to high water levels. Riparian vegetation provides refuge and shelter for fish

and other aquatic life forms.

Bank stabilisation provided by native vegetation: mature eucalypt trees,

saplings and native grasses.

Erosion visible where walking or 4WD tracks present

Foam generally visible on the

surface.

Bank stabilisation provided by abundant native vegetation:

mature eucalypt trees, saplings and native grasses.

Slight to moderate bank angle: Between 20 and 40°.

Most sites character-ised by abundant

riparian vegetation and in-stream habitat.

Riparian vegetation and habitats such as

submerged logs and rocks provide refuge

and shelter for fish and other aquatic life forms.

Abundant leaf litter visible at most sites.

Macroinvertebrate and fish sampling

area.



Figure 19. Longitudinal model of depth of the Blackwood from Nannup to Hut Pool. Data were recorded from an inflatable boat.



Figure 20. Depth categories along one stream reach (i.e. one meander or riffle-pool sequence) (other

details in Appendix VII). Arrow indicates direction of flow. Note, ‘slope’ refers to water level slope. The right hand plots show the discharge rates (Q) required to attain specific stage heights to meet ecological

objectives.

MacroinvertebratesFish

RiparianQbf=6.62 m3/s

Qfish=1.71 m3/s

Qmacro=0.63m3/s



Qfish=2.38 m3/s

Qmacro=1.46m3/s



Qfish=1.17 m3/s

Qmacro=0.29m3/s



Figure 20 (cont.). Depth categories along one stream reach (i.e. one meander or riffle-pool sequence) (other details in Appendix VII). Arrow indicates direction of flow. Note, ‘slope’ refers to water level slope. The right hand plots show the discharge rates (Q) required to attain specific stage heights to meet ecological objectives.



Qfish=3.62 m3/s

Qmacro=1.07m3/s



Qfish=1.04 m3/s

Qmacro=0.26m3/s



Qfish=1.54 m3/s

Qmacro=0.55m3/s






Qfish=2.40 m3/s

Qmacro=0.87m3/s



Qfish=4.02 m3/s

Qmacro=0.91m3/s



Qfish=2.07 m3/s

Qmacro=1.41m3/s






Qfish=2.66 m3/s

Qmacro=1.02m3/s



Qfish=2.03 m3/s

Qmacro=0.96m3/s



Qfish=2.96 m3/s

Qmacro=0.89m3/s






Qfish=3.87m3/s

Qmacro=2.16m3/s



Qfish=3.22 m3/s

Qmacro=1.99m3/s



Qfish=3.16 m3/s

Qmacro=1.84m3/s



Figure 20 (cont.). Water requirements at one river cross section. Other Blackwood sites shown in Appendix VIII. Refer to longitudinal model (Figure 25) for depth categories. Note, the thalweg is the “low flow” channel during seasonally dry periods. The plots show the discharge rates (Q) required to attain specific stage heights to meet ecological objectives.

Macroinvertebrates/ energy flows

Fish

RiparianQbf=197.5m3/s

Qfish=11.79 m3/s

Qmacro=0.29m3/s Low flow channel ~ thalweg

Floodplain

Benches

Blackwood Site 19


Fish


Qfish=10.92 m3/s


Floodplain

Benches

Blackwood Site 12


Fish


Qfish=9.71 m3/s


Floodplain

Benches

Blackwood Site 8


Fish


Qfish=9.01 m3/s


Floodplain

Benches

Blackwood Site 1



4.3 Water Quality

Results of water quality measurements taken in July 2004 are summarised in Table 12 and discussed below. 4.3.1 Salinity

The majority of Blackwood River sites were brackish to moderately saline2 (Table 12). Site 13 at Sue’s Bridge had the lowest salinity (6495µS/cm) while reaches at St Patrick’s Elbow (Site 7), Denny Road (Site 10) and Mas Road (Site 18) were all saline, i.e. ≥ 9,000µS/cm Econd. Salinity levels were markedly lower in tributary sites which were all fresh, ranging from 345µS/cm Econd in Milyeannup Brook (Site G) to 457µS/cm Econd at Layman Brook (Site F). 4.3.2 Temperature and DO

Water temperatures at all sites were cool (9.17 – 11.54oC) and strongly linked to both ambient temperature and water depth. Increases in temperature alone are often not the major cause of stress to aquatic organisms. Rather, synergistic effects related to temperature, for example, changes in DO (dissolved oxygen) concentrations which affect respiration may lead to mortality (Mitchell et al. 1996). Daytime dissolved oxygen (DO) levels at study sites showed minimal variation during July; most were supersaturated3 (>100%; >10mg/L). The exception was tributary Site A, (Ballan Creek) with moderate DO levels of 52.8 % (6mg/L). Stratification in deeper pools (during July 2004) in the Blackwood was not significant; with only temperature and DO showing changes near the river bed (see Appendix IV). 4.3.3 Dynamics of DO and Temperature Past surveys of the Blackwood River conducted during summer have shown conditions close to anoxia (0% DO) in many pools (Davies pers. comm.). The DO content of any stream is determined by both physical and biological processes. Physical processes include re-aeration, which is the exchange of oxygen between the surface of the stream and the atmosphere. Physical re-aeration can be increased by the presence of rocks or cobbles which break the surface (e.g. riffles) of the water resulting in areas of increased water turbulence. Biological processes influencing DO levels include metabolic rates, i.e. photosynthesis and respiration by aquatic biota (see Appendix V). In rivers where rates of metabolism are high (e.g. where high microbial, algal or plant growth occurs), DO levels may drop overnight as a result of aerobic respiration. In the Blackwood system, this is likely to occur during summer when light levels and temperatures are high and flows are at minimum. DO levels <2.0mg/L are considered the critical threshold at which respiration becomes difficult for many fish (ANZECC/ARMCANZ 2000).

2 Fresh defined as 2,700µS/cm; brackish/moderately saline 2,700 – 9,000µS/cm; saline 9,000 – 55,000µS/cm. Dept. Agriculture, Government of Western Australia, 2002. 3 Solubility of oxygen in water is dependent upon temperature, pressure, and salinity. Supersaturation occurs when the water holds more oxygen molecules than usual for a given temperature. Water is ‘saturated’ when percentage DO is 100% and ‘supersaturated’ at >100%.



Table 12. Results of measurements of water quality in the Blackwood River during July 2004. Note sites K,L sampled during October 2004.

System Site code

Date and time of day

Water temp. (°C)

(ambient air)

Turbidity (NTU)

DO (%)

DO (mg/L)

Redox (mV)

pH Salinity (mg/L)

Econd. (us/cm)

Total N (mg/L)

Total P (mg/L)

Blackwood River 1 19/6 16:23 11.20 (18.3) 29.7 106.4 10.9 -223 7.79 3900 7223 2.1 0.02 Blackwood River 2 19/6 14:58 11.29 (18.8) 36.5 106.2 10.9 -244 7.71 4800 7741 2.2 0.02 Blackwood River 3 19/6 14:00 11.45 (18.2) 19.1 101.8 10.2 -221 7.77 4300 7388 2.2 0.03 Blackwood River 5 20/6 13:30 11.01 (19.4) 19.4 104.9 10.8 -237 7.83 4600 7951 2.2 0.02 Blackwood River 6 20/6 16:00 11.29 (18.6) 11.2 100.7 10.4 -290 7.87 4400 7921 2.1 0.02 Blackwood River 7 20/6 16:35 11.36 (19.2) 12.2 103.6 10.7 -215 7.76 5000 9000 2.1 0.02 Blackwood River 8 20/6 17:00 11.52 (18.6) 20.5 103.2 10.5 -268 7.77 4000 6856 2.0 0.02 Blackwood River 10 21/6 15:30 11.37 (19.5) 11.0 104.1 10.8 -232 7.78 5200 9200 2.0 0.02 Blackwood River 11 21/6 14:30 11.36 (18.9) 8.3 103.9 10.7 -224 7.8 4500 8800 2.0 0.02 Blackwood River 12 21/6 15.30 11.25 (18.5) 10.5 102.4 10.8 -227 7.8 4500 8700 2.0 0.02 Blackwood River 13 21/6 17:00 11.54 (17.4) 14.5 103.1 10.3 -237 7.72 3900 6495 1.7 0.02 Blackwood River 14 22/6 10.30 11.20 (17.4) 12.2 100.4 10.5 -207 7.76 4000 6570 1.8 0.02 Blackwood River 15 22/6 11.30 11.14 (17.8) 11.4 100.5 10.6 -235 7.81 4300 7350 1.6 0.02 Blackwood River 16 nr 11.37 (17.7) 12.6 104.7 10.8 -227 7.8 5200 7562 2.2 0.02 Blackwood River 17 23/6 11.30 10.95 (19.3) 10.5 102.4 10.9 -224 7.8 5000 8800 2.1 0.02 Blackwood River 18 24/6 09:30 10.97 (16.6) 8.9 102.3 10.3 -197 7.95 4700 9100 1.9 0.02 Blackwood River 19 23/6 14:30 11.54 (17.5) 40.2 105.2 10.9 -239 7.74 4300 6924 1.5 0.02 “Ballan” Creek A 24/6 11:20 9.17 (16.7) 0 52.8 6.0 -63 7.02 280 384 0.09 <0.01 Rosa Brook B 26/6 11:20 10.72 (15.6) 0 106.7 11.0 -138 7.43 280 432 0.05 0.01 Rosa Brook (up) C 26/6 10:10 9.51 (16.4) 0 106.7 11.3 -103 7.5 360 449 <0.05 <0.01 Adelaide Brook D 26/6 13:15 10.30 (18.2) 21.0 104.7 11.3 -83 6.91 280 440 0.11 <0.01 Spearwood Creek E 27/6 14:30 11.17 (17.6) 0.2 100.5 10.8 -179 7.2 250 356 0.06 0.01 Layman Brook F 28/6 09:30 10.80 (17.1) 0 93.4 10.0 -96 7.27 510 457 0.07 0.02 Milyeannup Brook G 28/6 12.20 10.89 (18.2) 0 99.0 10.4 -102 7.45 244 347 0.05 0.01 Poison Gully H 28/6 14:55 9.94 (17.0) 0 107.0 11.4 -134 7.71 454 645 0.06 <0.01 Sollya Creek I 29/6 09.30 10.29 (17.2) 0 101.3 11.5 -123 7.85 310 423 0.06 0.01 Red Gully J 29/6 10.30 9.92 (16.5) 0 102.2 11.2 -109 7.67 435 607 0.05 0.01 McAfee Brook K 11/10 11.30 11.82 (21.2) 1.1 99.1 10.1 -111 7.17 225 410 0.04 <0.01 Sturke Creek L 11/10 1530 12.65 (23.4) 1.0 91.6 9.4 -126 7.36 205 362 0.03 <0.01 St Johns Brook SJ1 30/6 10.30 9.56 (17.9) 1.2 98.4 11.1 -224 7.76 214 378 0.18 0.01 St Johns Brook SJ2 30/6 12.30 9.78 (17.6) 1.8 95.9 11.0 -208 7.98 227 409 0.21 0.01 St Johns Brook SJ3 30/6 15.30 9.89 (18.0) 3.9 98.0 11.2 -206 7.74 245 468 0.28 0.01



Levels of 60 – 125% (i.e. typically >4mg/L) are generally considered suitable for aquatic fauna, however levels of >112% (11mg/L) may be dangerous to some fish species due to the formation of oxygen bubbles in blood. Low (<50% saturation) overnight DO levels may also increase the potential for other water quality problems through desorption (release) of nutrients (e.g. phosphorus) and heavy metals (e.g. from fertilizers) from sediments. In well-aerated waters, many metals readily adsorb (bond) to suspended matter (e.g. clay or organic particles suspended in the water column) and to river bed substrates, thereby reducing their bioavailability. The toxicity of many compounds such as copper, lead, zinc, cyanide and ammonia is increased by anoxia as become more bioavailable. Anoxia also leads to an increase in chemically-reduced compounds (see also redox potential below) such as ammonium (NH4

+)and hydrogen sulphide which can be toxic to certain aquatic fauna and, in extreme cases, can result in fish kills. The secondary sampling period (October 12-14th 2004) of the current study, measured the dynamics of DO and temperature in riverine pools over 24hr. This sampling period, with higher water temperatures and increased primary production, was expected to highlight any critical DO and temperature values to a greater extent than mid-winter sampling. Changes in water column temperature and DO are shown in Figure 21. The tributaries were characterised by relatively flat amplitudes in both temperature and dissolved oxygen across a 24 hr period (Figure 21, Appendix V). The narrow channels of these systems, allow high levels of shading from riparian vegetation and hence lower daytime temperatures. In addition, temperature fluctuations within these tributaries are possibly buffered by lower temperature groundwater. Groundwater is typically low in dissolved oxygen and this was reflected in the DO concentrations of the tributary sites. Blackwood River sites showed greater amplitudes in both temperature and concentrations of DO. The DO in the pool sites in the Blackwood (Sites 2, 14, 19) showed levels reducing to critical values during the night; these values (<2mg/L) are considered detrimental to fish if attained over longer periods of time. In contrast, the “riffle” sites showed “recovery” of DO values during the day (i.e. sites 4, 8). This emphasises the importance of the riffle zones aerating not just local sites but enabling this improvement in DO to be transported to downstream pools (see Appendix V).



Temperature at Millyeanup

11

13

15

17

19

21

23

0 50 100 150

Tem

p (C

)

MiddayMidnight

Temperature at St Johns Brook

11

13

15

17

19

21

23

0 50 100 150

Tem

p (C

)

MiddayMidnight

Temperature at Spearwood

11

13

15

17

19

21

23

0 50 100 150

Tem

p (C

)

Midday Midnight

Temperature at Rosa Brook

11

13

15

17

19

21

23

0 50 100 150Te

mp

(C) Midday

Midnight

Temperature at Blackwood site 2

11

13

15

17

19

21

23

0 50 100 150

Tem

p (C

)

MiddayMidnight

Temperature at Blackwood site 16

11

13

15

17

19

21

23

0 50 100 150

Tem

p (C

)

Midday

Midnight

Figure 21. Mid-depth measurements (at 10-minute intervals) of temperature and dissolved oxygen (following page). Measurements made using a TPS data-logger and a YSI DO/temperature sensor (calibrations made prior and after each logger run). Data were downloaded in the field into a laptop-computer and a series of sub-routines ensured data quality and enabled conversion to temperature (accuracy 0.1OC) and DO (0.25 mg/L). Note, measurements taken 12 weeks after the initial surveys,

consequently water temperatures were elevated. Note, the measurements represent a ~24 hour measurement period (at ten minute intervals= 144 records). Further sites shown in Appendix V.



Dissolved Oxygen at Blackwood Site 19

0

2

4

6

8

10

1 25 50 75 100 125 150

D.O

. (pp

m)

M idnightM idday


0

2

4

6

8

10

1 25 50 75 100 125 150

D.O

. (pp

m) M idnight

M idday

Dissolved Oxygen at St Johns Brook (Site 1)

0

2

46

8

10

1 25 50 75 100 125 150

D.O

. (pp

m)

M idnight

M idday


0

2

4

6

8

10

1 25 50 75 100 125 150

D.O

. (pp

m)

M idday

M idnight


0

2

4

6

8

10

1 25 50 75 100 125 150 175

D.O

. (pp

m) M idnight

M iddayM idday


0

2

4

6

8

10

1 25 50 75 100 125 150

D.O

. (pp

m)

M idnight

M idday

Figure 21 (cont.).

4.3.4 Redox Potential

Measurements of redox potential or ORP (Oxidation-Reduction Potential; chemical oxidation-reduction reactions) are another way of assessing river health and the potential for water quality problems. Redox potential is a measure of a systems capacity to oxidise materials (including metals) through chemical reactions. During reduction-oxidation reactions, one chemical species (type/form) loses electrons (is oxidised) while another gains electrons (is reduced). The conversion of ammonia to nitrite and nitrate during cycling of waste materials within ecosystems is also an example of oxidation. Redox is measured indirectly as the ability of an aquatic system to conduct electricity, in millivolts (mV). Redox potential reflects biological (BOD) and chemical (COD) oxygen demand (use). Data collected in the current study showed a wide range in redox potential from very low –290mV at Blackwood River Site 6 to high values of -63 mV at tributary Site A (Table 12). Redox potential was consistently higher in tributary sites compared to Blackwood sites. Typically, in well-aerated natural river systems, the water provides an oxidizing environment and has a positive, or nearing positive, ORP value. However, in any water body, ORP values can vary greatly throughout the day as relative rates of photosynthesis and respiration by aquatic biota vary. Anoxic (zero oxygen) waters and soils are often the result of high biological (BOD) and/or chemical oxygen demand (COD) and have low redox potential (often measured as negative millivolts, mV). Very high BOD and COD is often the result of agricultural runoff (e.g. fertilizers, animal manures etc).



