DATA ANALYSIS AND GROUNDWATER MODELLING · 3.2 Groundwater trends 8 3.3 Groundwater salinity 11 3.4...

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Assessment of salinitymanagement options for KyeambaCreek, New South Wales:DATA ANALYSIS AND GROUNDWATER MODELLING

Richard G. Cresswell, Warrick R. Dawes, Greg K. Summerell,Glen R. Walker

Assessment of salinitymanagement options for KyeambaCreek, New South Wales:DATA ANALYSIS AND GROUNDWATER MODELLING

Richard G. Cresswell, Warrick R. Dawes, Greg K. Summerell,Glen R. Walker

Authors: Richard G. Cresswell 1, Warrick R. Dawes 2, Greg K. Summerell 3,4,5, Glen R. Walker 6, 7

1. Bureau of Rural Sciences, Canberra, ACT2. CSIRO Land and Water, Canberra, ACT3. Centre for Natural Resources, NSW Department of Land and Water Conservation, Wagga Wagga, NSW4. CRC for Catchment Hydrology, Canberra, ACT5. University of Melbourne, Melbourne, Victoria6. CSIRO Land and Water, Adelaide, SA7. Rural Solutions SA, Adelaide, SA

CSIRO Land and Water Technical Report 26/03CRC for Catchment Hydrology Technical Report 03/9MDBC Publication 12/03

Published by: Murray-Darling Basin Commission

Level 5, 15 Moore Street

Canberra ACT 2600

Telephone: (02) 6279 0100

from overseas + 61 2 6279 0100

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Internet: http://www.mdbc.gov.au

ISBN: 1 876 830 52 2

Cover photo: Arthur Mostead Margin photo: Mat Gilfedder

© 2003, Murray-Darling Basin Commission and CSIRO

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(‘Assessment of salinity management options for Kyeamba Creek, New South Wales: Data analysis and groundwater modelling’) is clearly

acknowledged.

To the extent permitted by law, the copyright holders (including its employees and consultants) exclude all liability to any person for any

consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from

using this report (in part or in whole) and any information or material contained in it.

The contents of this publication do not purport to represent the position of the Murray-Darling Basin Commission or CSIRO in any way and are

presented for the purpose of informing and stimulating discussion for improved management of Basin's natural resources.

This report represents a synthesis of information garnered from a wide spectrum of workperformed on a relatively small catchment within the Murrumbidgee River system. This reportplaces Kyeamba Creek into the context of Catchment Characterisation, with emphasis on thesalinity perspective as outlined by Coram (1998) and Coram et al. (2000). The CatchmentCharacterisation Framework was made possible through the concerted efforts over many yearsof local and regional hydrogeologists who first developed and populated the concept from adryland salinity perspective. Many of these are mentioned in Coram (1998), and havecontributed to various aspects of this and other work over a period of years.

This report draws on the vast store of knowledge held in the archives and minds of peoplewithin the institutions listed with the authors. In particular, this report draws on work carried outfor local Landcare and communities by Department of Land and Water Conservation staff,particularly Don Woolley, Darice Pepper, Frank Harvey and Hugh Jones, and by formerAustralian Geological Survey Organisation (now Geoscience Australia) staff, particularly JimKellett (now with Bureau of Rural Sciences) and Phil Bierworth.

This work was funded under the Murray-Darling Basin Commission’s Strategic Investigationsand Education Program, Grant Number D9004: ‘Catchment characterisation andhydrogeological modelling to assess salinisation risk and effectiveness of management options’.

This report has benefited immensely from reviews from Ray Evans and Jai Vaze, and fromnumerous discussions with other members of the Catchment Characterisation project. Editorialsupport from Mat Gilfedder and Pauline English (CSIRO Land and Water) is gratefullyappreciated.

Acknowledgements

C A T C H M E N T C H A R A C T E R I S A T I O N , K Y E A M B A C R E E K C A S E S T U D Y

i

Executive summary

C A T C H M E N T C H A R A C T E R I S A T I O N , K Y E A M B A C R E E K C A S E S T U D Yii

Introduction

Kyeamba Creek catchment, located withinthe uplands of the Lachlan Fold Belt ofsouth-eastern Australia, comprises anintermediate-scale fractured rock aquifer withoverlying alluvial fill in drainage lines anddepressions. This study of thehydrogeological factors influencing salinity inthe Kyeamba catchment was undertaken to:

• describe the physical setting andcondition of the Kyeamba Creekcatchment and aquifer system

• examine various data interpretationson the conceptual model of flowprocesses for recharge and discharge

• model the historical and present-dayhydraulic head trends

• model possible future salinitymitigation scenarios for the aquifer.

Site Description

Within the Murray-Darling Basin, KyeambaCreek is a third-order catchment feeding theMurrumbidgee River. The catchment islocated south-east of the city of WaggaWagga in central New South Wales. Themajor surface drainage features areKyeamba, Livingstone and O’Briens Creeks.Average annual rainfall is 650 mm, with agradient decreasing from south to north fromthe granite highlands to the alluvial plains atthe confluence with the Murrumbidgee. Landuse is dominantly cattle grazing, withsubordinate cropping, horticulture and, in thehigher country, sheep grazing.

Groundwater Flow System

The catchment, covering an area ofapproximately 600 km2, lies within anintermediate-scale fractured rock aquifer.Overlying valley fill alluvium represents ashallow secondary, local-scale aquifersystem. The catchment thus contains adual aquifer system: upper local-scalealluvial aquifers and an intermediate-scale,deeper fractured rock aquifer.

Kyeamba Creek is represented asIntermediate and Local Flow Systems infractured rock aquifers (Palaeozoicfractured rock in the Coram et al. 2000classification). Suggested managementoptions for this type of flow system includerevegetation/reafforestation of uppercatchments using perennial pastures,native pasture, and native trees, possiblywith some groundwater pumpingapplications (Coram et al. 2000). Thesesystems commonly have only a smallproportion of land area actually salinised,less than two percent, but can be a majorsource of salt via saline discharge tostreams and larger river systems.Discharge typically occurs at breaks ofslope, and directly through sedimentsalong valley floors.

In the Kyeamba catchment, salinity ismanifest as small, scattered patches ofsalinised land and locally shallow, salinegroundwater. Increasing stream salinity andsalt export to the Murrumbidgee River arethe main salinity issues in the area. Thesesalinisation outcomes are particularlypromoted in the lower landscape by a lackof hydraulic gradient, as well as byrestrictions in the aquifer caused by sub-surface highs, typically of granite.

Location of ‘Intermediate and Local Flow Systems infractured rock aquifers’ in the Murray-Darling Basin.


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Current estimations suggest that the quantity of salt being exported from the Kyeamba catchment is the second largest per unit area in the Murrumbidgee region.Notwithstanding, the total salt contribution from Kyeamba of 20,000 t/yr constitutesonly a maximum of five per cent of the salt load measured in the Murrumbidgee River passing Wagga Wagga. Salt loads arehighly variable, however, ranging from200,000 to 700,000 tonnes per yearpassing Wagga Wagga.