4.3.5 Turbidity

Field measurements indicated that most tributary sites were clear (<1 NTU), with Blackwood sites being considerably more turbid. Turbidity values were also confirmed by direct observation, with visually brown, ‘murky’ water in Blackwood River sites (8.9 – 40.2 NTU) and generally clear water in tributary sites (0 – 21 NTU) (Table 12). Turbidity is the muddy appearance of water as a result of fine particles that are held in suspension. Nephelometric units (NTU) are measurements of the fraction of light scattered at 90° right angles to the path of light in water. Natural turbidity and sedimentation are dependent on the hydrology and geomorphology of a site including the upstream catchment. Turbidity may be increased through construction, vegetation clearing, erosion and stock trampling. In addition to affecting the appearance of water, when the particles causing turbidity settle, they can result in pool aggradation. Turbidity also interferes with light penetration and consequently photosynthesis and the feeding efficiency of visual predators such as fish and waterbirds (Lovett & Price 1999). Continuous, artificially high turbidity can adversely affect riverine biota – clogging gills of fish and aquatic insect larvae. There is some evidence (Streamtec 1997, Creagh et al. 2004a), that even small increases in turbidity may influence macroinvertebrate community structure. ANZECC/ARMCANZ (2000) guidelines for the ‘protection of aquatic ecosystems’ recommend turbidity in south-west upland rivers <10 – 20 NTU. 4.3.6 Nutrients

There was little variation in nutrient levels between reaches of the main channel of the Blackwood River (Table 12). However, there were considerable differences in nutrient loads between the main river channel and tributaries. Total nitrogen (TN) concentrations throughout the main channel (1.5 – 2.2mg/L) were at least an order of magnitude higher than those measured in the tributaries (0.05 – 0.11mg/L). Nitrogen concentrations in the main channel were typically double the recommended (ANZECC/ARMCANZ 2000) guideline levels for the ‘protection of aquatic ecosystems’ in lowland rivers (Table 13). Total phosphorus (TP) values were generally slightly higher in the main channel (0.02mg/L) than the tributaries (0.01mg/L). Periodic measurements of water quality by WRC showed similarly-elevated TN concentrations; for example, a concentration of 2.16mg/L was recorded at Hut Pool (WRC gauging station 609019) in July 1998, 2.37mg/L in December 1998 and 3.52mg/L in July 2002. WRC records also showed ammonia concentrations were often ten-fold higher than guidelines, nitrate concentrations often 20-fold higher and total phosphorus concentrations up to 30-fold higher. Water bodies containing elevated concentrations of nitrates and ortho-phosphates (the most common forms of N and P) are typically characterised by conspicuous algal growth which can lead to water quality problems. Excessive and problematic algae growth is more likely in systems where riparian shading is negligible or absent. Nutrient enriched waterbodies also can harbour significant stores of nitrogen and phosphorus within sediments or adsorbed to suspended particulate materials.



Nitrate is generally considered to have low toxicity in freshwater systems. Although tolerances of aquatic fauna to nitrate toxicity vary greatly, concentrations of < 35mg/L are not regarded as detrimental to fauna. In freshwaters, most nitrogenous materials tend to be converted to nitrate. Another form of biologically available nitrogen, ammonia, is also affected by changes in water chemistry. Ammonia (NH3) undergoes a chemical change when pH shifts from alkaline (>7.0) to acid (<7.0) to become ammonium (NH3

+). This process has biological implications for aquatic fauna (macroinvertebrates and fish), as ammonium is not considered harmful but conversely ammonia is acutely toxic, often at relatively low concentrations (Table 13). Large volumes of surface foam were also characteristic at most sites along the Blackwood River in July 2004 (Plate 7). The foam was likely caused by surfactants released during decomposition of organic matter and may indirectly be linked to high nutrient loads and increased in-stream plant and algal growth.

Table 13. Default trigger values for nutrients, dissolved oxygen and pH for protection of aquatic ecosystems for south-west Australia for slightly disturbed ecosystems (from ANZECC/ARMCANZ 2000).

Upland streams = streams at >150m altitude; TP = total phosphorus, FRP = filterable reactive phosphate, TN = total nitrogen, NOx = oxides of nitrogen, NH4+ = ammonium, DO = dissolved oxygen.

Ecosystem type

TP FRP TN NOx NH4+ DO2 pH

(mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (%) units Upland Rivera

0.02 0.01 0.45 0.2 0.06 90 6.0-8.0

Lowland Rivera

0.065 0.04 1.2 0.15 0.08 80-120 6.0-8.0

Freshwater lakes & reservoirs

0.01 0.005 0.35 0.01 0.01 90-120 6.0-8.0

Wetlandsb 0.06 0.03 1.5 0.1 0.04 90-110 7.0-8.5 a = all values derived during base flow conditions, not storm events; b = in highly colored wetlands (gilven >52 g440/m) pH typically ranges 4.5-6.5.

Plate 7. Foam on the surface of the Blackwood River, July 2004.



A significant portion of the nutrient suspended within the Blackwood River is likely to be derived from exogenous sources from surrounding land use coupled with the historical removal of native riparian vegetation. Dense riparian vegetation acts as a nutrient ‘buffer zone’ by effectively stripping nutrients from both surface runoff and seepage prior to it entering the river channel (Davies & Bunn 2000). Although most study sites were characterized by relatively pristine riparian vegetation, cleared sub-catchments upstream are likely to contribute to high nutrients loads downstream. The work of community catchments groups in continued rehabilitation of riparian zones may represent one effective method of reducing nutrient inputs to the Blackwood River. Spot measurements of nutrient concentration in the water column are not always adequate to accurately assess the degree of eutrophication (nutrient enrichment) in rivers. Most of the annual nutrient load to a river is mobilized during extreme events when surface runoff from surrounding lands is at a maximum. The amount of catchment material available is typically much greater prior to the start of the rainfall season and early wet-season runoff will result in relatively high loads. Nutrient levels recorded during the current winter study are therefore likely to be higher than those obtained under periods of baseflow.

4.4 Fish

Seven native fish species and one introduced species (the mosquitofish, Gambusia holbrooki) were recorded during July 2004 (Table 14). Native fish species included western minnows (Galaxias occidentalis), cobbler (Tandanus bostocki), nightfish (Bostockia porosa), Balston’s pygmy perch (Nannatherina bolstoni), western pygmy perch (Edelia vittata), south-western goby (Afurcagobius suppositus) and mud/blackstripe minnows (Galaxiella munda/nigrostriata). The western minnow (Galaxias occidentalis) was the most abundant fish species with a total of 85 individuals collected at nine of the sites. Both minnows and, to a lesser extent, gobies were the most widespread fish within the catchment. Many of the western minnows and nightfish (Bostockia porosa) collected were gravid. Relative abundances reflect qualitative sampling techniques and the difficulties associated with sampling at the Blackwood River sites due to high water levels. Most species found (with the exception of Balston’s pygmy perch and the mud minnow) are considered widespread and common throughout the south-west of the State (Allen et al. 2002). Not all native fish species expected to occur within the study area were collected during this survey. A recent study (Morgan 2004) in Rosa Brook (using similar methods to this study), recorded the native western hardyhead (Leptatherina wallacei), Swan River goby (Pseudogobius olorum) and one introduced species rainbow trout (Onchorhychus mykiss); these species are in addition to those recorded during the present study. The pouched lamprey (Geotria australis) has also recently been sampled in the system (Morgan 2004). Seasonal or snapshot protocols often under-sample the total species present. A total of 205,000 rainbow trout (Oncorhynchus mykiss) were released into the system during 2002 and 2003 at Milyeannup, Carlotta, Hester, Nannup, and St John Brook and above Sues Bridge (Rosa Brook) (Morgan 2004). However, none were recorded during the current survey and it is possible warmer water temperatures precluded survival over summer months. A brief overview of the life histories of species recorded during the current study is given below.



Table 14. Fish species recorded from Blackwood River catchment survey sites during July 2004. Note, no fish were collected from sites 9, 12 14, 15, 17 and sites K, L were not sampled for this component.

Sites Blackwood River Sites Tributary Sites

Species 1 2 3 5 6 7 8 10 11 13 16 18 19 A B C D E F G H I J SJ1

SJ2

SJ3

Native Fish

Afurcagobius suppositus (south-western goby) √ √ √ √ √ √ √

Bostockia porosa (nightfish) √ √ √ √ √ √

Edelia vittata (western pygmy perch) √ √

Galaxias occidentalis (western minnow) √ √ √ √ √ √ √ √ √ √ √ √ √

Galaxiella munda/nigriostriata.# (mud/black-stripe minnow)

√

?Nannatherina balstoni#

(Balston’s pygmy perch) √

Tandanus bostocki (freshwater cobbler) √

Introduced Fish

Gambusia holbrooki (mosquitofish) √ √ √ √ # Requiring further taxonomic confirmation.



4.4.1. South-western goby (Afurcagobius suppositus Sauvage)

The south-western goby, (formerly Favonigobius suppositus Sauvage; also known as the big headed goby; Plate 8) has a wide distribution from Moore River to Esperance, occurring in estuaries, rivers, streams, coastal lakes, and also penetrating inland waters (i.e. Warren, Scott and Blackwood rivers; (Morgan et al. (1996)). This species has a preference for riparian cover (Gill & Humphries, 1995), and consumes Hemiptera (waterbugs), Diptera larvae, bivalves, Ephemeroptera (mayflies), Trichoptera (caddisflies) and small fish (Young 1994; cited Morgan et al., 1996). Morgan et al. (1996) suggested the life cycle probably lasts two years, with breeding occurring after one year, and males guarding a nest under stones or amongst aquatic macrophytes where several females have laid eggs. In-stream flow requirements for south-western gobies are the maintenance of the predictable natural pattern of winter floods and lower summer flows.

Plate 8. South-western goby (Afurcagobius suppositus) collected from Hut Pool, Blackwood River (Site

19).

4.4.2 Nightfish (Bostockia porosa Castelnau)

The nightfish, (Percichthyidae; Plate 9), is abundant in rivers, streams, lakes and pools from Gingin in the north of south-western Australia, to Albany. Individuals are generally located under ledges and amongst inundated vegetation (Morgan et al 1998, Allen et al. 2002). Nightfish can enter tributary streams with flow initiation in late autumn and early winter (Pen and Potter 1990) and spawn in flooded creeks (Pen and Potter 1990, Pen et al. 1993).

Plate 9. Nightfish (Bostockia porosa) collected from St Patrick’s Elbow.



4.4.3 Western pygmy perch (Edelia vittata Castelnau)

The western pygmy perch, (Percichthyidae), together with the western minnow, are widely-distributed and endemic to the south-west of Western Australia, with a range from Moore River to Philipps River, east of Albany (Allen et al, 2002). This species is common in rivers, streams, and lakes, and readily re-invades seasonal wetlands via flood-ways. Western pygmy perch are often associated with riparian/emergent vegetation and feed on small benthic invertebrates, especially dipteran larvae (Pen et al. 1993) (see Plate 10). During the winter, western pygmy perch migrate from rivers into either adjacent flooded areas or tributary streams, where they spawn between late winter and late spring (Pen and Potter 1991c) or later (Shipway 1949). Densities in main rivers fall sharply and the habitats provided in tributaries associated with winter flooding are critical to ensure spawning and enable subsequent growth of juveniles (Pen and Potter 1991c).

Plate 10. Western pygmy perch Edelia vittata (Photo Allen et al, 2002).

4.4.4 Western minnow (Galaxias occidentalis Ogilby)

Western minnows (Plate 11) are the most widely-distributed endemic species in south-west Western Australia, with a range extending from Winchester, about 150km north of Perth, to Waychinicup Creek, 80km east of Albany (Allen 1989). They are found in a diverse range of habitats, including streams, lakes, and are known to readily invade seasonal creeks and swamps connected to permanent water. Western minnows have often been found at the base of waterfalls (and V-notch gauging weirs). Fish have been observed jumping through V-notch weirs and 'crawling' up wet rock faces in an attempt to traverse barriers (ARL 1990).

Plate 11. Western minnow (Galaxias occidentalis) collected from Tributary Site F.

Photo: Mark Allen



The western minnow feeds at night mainly on freshwater shrimp (Fairhurst unpub. dat., cited Morgan et al., 1996) and commence an upstream spawning migration from main river channels into tributaries and temporary headwater streams during late winter/spring. Flows for this species are required to enable migration of fish upstream during the breeding season. 4.4.5 Freshwater cobbler (Tandanus bostocki Whitley)

Freshwater cobbler (Plotosidae; Plate 12) are distributed in the coastal region of south-western Australia between Moore River (Gingin) in the north and the Frankland River (Walpole) on the south coast (Morgan et al, 1998; Allen et al, 2002). This species is recorded from lakes and slow-flowing rivers and streams (Morgan et al, 1998; Allen et al, 2002). Freshwater cobbler often feed on marron (Cherax tenuimanus).

Plate 12. Freshwater cobbler (Tandanus bostocki) collected from Blackwood River Site 3, near

Longbottom Rd.

Freshwater cobbler (see Plate 12) are ‘nest’ builders which are often constructed in gravel beds. In these nests, spawning occurs during spring and summer. Unpredictable or unseasonal high flows can dislodge ‘nests’ downstream, while low flows may result in nest exposure and desiccation (drying out) (see Glossary). 4.4.6 Balston’s pygmy perch (Nannatherina balstoni Regan)

Balston’s pygmy perch (Plate 13) is one of the rarest of all endemic freshwater fishes of south-western Australia, and has a distribution between Two Peoples Bay in the east and Margaret River in the west (Allen et al. 2002). There is an isolated population at Gingin, approximately 100km north of Perth (Allen et al. 2002). Museum records indicate that Balston’s pygmy perch have been previously-collected from the Blackwood River catchment (Morgan et al. 1996). This species is often found in shallow, isolated pools with acidic water (pH 3.0 – 6.0), but also has been sampled in larger rivers, lakes and seasonal creeks. In late winter and spring, the species utilises inundated riparian vegetation, for both direct feeding and spawns. This species reaches sexual maturity by the end of the first year, to spawn during late winter/ spring.



Plate 13. Balston’s pygmy perch (Nannatherina balstoni) collected from Blackwood River Site 8, near

Judy Rd.

4.4.7 Mud minnow (Galaxiella munda McDowall) and black-stripe minnow (G. nigostriata Shipway)

Specific differences between the mud minnow and black-stripe minnow (Plate 14a) are difficult to determine (Allen et al. 2002). The mud minnow is known to occur within the Blackwood system, having been recorded from Rosa Brook (Morgan 2004). The mud minnow (Plate 14b) is common to coastal drainages of south-western Australia between the Goodga River (near Albany) and Margaret River and is typically found in small flowing streams near submerged vegetation and occasionally in still waters (Allen et al. 2002). Mud minnows are relatively small (<60mm total length) and have a one year life-cycle, with adults usually dying within a few months of spawning (Pen et al. 1991). Plate 14. Black-stripe minnow (a) and mud minnow (b) (photos courtesy of Fisheries WA) collected from

Layman Brook (Site F).

The black-stripe minnow (Plate 14a) is restricted to wetlands within 100km of the coast of south-western Australia, between Albany and Augusta (Allen et al. 2002). It is typically found in permanent or ephemeral ponds in small creeks (Allen et al. 2002). It exhibits similar spawning habits to G. munda, with most individuals dying after spawning (Allen et al. 2002). Black-stripe minnows are considered to be capable of withstanding desiccation.

4.4.8 Pouched Lamprey (Geotricha australis) Although the pouched lamprey was not collected during the present study, recent sampling showed the species occurs in the system (Morgan 2004) (Plate 15). This species is significant as it is one of only 38 surviving species of a lineage of ancient (approx. 540 million years old) jawless fishes (Morgan 2004).



Though most abundant in river systems south of Margaret River, Morgan et al. (1996) also collected pouched lampreys from the Donnelly and Warren rivers. The last recorded observation of pouched lampreys in the Collie River, however, was in 1936 (Morgan et al. 1998). Its absence from that system during more recent surveys may be due to loss of suitable in-stream habitat and/or salinisation. The life cycle of the pouched lamprey includes a marine phase that is thought to last about two years and during this time they are parasitic on other fish. Once mature, the adults cease feeding, enter coastal river systems to migrate upstream to spawn.

Plate 15. Pouched lamprey Geotricha australis (Photo shown in Allen et al, 2002).

4.4.9 Mosquitofish (Gambusia holbrooki Girard)

Mosquitofish were introduced in 1936, under government authority, to fresh waters around Perth (Mees 1977) to control mosquitoes and are now both widespread and abundant in south-west streams and reservoirs (Morgan et al. 1998), often dominating the fish fauna in lowland areas (Pusey et al. 1989) (Plate 16). They are regarded as a pest in Australian waters and have been implicated in the decline of native species (Myers 1975; Arthington and Lloyd 1989). Modifications to the flow regimes of these catchments have important implications for the dynamics and management of Gambusia populations. Pusey et al. (1989) suggested that natural winter spates regularly reduce the population density to low levels, permitting the coexistence with indigenous species.

Plate 16. Mosquitofish Gambusia holbrooki (Photo shown in Allen et al, 2002).



4.4.10 Salmonids Salmonid fishes have been introduced throughout the south-west Western Australia largely by stocking reservoirs (Plate 17). Trout often have an adverse effect on native fishes through predation and competitive exclusion, as hypothesised by the fragmented distributions of some native species in eastern states of Australia where trout have been introduced (Wager & Jackson 1993).

Plate 17. A salmonid (rainbow trout) Oncorhynchus mykiss (Photo Allen et al, 2002).

4.4.11 Water requirements of fish

Native fish species occurring in the Blackwood River (and tributaries) have a requirement for permanent water of adequate quality and suitable habitat. Although several of the species readily invade seasonal creeks to reproduce (Table 15), only the mud minnow is considered to have adaptations to withstand desiccation. Both juveniles and adults of the native fish species found in the Blackwood system have generalist diets, comprising aquatic and terrestrial insects. Given the generalist nature of the diets, it is unlikely that the diet of any species will be limited by changes due to altered flow regimes. Migration and reproduction are likely to be the aspects of fish biology most affected by altered flow regime within the Blackwood catchment. Adults of most species were present in the Blackwood River, indicating some tolerance to the higher salinities. The tolerance of fry to high salinity waters is largely unknown but the fresher tributaries are likely to play an important role as nursery habitat. Only the mud minnow/black stripe minnow was absent from the main channel.



Table 15. Summary of native fish life history characteristics (in species where this is known) in

relation to reproduction.

SPECIES ADHESIVE EGGS?

SPAWNING PERIOD

SPAWNING MIGRATION TO SMALL CREEKS

western minnow: Galaxias occidentalis

Yes Late September / early October

Yes

pygmy perch: Nannatherina balstoni

Yes July to November Yes

nightfish: Bostockia porosa

Probably Late August / early September

Yes

catfish: Tandanus bostocki

No September to February

No

Fish – Conclusion of flow requirements:

(i) Permanent flows required to maintain fish habitat.

(ii) Adequate water quality.

(iii) Sufficient flows to retain a minimum water depth of 20cm in all main stem reaches are required throughout August – October, to enable reproductive migration and spawning in flooded streamside vegetation.

(iv) High winter flows may be beneficial in controlling numbers of the introduced mosquitofish.

(v) High water temperature may reduce the numbers of introduced salmonids.

4.5 Macroinvertebrates

Macroinvertebrate fauna was collected using a methodology based on AusRivAs protocols (see Davies 1994). Generally, the biodiversity was low; reflecting the ambient conditions of elevated flows and moderately saline water (in the Blackwood). These flow conditions typically scour the resident macroinvertebrate fauna from the predominantly benthic habitats. Sensitive taxa including the Plecoptera were largely absent from the main stem of the Blackwood (Table 16). Typically, the fauna of the Blackwood was dominated by cosmopolitan, generalist species (i.e. Coleoptera) characterised as being able to tolerate a wide range of conditions. A systematic list of aquatic macroinvertebrates collected in July 2004 is given in Table 16 (and Appendix III). A total of 67 taxa (=“species”) were identified with 56 of these occurring in the main channel and 47 in the tributaries. Actual species diversity is likely to be higher as not all taxa could be identified to species-level. Spatial variation was moderate with 54% of taxa recorded from the main channel and its tributaries, but only one taxon, the Chironomidae (midge larvae), common to all sites. A comparison of taxa richness at each site is graphically represented in Figure 22. Average number of species per site was similar between the main channel and tributary sites; 17.7 ± 2.03 (SE) in the main channel and 17.7 ± 1.71 (SE) in tributaries. Site 7 (St Patrick’s Elbow) had the highest species



richness, while Site 16 the lowest. ‘Low-occurrence’ taxa (i.e. taxa recorded from <10% of sites) accounted for 15% of all species.

Blackwood Macroinvertebrate Species Richness, July '04

0

5

10

15

20

25

30

35

40

1 2

3,4 5 6 7

8,9 10

11,1

2

13-1

5 16 18 19 A B C D E F G H I J

SJ1

SJ2

SJ3

Blackwood Main Channel Sites Tributary Sites

No.

Spe

cies

Figure 22. Macroinvertebrate ‘species’ richness at surveyed sites in the Blackwood River and tributaries.

For comparative purposes, some taxa have been grouped at family-level or order-level. Sites K, L not sampled for macroinvertebrates (Site 17 excluded from analysis).

The macroinvertebrate fauna was dominated by Insecta (70-75%), in particular detritivores but with a high diversity of predatory aquatic beetles. Numerically dominant groups included Diptera (two-winged flies) with at least 13 species from 11 families and Coleoptera (aquatic beetles) with 19 species from ten families. Coleoptera were far more abundant in the main channel with 16 species present cf six species in the tributaries. Also well represented were the crustacea with ten species from eight families. Decapod crustacea included species of Cherax (particularly C. cainii) which were widespread and abundant throughout the tributaries, but only a single individual was recorded from one site in the main channel, Site 7 (St Patrick’s Elbow). Gilgies (C. quinquecarinatus) were only recorded from tributary Site E on Spearwood Creek (Plate 18).

Plate 18. Gilgie (Cherax quinquecarinatus).



Table 16. Aquatic macroinvertebrates collected from the Blackwood River and tributaries in July 2004 (see Appendix III for full systematic listing). Sites with similar community structure listed together for emphasis. Site 17 excluded from analysis, sites K, L not sampled. Qualitative abundance categories: 1 = (1), 2 = (2-10), 3 = (11-100), 4 = (101-1000). *Regional endemic;

**local endemic.

Blackwood River Main Channel Sites Tributary Sites Taxa

1 2 3,4 5 6 7 8,9 10 11,12 13-15 16 18 19

% occurrence

A B C D E F G H I J SJ

% occurrence

NEMATODA 1 3,2 1 1,1,1 1 38 2 2 1 1 1 29

TEMNOCEPHALA 3 2 1 14

MOLLUSCA

GASTROPODA

Glacidorbidae

*Glacidorbis occidentalis 1 2 14

Ancylidae

Ferrisia petterdi 1 8

ANNELIDA

OLIGOCHAETA 2 3 3,1 3 3 2,2 2 3,2,3 3 2 2 85 2 3 2 2 2 3 2 1 2 2 2 100

ARACNIDA

ARANAE 1 2 1,1 2 31 1 2 1 1 1 43

HYDRACARINA 3 3 3,3 2 3 3 2,1 1 3,2 3,2,3 2 3 92 3 2 3 3 3 2 1 1 71

CRUSTACEA

OSTRACODA 1 2 2 2 31 2 1 1 2 29

COPEPODA

Calanoida spp. 3 2 3 2,2 3 4,3 3,3,3 2 2 3 77 2 2 14

Cyclopoida spp. 3 2,2 1 23 2 3 1 1 29

CLADOCERA 2 8

AMPHIPODA

Perthidae

*Perthia acutitelson/branchialis 1 8 3 2 3 3 3 1 1 71

ISOPODA

Oniscoidea 1 2 3 2 2,2 2,1,2 2 2 62 2 1 1 29

DECAPODA

Palaemonidae

*Palaemonetes australis 3 3,2 4 3 2,2 3 3,2 2,0,2 3 4 4 85

Parastacidae

*Cherax quinquecarinatus 1 8 2 2 2 2 1 43



Table 16. (cont.).


1 2 3,4 5 6 7 8,9 10 11,12 13-15 16 18 19

% occurrence


% occurrence

*Cherax cainii 1 8 1 1 1 3 1 1 1 2 71

*Cherax preissi 2 14

INSECTA 1 1

COLLEMBOLLA

Poduridae 3 4,4 4 3 2,1 2 3,2 3,3,2 1 69 1 1 1 2 1 29

Entomobryoidea 2 1 2 3 2 1 3 2 62 2 1 2 1 57

SYMPHYPLEONA 1 3,2,3 15 2 14

DIPLURA 1 4,4 2 4 3,3 4,3,2 1 2 62 1 1 1 29

EPHEMEROPTERA

Caenidae

Caenidae spp. (immature) 1 2 1 2,1 2 38 1 2 2 1 29

Tasmanocoenis sp. 2 2 3 23

Baetidae (immature) 2 8 3 1 3 14

PLECOPTERA

*Gripopterygidae (immature) 2 2,1 15 3 3 3 3 2 3 4 2 3 4 2 100

ODONATA

ANISOPTERA

Anisoptera spp. (immature) 2 8 4 1 2 1 1 1 2 3 1 1 86

Gomphidae

*Austrogomphus lateralis 2 1 2,1 1,1,1 2 38

Synthemistidae

*Archaeosynthemis macrostigma 2 14

ZYGOPTERA (immature) 2 2 1 1 29

LEPIDOPTERA

Pyralidae 2,1,3 8 1 14

HEMIPTERA

Hemiptera spp. (instar) 1 2,1 2 3 2 2,2 3 54 3 2 2 1 1 1 57

Corixidae

*Diaprepocoris personata 1,1 8

Micronecta sp. (female) 1,1 8

Veliidae

Veliidae sp. 3 14



Table 16. (cont.).


1 2 3,4 5 6 7 8,9 10 11,12 13-15 16 18 19

% occurrence


% occurrence

Microvelia sp. 1 8 1 14

DIPTERA

Culicidae 2 2 29

Chironomidae 4 4 3,3 4 2 3 2,3 3 4,4 3,3,3 3 3 4 100 3 3 4 3 3 3 4 2 3 3 2 100

Ceratopogonidae

Ceratopogonidae spp. 2 2 2 2,1,2 1 2 2 54 2 3 3 2 1 43

Dasyheliinae sp. 1 2,2 2 2,1 2 2,2,2 46 1 1 1 1 1 1 29

Dolichopodidae 1 1 2 29

Empididae 1,1 2 1,2 23 1 14

Muscidae 2 2 15 1 2 2 29

Psychodidae 3,1 2 1 2 2,1 3,3,3 2 1 62

Simulidae

Austrosimulium bancrofti 1 8

Austrosimulium sp. 3 8

Simulium ornatipes 2 8 2 3 3 43

Simulidae spp. (immature) 3 3 2,1 23 3 1 2 1 1 2 43

Tabanidae 1 1,3 15 1 2 29

Thaumeleidae 3,1,2 8 1 14

Tipulidae 2 3,3 3 3 2,2 2 3,2 3,3,2 3 3 77 4 2 2 2 3 2 3 1 2 71

TRICHOPTERA

Ecnomidae (immature) 1 8 1 2 29

Hydroptilidae

*Acritoptila/Hellyethira sp. 2,1 2 15 2 14

Leptoceridae

Leptoceridae spp. (immature) 2 2,1 2,1,2 2 31 3 2 3 1 3 2 3 3 4 1 1 100

*Lectrides parilis 1,1 8

*Notalina sp. ?AV15 2 14

Hydropsychidae (immature) 2 2 14



Table 16. (cont.).


1 2 3,4 5 6 7 8,9 10 11,12 13-15 16 18 19

% occurrence


% occurrence

COLEOPTERA

Dytiscidae

Allomatus sp. (larvae) 1 2 15

**Allomatus nannup 2 1 2,1 2,2,2 2 38

Allodesus bistrigatus (male) 1,1 8 1

*Liodessus inornatus 1 14

*Megaporus solidus 2 8

*Necterosoma darwini (male) 1 1 1 23

*Sternopriscus marginatus (male) 1 8 1 1 14

*Sternopriscus minimus 1 1 2 23 1 14

*Sternopriscus multimaculatus 1 1 15

*Sternopriscus wattsi (female) 1,1 8

Rhantus sp. (larva) 1 14

Gyrinidae

Macrogyrus sp. 2 8

Hydraenidae

Ochthebius sp. 1 1,1 3 1,1 1 1 46

Hydrochidae

Hydrochus sp. 1 8

Hydrophilidae

Hydrophilidae spp. (larva) 1 8

Helochares tenuistriatus 1 8

Scirtidae (larva) 2 2 1 14

Staphylinidae

Staphylinidae sp. (larva) 1 2 1,1 23 1 1 1 29

Staphylinidae sp. (adult) 1 2 2,3 23 1 14

Carabidae (adult) 1,2 1,1 1,1,2 23

Cucurlionidae (larva) 3 1 2,1 23

Tenebrionidae (larva) 1 2 2,0,1 23



Other taxa of note were immature Plecoptera (stoneflies), recorded in high numbers from all tributary sites. Only a very few individuals of this group were present in the main channel at St Patrick’s Elbow (Site 7). The small Gondwanic freshwater snail Glacidorbis occidentalis was collected from Milyeannup Brook (Site G) and the local endemic aquatic beetle Allomatus nannup was present at five sites in the main channel of the Blackwood River. Glacidorbis is considered a bio-indicator of temporary systems (Bunn & Davies 1989). Chironomidae (midge larvae) were common and abundant at all sites. Oligochaetes (aquatic worms) were common at >80% of sites and acarina (water mites) and tipulids (soldier fly larvae) common at 70% of sites. There were many taxa whose distribution was restricted to the tributaries, as well as numerous species found only in the main channel. Taxa ‘unique’ to one system (or the other) are listed in Table 17.

Table 17. Aquatic macroinvertebrate taxa ‘unique’ to either the main channel or to tributaries.

*Regional endemic; **local endemic.

Taxa recorded only from tributaries Taxa recorded only in the Blackwood River main channel

Temnocephala Ferrissia petterdi *Glacidorbis occidentalis Cladocera spp. *Cherax plebejus *Palaemonetes australis *Archeosynthemis macrostigma Corixidae spp. Zygoptera spp. Psychodidae spp. Culicidae spp. **Allomatus nannup Dolichopodidae spp. *Megaporus solidus Hydropsychidae spp. *Necterosoma darwini *Liodessus inornatus *Sternopriscus multimaculatus & *S. wattsi Rhantus sp. Gyrinidae spp. Scirtidae sp. Hydraenidae spp. *Plecoptera spp. Hydrophilidae spp.

Also recorded in the main channel, but only in low numbers at two sites.

Both lentic (still-water) and lotic (flowing-water) species were present. For example, Cherax cainii (marron), Perthia acutitelson (amphipod) and many of the aquatic beetle species are more commonly collected from permanent pools (lentic) but were present at many tributary sites. Glacidorbis occidentalis (snail) and Plecoptera (stoneflies) have a known preference for higher-current habitats in winter-wet ephemeral streams. Species diversity, diversity of functional feeding groups and by implication the functional complexity of macroinvertebrate communities was similar within Blackwood sites. Though overall species diversity was only moderate, most macroinvertebrate groups expected to be present were represented in both tributaries and the main channel. Low numbers were considered a function of “season” as many taxa present were only represented by juvenile or immature phases. Differences between tributaries and main channel were likely due to the higher salinity in the main channel coupled with higher winter flows.