Groundwater modelling

The FLOWTUBE model, a simplegroundwater model based on Darcy’s Law,was used to simulate the variation ingroundwater on the groundwater flowsystem. The model resolves for changes inhydraulic head induced by recharge anddischarge fluxes, and lateral transfers in thedirection of flow, and is represented by ahydraulic head transect along the aquifer.For the Kyeamba catchment, parametersfor intermediate-scale, fractured bedrockand local-scale, alluvial aquifer systemswere modelled.

Outputs from the simulation of past andpresent heads emphasise the dominanceof the upper alluvial aquifer systemgenerating shallow water tables andsalinised areas, fed by salt pushed upwardby heads in the fractured rock aquifer. Themodelling generated a rapid response ofwater levels to modelled rechargereduction scenarios. This finding reinforcescurrent on-ground mitigation measures inthe catchment in the form of targetedrevegetation, but questions the applicabilityof widespread reforestation.

Portability of conceptualmodel, tools and results

This case study emphasises the need forgood local knowledge and understandingof the groundwater system. While classifiedas an intermediate fractured rock aquifersystem, the dominant system controlling

the outbreak of surface salinity is the overlying local alluvial system. Thesystem is highly responsive to revegetation /reafforestation management options. Further,sub-surface salt stores can be mobilisedupward by the hydraulic heads in thefractured rock, and become available fordelivery to the stream network from thealluvial fill.

While broad-scale reafforestation mayalleviate salinity concerns in the long term,the fact that groundwater levels are highand stable, i.e. in dynamic equilibrium,means that the system may continue as aviable agricultural region for the foreseeablefuture.

Kyeamba Creek catchment may be typicalof many within the Lachlan Fold Beltcountry of central New South Wales andnorthern Victoria. Extension of findings toother catchments is feasible, followingdetailed evaluation of local hydrogeologicalfactors. Rainfall considerations areparamount in the findings; higher rainfallregions will likely require more drasticinterventions and must be evaluated withinthe context of local information.

Conclusions

• Groundwater levels, and hencesalinity concerns in the catchment,are highly dependent on climatic,i.e. rainfall, conditions.

• Targeted perennial plantings wouldallow direct management ofindividual saline areas, while longer-term and more extensivereforestation would be required togenerally lower groundwater levels.

• Increased use of pumped aquifersnear the confluence with theMurrumbidgee River may negate theneed for groundwater level reduction,though the effects are likely to berestricted to the region within tenkilometres of the confluence with theMurrumbidgee due to bedrockconstrictions up valley.


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• Extension of the findings to similarcatchments along the west of theGreat Dividing Range of New SouthWales are encouraged, but not tothe higher rainfall regions.

Recommendations

• Continued monitoring of thecatchment water levels, stream flowand salinities to enable confidentevaluation of the response of thesystem to anticipated land usechanges. Continue local strategy oflocalised management of salineoutbreaks.

• Compare catchment behaviour toother catchments of a similar typeto gain confidence in the catchmentclassification process.

• Extend the study to encompass theadjoining Tarcutta Creek catchment.

Acknowledgements i

Executive summary ii

1. Introduction 1

2. Physical setting 32.1 Location and catchment description 32.2 Salinity issues 52.3 Salinity in the context of catchment surface morphology 52.4 Rainfall considerations 7

3. Conceptual hydrogeological model 83.1 Surface water 83.2 Groundwater trends 83.3 Groundwater salinity 113.4 Stream salinity 12

4. Groundwater modelling using FLOWTUBE 144.1 Numerical model 144.2 Special considerations 144.3 Composite aquifer model 194.4 Alluvial aquifer model 194.5 FLOWTUBE modelling summary 214.6 Future tree planting 214.7 CATSALT modelling 24

5. Discussion and conclusions 26

6. Future directions 27

References 28

Table of contents


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Dryland salinity is a major issue in Australia,and clear understanding is required to guideappropriate investment toward managementof the problem. Understanding catchmentscale processes is crucial towards identifyingmanagement options, although in mostAustralian catchments the existingknowledge-base and data collection is toolimited to provide this.

The combination of physical factors governingdryland salinity varies across Australia. Thediversity in geology, landscape development,the quantities of salt stored in the landscape,and climatic characteristics all contribute.Similarly, the viable options for managingdryland salinity, and the timescale ofgroundwater and salinity responses vary fromregion to region. The variation ofgroundwater-driven dryland salinity, accordingto these first-order factors, has beendescribed for the whole of Australia throughthe National Land and Water Resources Audit(NLWRA) project ‘Australian GroundwaterFlow Systems Influencing Dryland Salinity’(Coram 1998, Coram et al. 2000).

Within the NLWRA four dryland salinity casestudies have been published. Each describesthe conceptual understanding of a specificgroundwater flow system; models the priorand current situation in terms of land use andgroundwater recharge and examinespossible future options for recharge reductionthrough revegetation and groundwaterpumping (Stauffacher et al. 2000, Short et al.2000, Baker et al. 2001, Hekmeijer et al.2001).

Four further catchments have now beenstudied as part of this CatchmentCharacterisation project—the South Loddonplains and Axe Creek in Victoria, andKyeamba Creek and Brymaroo in NSW. The aim of such case studies is to describethe different groundwater flow systems (GFS)identified by Coram (1998) and Coram et al.(2000).

The Kyeamba Creek catchment is locatedsouth-east of the city of Wagga Wagga incentral New South Wales. It lies within an

intermediate-scale fractured rock aquifersystem comprised of the Kyeamba andTarcutta catchments. The major surfacedrainage features, however, are KyeambaCreek and O’Briens Creek, lying on analluvial plain, whose sediments contain aseries of shallow alluvial aquifers. Thisshallow system is readily delineated fromaerial photographs and can be considered asa local scale flow system (Figure 1).

Land salinisation in Kyeamba Creek is verylocalised, with small patches scatteredacross the central and northern areas of thecatchment. Some shallow salinegroundwaters do exist, and in the past havehampered some efforts to establish trees,such as at Turkey Flat. The more seriousenvironmental problem in the catchment,however, is that of variable, and often high,stream salinity. This catchment produces alarge amount of salt per unit area (38.5 tonnes/year/km2—Beale et al. 2000)compared with other catchments in theimmediate area of the mid-Murrumbidgee,which average 18.2 tonnes/year/km2

(12 catchments) and across New SouthWales (14.7 tonnes/year/km2 for 63 third-

1

1. Introduction

Figure 1. Extent of the alluvial system in KyeambaValley, deduced from bore logs and break of slopedeterminations using the model FLAG (courtesy T.Dowling, CSIRO Land and Water). Bores indicated bydots; indicative thickness of alluvials shown bydarkening colours.


2

order catchments evaluated by NSWDLWC—Beale et al., 2000).

Kyeamba Creek catchment is also the focusof stream flow and salinity measurementanalysis (Harvey & Jones, 2003) and surfacewater and salt balance modelling(Tuteja et al. 2002), work carried out by theNSW Department of Land and WaterConservation, and several aspects of thesestudies will be touched upon within this report.