4.5.1 Gondwanic (Relict) Fauna

Of note, was the presence of large numbers of juvenile gripopterygid Plecoptera (stoneflies) at some tributary sites. The stonefly fauna of Western Australia is poorly known; only four species have been described, three of which appear to be endemic and restricted to freshwaters in upland streams of the south-west (Hynes & Bunn 1984). These plecopterans are Gondwanic4

species and are often located in seasonal and ephemeral streams; nymphs and larvae can survive dry periods by burrowing into soft, damp sediments in the stream bed. Though plecopterans are known to occur (in low abundances) in degraded systems (see Creagh et al. 2004a) their presence, together with a diversity of Ephemeroptera and Trichoptera (EPTs) is often considered indicative of relatively undisturbed or ‘healthy’ systems. Other Gondwanic species included the dragonfly Archaeosynthemis macrostigma from Rosa Brook and the freshwater snail Glacidorbis occidentalis from Milyeannup Brook. The latter species was first described as a separate species in 1983 (Bunn & Stoddart 1983). It is spatially restricted throughout the northern jarrah forest and usually occurs in low numbers in scattered populations (Bunn et al. 1989). Because of this, G. occidentalis is currently listed as vulnerable (category D25) on the 2003 IUCN Red List of Threatened Species. Adults survive dry periods by burrowing into the stream bed and emerge after the first winter flows. The dragonfly Archaeosynthemis macrostigma is endemic to south-western Australia and known to inhabit boggy seepages and summer-dry swamps where the larvae can withstand drying (Watson et al. 1991). Plate 19. Freshwater Crayfish

Three freshwater crayfish species endemic to south-western Australia, marron (Cherax cainii Austin and Ryan), gilgies (Cherax quinquecarinatus) and one of the species of koonac (Cherax crassimanus), were collected from the Blackwood River and tributaries during the July 2004 survey (Plates 18, 19). Prior to the arrival of Europeans in south-west Australia, the natural distribution of marron was believed (Morrissy 1978) to be restricted to rivers within the region bounded by Harvey, Kojonup and Denmark. More recent genetic studies suggested the original distribution was even more restricted (Austin 1996). Subsequently, marron have been spread throughout much of the south-west and into the wheatbelt by introductions into farm dams (Horwitz 1990). By contrast,

natural occurrence has substantially declined to the point where they no longer occur naturally in inland waters. Marron typically develop, stable populations in low nutrient waters. Marron are considered weak burrowers and consequently would be unable to withstand even occasional impermanence of stream pools and there is a tendency for breeding failure in highly eutrophic waters (Morrissy 1983). 4Gondwanic: relict species from the southern super-continent Gondwana that existed approximately 144 to 195 mya and included what is now Australia, Africa, Antarctica, South America, India, New Zealand and Madagascar. 5“Population with a very restricted area of occupancy (typically less than 20 km²) or number of locations (typically five or fewer) such that it is prone to the effects of human activities or stochastic events within a very short time period in an uncertain future, and is thus capable of becoming Critically Endangered or even Extinct in a very short time period.” (IUCN 2003).



Gilgies exploit almost the full range of freshwater environments, and are found in habitats ranging from semi-permanent swamps to deep rivers (Austin and Knott 1996) (see Plate 19). Gilgies tend to occur in the shallower pools and along the margins of larger pools (Shipway 1951). A study on the microhabitat characteristics of marron, gilgies and the introduced yabby within the Canning River system near Perth, showed that gilgies were more commonly found in higher flows with elevated dissolved oxygen concentrations than marron (Lynas et al. in press). Three koonac species (C. glaber, C. preisii and C. crassimanus) are known from south-western Australia and specifically the Blackwood River system. C. glaber is an endemic species with a narrow distribution range and has been collected from tributaries of the Blackwood (i.e. McLeod Creek) as well as other smaller creeks. As a consequence of its’ limited range, a more comprehensive study of the distribution of this species in the lower Blackwood and tributaries is recommended. As identification of the koonacs, based on morphological characteristics, is difficult due to their cryptic appearance, genetic markers should be used to distinguish koonac populations. CENRM has already determined diagnostic allozyme loci MDH, IDH, EST and LT-1 which can be used to “separate” species of koonacs. Recent sampling of the Blackwood (Dr B. Cook; CENRM) has revealed the presence of C .preisii, C. crassimanus, C. cainii and C. quinquecarinatus . This confirms the Blackwood as a “hotspot” of freshwater crayfish biodiversity as it contains five of the six Cherax species endemic to south-western Australia. In south-western Australia, Gondwanic or relict species are believed to be particularly at risk because they have specialized requirements and habitats that are usually topographically restricted and consequently vulnerable to disturbance and fragmentation (York Main 1996). Relict fauna have survived from an era that was typically more humid and wetter, with a less markedly seasonal climate than what currently prevails. As the climate became drier and environments more fire-prone, relict fauna were increasingly restricted to specialized micro-habitats in damp, wet, poorly-drained areas such as swamps, winter-wet depressions and pools in granite outcrops (York Main 1996). Gondwanic flora and fauna are considered important and unique elements of the jarrah forest bioregion; i.e. they have significant conservation and National Estate value (Main 1996). They are typically more sensitive to current land management practices (e.g. frequent controlled burns, land clearing) than are “later-evolved species” (Hopper et al. 1996, Main 1996). Relict fauna tend not to be well-represented in current reserves as summer-dry habitats are often overlooked for inclusion in stream reserve systems (Trayler et al. 1996).



4.5.2 Community structure

To investigate patterns in macroinvertebrate community structure of the species/sites sampled, spatial patterns in the macroinvertebrate community was investigated using classification (UPGMA) and ordination techniques (PATN). The dendrogram (Figure 23) produced by UPGMA (Unweighted Pairgroup Arithmetic Averaging) classification of the July 2004 presence/ absence data set, separated sites into three distinct groups:

i. tributary sites, ii. main channel sites 5 and 16, and iii. all other main channel sites.

There was a statistically significant (ANOSIM, p <0.0001) separation of these groups within ordination space (optimum solution in three dimensions, stress 0.147) (Figure 24). Major groupings were directly influenced (significance p<0.04) by the presence/absence of ‘indicator’ taxa such as griptopterygid plecoptera (stoneflies), the dragonfly Austrogomphus lateralis, psychodid Trichoptera (caddisflies) and the freshwater prawn Palaemonetes australis (Figure 22). There were significant (p<0.02) gradients for six physico-chemical variables (Figure 25) in relation to macroinvertebrate groupings:

i. salinity (as Econd.), ii. pH, iii. water temperature, iv. nutrient concentration (TN & TP), v. average channel width, and vi. redox potential.

0.2630 0.3672 0.4714 0.5756 0.6798 0.7840 | | | | | | Site 1 ________________________ Site 10 ____________ | Site 13-15_______ | | Site 17-19 _____|__|___________| Site 2 _______________________|____ Site 7 _____ | Site 11,12 ____|______________________| Group 3 Site 3,4 _ | Site 6 |____ | Site 19 _______________________ | Site 8,9 ______________________|_____|_____________ Site 5 __________________ | Group 2 Site 16 _________________|_________________________|_________________ Site A _ | Site F |_________ | Site D,SJ3 _____|_____ | Site B, SJ1_| | | Site G,H,I_____________|_______________ |Group 1 Site C,J,K_____________________________|____ | Site E,SJ2 ______________________________|____________________ ____| | | | | | | 0.2630 0.3672 0.4714 0.5756 0.6798 0.7840

Figure 23. UPGMA classification of July 2004 presence/absence macroinvertebrate dataset. (Three groups, statistically significant at p<0.001).



-1.5

-1

-0.5

0

0.5

1

1.5

-1.5 -1 -0.5 0 0.5 1 1.5

Vector 1

Vect

or 2

Tributaries Main channel Main channel sites 5 & 16 Species gradients

Perthia spp.

GriptopterygidaeLeptoceridae

SimulidaeTipulidae

Ceratopogonidae

Palaemonetes australisPsychodidaeCalanoida

Austrogomphus lateralisHydracarina

Figure 24. SSH (semi-strong hybrid) ordination of July 2004 macroinvertebrate presence/absence data set

(optimum solution in three dimensions, stress 0.147). Significant (p<0.04) species gradients are indicated with arrows. Vectors represent the “best” separation in ordination space.

Figure 25. SSH (semi-strong hybrid) ordination of July 2004 macroinvertebrate presence/absence data set

overlain with environmental gradients statistically significant (p<0.02) to the macroinvertebrate groupings. Vectors represent the “best” separation in ordination space.

-1.5

-1

-0.5

0

0.5

1

1.5

-1.5 -1 -0.5 0 0.5 1 1.5 Vector 1

Vec

tor 2

Tributaries Main channel Main channel sites 5 & 16 Environmental gradients

Total-P

Temp., Econd., redox pH, ave. width, Total-N



4.5.3 Macroinvertebrate fauna: conclusions

The fauna was characterised by both cosmopolitan species and regional endemics. Also present was one local endemic, Allomatus nannup and one species considered rare or restricted in distribution; the relictual freshwater snail Glacidorbis occidentalis. The tributaries represent a hotspot of freshwater crayfish diversity. Multivariate analyses clearly separated Blackwood from tributary sites with salinity the major determinant of community structure. These tributary sites could be further separated on the basis of flow permanence (Figure 26). Differences among the Blackwood sites could be explained on the basis of salinity and to a lesser extent, nutrient status. The presence of both amphipods and isopods in the Blackwood are indicators of saline conditions (Bunn and Davies 1992). Lower species diversity in the tributaries may be a function of seasonal flow conditions. In particular, many species in temporary streams require permanent water e.g. those that can’t burrow or aestivate or don’t have a mobile adult phase (i.e. holometabolous). Although overall biodiversity was low, there is supporting evidence of the tributaries, particularly the fresher, permanent sites acting as refugia for fauna. These fauna would then re-invade the Blackwood if/when seasonal conditions (particularly high winter salinities) ameliorate. This is also supported by the fish surveys which showed Galaxiella restricted to the tributaries. A water depth of 5cm over riffle zones is considered the minimum depth necessary to support benthic invertebrate communities in riverine systems in the south-west. These riffle zones are typically areas of high aquatic insect production and biodiversity (Davies 1994).

Figure 26. Multivariate ordination (PATN) of each site on the basis of community structure (macroinvertebrate families). Vectors represent the “best” (vector 1) separation of the multivariate data in n-dimensional space.

- 1.5

- 1

- 0.5

0

0.5

1

1.5

- 1.5 -1 - 0.5 0 0.5 1 1.5vector 1

vector 2

Blackwood RiverTribs (permanent)Tribs (temporary)

Gradients

Total P

salinity

Flow permanenceTotal N

- 1.5

- 1

- 0.5

0

0.5

1

1.5

- 1.5 -1 - 0.5 0 0.5 1 1.5vector 1

vector 2


Gradients

Total P

salinity

Flow permanenceTotal NTotal N

SJ1

SJ2

SJ3

Red Gully

Milyeannup

Adelaide

Poison

Site 5 Site 16

Ballan

RosaSpearwood

Rosa Up

Sollya

St John (up)

Layman McAfee

Sturke

- 1.5

- 1

- 0.5

0

0.5

1

1.5

- 1.5 -1 - 0.5 0 0.5 1 1.5vector 1

vector 2


Gradients

Total P

salinity

Flow permanenceTotal N

- 1.5

- 1

- 0.5

0

0.5

1

1.5

- 1.5 -1 - 0.5 0 0.5 1 1.5vector 1

vector 2

Blackwood RiverTribs (temporary)Tribs (permanent)

Gradients

Total P

salinity

Flow permanenceTotal NTotal N

SJ1

SJ2

SJ3

Red Gully

Milyeannup

Adelaide

Poison

Site 5 Site 16

Ballan

RosaSpearwood

Rosa Up

St John (up)

Layman



5. ECOLOGICAL WATER REQUIREMENTS

5.1 Recommended Flow Requirements

Water volumes required for key ecological values were calculated using the Manning’s Equation (see Section 3.4) and measurements of discharge. The annual water needs of the riverine ecosystems were calculated from the sum of the flow requirements throughout the year and additional small and medium-sized floods. It should be noted, that EWRs can only be applied to defined water dependent ecosystems and there may be other, as yet, undefined ecological components requiring a specific water allocation. 5.1.1 EWRs for River Morphology

The coefficients of variation of daily flows in each month (calculated from unregulated flow records from Hut Pool and Darradup) were used to estimate the desired magnitude of flow variation that would permit flushing flows without excessive erosion, and maintain the distinctive features of winter flows downstream. A flood hydrograph is recommended (Fig. 27) with a four hour ascending limb, 12 hours at the bankfull stage and an eight hour descending limb. A number of flood hydrographs (provided by the WRC) were investigated. Essentially, a wide range of shapes of flood hydrographs is possible. Although idealised hydrographs would have a short period at the bankfull stage and an extended trailing limb, this “shape” was not observed in jarrah forest flood hydrographs. The flood hydrograph chosen is designed to increase the period at the bankfull stage. As catchments of the Blackwood are still generating sediment, pool aggradation is a significant problem for the maintenance of biodiversity, particularly over summer. Increasing the period at bankfull stage, enhances the capacity to remove accumulated material in pools. Example of the calculation (for a smaller tributary): Flows for channel maintenance:

Qbf. = 4.25 m3/s. Flood (~Q2) flow = peak flow + ascending flow + descending flow

= (Qbf × 12 hrs) + (Qbf × 4hrs × 0.5) + (Qbf × 8 hrs × 0.5). Volumes for flood flow additional to baseflow. Winter baseflow typically ~ 15th percentile historic flow.

The slope (dA/dT) of the ascending limb is about 0.8 and the descending limb (dD/dT) 0.6.

Figure 27. Proposed flood hydrograph for channel maintenance flows.

12 hours 8 hours4 hours

Ascending limb Descending limb Peak flow

Qbf = m3sec-1

Baseflow



5.1.2 EWRs for Aquatic Macroinvertebrates Permanent flows and a minimum depth of 5cm over riffle zones should be maintained every month for macroinvertebrate fauna. The cease-to-flow longitudinal model was used to survey and identify areas that will act as important control points. 5.1.3 EWRs for Fish

The months of August to October are considered critical for reproduction and migration of native fish in the study area, based on known periods of spawning and dispersal. It was estimated that for the rest of the year, fish EWRs would be adequately met by the baseflow as recommended for macroinvertebrates. 5.1.4 EWRs for Riparian Vegetation

Measurements of the morphology of the river indicated that flows to inundate vegetation and aid in seed set and recruitment would occur during August. These flows would inundate the lower extent of the “floodplain”. 5.1.5 EWRs for Energy Flows

In order to maintain upstream-downstream linkages, flow is retained in the system year-round. Baseflows recommended for macroinvertebrates were also considered adequate to maintain these linkages. Currently unregulated tributaries also provide for parts of this linkage. 5.1.6 EWRs for Pool Water Quality

Sufficient pool volumes are required to maintain dissolved oxygen in pools >2mg/L over each 24 hour period over summer. Data-logging of the pool sites on the Blackwood showed that very low (natural) DO levels can occur at night. The flow model for the Blackwood is therefore aimed at minimising the temporal duration of low DO values (i.e. those < 2mg/L).

5.2 Constructing a flow model

The models shown below (Table 18, 19 & 20) are constructed using survey data and existing flow information. The aim of the models, were to maintain important defined water dependent ecosystems at a low level of risk. The channel morphology (at the gauging sites) is then used to determine the water volumes required for these values. To construct a modified flow regime, flows required for each day of the year were calculated. In all cases, the modified flow regime has been made to mimic the “shape” of the natural flow regime. Where appropriate, some variation has been “built into” the short-term hydrograph. The flow model requires knowledge of the linkage between flows and ecological processes and biodiversity. Globally, this information is not well unknown which is particularly the case in south-western Australia. Therefore, flow models must be considered testable hypotheses. Although the Yarragadee proposal is obviously not a dam-site, abstraction has the potential to reduce water levels in the main stem of the Blackwood and consequently function as a mechanism of flow regulation.



EWRs are the total of significant flow events over nominal baseflow conditions. Therefore, the following flow scenarios are based on “baseflow” conditions which are seasonal flows outside of significant rainfall events (Pilgrim & Cordery 1993). The elevated or “quick” flows are built upon these seasonal baseflows (e.g. Grayson et al. 1996). Flows to meet ecological values were determined from channel morphology surveys and existing flow records (refer Figures 3-5) and expressed as:

• flow volume (kL/s and/or ML/month); • flow duration (days); • timing (at what times of the year); • frequency (how many times in a year or in a longer period).