The main aims of this case study report are:

• to describe the physical setting andcondition of the Kyeamba Creekcatchment and aquifer system

• to examine various datainterpretations on the conceptualmodel of flow processes forrecharge and discharge

• model the historical and currenthead trends with FLOWTUBE

• model future tree-planting scenariosfor the aquifer system.


3

2.1 Location and catchmentdescription

Kyeamba Creek is a third-order tributaryfeeding the Murrumbidgee River just to thesouth-east of Wagga Wagga, New SouthWales (Figure 2).

The Kyeamba Creek catchment (Figure 3)covers 602 km2, with the sharp relief of thehills to the south contributing to a total landsurface of 755 km2. The catchment has anaverage (over the last 50 years) rainfall of 650mm/year, exhibiting a south to north gradientfrom 800 mm/year over the granite hills tothe south, decreasing to 600 mm/year at itsconfluence with the Murrumbidgee River tothe north. The main creek is structurallycontrolled, and follows the general northnorth-west (NNW) trend of the underlyingfractured Palaeozoic sediments.

Kyeamba Creek has been characterised, byCoram et al. (2000), as a local flow system infractured rock. The catchment is comprisedof Silurian age granite intrusions, emplacedinto older Ordovician turbidite sediments. Thevalley floor is now covered with extensivealluvial sediments, the variable thickness ofwhich being governed by bedrocktopography. Lineaments observed in airbornemagnetic survey data indicate NE trendingdykes and faults, which are responsible foroffsets in the creek’s general NNW trend. Amajor tributary to the west, O’Briens Creek,follows one of these offset trends.Constrictions in the catchment occur wheresubsurface features cross-cut the creek’sNNW trend. One particularly prominentobstruction is caused by a basement high inthe vicinity of Ladysmith, 10 km from theconfluence with the Murrumbidgee River.

The regional geology shows a ring of granitehills that encompass both the Kyeambacatchment and the easterly adjacent TarcuttaCreek catchment. Topography between thetwo catchments becomes quite subdued tothe north (Figure 4a) and consideration ofpotentiometric contours for groundwaters in the fractured Palaeozoic sediments (J. Kellett, pers. comm. 2001) suggests

a hydrogeologic connection between the twocatchments beneath the alluvial plains (Figure 4b). The fractured bedrock aquifer isprobably more extensive then the surfacecatchment and, thus, is representative of anintermediate flow system in the classificationscheme of Coram et al. (2000).

Kyeamba Creek is therefore regarded as atandem aquifer system comprising a shallow,local flow system that is defined by the valleyfloor alluvial sediments, and an underlyingdeeper intermediate system in fracturedrocks, the extent of which is defined bysurrounding granites.

2. Physical setting

Figure 2. Location of Kyeamba Creek Catchment,NSW.

Figure 3. Locality and topographic map for KyeambaCreek catchment .

Figure 4b. Regional DEM superimposed by the potentiometric surface for the main fractured rock aquifer.


4

Figure 4a. Regional DEM, showing the stream network of Kyeamba Creek.


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2.2 Salinity issues

The New South Wales Department of Landand Water Conservation (DLWC) SalinityAudit (Beale et al. 2000) determined thatKyeamba Creek released the second highestproportion of salt per unit area of thecatchments feeding the Murrumbidgee River(after the much smaller Adelong Creek—48.4 tonnes/year/km2 from 155 km2). Anaverage annual salt-load (1975-1995) of20,400 tonnes flows past Ladysmith, 12 kmfrom the confluence with the MurrumbidgeeRiver (Beale et al. 2000). As a comparison,the slightly larger (758 km2) Billabung Creekcatchment contributes only 6600 tonnes/yearto the Murrumbidgee River. Tarcutta Creek,at two and a half times the area (1660 km2),contributes a similar 26,200 tonnes/year.Kyeamba Creek only contributesapproximately five percent of the salt in theMurrumbidgee River passing Wagga Wagga,but is currently exporting roughly ten timesthe amount of salt being brought in viarainfall.

While land salinisation is not a major problemin the catchment, constituting less than onepercent of the area (Figure 5), catchmentswith similar output/input ratios, such asBoorowa and Yass, are facing major landsalinisation problems. Salinity in the Kyeambacatchment, however, is not directly related tosoil type, and only weakly to slope. Thedominant influence is the structural control ofthe valley by underlying geologic features.Specifically, surface ridges (identified in Figure 6) belie the presence of sub-surfacebarriers to the groundwater movementtowards the Murrumbidgee. Theseimpediments to flow cause pooling ofgroundwater and local rises in water table.

2.3 Salinity in the Context of Catchment SurfaceMorphology

Surface morphology for the catchment hasbeen modelled using the digital elevationmodelling tool FLAG (Fuzzy Logic Applied toGeographical Information Systems) ofRoberts et al. (1997) and Dowling (2000).This model evaluates each location for itsposition in the landscape relative to all otherlocations in the study catchment area.

Figure 5. Mapped surface salinity outbreaks inKyeamba Valley, 1995.

Figure 6. Kyeamba geology and structural controls.

Two main functions are employed:

(i) Each position is interrogated todetermine how much of thesurrounding landscape liesmonotonically above that point(termed UPNESS).

(ii) What is the relative position in thelandscape of any point relative to allthe points around it (LOWNESS)?


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The former is used to determine the potentiala position has as a regional, or catchment,depocentre. That is, if water were to beintroduced uniformly across the landscape(e.g. rainfall), how much would potentiallycross any given point? This gives a goodindication of areas prone to waterlogging.The latter function assesses each point as alocal depocentre. That is, if water were tocross that point, how likely is it that the waterwould stay there, or lose sufficient energy todrop its suspended load? This gives a goodindication of sediment accumulation zones.

FLAG UPNESS analysis for Kyeamba Creekis shown in Figure 7. Stream channels aredepicted and the trajectories of the creeksare outlined. Comparison to othercatchments in the mid-Murrumbidgee region(Figure 8) shows similarities and differencesbetween Kyeamba Creek and othercatchments. Interestingly, the main KyeambaCreek is similar to the majority ofcatchments, including the neighbouringTarcutta Creek, while O’Briens Creek issimilar to Billabung, Muttama and Tumutcatchments, but not the adjoining TarcuttaCreek catchment, or many of the others.

While salinity outbreaks show somecorrespondence to high FLAG index, thisappears to be a second order effect,confirming the primary effect of structuralcontrol on water tables and hence salinity.

Figure 7. FLAG UPNESS index for Kyeamba CreekCatchment scaled between maximum (1) andminimum (0) values for this catchment alone.

Figure 8. FLAG UPNESS index for the Mid-Murrumbidgee region. Scales are normalised to minimum andmaximum values or each entire study region.


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2.4 Rainfall Considerations

Annual rainfall records for Humula (within theadjoining Tarcutta catchment, but close tothe watershed at the southern end ofKyeamba Creek) and Wagga Wagga (as aproxy for the northern end of KyeambaCreek) are shown in Figure 9.

Rainfall records from 1900 to 1950 aresparse, but suggest a lower average monthlyrainfall than for the latter half of this century.From the daily records at Humula, we candeduce that rainfall events have decreased inintensity (from a median of 4.3 to 3.8mm/day), but increased in frequency (from86 to 107 days/year). Average yearly rainfallfor the last 50 years is 20-30% higher thanthat for the first half of the last century. As wehave an incomplete record for these stations,the continuous record from Cootamundra (80 km NE of Kyeamba) has also beenevaluated. Cumulative deviation from themean rainfall is plotted for monthly data inFigure 10, and shows a drying trend prior to1945, followed by a predominantly wettingtrend to 2000. The past 50 years have beenwetter than the previous 50 years (lowercurve in Figure 10—ten year movingaverage), and a distinction between relativelywet and relatively dry periods can be made,highlighted as spikes in the lower curve (1 year moving average) in Figure 10.

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HumulaaveragesWagga Waggaaverages

581 mm/a

791 mm/a

480 mm/a

598 mm/a

Figure 9. Rainfall records for Humula (near theKyeamba source) and Wagga Wagga (near KyeambaCreek’s outlet to the Murrumbidgee) for the past 100 years.

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Figure 10. Rainfall records for Cootamundra (80 kmNE of Kyeamba) for the past 100 years. Upper graphshows cumulative monthly deviation from the mean.Steep slopes indicate dry (down) and wet (up)periods. The lower graph summarises this into yearlyand decadal information (but based on monthlyfigures). Wet periods are denoted by spikes in theannual trace above the 10 year average, while dryperiods are below the line. Overall, the last 50 yearshave been wetter than the previous 50, although thefrequency of flood periods has been similar.

3. Conceptual HydrogeologicalModel

3.1 Surface water

Recently, stream surveys have been carriedout with an aim of discerning the regions ofimportance regarding salt storeremobilisation. Using FLAG analysis to helpprioritise creeks for surveying, streamsalinities and approximate flow rates havebeen collected for a number of rain events. A typical high flow event is illustrated inFigure 11. Salinities throughout (indicated by


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Figure 11. A snap shot of the salinities and relativeflows of the creeks of Kyeamba Catchment after thestorm of 16/8/2000. Streams are coloured based ontheir relative salinities, and are overlaid on anartificially shaded digital elevation model. Note thatsalinities are not exactly contemporaneous, as ECvaries throughout a storm as salt loads and watervolumes vary. Measurements were taken over thecourse of 6 hours following the rain event. Flow ratesare estimates based on the rate of filling of a 9Lbucket, and are scaled to represent to potentialcontribution to the gauging station at Ladysmith.

conductivity values) are low, but the variablesalinities of the tributaries indicate the sub-catchments that hold potential salt stores.Flow rates are generally low. The tributariesto O’Briens Creek, however, have mediumflow and contribute most salt to the mainchannel.

Kyeamba Creek represents a system indisequilibrium. Alternating erosional anddepositional stretches result from changesin flow regime, probably caused byvegetation clearing, heavy grazing anddrainage of reed-swamps mainly during thelate 19th Century, but continuing through tothe present in a similar manner to thatrecorded for Tarcutta (Page & Carden1998). Knowledge of erosion anddepositional environments, which can beindicated by FLAG analysis, helps delimitareas that may now be releasing saltstored in soils into stream channels, andcan indicate which sub-catchments wouldbenefit from revegetation, and those thatwould not.

3.2 Groundwater trends

Mapping in the 1990s revealed a sympathybetween the Kyeamba and Tarcuttagroundwater systems, particularly in thelower reach aquifers. Water tables shallowtowards the Murrumbidgee, then deepenwithin the Murrumbidgee alluvial sediments(J. Kellett, pers. comm. 2001). Pooling ofgroundwater upstream of Ladysmithcorresponds to rising water levels seen in thealluvial aquifers of Tarcutta to the east, in thearea known locally as Corienbob Catchment.Groundwater flow is from the south-east,from the ranges around Tumbarumba, andheads NW towards the Murrumbidgeethrough the Palaeozoic sediments,constrained by the surrounding granites.Groundwater in the fractured rock aquiferscross the surface catchment divide betweenTarcutta and Kyeamba Creeks, while surficialwaters follow the routes outlined by thealluvial sediments.

Prepared by the Wagga Wagga Research Centre, Centre for Natural Resources, Wagga Wagga.

Salt Load

>20 t/day11-20 t/day6-10 t/day4-5 t/day2-3 t/day0- 1 t/dayNo flow

Coolarado CreekFlow: N/A

EC:

Kyeamba Creek@ MonavaleFlow:

EC:

Salt

23 mgl/day920 uS/cm

: Load 13.54 t/day

Kyeamba CreekFlow:

EC:

Salt

23 mgl/day881 uS/cm

: Load 12.9 t/day

Kyeamba CreekFlow: 19.5

EC:

Salt

mgl/day478 uS/cm

: Load 5.96 t/day

Kyeamba CreekFlow:

EC:

Salt

18 mgl/day529 uS/cm

: Load 6..09 t/day

Book Book CreekFlow:

EC:

Salt

0.005 mgl/day478 uS/cm

: Load 0.001 t/day

Kyeamba CreekFlow:

EC:

Salt

20 mgl/day635 uS/cm

: Load 8.128 t/day

Obriens CreekFlow:

EC:

Salt

10 mgl/day1230 uS/cm

: Load 7.8728 t/day

Clares laneFlow:

EC:

Salt


: Load 0.012 t/day

Clares laneFlow:

EC:

Salt


: Load 0.0001 t/day

Spring CreekFlow:

EC:

Salt


: Load 0.015 t/day

Obriens CreekFlow:

EC:

Salt

1.04 mgl/day155.9 uS/cm

: Load 0.1 t/day

Pinnacle CreekFlow:

EC:

Salt


: Load 0.079 t/day

Livingstone CreekFlow:

EC:

Salt


: Load 0.08 t/day

Kyeamba CreekFlow:

EC:

Salt

23 mgl/day875 uS/cm

: Load 12.8 t/day

Wrights Gully CreekFlow: N/A

EC:

Yirrkala CreekN/AFlow:

EC:

TywongN/AFlow:

EC:

Tooles CreekFlow:

EC:

Salt

0.346 mgl/day2.4 mS/cm

: Load 0.53 t/day

Obriens CreekFlow:

EC:

Salt


: Load 5.534 t/day

The WillowsFlow: N/A

EC:

Near GinninderraFlow:N/A

Near TantanoolaFlow:N/A

EC:

Near Hume HwyFlow:

EC:

N/A


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Figure 12. Hydrographs for nested piezometer sites in the Kyeamba Valley and NW Tarcutta.

Most domestic and farm supplies are derivedfrom the unconfined aquifers in the alluvialsediments of the lower reaches. These aquifers,and those sourced in the weathered bedrockhorizon immediately below, provide good quality water, but variable yield. Transmissivityand storativity are quite variable. Whiletransmissivity can be high (>100 m2/day),storativity is generally low (<0.01). In general,the alluvial aquifers have higher hydraulicconductivity (K) (8x10-10 m/day) than theweathered horizons (2x10-10 m/day). Theunweathered fractured bedrock exhibits variableK (2 – 6x10-10m/day), but often very hightransmissivity (>100 m2/day), presumably due to fracture networks. Fractured bedrock is comprised of Ordovician shales and siltstones in the lower reaches, and granitesat higher elevations. Connectivity betweenthe alluvials & fractured rocks is good, with nested

piezometers giving similar heads (Figure 12)despite the differing conductivity andstorativity of the respective aquifers.