The flow models show the quantitative EWRs for focal nodes where adequate flow data were available (i.e. WRC gauging stations). Typically EWRs for sites in the Blackwood, are substantially met by current flows (Tables 18, 19). In the tributaries (Tables 20, 21), the flow requirements are also met, however, there is relatively more of the summer flows (compared to the Blackwood) required for identified water dependent ecosystems, particularly over summer. Note, the requirements for “low flows” (i.e. macroinvertebrates, energy flows) are met by inundation of the low flow channel (the thalweg during higher flows) (see Appendix VIII).

The EWRs are generally the maximum flow requirement for a specific ecological value in each month. For example, if high flows are necessary for pool water quality, then lower flows for other issues (e.g. macroinvertebrates) will also be adequately catered for. However, for some issues (e.g riparian inundation), requires a flood flow over one day; flows must also maintain the system for the other days of the month. The “seasonal adjustment” is to ensure flows mimic the shape of the natural hydrograph (and to ensure adequate flows in months where no ecological issue has been specified). The “fish migration” allocation is to ensure fish can successfully migrate upstream. This usually requires flooding-out of obstacles (woody debris etc). During this month, flows are naturally pulsed enhancing the required flooding. Again, flows are required for periods outside of these smaller, freshers; in this case a “seasonal adjustment” is calculated



Table 18 a. EWRs for the Blackwood River at 609058 (Node 1), Values in ML. MONTHLY FLOWS (ML) TO MEET EWRS FOR BLACKWOOD NODE (1)

Month Channel form

Energy linkages

Macro- invertebrates

Fish migration

Pool water quality

Riparian vegetation

Seasonal adjustment

TOTAL (ML)

Existing median flows

Jan 12 12 12 15.38 Feb 11 11 65.5 65.5 320.72 Mar 12 12 12 12.39 Apr 13 13 107.6 107.6 449.86 May 12 12 111.2 111.2 111.2 3958.93 Jun 13 13 100.4 299.8 299.8 4654.495 Jul 12 12 111.2 569.6 569.6 83151.98 Aug 362.881 12 12 107.6 120092 255.83 12265 60574.83 Sep 12 12 787.6 787.6 49425.82 Oct 12 12 881.8 882 13226.49 Nov 13 13 107.6 107.6 4729.28 Dec 12 12 111.2 111.2 2076.08

1. Corresponding to an intense flood event over 24 hours (annual probability of 62%). 2. Flows exceeding bankfull. 3. Seasonal flows adjusted for the other days in the month when there are no flood flows. TOTAL ESTIMATED EWR= 15815.4 ML/ANNUM Present median flows = 208,505 ML/annum EWRs correspond to 23.9% of median annual flow Table 18b. Percentile flows for the Blackwood River at 609058 (Node 1), Values in ML.

Stn 609058 – Percentile flows Blackwood River (Old Nannup Caravan Park) mean median pctl 10 pctl20 pctl 30 pctl 40 pctl 50 pctl 60 pctl 70 pctl 80 pctl 90

January 366.7466667 15.38 3.996 6.842 9.688 12.534 15.38 229.046 442.712 656.378 870.044February 287.4566667 320.72 65.624 129.398 193.172 256.946 320.72 364.536 408.352 452.168 495.984March 18.66 12.39 2.518 4.986 7.454 9.922 12.39 18.62 24.85 31.08 37.31April 3214.773333 449.86 90.1 180.04 269.98 359.92 449.86 2198.748 3947.636 5696.524 7445.412May 5451.613333 3958.93 1359.794 2009.578 2659.362 3309.146 3958.93 5504.324 7049.718 8595.112 10140.506June 7305.395 4654.495 907.512 1661.634 2415.756 3462.076 4654.495 5846.914 7953.594 11888.796 15823.998July 60442.20333 83151.98 20258.684 35982.008 51705.332 67428.656 83151.98 85249.438 87346.896 89444.354 91541.812August 87937.14333 60574.83 24708.39 33675 42641.61 51608.22 60574.83 85958.828 111342.83 136726.82 162110.822September 49878.32667 49425.82 20436.868 27684.106 34931.344 42178.582 49425.82 56944.562 64463.304 71982.046 79500.788October 20312.91 13226.49 9518.45 10445.46 11372.47 12299.48 13226.49 18405.352 23584.214 28763.076 33941.938November 3984.986667 4729.28 2506.536 3062.222 3617.908 4173.594 4729.28 4838.39 4947.5 5056.61 5165.72December 2887.01 2076.08 649.264 1005.968 1362.672 1719.376 2076.08 2919.342 3762.604 4605.866 5449.128



Table 19a. EWRs the Blackwood River at 609019 (Hut Pool) (Node 2). Values in ML.

MONTHLY FLOWS (ML) TO MEET EWRS FOR BLACKWOOD NODE (2); HUTT POOL) Month Channel

form Energy linkages


Fish migration

Pool water quality

Riparian vegetation

Seasonal adjustment

TOTAL Existing median flows

Jan 440 440 440 2811.77 Feb 410 410 509.9 509.9 1835.07 Mar 440 440 600.2 600.2 2204.27 Apr 458 458 853.2 853.2 2799.185 May 440 440 555.7 - 555.7 6380.06 Jun 458 458 605.3 - 605.3 24279.79 Jul 440 440 664.4 - 664.4 92551.26 Aug 75,5681 440 440 789.0 87,6292 12255.83 12,256 155092.62 Sep 440 440 36,875 36,875 124390.09 Oct 440 440 39,098 39,098 44215.71 Nov 458 458 645.7 3,423 3,423 18579.03 Dec 440 440 760.4 760.4 5406.61

1.Corresponding to an intense flood event over 24 hours (annual probability of 66%). 2.Flows exceeding bankfull. 3.Seasonal flows adjusted for the other days in the month when there are no flood flows. TOTAL ESTIMATED EWR= 104,852.3 ML/ANNUM Present median flows = 480,545.5 ML/annum EWRs correspond to 21.9% of median annual flow Table 19b. Percentile flows in the Blackwood River at 609019 (Hut Pool) (Node 2). Values in ML.

Stn 609019 - Blackwood River (Hut Pool) Percentile Flows mean median pctl 10 pctl20 pctl 30 pctl 40 pctl 50 pctl 60 pctl 70 pctl 80 pctl 90

January 3239.239524 2811.77 1887 2146.5 2200.28 2763.14 2811.77 3187.21 3480.26 3800.04 3969.02February 2320.676667 1835.07 1532.21 1655.27 1663.36 1760.35 1835.07 1911.58 2134.63 2796.04 3556.63March 3424.569545 2204.27 1536.904 1641.358 1685.493 1766.782 2204.27 2455.916 2626.629 3034.112 3882.264April 4329.567273 2799.185 1616.674 1717.054 2344.139 2616.61 2799.185 2828.034 3277.101 4040.206 8268.252May 7761.805714 6380.06 3888.42 4768.08 5313.74 6008.27 6380.06 7456.72 7928.94 10136.43 13400.91June 33013.52619 24279.79 9773.2 11225.5 17462.42 18300.52 24279.79 26345.89 28981.52 48098.56 58142.77July 127784.7971 92551.26 41567.7 62379.77 79859.97 86115.72 92551.26 141411.27 171000.09 201387.04 230941.58August 173136.4586 155092.62 85100.96 95891 106335.86 139478.6 155092.62 162747.64 171842.1 204516.68 313731.19September 148146.4229 124390.09 50283.43 61606.35 80076.31 112309.75 124390.09 152894.89 155062.71 192248.07 260975.48October 55342.42524 44215.71 24979.92 28059.85 33476.95 35596.75 44215.71 56109.17 58570.51 69919.03 110892.42November 18120.04857 18579.03 6571.33 11662.09 12874.68 16202.05 18579.03 19918.44 24137.45 24479.32 27084.68December 6829.154762 5406.61 3556.78 3637.4 4774.37 5267.61 5406.61 6446.48 8301.18 8637.72 10659.08



Table 20a. EWRs at Rosa Brook at 609001 (Crouch Rd) (Node 3). Values in ML.

MONTHLY FLOWS (ML) TO MEET EWRS FOR ROSA BROOK NODE (3) Month Channel



Fish migration

Pool water quality Riparian vegetation

Seasonal adjustment


Jan 0 0 0 0 Feb 0 0 0 0 Mar 0 0 0 0 Apr 0 0 0 0 May 0 0 - 0 0 Jun 14.1 0 85.4 - 85.4 366.425 Jul 13.9 13.9 199.6 - 199.6 833.72 Aug 4521 13.9 13.9 789.0 4852 . 789 1416.35 Sep 13.9 13.9 - 134.53 134.5 1553.94 Oct 13.9 13.9 - 209.2 209.2 942.17 Nov 13.9 13.9 85.6 - 85.6 195.24 Dec 0 0 0 3.24

1.Corresponding to an intense flood event over 24 hours (annual probability of 59%). 2.Flows exceeding bankfull. 3.Seasonal flows adjusted for the other days in the month when there are no flood flows. TOTAL ESTIMATED EWR= 1399.6 ML/ANNUM Present median flows = 5311.1 ML/annum EWRs correspond to 26.3% of median annual flow Table 20b. Percentile flows in the Blackwood River at 609001 (Rosa Brook) (Node 3). Values in ML.

Stn 609001 - Rosa Brook (Crouch Road) Percentile flows mean median pctl 10 pctl20 pctl 30 pctl 40 pctl 50 pctl 60 pctl 70 pctl 80 pctl 90

January 7.7775 0 0 0 0 0 0 0 0 0 0February 0 0 0 0 0 0 0 0 0 0 0March 0 0 0 0 0 0 0 0 0 0 0April 0 0 0 0 0 0 0 0 0 0 0May 12.497 0 0 0 0 0 0 0 0 5.008 32.529June 510.533 366.425 59.868 109.688 183.452 290.288 366.425 523.778 793.61 970.374 1062.71July 2155.851818 833.72 308.55 332.91 435.3 619.73 833.72 2679.79 3504.3 4069.06 4323.56August 2384.485455 1416.35 936.3 1132.9 1159.67 1399.56 1416.35 1529.78 3238.75 3272.71 4200.66September 1460.467273 1553.94 456.35 529.84 1175.3 1251.26 1553.94 1690.67 1730.36 1846.02 2168.66October 996.9490909 942.17 147.71 517.85 819.74 849.25 942.17 973.98 1259.8 1562.19 1733.86November 255.02 195.24 56 72.51 76.92 194.68 195.24 228.03 317.69 403.08 509.46December 19.76416667 3.24 0 0 0.192 0.764 3.24 12.766 31.331 44.364 62.323



Table 21a. EWRs the St Johns Brook at 609018 (Barrabup Pool) (Node 4). Values in ML.

MONTHLY FLOWS (ML) TO MEET EWRS FOR ST JOHNS BROOK NODE (4); BARRABUP Month Channel



Fish migration

Pool water quality Riparian vegetation

Seasonal adjustment


Jan 18 18 18 33.45 Feb 16 16 16 18.19 Mar 18 18 18 20.71 Apr 17 17 22.4 22.4 34.33 May 18 18 29.5 29.5 61.65 Jun 17 17 289.5 - 289.5 1085.11 Jul 18 18 356.9 447.8 447.8 8053.29 Aug 1920.61 18 18 789.0 2005.52 823.33 2,828 13136.37 Sep 17 17 - 2221.3 2,221 11249.43 Oct 18 18 - 996.4 996.4 3670.14 Nov 17 17 - 24.5 24.5 998.9 Dec 18 18 18 125.32

1.Corresponding to an intense flood event over 24 hours (annual probability of 67%). 2.Flows exceeding bankfull. 3.Seasonal flows adjusted for the other days in the month when there are no flood flows. TOTAL ESTIMATED EWR= 4786.7 ML/ANNUM Present median flows = 38,486.9 ML/annum EWRs correspond to 32.3% of median annual flow Table 21b. Percentile flows at St Johns Brook at 609018 (Barrabup Pool) (Node 4). Values in ML.

Stn 609018 - St John Brook (Barrabup Pool) Percentile Flows Mean Median pctl 10 pctl20 pctl 30 pctl 40 pctl 50 pctl 60 pctl 70 pctl 80 pctl 90

January 42.4552381 33.45 10.63 16.51 18.72 23.3 33.45 37.21 49.88 53.86 92.27February 21.6647619 18.19 8.72 11.21 13.21 16.38 18.19 22.71 31.87 33.99 35.16March 24.10809524 20.71 8.81 9.44 15.08 16.94 20.71 27.88 32.97 37.48 43.69April 38.58409091 34.33 6.799 13.908 18.469 25.6 34.33 39.242 41.3 52.63 58.426May 154.6704762 61.65 26.81 40.45 41.96 56.4 61.65 64.48 73.68 76.02 92.78June 2783.468095 1085.11 59.61 71.83 365.6 493.64 1085.11 1409.17 2732.88 4728.68 6737.17July 9382.623333 8053.29 3261.69 3961.12 4523.08 7507.6 8053.29 9802.04 13417.19 13934.82 15406.04August 12976.93238 13136.37 4824.18 6301.06 8313.21 12075.5 13136.37 14114.92 16275.3 17673.5 22458.66September 11388.4319 11249.43 3284.34 6000.86 7395.38 8975.49 11249.43 11416.58 13392.4 14297.64 18850.55October 4777.801905 3670.14 1538.43 2558.61 2812.27 2930.27 3670.14 4060.42 4195.38 4502.66 8629.59November 1251.239048 998.9 183.9 632.99 677.89 812.06 998.9 1153.21 1690.86 2194.45 2396.88December 228.6185714 125.32 59.41 65.16 73.66 115.88 125.32 173.04 232.28 253.63 440.69



The formal EWR process of determining the required flow volume to maintain existing ecological values at a low level of risk show that about 25-35% of current flows are necessary (Tables 18 - 21). This process, however, has to recognise that the predictions of the Blackwood River (without Yarragadee) are for a system of increasingly degraded conditions. Presumably this will lead to reduced ecological values over time. The list over-page shows, by month, what the EWR are necessary to maintain. January This is a month of summer baseflows which reduce towards the end of the month. The seasonal adjustment is descending “shoulder” type hydrograph.

February This is a month of summer baseflows delivered as a “steady state” flows each day; a minimum flow to maintain perennial conditions. Substantially elevated flows should be avoided.

March March is a period of a summer-autumn transition.

April This is a month of autumn baseflows. Within-month flows have an ascending shoulder mid-month and steady state flows for the end of the month. Again, these flows mimic the natural hydrograph.

May May is a period of autumn baseflows with a “steady state” situation throughout the month.

June This as a month of autumn-winter transition, with ascending baseflows.

July July is characterised by winter “steady-state” baseflows.

August This is a period of winter-spring transition with flows undergoing an ascending transition. During late August, small fish “flushes” are necessary as an initial stimulus for migration.

September September is the month of initial reproductive migration of native fish species. The baseflow in this month (spring baseflow) has the required “significant flow events” for fish migration.

October October is another month of significant fish migration.

November The flows in November are descending in a spring-summer transitional series. December This month starts as the continuation of the descending flow series until a period of steady state interspersed with a mildly descending series until the end of the month. Flows for pool water quality.



6. SCENARIO TESTING

Scenario testing is a formal method of forecasting possible states of the Blackwood under a range of plausible future conditions (in this case, differing influences of Yarragadee abstraction on surface waters). “Good” scenarios help us to understand and predict how key drivers (eg. water volume, salinity) might interact and what the final conditions may be and consequently how they should be managed. There are two important considerations related to scenario testing of the possible impacts of abstraction from Yarragadee:

• The long-term increase in salinity as a consequence of catchment clearing (see Figure 12). • The reduction in rainfall and consequently runoff from the mid-1960’s (Figure 28 shows the

annual rainfall and long-term mean emphasizing the less than average since the mid-1970s.)

(a) Stn 009585 - Nannup - Annual Rainfall

0

200

400

600

800

1000

1200

1400

1600

1800

1900

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

Rainf

all (m

m)

Annual total (mm) Long-term mean

Figure 28. Long-term and mean rainfall at Nannup (in mm) at Station 009585. Note, the long-term annual

mean is about 890mm, the mean from 1978-present is approximately 775mm (a 16% reduction).