Groundwater levels in the alluvials across theKyeamba catchment have remained steady over the last 30 years (Figure 13), in contrastto predictions based on two-point analysis ofgroundwater levels by DLWC, shown inFigure 14—note, however, the lack oftopographic constraint on this model (D. Woolley, written comm. 2001). Variabilityin the standing water levels suggests anassociation with rainfall events, reflecting thelargely unconfined nature of the system andrapid equilibration between different aquifers.

Figure 13. Hydrographs for bores in the Kyeamba catchment (includes two bores from the adjoining Tarcuttacatchment).

-5

0

5

10

15

20

25

30

Jan-70 Jan-75 Jan-80 Jan-85 Jan-90 Jan-95 Jan-00

date

SW

L(m

)

GW025383

GW030032

GW030033

GW030034

GW030286

GW030351

GW030355

GW030385

GW030386Tarcuttta


10

Interestingly, while rainfall records (Figures 9and 10) indicate the 1990s to be wetter thanaverage, the bore records in Kyeambaindicate a generally downward, or drying,trend.

Using water levels recorded at the time,a bore was drilled, compared to the levelmeasured during a bore survey in 1990, wecan determine average rates of rise for borewaters across the region. These show a widerange of rates, from slightly falling to rising atnearly 2 m/year (Figure 15). The fastest ratesof rise appear to be for bores sampling thefractured Palaeozoic aquifers installed since1950, with lowest rates consistently from thealluvial aquifers. It should be apparent fromexamination of rainfall and bore records thatthe time of measurement is a critical factordetermining this rate, particularly for two-point analysis.

By estimating the specific yield—a function ofporosity and connectivity—for the differing rocktypes, and assuming no drainage, or removalof excess water from the system, we canestimate the minimum amount of waterrequired for this rise. Assuming specific yield valuesof one, three and five percent for the fracturedrocks, weathered granite bedrock and alluvialsrespectively, gives a more restricted range upto 20 mm/year, with an average of 7 mm/yearexcess recharge to the system (Figure 16). Acomplex model, CATSALT, developed by

Figures 14a-d. Postulated water levels for KyeambaCreek for the years 2000, 2020, 2050 and 2100 (afterWoolley, 1996).

Figure 15. Rate of water level rise for Kyeamba Creek bores.

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990

year of construction

Alluvials

Silurian granites

Ordovician sediments

av

era

ge

rate

of

wa

ter

lev

el

ris

e(m

/a)

DLWC for water balance in the catchmentgives a figure of 10 mm/year for its equivalent parameter: ‘routed groundwater’(Tuteja et al. 2002) (Figure 17).

3.3 Groundwater salinity

Groundwater salinity varies markedly acrossthe catchment, with variability of up to twoorders of magnitude within a few kilometresin some areas (Figure 18). In general, deeperaquifers are slightly fresher than upper ones,but the connectivity of the system ensuresreasonable vertical mixing throughout. Twozones of higher salinity waters (>1500 mg/LTDS) coincide with deep structuralanomalies, which are expressed as surfacelineations (Figure 6). These occur in bandstrending NE-SW, one through Ladysmith,and a second extending SW from Turkey Flattowards Livingstone. This latter may extendto the NE across Tooles Creek, althoughthere are insufficient bores to be certain. Wesurmise that pooling is occurring upstream ofthese features.

Kyeamba Creek experiences significant waterlevel rise during major storm events.Recharge occurs across the entirecatchment. Discharge of groundwater via

the Murrumbidgee, however, is restricted bythe cross-sectional area of the dischargeconduit and the transmissivity of the aquifers.Since Kyeamba Creek’s discharge zone isconstricted by granite highs, the timerequired to discharge any excess waterreceived from recharge will be longcompared to the period of wateraccumulation and would require extendedperiods of drought to maintain constantaverage water levels.


11

Figure 16. Equivalent increase in water level fordifferent lithology aquifers in Kyeamba Creek.

0

2

4

6

8

10

12

14

16

18

20

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990

year of construction

alluvials

Silurian granites

Ordovician sediments

average excess water

6.6 mm/a

Incre

ase

ine

quiv

ale

ntfr

ee

wa

ter

leve

l(m

m/a

)

Figure 17. Cartoon illustrating the derived water balance for Kyeamba Creek, based on CATSALT modelling (after,Tuteja, et al, 2002).


12

Current annual discharge of water fromKyeamba into the Murrumbidgee is about 55 GL, equivalent to 94 mm of stream flow.This carries the average annual salt load of20,000 tonnes, and relates to roughly tentimes the amount of salt being brought intothe catchment via rainfall. Observed saltloads at Wagga Wagga over the past tenyears have varied from below 200,000 toover 700,000 tonnes per year, largelydependent on stream flow. Reduction of thesalt load in Kyeamba, therefore, can have nomore than a five percent effect on the loadseen at Wagga Wagga.

The last century shows an average of 20 mmexcess rainfall over annual recharge acrossthe region. Salinities across the region aregenerally low, and in higher salinity areas the

use of moderately halophytic plants may besuccessful. A stand of poplars that failed tosurvive at Turkey Flat in the 1980s, forexample, have been successfully replaced bycasuarinas (Woolley 1991).

A related issue is illustrated to the west ofO’Briens Bridge where waterlogging withmoderately saline waters has occurred dueto damming of a natural flow-line to the riverby the road. To the west, on the upstreamside of the road, salinity is evident in poorpasture with salt bush. To the east of theroad, free drainage to the creek haspermitted good pasture to develop.

3.4 Stream Salinity

Stream surveys (Figure 11) delimit regionswhere salt in the landscape is being recycledinto the surface waters. Livingstone Creekfeeding into O’Briens Creek south of Mt.Flakney and Tooles Creek feeding intoKyeamba Creek at Turkey Flat are streamswith known high salinities (>1000 µS/cm EC),as are streams feeding Kyeamba Creek atLadysmith. Lower salinity streams feedingLadysmith from the granite hills to the westare reflecting surface runoff from the granites.

Stream surveys during dry spells delimitregions where baseflow is entering thesurface system. Livingstone Creek feeds intoO’Briens Creek south of Mt. Flakney, andshows a progression of stream salinitiestowards its confluence with the main channel(Figure 19). A prior preferential flow isdelimited by the sudden increase in salinityseen at location 4 in Figure 19b, marking there-emergence of the old Livingstone Creekinto O’Briens Creek.

Harvey and Jones (2003) have analysed30 years of stream flow and salinity datafrom four catchments in the UpperMurrumbidgee, including Kyeamba andTarcutta Creeks. For the available data, time,volume (flow) and surface run-off salinity(electrical conductivity) relationships wereexamined. Specifically, a general relationshipexists of the form:

C = a Q b

where C is the total dissolved concentrationof salts (using EC as proxy), Q is theinstantaneous flow-rate (ML/day), and a and

Figures 18. Postulated water levels for KyeambaCreek for the years 2000, 2020, 2050 and 2100 (afterWoolley, 1996).


13

b are constants (with b<0). This describesthe generally accepted inverse relationshipbetween salinity and flow, which is dueprimarily to dilution as flow increases(Gregory & Whaling 1973). For baseflow, theEC was found to be time dependent forsome sites.

The observed trends adequately discriminatebase (groundwater) flow from stream(overland) flow. Baseflow in Kyeamba seemsto range between 400 and 3000 µ S/cm, andis evident in flows at Ladysmith up to 20ML/day. Beyond these flow rates ECdecreases, though a large number of eventsaround the maximum of 400 ML/day show arange of EC up the maximum observed inthe baseflow. Data is insufficient to determinethe causal relationship between this andextreme rainfall events.

Comparing the more complete record offlows and EC measurements taken fromJugiong Creek to the east, Harvey & Jones(2003) observed a progressive increase in EC for any given flow is observed with time. Thus, for the same instantaneous flow rate measuredthrough the 1970s and1980s, the EC increasesby 1.7% per year.Similar trends are seen in the Tarcutta andMuttama data, and by extrapolation we expect Kyeamba to show the same trend.A 1.2% increase in EC per year for Tarcutta,and 3.1% for Kyeamba up to the 1990s wasobserved. In the early 1990s, this trend for

Jugiong catchment appeared to plateau andmay be decreasing, though data becomemore sparse after 1998, and variance in thedata is less well constrained. There is no datafor Kyeamba for this period as the flowstation was removed from Ladysmithin 1985 and relocated upstream at BookBook. This station was relocated atLadysmith in 1997.

Fitting the data to the power functiondescribed above suggested to Harvey & Jones (2003) that the parameter ‘b’ is similar for all catchments, and probably represents a regionalparameter. The parameter ‘a’, however, variesbetween catchments, and we suggest thatthis represents local variations and is catchmentspecific. Broadly, ‘b’ relates to the slope ofthe EC vs flow data, and may be related toclimatic effects and regional managementresponses. ‘a’ is a measure of the magnitudeof the salinity response and may relate tovariations in catchment geology,geomorphology and local land use practices.

Figure 19. Baseflow measurements along tributaries of O’Briens Creek.a) Survey sites are superimposed over a DEM for the region. b) EC , salt load and flow for the sites along the 9 km survey stretch (figure from Summerell, 2001).

2000

1600

1200

800

400

0

EC

(µS

/cm

)

Sites

Sa

ltlo

ad

(t/d

)o

rF

low

(ML/d

)

2.5

2.0

1.5

1.0

0.5

0.01 2 3 4 5 6 7 8 9

EC (µ S/cm)Salt load (t/d)Flow (ML/d)

1 23

45

67

8

9

OBriens Creek

Liv

ingsto

ne

Creek


14

4.1 Numerical model

FLOWTUBE (Dawes et al. 1997, 2000, 2001)is a simple numerical one-dimensionalgroundwater flow model. It is a mass-balance model that solves for a change inhydraulic head induced by recharge anddischarge fluxes, and lateral transfers in thedirection of flow. The results of FLOWTUBEare considered to be a hydraulic headtransect along an aquifer.

The model considers a one or two layersystem. In the case of a single layer theaquifer is assumed to be unconfined andhaving variable transmissivity dependent onthe saturated thickness of aquifer. In the caseof a two-layer system, the lower layer isassumed to contain any lateral transmissionof water while the upper layer contributesstorage capacity only. In this case the lowerlayer is usually confined or semi-confined,and how this is conceptualised controls thesimulated mechanism for groundwaterdischarge.

4.2 Special considerations

FLOWTUBE is ideally suited to homogenousuniform isotropic media, such as sand andgravel aquifers, and massive clay depositswithout preferred pathways or barriers. In theKyeamba Creek system there are both analluvial aquifer consisting of porous sands andsilts intercalated with silty clays, and a deeperfractured rock aquifer that controls the deeperflow directions. For the alluvial system it isexpected that FLOWTUBE will be veryappropriate and well suited to simulation. Inthe deeper fractured rock aquifer there arecaveats that need to be placed on parametersand conclusions. Unlike some environments,such as Axe Creek in Victoria (Hekmeijer &Dawes 2003), in Kyeamba Creek thedominant fracture direction and hydraulicgradients are coincident. In this case there isconfidence that using estimated properties ofthe fractured media will be representative in aDarcian framework.

The two main aquifer parameters inFLOWTUBE are hydraulic conductivity andspecific yield, both of which are often difficultto measure or estimate directly in fracturedrock environments (Freeze & Cherry 1979,Lapsevic et al. 1999, Love & Cook 1999).Measurements have been taken in KyeambaCreek by the use of pump tests, but theparameters ultimately remain fitted valuesthat are representative of the Darcian flowmodel at the scale of the FLOWTUBEsegments. Freeze and Cherry (1979) suggestthat in fractured rock environments simplyincreasing the size of computational cellsallows the common solution methods to beapplied to groundwater flow.

The two different aquifers were modelled instages. First, data from the more limitednumber of bores in the fractured rockaquifers were combined with the morecomprehensive data from the alluvialunconfined aquifers to give compositehydraulic properties for the system as awhole (the intermediate system). Second thealluvials were treated as a single aquifer (localsystem). The former was modelled at acoarse scale with five kilometre cells, whilethe alluvial model used finer two kilometrecells. This reflected the greater confidence inthe parameters available for the alluvialaquifers based on existing bore data. Thealluvials included the basal leads where thesewere the dominant aquifers, regardless ofwhether this included the upper weatheredzone or not. The distribution of modelledzones is shown in Figures 20 and 21.

Input parameters for the two scenarios arelisted in Table 1a and b, and illustrated inFigures 22 and 23.

4. Groundwater modelling using FLOWTUBE


15

Figure 20. Modelled cell distribution for the fractured-rock aquifer scenario.

Figure 21. Modelled cell distribution for the alluvialaquifer scenario.

TABLE 1a. Input parameters for Scenario 1

GW Surf Width Thick Base Cond Length Por Idc

311 320 10,000 60 260 15 5000 0.01 2

292 300 11,500 60 240 15 5000 0.01 3

273 280 13,000 65 215 20 5000 0.02 4

254 260 11,500 70 190 25 5000 0.03 5

235 240 10,000 70 170 30 5000 0.04 9

271 280 23,000 60 220 20 5000 0.02 7

238 243 14,500 65 178 25 5000 0.03 8

220 222 7000 70 152 30 5000 0.04 9

210 211 10,000 80 131 35 5000 0.05 10

202 205 7000 80 125 40 5000 0.05 11

195 199 4500 80 119 45 5000 0.05 12

187 191 3000 80 111 50 5000 0.05 -1

GW:Initial groundwater elevation (m); Surf: Ground surface elevation(m); Width: Aquifer width (m);Thick: Aquifer thickness (m); Base: Aquifer basement elevation (m); Cond: Hydraulic Conductivity (m/yr);Length: Length of segment (m); Por: Porosity; Idc: the segment immediately downstream (-1=end of tube)

Flowtube groundwater model input parameters. Each row is a segment along the flowtube.