The scenario testing and modelling assessed two fundamental issues:

• Water quality. Modelled water quality data (i.e after different abstraction scenarios) were compared to ANZECC/ARMCANZ (2000) guidelines which state an 80th percentile of salinity values in the reference system is the “low risk” (upper) trigger for salinity targets.

• Water quantity. Modelled water quantity values (as per scenario testing) were compared to the quantitative EWRs for the Blackwood as outlined in Section 5 (see Tables 18 – 21). These values were compared month-month for each identified water-dependent ecological value.



6.1 Methods used for Scenario Testing Data was obtained from Hut Pool gauging station (site 609019) with daily discharge and Total Dissolved Salts (TDS) values covering a period of twelve years. The 80th percentiles for TDS were calculated for each month. The mean contribution of the Yarragadee aquifer to surface water flows (at Hut Pool) ranges from about 400ML/month during February to over 900ML/month during winter. These rates are equivalent to about 8-11GL/annum. Table 22 shows how this may vary annually. For the subsequent scenario testing, a conservative approach has been taken by using the maximum figure of Yarragadee discharge into the surface water of the Blackwood (of 10.8GL/annum) (Varma et al. 2003). The daily groundwater discharge from the Yarragadee Formation of 29.8ML/day (=10800/365) was therefore used in this model. The surface water and groundwater (Yarragadee) components of the Hut River Pool dataset were separated by subtracting 29.8ML from the Blackwood discharge data. Median flows for the Hut River Pool site are currently 480GL/annum (Table 19), with an estimated EWR of 104GL/annum to maintain existing ecological values. The removal of 10 GL/annum to the surface flows from Yaragadee (the most extreme case) is therefore considered to be a low ecological risk. The initial modelling investigated the estimated maximum and minimum salinity levels of 100mg/L and 400mg/L for Yarragadee to set the lower and upper case. For sensitivity analysis (conducted using differing reductions in groundwater inputs), 200mg/L used as a median case for the model. The separate values for daily salt loads for the Yarragadee contribution and the Blackwood were also quantified where:

[ Load (mg) = TDS (mg/L) * Discharge (ML) / 1000000 (M) ] From this the Blackwood Surface Water (BSW) load and salinity were calculated.

[ BSW load (mg) = Blackwood load – Yarragadee load ]

[ BSW TDS (mg/L) = 1000000 (M) * BSW load (mg) / BSW discharge (ML) ]

The model investigated 10%, 20%, 40%, 60%, 80% and 100% reductions to the Yarragadee (%Yarra) discharge to determine the effect of changes in salinity inputs on the Blackwood River. Firstly the Estimated Blackwood (Est. BW) load at the reduced flows was calculated:

[ Est. BW load @ 90% Yarra = Blackwood load – (Yarragadee load * 0.1) ] [ Est. BW load @ 80% Yarra = Blackwood load – (Yarragadee load * 0.2) ] [ Est. BW load @ 60% Yarra = Blackwood load – (Yarragadee load * 0.4) ] [ Est. BW load @ 40% Yarra = Blackwood load – (Yarragadee load * 0.6) ] [ Est. BW load @ 20% Yarra = Blackwood load – (Yarragadee load * 0.8) ]

Finally the Estimated Blackwood salinities (Est. BW TDS (mg/L)) were calculated for various levels of reduced Yarragadee discharge.

[ 1000000(M) * {Est. BW load @%Yarra (mg) / Blackwood discharge (ML) - (Yarra discharge (ML) * %Yarra)} ]



Table 22. Groundwater discharge between Darradup and Hut Pool. (Data from S. Varma et al. “Groundwater Discharge to the Lower Blackwood and Donnelly Rivers” (WRC: 2003))6.

Year Estimated annual

groundwater discharge (GL)

1983 11.1 1984 12.9 1985 9.7 1986 8.7 1988 13.1 1990 10.7 1993 9.3 1998 10.7

Average 10.8 To investigate the extreme case, (i.e. assuming no contribution of Yarragadee to surface flows) and a base Yarragadee salinity of 100mg/L (TDS), there is exceedance of the 80th percentile salinity values in the Blackwood during December, January, February and March during low flow conditions in the Blackwood (Figure 29). There are lesser exceedances of the 80th percentile for high Blackwood flows (January, February). Note, the 80th percentile is the “low risk” trigger (for further monitoring and assessment, rather than a threshold value). The impacts of the complete removal of Yarragadee flows during winter/spring are negligible. If the salinity of Yarragadee is modelled at 400mg/L, there are exceedances during “dry” Blackwood flows during January, February and March (Figure 30). The modelled salinity of the Yarragadee has little impact on the levels of exceedance on Blackwood flows (Figure 30). Consequently, the flow volumes from Yarragadee appear to have the greater influence on overall Blackwood salinity rather than the salinity of Yarragadee per se. To investigate these further, modelled salinities in the Blackwood were estimated using differing contributions of Yarragadee (10, 20, 40, 60, and 80%). This acknowledges the unlikely scenario of complete loss of groundwater flows as a consequence of abstraction. This range of different Yarragadee inputs was also to conduct a sensitivity analysis (are there critical levels of groundwater input) and the analysis was conducted using median Blackwood flows. This modelling shows (using median Blackwood flows) that only when the Yarragadee contribution is down to about 20% (of present flows) do the salinities in the Blackwood exceed the 80th low risk trigger (Figure 30). Analysis of the number of days the 80th percentiles are exceeded is shown in Figure 31. At 0% contribution from Yarragadee, values are exceeded about 100days/year, at 40% contribution about 87days and 80% about 77 days. (Note, an 80th percentile, be definition, will be exceeded, on average, 20% of the time or about 73 days/year).

6 An earlier study by Len Baddock (1995) showed that most of the groundwater discharge for this river reach occurs from the Yarragadee Formation where it outcrops over a 15km stretch of the Blackwood River between Layman Flat and the Darradup gauging station. Assuming that the above groundwater discharge is entirely via that river reach of 15km then the rate of groundwater discharge via this reach will be 2.0ML/km/day (=10800/15/365).



A qualitative sensitivity analysis shows the overriding influence of flow quantity from Yarragadee rather than flow quality on values in the Blackwood (within the quality/quantity parameters likely as a consequence of the abstraction from Yarragadee). For example, changing the salinity from 100mg/L to 400mg/L (a factor of four) has less influence on Blackwood salinity than reducing flow volumes by 30%.

Estimates of Blackwood River TDS (mg/L) with no Yarragadee contribution(Mean monthly values)

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

4000.00

1 2 3 4 5 6 7 8 9 10 11 12

Month

TDS

mg/

80th percentile ofcurrent TDS (mg/L)

Est. TDS 0% Yarra @100mg/L

Est. TDS 0% Yarra @200mg/L

Est.TDS 0% Yarra @400mg/L

Figure 29. Long-term 80th percentile salinity concentration (as TDS in mg/L) and modelled monthly salinities in the Blackwood assuming mean flows and a Yarragadee salinity of 100, 200, 400mg/L and 0%

groundwater contribution.



Estimates of Blackwood River TDS (mg/L) [median] with various levels of Yarragadee contribution

0.0

500.0

1000.0

1500.0

2000.0

2500.0

3000.0

3500.0

4000.0

1 2 3 4 5 6 7 8 9 10 11 12

Months

TDS

(mg/

L

Median @90%Yarra

Median @80%Yarra flow




80th percentileof current TDS(mg/L)

Figure 30. Long-term 80th percentile salinity concentration (as TDS in mg/L) and modelled monthly salinities in the Blackwood assuming a Yarragadee salinity of 200mg/L and 20, 40, 60, 80, and 90%

contribution (from Yarragadee) during median Blackwood River flows.

No days TDS exceeds current 80th percentile

7580859095

100105110

0% 20% 40% 60% 80% 100%

Yarragadee flow

no. d

ay

No days >80%ile Linear (No days >80%ile)

Figure 31. Number of days the 80th percentile will be exceeded under different modelled Yarragadee inputs (groundwater salinity at 200mg/L).



7. ECOLOGICAL RISK ASSESSMENT

The quantitative EWRs for the Blackwood and tributaries may be impacted by the Yarragadee proposal by differing levels of ecological risk. This risk is “informed” by the scenario testing in Section 6. A qualitative assessment or, where possible, a weight-of-evidence approach was made of ecological risk (as likelihood times consequence) (Table 23). The scientific uncertainty of the methods used in this study is presented in table form in Appendix IX. Each of the important water-dependent ecosystems is evaluated for risk in the context of the Yarragadee proposal:

• Channel maintenance High winter flows are important for channel maintenance (scour etc). These flows will be negligibly impacted by a reduction in Yarragadee inputs (see Figure 10). Therefore, the likelihood of an ecological impact is considered low, although the consequence of a lack of flushing flows is a “medium” risk. Overall the proposal is considered (assessed by likelihood x consequence), a low ecological risk (Table 23).

• Water quality (salinity) Water quality in the Blackwood is the major determinant of the structure and composition of the aquatic fauna (see Figures 23-24). Therefore, change in salinity has the potential to further impact on the aquatic fauna. The scenario testing in Section 6, shows, that even in extreme conditions (0% Yarragadee inputs of low salinity water 100mg/L), the overall exceedance of the 80th percentile salinity values only increases by 38% (from 73 days at present to about 98 days; only over summer). This is the extreme case; a more reasonable case would be Yarragadee salinities at 200mg/L and about a 20-30% reduction in inputs as a consequence of abstraction. In this case (using median Blackwood flows) there is a negligible increase in the 80th percentile exceedance. It should be noted, that the 80th percentile is the “low risk” guideline that is designed to elicit a program of further investigation. In the Blackwood, this would be over summer. Therefore, due to some uncertainties (unknown %Yarragadee losses due to abstraction), this is considered a medium risk. However, the present community structure of the Blackwood is typified by generalist, cosmopolitan species. A small, at worse, change in salinity over summer is not considered to further change the nature of the fauna. Therefore, the likelihood of an ecological impact is considered low (Table 23). In addition, the salinity in the Blackwood is expected to double (without groundwater abstraction) over the next 50 years (see Figure 12).



• Water quality (DO)

Low pool DO levels have the potential to make these habitats unusable for aquatic fauna, and in extreme cases, cause fish deaths. Low pool DO levels are highly seasonal and the consequence of low flow, elevated water temperatures and increased benthic respiration (e.g. BOD) (see Section 4.3.3 and Figure 19). The quantitative measures of EWRs for pools in the Blackwood (see Section 4.3.3, Node 2) showed that approximately 30% of the summer flows are required to ensure no temporal increase in the existing levels of pool anoxia. The flow model for the Blackwood was aimed at minimising the temporal duration of low DO values (i.e. those < 2mg/L). The process of anoxia is already common in deeper pools during warmer conditions and therefore DO levels may require further monitoring to determine the ecological consequence of pool anoxia during late summer. The likelihood of an increase over the present conditions as a consequence of abstraction is therefore considered low with the potential for medium risk during summer.

• Riverine macroinvertebrates A major influencing factor for macroinvertebrates (apart for salinity as discussed above) is flow permanence. In the tributaries, the structure of the fauna was different between temporary and permanent sites (see Figures 20, 24). The flows required in the main stem of the Blackwood to maintain permanence in lower reaches (listed in Node 2) would be adequately met even if the maximum impact of Yarragadee (0% input during dry year) was experienced by the system. Therefore, the likelihood of an impact is low and the consequences considered medium (faunal shift to a temporary river fauna). In the tributaries, the fresher, permanent sites were considered important refugia for fauna including species such as the mud minnow (see Section 4.4.11). The loss of the permanent streams reduces the ability of the fauna to recolonise the Blackwood when conditions seasonally ameliorate. The consequence of a loss of the flow permanence is considered a medium-high risk. However, these types of tributaries are well-represented at a sub-regional scale. The likelihood of change from permanent to temporary flows, as a consequence of Yarragadee abstraction, is largely unknown; it is therefore listed as a medium risk. There are a few points to note if streams are driven temporary; the spatial arrangement (how much stream will be temporary in flow) and when this would occur. Based on studies elsewhere on population dynamics of aquatic fauna it is considered that to be “viable” (i.e. as a nursery habitat of refuge) a permanent reach would have to be 100’s of meters in size.

• Riverine fish The fish in the Blackwood have a wide tolerance to salinity levels (see Section 4.4) and the flows (even with total Yarragadee abstraction), would be more than adequately met (see Section 5, Node 2). The likelihood of an impact is therefore low and the consequence (of a loss of fish) is medium.

• Energy flows These are ecological connectivity between the forested and the lower reaches of the river system. The likelihood of a loss of longer-term connectivity is low (see longitudinal model Figure 19) and the consequence is low (this is based on the number of tributaries which would provide a connection between forested and lower reaches).



• Estuarine flows

Flows from the river system are important to ensure productivity of their estuaries. The Blackwood system is characterised by substantial transmission in lower reaches (see Figure 9). These transmission gains are from other aquifers than Yarragadee. The consequence of a loss of river flows into the Hardy Estuary is medium in risk and the likelihood low (Table 23).

There were two ecological risks associated with the proposed Yarragadee abstraction; increases in the duration of pool anoxia in Blackwood river and a decrease in flow and a possible change in flow permanence of the tributary sites (Table 24).

Table 23. Ecological risks of proposed groundwater abstraction associated with the ecological values in the Blackwood River and tributaries.

Ecological Risk ECOLOGICAL ISSUE Likelihood Consequence Channel maintenance * ** Pool water quality salinity ** * Pool water quality DO * ** Riverine macroinvertebrates Blackwood River

* **

Stream macroinvertebrates Tributaries

** ***

Riverine fish * ** Energy flows * * Estuarine linkages * *

Table 24. Overall ecological risks on issues associated with the modelled abstraction rates.

Abstraction from Yarragadee

Ecological Issue

Ecological Risk

Channel maintenance Low Risk Pool water quality (salinity) Low Risk Pool water quality (DO) Low Risk (possible Medium risk

during summer) Macroinvertebrate biodiversity Low Risk Fish recruitment Low Risk Riparian vegetation Low Risk Fresh tributaries (changes to flow permanence)

Medium Risk

Energy flows Low Risk

EWRs for all identified water dependent ecosystems. Minimal levels of ecological risk.

Estuarine processes Low Risk



7.1 Possible Ecological Consequences

7.1.1 Increases in anoxia in pools in the Blackwood River The consequences would only be an issue during summer when flows are naturally low, water temperatures high and rates of DO consumption in pools are elevated. If widespread, these habitats would be unusable for fauna which would have to migrate to other more benign reaches. Other issues associated with increased anoxia are the releases of some heavy metals and nutrients from river sediments (see Section 2.3). Bunn and Davies (1992) described conditions in the Hotham River (Western Australia) where river anoxia (following a summer storm) resulted in substantially elevated concentrations of manganese, iron, total N and total P in the water column. 7.1.2 Changes to the spatial and temporal extent of fresher tributaries The fresher tributaries are considered important as refugia for native species intolerant to elevated salinities of the main stem of the river. For example, some species including the mud minnow were only collected from tributary sites. The cross sectional profiles showed that small changes in flows can have a disproportionately large impact in the wetted perimeter of the stream and consequently the available habitat. The community composition (fish, invertebrates) of permanent streams differs significantly from the temporary (Bunn, Davies and Edward 1989). Temporary systems are typically colonized by cosmopolitan fauna, which, by definition, is widespread. However, at a sub-regional scale, permanent fresher tributaries are well-represented in the mid reaches of the Blackwood River.



8. MONITORING AND ASSESSMENT

Comprehensive and valid in-stream flow recommendations can only be made in the context of a sound knowledge of the river and its ecological systems, or where there is sufficient time to study and quantify responses to natural flow events before water developments are commenced. In the absence of sound ecological understanding (the usual case), the best available approximations of significant flow events and temporal patterns of flow must be used. Consequently, provision must be made within the budget of all water resource projects for these initial estimates to be refined and adjusted over time as the effects of the initial recommendations are monitored and/or special issues are researched in each river system (Arthington et al. 1992, 1993, 1994) (see Figure 32).

Figure 32. Conceptual framework and process for setting a monitoring and evaluation program

(after Marsh 2004). “Circled” areas emphasise stages in the process.

8.1 Monitoring Program

To adequately monitor the possible impacts of the Yarragadee proposal the ecological risk assessment (Section 7), serves as a guide for the parameters to be monitored. One issue highlighted as “medium risk”, was the flow permanence of the (now permanent) fresher tributaries. There is also the possibility that riverine pool DO levels are at risk of reaching anoxic levels during summer.