16

TABLE 1b. Input parameters for Scenario 2

GW Surf Width Thick Base Cond Length Por Idc

420 440 500 20 420 10 2000 0.01 2

404 424 750 20 404 10 2000 0.01 3

380 400 1100 20 380 10 2000 0.01 4

350 370 1650 20 350 10 2000 0.01 5

323 325 3450 20 305 10 2000 0.01 6

298 300 3100 20 280 10 2000 0.01 7

269 273 2000 20 253 10 2000 0.02 8

263 270 3450 20 250 10 2000 0.03 9

261 263 2550 20 243 10 2000 0.04 10

253 255 2200 20 235 10 2000 0.05 11

231 237 1300 20 217 10 2000 0.06 12

223 236 1300 20 216 20 2000 0.07 13

220 234 1600 20 214 20 2000 0.08 14

217 221 1100 20 201 20 2000 0.09 15

209 215 1450 20 195 20 2000 0.1 26

310 330 500 20 310 10 2000 0.01 17

290 310 2000 20 290 10 2000 0.02 18

281 301 2000 20 281 10 2000 0.03 19

265 270 4750 20 250 10 2000 0.04 20

255 260 6400 20 240 10 2000 0.05 21

245 250 6200 20 230 10 2000 0.06 22

231 240 2200 20 220 10 2000 0.07 23

225 235 2750 20 215 10 2000 0.08 24

216 226 2550 20 206 10 2000 0.09 25

209 218 3300 30 188 20 2000 0.1 26

203 212 2400 30 182 20 2000 0.1 27

202 208 1100 35 173 20 2000 0.1 28

201 206 1300 40 166 20 2000 0.1 29

200 205 1100 45 160 20 2000 0.1 30

198 202 1100 50 152 20 2000 0.1 31

188 198 1100 55 143 20 2000 0.1 32

187 194 1300 60 134 20 2000 0.1 33

183 190 3650 70 120 20 2000 0.1 34

171 179 1000 80 99 20 2000 0.1 -1

GW:Initial groundwater elevation (m); Surf: Ground surface elevation(m); Width: Aquifer width (m);Thick: Aquifer thickness (m); Base: Aquifer basement elevation (m); Cond: Hydraulic Conductivity (m/yr);Length: Length of segment (m); Por: Porosity; Idc: the segment immediately downstream (-1=end of tube)

Flowtube groundwater model input parameters. Each row is a segment along the flowtube.


17

Figure 22. Parameters used for modelling the combined aquifer system.

100

150

200

250

300

350

400

0 10 20 30 40 50 60

Relative distance along creeks (km)

ground surfacegroundwater surfacebase of aquifer

Kyeamba Creek

O’Briens Creek

Ele

va

tio

n(m

AH

D)

0

0.5

1

1.5

2

2.5

0 10 20 30 40 50 60 70 80

0

10

20

30

40

50

60

70

volume of aquifer

conductivity (m/s)

porosity (%)


Kyeamba Creek

O’Briens Creek

Volu

me

(km

)3

Hyd

raulic

co

nductivity

or

Poro

sity

0

2000

4000

6000

8000

10000

12000

14000

16000

0 10 20 30 40 50 60 70 80

wid

th

Kyeamba Creek

0

1000

2000

3000

4000

5000

6000

7000

8000

9000


Width of outcrop (m)Thickness of aquifer (cm)

Thic

kness

O’Briens Creek

Figure 23. Parameters used for modelling the alluvial aquifer system only.

100

150

200

250

300

350

400

450

0 10 20 30 40 50 60

O'Briens Creek

Kyeamba Creek

0

1000

2000

3000

4000

5000

6000

7000

0 10 20 30 40 50 60 70 80

0

1000

2000

3000

4000

5000

6000

7000

8000

9000width of outcrop (m)thickness (cm)

O'Briens Creek

Kyeamba Creek

0

0.1

0.2

0.3

0.4

0.5

0.6

0 10 20 30 40 50 60 70 80

0

10

20

30

40

50

60

70

volume of aquifer (km )3

conductivity (m/s)

porosity (%)

O'Briens Creek Kyeamba Creek




Vo

lum

e(k

m)

3

Hyd

rau

licco

nd

uctivity

or

Po

rosity

Wid

th

Th

ickn

ess

Ele

vatio

n(m

AH

D)

ground surfacegroundwater surfacetop of aquiferbase of aquifer

O’Briens Creek offset for clarity


18


19

4.3 Composite aquifer model

The coarse-scale model was dominated bythe parameters of the fractured bedrock inthe upper regions and by the deep alluvialsdownstream. Aquifer thickness and porosityincreased towards the Murrumbidgee. Thismodel reasonably recreates the observed,present-day, groundwater surface along themain Kyeamba Creek. It does not, however,indicate the high groundwater levels seenalong the main western tributary, O’BriensCreek. Figures 24a and 24b show thesimulated groundwater heads in thecomposite aquifer.

A pre-clearing recharge rate of 1 mm/yearwas assumed for the native condition, whilea uniform post-clearing recharge rate of 20mm/year was applied in this simulation. It issuggested by Tuteja (pers. comm. 2002) thatthe current recharge is distributed with rainfalland soil type, at rates between 15 and 40mm/year. The resulting catchment averagerate is slightly higher than that used here.

Many of the heads prior to widespreadclearing are shown near the base of theaquifer, indicating that elevated water tableswere not present under native vegetation. Inthe simulations, significant filling is generatedpost clearing, and particularly occurs in thevicinity of the confluence of O’Briens andKyeamba Creek, and in the narrow neckbetween that confluence and theMurrumbidgee River.

In general, FLOWTUBE delimits theconfluences of the major tributaries asregions of elevated water tables. Theseregions also correspond to thinning aquifersover basement highs, and thicker sequencesof alluvial material immediately upstream. The

Kyeamba system and Murrumbidgee systemcan be approximately separated just north ofLadysmith, coincident with the majorstructural feature mentioned earlier.

4.4 Alluvial aquifer model

Using the parameters in Table 1b, Figure 25shows the simulated results of adding aconstant 20 mm/year recharge for 100 years.The right-hand slope is the main part ofKyeamba Creek above the confluence withO’Briens Creek. The slope between 16 and36km is the arm of O’Briens Creek itself. The black and red lines show present-daysurfaces; the green represents 100 years of 1mm/year recharge; the blue line is for 20mm/year added to the aquifer for a further100 years. These values represent extremesin recharge for the catchment, and giveupper and lower bounds to the ultimate stateof the water table. Plotted in a brown dashedline is the aquifer capacity, the amount ofwater the aquifer can carry, with theparameters as given. This clearly shows whywe have such a variable pattern ofgroundwater heads—the thickness varies byan order of magnitude between nodes, andis up to 49 m thick in places. This sawtooth

Figure 24. Simulated groundwater heads within the composite Kyeamba Creek system, for (a) O’Briens and lowerKyeamba Creek, and (b) upper Kyeamba Creek, with pre-clearing recharge of 1 mm/year, and post-clearing of 20 mm/year.