DO levels At a range of riverine pools, DO levels should be monitored during periods when water temperatures are elevated and when the models predicted low water levels (December-March). Data should be recorded at 10min intervals over at least 24 hours. Parameter Sites Frequency Dissolved Oxygen 2, 4, 8, 14, 16, 19 Summer annually Tributary permanence At focal permanent tributaries, flows should be gauged daily, particularly over late summer. If a gauging station is used then it should be constructed as to not interfere with upstream movement of fish (e.g. a broad-crested Crump weir). However, it would be more preferable that a natural control point is used and having a data-logger record depth (and through use of a rating curve, consequently flow). Parameter Sites Frequency Flows Rosa, Adelaide, Spearwood,

Milyeannup, St Johns (at range of sites)

Daily flows over late summer/ autumn

8.2 Blackwood monitoring The Yarragadee monitoring and evaluation program should be viewed in a great catchment management context. It will remain difficult to “remove” the impacts of the Yarragadee proposal from other catchment-related issues. Consequently, a comprehensive physical, hydrological and a biological monitoring program is recommended (Table 25). The physical monitoring would entail measurements of water quality (turbidity, dissolved oxygen, pH, Salinity, conductivity, nutrients [Total N and Total P], redox and water temperature), channel erosion and pool aggradation. Hydrological monitoring would involve continued gauging of flows at existing stations; preferably at daily intervals.



Table 25. Recommended monitoring regime for the Blackwood M & E program.

RECOMMENDED MONITORING REGIME FOR THE BLACKWOOD M& E PROGRAM.

Parameter Methodology Sites/ Frequency

Hydrology Gauging station Daily flows at the existing gauging stations Physical Water quality sampling

Pool aggradation Channel morphology

Bi-monthly at two focal “nodes” (Darradup to Hut Pool). DO in pools (as listed above). Annually at areas within focal “nodes” (Darradup to Hut Pool) Annually at areas within the focal “nodes” (both banks).

Biological Aquatic macroinvertebrates

Fish recruitment

Riparian assessment

Twice yearly (“wet” and “dry” seasons at four sites between Darradup and Hut Pool in the Blackwood and six of the major tributaries. Annually at four sites between Darradup and Hut Pool in the Blackwood and six of the major tributaries (coincide with breeding). Annually (summer) at a range of sites between Darradup and Hut Pool (~10 sites) in the Blackwood and six of the major tributaries.



9. SUMMARY

The Blackwood River is a moderately-degraded, brackish to saline system draining cleared farmland predominantly to the east of the Scarp. The Yarragadee proposal, by abstracting fresher water, has the potential to further degrade the water quality and quantity in the lower Blackwood River particularly between Darradup and Hut Pool. The hydrology of the river system shows a tight linkage between tributary flows and local rainfall. The river itself is more de-coupled and reliant on upstream flows and aquifer inputs. The catchment of the Blackwood is unlikely to undergo a major change in current land-use practices and consequently broad-scale rehabilitation of the river will be restricted. Current models predict a doubling of the salinity of the Blackwood River over the next 50 years. At present, the Blackwood River supports a relatively diverse group of native fish and a moderately diverse macroinvertebrate community. These species are obviously tolerant of elevated salinity and, as such, are relatively cosmopolitan, generalists. However, the region does include an overlap of the distribution and is therefore a “hotspot” of native crayfish (marron, koonacs, gilgies etc). The tributaries may function as a refuge for less tolerant aquatic fauna (i.e. mud minnows, stoneflies, crayfish; which were only recorded in numbers from the tributaries). Predictions based on removal of water from the Yarragadee aquifer were based on a range of scenarios (as the exact contribution, with and without Yarragadee, on surface flow is not well known). Modelling showed exceedance of the 80th salinity percentile (an ANZECC recommended “low risk” trigger value) in the Blackwood for a few months over summer with (modelled) complete abstraction of the Yarragadee flows. More plausible scenarios showed little change in the current levels of exceedance. Based on scenario testing, an ecological risk assessment highlighted two ecological attributes which have may have “risk” of degradation and consequently need to be monitored (in an adaptive framework); dissolved oxygen levels in riverine pools during summer and the extent of flow permanence in the currently-perennial tributaries. A monitoring and evaluation program is recommended to further investigate these issues along with a broader-scale (M&E) program to assess catchment management issues and how these influence riverine health in the Blackwood.



10. RECOMMENDATIONS

The following recommendations are made for ecological issues associated with the Blackwood and tributaries: 1. Conduct the monitoring and evaluation program specific for the potential impacts of

the Yarragadee proposal as listed above. 2. Conduct or select important components (as shown in Table 25) of the Blackwood

River to be monitored in a larger-scale M&E program (as listed above). 3. Conduct more detailed scenario testing when the relative contribution of Yarragadee

to surface flows is better known. 4. In a focussed longer-term study, investigate the role of the fresher, permanent

tributaries as refugia for aquatic fauna. 5. Conduct a detailed assessment to ascertain freshwater crayfish species’ distribution

(using population genetics protocols such as allozyme electrophoresis).



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GLOSSARY

Abiotic Non-living characteristic of the environment; the physical and chemical components that relate to the state of ecological resources. Abstraction Withdrawal of water for anthropogenic purposes, usually by means of pumping (and often regulated), from surface water sources such as rivers and streams, and groundwater sources such as aquifers (via boreholes and wells). Abundance - The relative quantity or number of animals present. Aggradation- The infilling of pools by sediment by deposition, typically a consequence of upstream erosion. Allocation - Giving an entitlement to use water or setting aside a water resource for a designated use. Allochthonous - of matter originating from outside a stream system i.e. inputs of leaf litter to a stream. Alluvial relating to or consisting of any material that has been carried or deposited by running water Anadromous referring to fish, such as salmon, that live most of their lives in the ocean but migrate up into freshwater streams and rivers to spawn (produce eggs). Analysis of variance - statistical technique for comparing data points using the degree of variation about the mean value. ANOVA - see analysis of variance. Anoxic – without or lacking oxygen. Anthropogenic of, relating to, or resulting from the influence of human beings on nature Aquifer A geological formation or group of formations capable of receiving, storing and transmitting significant quantities of water. Arthropod any of a phylum (Arthropoda) of invertebrate animals (as insects, arachnids, and crustaceans) that have a segmented body and jointed appendages, a usually chitinous exoskeleton molted at intervals, and a dorsal anterior brain connected to a ventral chain of ganglia. Autochthonous - of matter originating from within a stream system i.e. growth of algae or aquatic plants. Beneficial use The current or future uses for a water resource which have priority over other potential uses because of their regional significance to the community. Beneficial use designations provide guidance in determining the management and protection of the quality and quantity of the resource. Benthic/Benthos - (pertaining to) organisms that occur on or in sediments of the stream/river bed. Catadromous diadromous migrations to the sea/estuary for breeding. Catchment means the surface area from which run-off flows to a river or a collecting reservoir such as a lake. Channel - areas of the stream where surface water flow is unbroken by rocks, vegetation etc. Channelisation means formation of a water carrying network. Classify - to arrange values of a variable into ranks or groups, with similar values placed in the same group and dissimilar separated by groups. Consumptive use means any activity that depletes the total flow or volume of water in a water body.



Correlation Coefficient - value showing the relationship between two variables. CPOM - Coarse Particulate Organic Matter; organic material, usually dead leaves forming particles >1.00 mm diameter, utilised as a food source by aquatic macroinvertebrates. Crustacean any of a large class (Crustacea) of mostly aquatic mandibulate arthropods that have a chitinous or calcareous and chitinous exoskeleton, a pair of often much modified appendages on each segment, and two pairs of antennae and that include the lobsters, shrimps (as shown below, sourced from the Dictionary of Science and Technology, 1992), crabs, wood lice, water fleas, and barnacles Dam a structure constructed across a river valley to store stream flow and allow it to be diverted for water supply use and for release in a controlled manner for downstream use. Demand the amount of water required from the water supply system. Desiccation to dry out. Detritus loose material (as rock fragments or organic particles) that results directly from disintegration or decay. Diadromous moving between the sea/estuary and rivers/streams. Diel - over a day/night period; 24 hr period. Diversion means development of a water resource to harvest some or all of its divertible water. Divertible water means the average annual volume of water which could be removed from developed or potential sources on a sustainable basis. Drain means every channel, gutter, ditch, tunnel, pipe, cutting, or passage on, above, or underground, constructed, used, or intended to be used for draining or diverting water from land, except a navigable river, and except a main or branch water-race made for the supply of any reservoir, dam, or pit for the conservation of water. Ecological water requirements means water regimes needed to sustain the ecological values of aquatic ecosystems at a low level of risk. Ecologically Sustainable Development means development that improves the total quality of life, both now and in the future, in a way that maintains the ecological processes on which life depends. Endemic - natural distribution confined to a particular region or area. Environmental water provisions Are that part of environmental water requirements that can be met. Epilimnion - in summer months a reservoir or lake may stratify, whereby a temperature change (thermocline) develops within the water body. The area of water above the thermocline is termed the epilimnion. Eutrophic - category used to describe trophic status of a water body with nutrient concentration in the following ranges: TP ≥ 0.03 mg/ L, TN ≥0.5 mg/L & Inorganic-N ≥ 0.5 mg/L. Eutrophication a process that increases the amount of nutrients, especially nitrogen and phosphorus, in a marine or aquatic ecosystem, leading to an increase in algae and a decrease in diversity (stimulating the growth of aquatic plant life, usually resulting in the depletion of dissolved oxygen); it occurs naturally over geological time but may be accelerated by human activities, such as waste disposal or land drainage. Fauna - the animal population present in a certain place. Flora - the plant population or vegetation present in a certain place.



FPOM - Fine Particulate Organic Matter; organic material forming particles < 1.00 mm diameter, usually derived from the breakdown of leaf material and utilised as a food source by aquatic macroinvertebrates. Freshwater means water of salinity less than 500 mg/L TSS. Gabion Deflectors - a structure designed to increase stream flow and sediment transport. Consists of deflectors made of chain-link cyclone fencing cut into 2.4 m sections, filled with large rocks, and bound with heavy gauge wire. The ends of the deflectors are set at an angle into the stream banks approx. 60 cm. Geomorphology the study of the surface configuration of the earth, especially the nature and evolution of present landforms, their relationships to underlying structures, and the history of geologic activity as represented by such surface features. Geotechnical releases means releases from storages for safety testing purposes. Gigalitre means one million kilolitres. Groundwater means water which occupies the pores and crevices of rock or soil. sub-surface water in the zone of saturation. Heterogeneous - diverse in character; composed of different elements; used to describe a section of stream in which a high number of different habitats may be defined, promoting high species richness. Homogeneous - consisting of parts all of the same kind, uniform; used to describe a section of stream in which few different habitats may be defined, limiting species richness. Hydrogeology - groundwater geology. Hypolimnion - in summer months a reservoir or lake may stratify, where by a temperature change (thermocline) develops within the water body. The area of water below the thermocline is termed the hypolimnion. Hyporheic - a zone of the stream bed, below the water/sediment interface bet above the ground-water system, extending laterally into the stream banks. Possibly an important habitat/refugia in permanent streams when surface flow is reduced or non existent. Instream water use Means any use of the flow or waters of a water body that does not remove the water from the water body (eg. swimming). Inundation means covered with water. Irrigation Any method of causing water from a watercourse, water services works or an artificial collection of water to flow upon and spread over land; or applying water to land from a watercourse, water service works or an artificial collection of water, for the purpose of cultivation of any kind or of tillage or improvement of pasture. Key stakeholders means persons or organisations that have a substantial interest in a particular matter. Leaf pack - an accumulation of dead leaves found in a stream, caught in log jams and deposited in backwaters. Lentic - belonging to or associated with standing/still waters as in lakes, ponds and reservoirs. Lotic - belonging to, or associated with, flowing waters, as in streams and rivers. Macroinvertebrate - aquatic fauna, excluding fish retained by 0.25 mm mesh aperture net. Macrophytes - aquatic plants, excluding algae, that are either fully submerged of partially submerged (emergent) e.g. sedges, rushes, pond weed etc. Margins - area of stream adjoining the bank exhibiting reduced flow and increased sediment deposition.



Mesotrophic - category used to describe trophic status of a water body with nutrient concentration in the following ranges: TP 0.0075 - 0.02 mg/ L, TN 0.425 - 0.7 mg/L & Inorganic-N 0.475 - 1.5 mg/L. MPS - Mean Particle Size; mean of the dry weights of sediment particle size classes used to describe the sediment on the stream bed at a sampling site. Multivariate statistics - examining more than variable at a time. Oligotrophic - category used to describe trophic status of a water body with nutrient concentration in the following ranges: TP ≤ 0.0075 mg/ L, TN ≤ 0.425 mg/L & Inorganic-N ≤ 0.475 mg/L. Permanent stream - a stream at which water is always present. Pipehead - means a small dam from which water is piped directly for use or into a storage dam. Plankton - a collective term for the wide variety of plant and animal organisms, often microscopic in size, that float or drift freely in water because they have little or no ability to determine their own movement; found worldwide in both aquatic and marine environments and representing the basic level of many feeding relationships. Pumpback - means diverting some streamflow by pumping from a dam through a pipeline into another storage. Pycnocline - region of vertical salinity gradient Qualitative - an expression of abundance in which data are scored as either present (1) or absent (0). Often used for species data. Quantitative - an expression of abundance in which data are scored as the actual number of occurrences, i.e. the number of species or individuals to a known area or volume. Refugia - areas that remain unaffected by a general climatic change and which therefore contain a population of organisms typical of those once spread over the whole region. Regional water resource allocation plan - means a document prepared by the Water and Rivers Commission setting out the background, policy and rules relating to protection of the water resource, the environment and allocation of water resource to classes of use. Regulated stream - means a stream on which are located substantial dam(s) or barriers which divert a major proportion and substantially alter the pattern of streamflow. Riffle zone - a shallow, fast flowing section of stream which is distinctive through the surface flow being broken and turbulent. Riparian - of or on the river bank, as in riparian vegetation. Riparian rights - The owner or occupier of any land alienated from the Crown through or contiguous to which runs any watercourse, or contiguous to which, or partly within which, is situate any lake, lagoon, swamp or marsh, has the right, as such owner or occupier, to take water in that water-course, lake, lagoon, swamp or marsh, free of charge for the domestic and ordinary use of himself and of his family and servants; and for watering cattle or other stock, and every owner of land alienated from the Crown before the relevant day has a further right to take such water for the irrigation of a garden not exceeding 2 hectares in extent, being part of that land and used in connection with a dwelling. River basin means the catchment of river(s) as defined by the Australian Water Resources Council for presenting hydrological data. Samphire (Salt marsh) means a type of vegetation found in sheltered river estuaries subject to frequent covering by tides.



Scheme supply means water diverted from a source (or sources) by a water authority or private company and supplied via a distribution network to customers for urban, industrial or irrigation use. Self-supply means water diverted from a source by a private individual, company or public body for their own individual requirements. Semi-regulated stream means a stream that is subject to some damming or barriers which may divert a significant proportion and significantly alter the pattern of streamflow. Spatial - to describe a variable changing within space. Species Richness - the number of different species found in a defined area. Specific volume the volume per unit mass; the reciprocal of density. Storage reservoir means a major reservoir of water created in a river valley by constructing a dam. Stratification a density gradient in a water column caused by temperature and salinity variations Surface water means water flowing or held in streams, rivers and other wetlands in the landscape. Sustainable use means diversion of water at a replenishable rate. Sustainable yield means the rate of water extraction from a source that can be sustained on a long-term basis without exceeding the rate of replenishment. System yield means the maximum demand that the water supply system can sustain under specified expectation of restrictions (currently restrictions are expected in 10% of years). Temporal - to describe a variable changing over time. Thalweg- the deepest point in the river channel. Typically arranged longitudinally. Transferable water entitlements means a private water allocation which is marketable. Treatment means the application of techniques such as settlement, filtration, chlorination, to render water suitable for drinking purposes. Trophic level one of the hierarchical strata of a food web characterised by organisms which are the same number of steps removed from the primary producers Trophic Status - nutrient status/concentration of a water body; determined by nutrient concentration (Total Phosphorus, Total Nitrogen and inorganic Nitrogen levels); see eutrophic, mesotrophic, oligotrophic. Turbidity means the clouding of water by suspended material causing a reduction in light transmission. Univariate statistics - examining one variable at a time. Unregulated stream means a stream that is not subject damming or barriers. Water resources means water in the landscape (above and below ground) with current or potential value to the community and the environment. Wentworth scale - used to separate stream sediment into a range of size classes ranging from 0.25 mm to > 32.0 mm diameter enabling characterisation of sites on the basis of substratum. Wetland means an area of seasonally, intermittently or permanently waterlogged soils or inundated land, whether natural or otherwise, fresh or saline. Yield benefit means the increase in system yield which occurs when a new source is added to the water supply system.



ABBREVIATIONS AFFA Agriculture, Fisheries and Forestry Australia AHD Australian Height Datum ANZECC Australian and New Zealand Environment and Conservation Council AWRC Australian Water Resources Council CALM Department of Conservation and Land Management COAG Council of Australian Governments CSIRO Commonwealth Scientific and Industrial Research Organisation DO dissolved oxygen EA Environment Australia EFI Environmental Flows Initiative EPA Environmental Protection Authority FSL Full supply level GL Gigalitre ha Hectares km Kilometres LCDC Land Conservation District Committee LWRRDC Land and Water Resources Research and Development Corporation m Metres MAF Mean Annual Flow ML Megalitre NHT Natural Heritage Trust NRHP National River Health Program PIMA Peel Inlet Management Authority PMWSS Perth Metropolitan Water Supply Scheme ppt parts per thousand, equal to g/kg, symbolised by ‰; in the measurement of

salinity, ppt is equivalent (or very close, see Dauphinee, 1980; Lewis and Perkin, 1981) to practical salinity units (psu)

SWI South West Irrigation TDS Total Dissolved Salts. USA United States of America WRC Water and Rivers Commission yr Year



APPENDICES



Appendix 1. RIVER CONDITION ASSESSMENT CATEGORIES (W&RC, 1997; Pen & Scott, 1995).

The evaluation of river reaches was conducted in a hierarchical fashion, from least disturbed to most disturbed, into the following groups: A. Conservation river reaches A1. Pristine: the catchment of the stream is pristine A2. Near pristine: the catchments is almost pristine but there is some evidence of human activity,

feral animals and weeds (i.e. large Conservation Reserves and distant National Parks). A3. Relatively natural: the catchment is dominated by native species, but is modified by human

activity such as logging and recreation (i.e. typical National Parks, State Forest). B. Natural resources river reaches B1. Relatively natural river section: In this category the river section lies within the reserve or

National Park, but the upstream catchment has been significantly altered. Adjacent land has the character of an A3 catchment, but upstream the catchment may be partially or wholly cleared, support agriculture, plantations, urban development and mining.

B2. Corridor river: A corridor river reach, for the most part, retains natural vegetation along its

immediate river valley or flood plain sufficient to provide a substantial area of habitat. B3. Habitat river reach: A habitat river has been greatly impacted by upstream and adjacent land

use, but retains sufficient habitats to sustain viable populations of native plants and animals.

C. Multiple Use rivers. C1. Landscape river: The river has been heavily impacted by upstream and adjacent land use to

the extent that most native plants and animals are extinct. However, important landscape components remain, such as river form (deep valleys, undulations), native trees and bodies of water, contributing to the character of the local area.

C2. Multiple enhancement: Highly degraded streams in rural, rural/residential or residential land

which have been or have some potential to be rehabilitated as part of the provision of local parkland or open space fall into this category. In other words the stream retains its natural form, though it is highly degraded.

C3. Drain: The stream has little value other than to convey water. It may be part of a drainage or

irrigation scheme, it may be heavily eroded or completely channelised, lined with concrete or not and support a few remaining native trees and abundant weeds.



Appendix II. Analysis of hydrology (mean, median flows and average recurrence intervals of floods) from WRC gauging stations.

Stn 609058 - Blackw ood Riv er (Old Nannup Carav an Park)

0100002000030000400005000060000700008000090000

100000

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ary

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ch

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st

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embe

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(ML)

mean median

Stn 609058 - Blackw ood Riv er

0

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0.0 0.5 1.0 1.5 2.0 2.5ARI (y ears)

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Stn 609019 - Blackw ood Riv er, Hutt Pool

020000400006000080000

100000120000140000160000180000200000

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Stn 609019 - Blackw ood Riv er (Hutt Pool)

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Stn 609001 - Rosa Brook (Crouch Road)

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Stn 609001 - Rosa Brook

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Stn 609019 - St John Brook, Barrabup Pool

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Stn 609018 - St John Brook, Barrabup Pool

0500

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0 2 4 6 8 10 12

ARI (y ears)

Tota

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=========================================================================

Appendix III. Systematic (i.e. in phylogentic order) list of taxa, with codes and authorities. Note, capitalised headings represent Order, lower case ending in ae Family and italics Genus and Species. Common names in brackets. Names after Species are the “authority” (without brackets represents the original naming authority and in brackets is a re-naming). “Code” is the UWA voucher system.

========================================================================= TAXA CODE NEMATODA (thread worms) Mermithidae 030000 GASTROPODA (snails) 050000 PROSOBRANCHIA ?Hydrobiidae 050100 Glacidorbis occidentalis Bunn and Stoddart 050101 PULMONATA Ancylidae (limpits) 050200 Ferrissia aff. petterdi (Johnston) 050201 ANNELIDA (jointed worms) OLIGOCHAETA (”earth” worms) 060000 Oligochaeta spp. 060001 ARTHROPODA ARACHNIDA (spiders, ticks, mites) HYDRACARINA (water mites) 090000 OSTRACODA (seed shrimp) 100000 COPEPODA 110000 CYCLOPOIDA Cyclopidae 110100 CALANOIDA 110300 ISOPODA (water slaters) 120000 AMPHIPODA (side swimmers) 130000 Gammaridae 130100 Perthia branchialis (Nicholls) 130101 Perthia acutitelson Straskraba 130103 Ceinidae 130200 Austrochiltonia subtenuis (Sayce) 130201 DECAPODA (shrimps, crayfish) 140000 Parastacidae (crayfish) 140100 Cherax 140101 INSECTA PLECOPTERA (stoneflies) 150000 Gripopterygidae 150100 EPHEMEROPTERA (mayflies) 160000 Leptophlebiidae 160100 Baetidae 160200 Caenidae 160300 Tasmanocoenis tillyardi (Lestage) 160301 ODONATA (dragonflies, damselflies) 170000 ZYGOPTERA (damselflies) ANISOPTERA (dragonflies) Gomphidae 170500 Austrogomphus lateralis (Selys) 170501 DIPTERA (true flies) 220000 Simuliidae (blackflies) 220100 Chironomidae (non-biting midges) 220200 Ceratopogonidae (biting midges) 220300 Tipulidae (crane flies) 220400 Empididae (soldier or desmo flies) 220500 TRICHOPTERA (caddisflies) 240000 Ecnomidae 240100 Hydrobiosidae 240300 COLEOPTERA (water beetles) 250000 Dytiscidae 250200



Appendix IV. Profiles of water chemistry at sites where top-bottom changes were measured. Note, DO and temperature were the only parameters to show stratification.

Site Depth from surface (m)

DO (mg/L) Temperature (OC)

Site 19 Blackwood 0 9.1 19.7 0.2 9.0 19.7 0.4 9.0 19.3 0.6 9.0 18.6 0.8 9.0 18.5 1.0 9.0 18.5 1.2 9.0 18.3 1.4 9.0 18.1 1.6 9.0 17.5 1.8 8.9 17.4 2.0 8.6 17.5 2.2 6.7 17.2 2.4 2.5 16.8 2.6 2.2 16.5 Site 18 Blackwood 0 8.9 20.1 0.2 8.9 20.0 0.4 8.5 19.7 0.6 8.2 19.7 0.8 8.3 19.3 1.0 8.0 19.1 1.2 7.8 18.9 1.4 7.5 18.8 1.6 5.3 18.8 1.8 3.9 18.8 2.0 2.8 18.8 2.2 2.2 18.6 Site 17 Blackwood 0 7.8 20.4 0.2 7.6 20.0 0.4 7.8 18.9 0.6 7.5 18.7 0.8 7.4 18.7 1.0 7.2 18.4 1.2 6.8 18.5 1.4 5.5 18.0 1.6 2.9 17.6 1.8 2.4 17.4 2.0 1.8 17.5 Site 4 Blackwood 0 8.1 19.8 0.2 8.2 19.6 0.4 8.0 18.9 0.6 7.5 18.7 0.8 7.4 18.5 1.0 7.2 18.1 1.2 7.0 17.6 1.4 4.6 17.3 1.6 3.2 16.1 Site 1 Blackwood 0 8.6 20.4 0.2 8.4 20.3 0.4 8.4 20.1 0.6 7.9 20.0 0.8 7.7 19.8 1.0 7.5 19.6 1.2 7.6 19.5 1.4 7.5 18.9 1.6 6.4 18.8 1.8 5.2 18.6 2.0 3.3 17.9 2.2 1.8 17.8



Appendix V. Range of 24 hour temperature and DO plots (recorded at mid depths at 10min intervals).

Temperature at Sollya

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Temperature at Ballan Creek

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Temperature at Adelaide Brook

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Temperature at Poison Gully

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p (C

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Temperature at Red Gully

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Temperature at McAfee Brook

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Temperature at Sturke Creek

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Temperature at St Johns (mid) site 2

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Temperature at St Johns (low) site 3

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Temperature at Rosa Brook (up)

11 13 15 17 19 21 23

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Appendix V. (cont). 24 hour temperature and DO plots (recorded at mid-depths at 10min intervals).

Temperature at Blackwood Site 1

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Appendix V. (cont). 24 hour temperature and DO plots (recorded at mid-depths at 10min intervals).


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Dissolved Oxygen at Ballan Creek

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Dissolved Oxygen at Rosa Brook

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Dissolved Oxygen at Rosa Brook (up)

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Dissolved Oxygen at Adelaide Brook

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Dissolved Oxygen at Spearwood Creek

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Dissolved Oxygen at Layman Brook

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Dissolved Oxygen at Milyeannup Brook

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Dissolved Oxygen at Poison Gully

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Dissolved Oxygen at Sollya Creek

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Dissolved Oxygen at Red Gully

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Dissolved Oxygen at McAfee Brook

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Dissolved Oxygen at Sturke Creek

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Dissolved Oxygen at St Johns Site 1

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Appendix VI. Photographs of sampling sites, July 2004.

Plate 20. Blackwood River Site 1.

Plate 21. Blackwood River Site 2




Plate 23.Blackwood River Site 5.















Appendix VII. Cross-sectional diagrams and photographs of tributary sites. Note, not all sites shown.

Plate 32. Tributary A, ‘Ballan’ Creek.

Channel width 1.84 m

Max depth 35 cm

Bank stabilisation provided by native vegetation:

Sparse mature eucalypt trees (overstorey),

continuous saplings and native grasses (middle and

understorey).

Overhanging vegetation and fallen logs providing almost continuous shade

Steep bank angle: 45-

60°

Very steep bank angle: 90°+ (some under-

cutting)

Diverse instream habitat: submerged

roots, crayfish burrows and macrophytes.

No measurable stream velocity

Grass trees



Plate 33. Tributary Site B, Rosa Brook (downstream).

Steep bank angle: 45-60°

Abundant leaf litter and fungi

Stream velocity 10 cm/s

Bank stabilisation provided by native vegetation: continuous

mature eucalypt trees (overstorey), saplings, ferns and

native grasses (middle and understorey).

Numerous fallen logs

Good diversity of instream habitat: rocks, submerged

logs, branches and two species of aquatic

macrophyte.

Crayfish burrows providing refuges for nightfish, gilgies and koonacs.

Channel width 5.88 m

Max depth 100 cm in deep pool

Sedimentation 5-10 cm



Plate 34. Tributary Site C, Rosa Brook (upstream).

Channel width 3.5 m (at bridge).

Max depth 100 cm in deep pool.

Sedimentation 20 cm in deep pool.


Stream velocity 25 cm/sec within rifle area. No visible flow in deep

pool.

Bank stabilisation provided by native vegetation: patchy

mature eucalypt trees (overstorey), continuous

saplings and native grasses (middle and understorey).



Plate 35. Tributary Site D, Adelaide Creek.

Channel width 3 m

Sedimentation 20 cm in places

Abundant leaf litter

Moderate flows, low turbidity.


Bank stabilisation provided by continuous native vegetation:


Max depth 60 cm



Plate 36. Tributary Site E, Spearwood Creek.

Channel width 1.6m

Max. depth 20cm

Sedimentation 5-10cm

Dense thickets of native grasses

dominating stream channel and banks

Stream velocity: 11 cm/sec

Moderate bank slope: 10-45°





Plate 37. Tributary Site F, Layman Brook.

Channel width 5.7 m

Max depth 85 cm Limited sedimentation 1 – 5 mm

Habitat such as fallen logs, native grasses and in-stream snags

Bank stabilisation provided by abundant native vegetation: mature

eucalypt trees, saplings and native grasses.

Abundant leaf litter

Minimal stream velocity

Steep banks: 45-60°



Plate 38. Tributary Site G, Milyeannup Brook.

Width 4.2 m

Max. depth 55 cm

Man made bridge

Man made rocky habitats providing refuge for

numerous fish species and native crayfish

Snags providing habitat for native minnow and

perch species.

Abundant native grasses



Stream velocity: 3 cm/sec

Very steep banks: 60°+



Appendix VIII. Flow requirements for Blackwood sites during “steady state” conditions (and without elevated flows for specific ecological events i.e. fish migration). Note, low flows for macroinvertebrates are for inundation of the ‘low flow” channel only. Variation between sites reflects the influence of transmission gains channel morphology and also reflects errors in measurements of cross sections.

Site Macroinvertebrates m3/s

Fish m3/s Riparian m3/s

Blackwood 1 0.18 9.01 179.5 Blackwood 2 0.22 9.87 180.8 Blackwood 3 0.34 9.90 181.5 Blackwood 4 0.43 10.01 184.4 Blackwood 5 0.26 10.11 182.5 Blackwood 6 0.32 10.55 188.5 Blackwood 7 0.33 10.63 189.3 Blackwood 8 0.33 9.71 188.4 Blackwood 9 0.29 10.15 190.5 Blackwood 10 0.45 10.23 191.2 Blackwood 11 0.42 10.01 198.9 Blackwood 12 0.56 10.92 190.2 Blackwood 13 0.45 10.12 192.3 Blackwood 14 0.66 10.28 199.8 Blackwood 15 0.23 12.09 202.1 Blackwood 16 0.45 13.42 199.6 Blackwood 17 0.42 12.55 200.9 Blackwood 18 0.32 12.49 199.0 Blackwood 19 0.29 11.79 197.5



Appendix IX.

Scientific uncertainties requiring research to further justify the basis of EWRs in the Blackwood River.

Water dependent issue

Research issue

Recommended design

Flows to maintain the active channel, reduce pool infilling (aggradation) and channel incursion

(i) Shear stress at bankfull discharge

(ii) Pool scouring at bankfull

(i) Field-based measurements of shear stress (e.g. Statzner and Higler 1986, Statzner et al. 1988).

(ii) Measurements of pool aggradation (Bunn et al. 1998).

Flows to maintain macroinvertebrate biodiversity Macroinvertebrate biodiversity in different flow conditions.

Macroinvertebrate community structure at a range of streams differing in flow permanency.

Flows for native fish migration and reproduction. (i) Flows required by fish during summer.

(ii) Flows required during reproductive migrations

(i) Measurements of pool water quality during low-flows.

(ii) Population genetics study showing dispersal ability and current fragmentation.

Flows for maintenance and recruitment of riparian vegetation

Does riparian vegetation intercept channel or groundwater

An isotope study using O18 to determine the proportion of surface water: groundwater in riparian vegetation.

Flows to maintain both upstream-downstream and floodplain carbon/energy linkages.

What are the appropriate catchment-scale ecological models

Catchment-scale carbon budgets and food web structure (i.e. Bunn and Davies 2000).

Flows to maintain pool water quality; particularly during summer

Flows to ensure nightime dissolved oxygen > 2 mg/L

Extensive data-logging of pools during summer to test model.

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