150

200

250

300

350

0 5 10 15 20 25 30

Distance (km)

SurfaceYear 1900Year 2000

O'Briens + lower Kyeamba Creek

Ele

va

tio

n(m

,A

HD

)

Ele

vatio

n(m

,A

HD

)

150

200

250

300

350

30 35 40 45 50 55 60Distance (km)

upper Kyeamba Creek

SurfaceYear 1900Year 2000

Figure 25. Results from FLOWTUBE for the alluvialmodel.

150

200

250

300

350

400

450

0 10 20 30 40 50 60 70

Distance (km)

Ele

vati

on

(mA

HD

)

0

5000

10000

15000

20000

25000

30000

Aq

uife

rC

ap

acity

(m3/d

ay)

Surface

Initial

100yr @ 1mm

100yr @ 20mm

Aq. Capacity


20

is partly a relic of sporadic bore informationon a system with complex interconnectivityand we suspect that the actual stream mightgive a more monotonically decreasing trend,not a saw-tooth.

The alluvial model gives a poor description ofpresent-day levels along the main creek, buthighlights areas along O’Briens Creek thatcorrespond to present-day near-surfacelevels. This result is important both forunderstanding the catchment and theprocesses within it that drive drylandsalinisation. If only one of the two modeldescriptions adequately showed all mappedareas of high water levels, then the otherwould be redundant. But since both modelshave features the other does not show, thishas important implications for remediation.

4.4.1 Alternative alluvial models

Noting that deficiencies in bore informationmay mean that the modelled profile may notaccurately reflect the true profile, with boresrarely sited along a flow path, not wellspread, not well spaced, nor representativeof the entire alluvial body, we can postulate amore smoothly varying profiles using somebasic principles of hydrogeology. We canmodify parameters such that we achieve amonotonic increase in those parameters thatwe might expect to increase downstream, orwe can take the postulated groundwatergradient and fit appropriate parameters to fitthat gradient. Specifically, in the former casewe assume an increase in hydraulicconductivity, aquifer thickness and porosityas we move towards the confluence with theMurrumbidgee. In the latter case,transmissivity is varied to conform with themodelled groundwater gradient towards themouth of the creek.

4.4.1.i Monotonically-increasing conductivity,thickness and porosity downstream

The conductivity, thickness and porosity aremodified so that they all increase as wemove downstream along the FLOWTUBE.This reflects a general coarsening of depositstowards the mouth of the main creek. Themajor factor in capacity is now the width andslope of the FLOWTUBE, but for the scenariodepicted in the following graph (Figure 26)the slope component has been removed.

4.4.1.ii Use the current groundwatergradients to model transmissivity

The next modelling approach is to fittransmissivity to apparent currentgroundwater gradients and see what evolves;this will produce an independent assessmentof porosity. The most obvious features occurwhere we require very large conductivityvalues to maintain drainage through theaquifer. Those areas are likely to be whereshallow water levels are and where futuredischarge will occur. From this, we canmodel heads using fitted transmissivity, asillustrated in Figures 27a and 27b.

Groundwater levels reach the surface: at theconfluence of the main creeks; upslope in

Figure 26. Results from FLOWTUBE for the‘smoothed’ alluvial model.

150

200

250

300

350

400

450

0 10 20 30 40 50 60 70

Distance (km)

Ele

va

tio

n(m

AH

D)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Aq

uife

rC

ap

ac

ity(1

06

m3/d

ay

)

Surface

Initial

100yr @ 1mm

100yr @ 20mm

Aq. Capacity

Figure 27. Modelled heads for (a) O’Briens Creek and (b) Kyeamba Creek.

150

200

250

300

350

400

450

0 6 12 18 24 30 36

Distance (km)

Ele

vati

on

(mA

HD

)

Surface

Current

100yr @ 1mm

100yr @ 20mm

Confluence of

O'Briens + Kyeamba

Confluence of

O'Briens + Pilliga

150

200

250

300

350

400

450

36 42 48 54 60 66 72

Distance (km)

Ele

vat

on

(mA

HD

)

Surface

Current

100yr @ 1mm

100yr @ 20mm

Turkey Flat


21

O’Briens Creek where several streams cometogether; up-gradient in Kyeamba Creek atTurkey Flat; and further up where ToolesCreek enters from the east. Because of thereverse engineering, modelled and ‘current’heads now match more closely, and weappear to be pin-pointing the major areas ofshallow water tables. Some of the fittedhydraulic conductivity values, however, maynot be physically realistic for the aquifermaterial.

4.5 FLOWTUBE modellingsummary

The coarse-scale model was dominated bythe parameters of the fractured bedrock inthe upper regions and by the deep alluvialsdownstream. Aquifer thickness and porosityincreased towards the Murrumbidgee. Thismodel reasonably recreates the observed,present-day, groundwater surface along themain Kyeamba Creek (Figure 24a and 24b).It does not, however, indicate the highgroundwater levels seen along the maintributary, O’Briens Creek. The alluvial modelgives a poorer description of present daylevels along the main creek, but highlightsareas along O’Briens Creek that correspondto present day near-surface levels (Figure 25). It should be emphasised thatFLOWTUBE models groundwater movement

through an artificial construct, and does notexplicitly describe salt movement.

In general, FLOWTUBE delimits theconfluences of the major tributaries asregions of elevated water tables (Figures 28aand 28b). These regions also correspond tothinning aquifers over basement highs, andthicker sequences of alluvial materialoccurring immediately upstream. TheKyeamba system and Murrumbidgee systemcan be approximately separated just north ofLadysmith, coincident with the majorstructural feature mentioned above.

4.6 Future tree planting

In the late 1990s, regional reafforestation was considered as an option for salinity mitigation.To investigate this, we examined a tree planting scenario, and its impact on recharge & dischargewithin the Kyeamba Creek catchment. A land capability analysis of Kyeamba Creek has indicated lonly small areas in the highest rainfall parts of the catchment are most suitable for commercial ...

Figures 28. Modelled regions of elevated water table according to FLOWTUBE for (a) the fractured-rock, and (b)alluvial aquifer scenarios. Red areas are within 1m of the surface, and yellow areas are within 2 m.


22

tree planting, while the bulk of the catchmentis economically marginal for both soft andhard woods. Figures 29a and 29b show theresult of GIS analysis of land capability forcommercial planting (NSW Forests & NSWDLWC 2001), with ratings from 1 (mostfavourable) to 6 (no return), for softwood andhardwood, respectively. Kyeamba Creek isslightly more suitable for softwoodplantations, which have enhancedproductivity in higher rainfall areas found inthe southern parts of the catchment.

A FLOWTUBE simulation was run with acomposite alluvial and fractured rock aquiferset-up, and distributed annual rechargeranging from 40 mm in the south to 20 mmin the north. Aquifer parameters are given inTable 2. For simplicity, a recharge reductionzone (e.g. produced by introduction of aswathe of trees) was introduced across thecentral 13% of the catchment. This roughly

corresponds to the area of Class 3 softwoodin the O’Briens Creek area and extendslaterally to the topographic catchment divideon both the eastern and western sides. Thetree belt was assumed to reduce rechargefrom the current rate to zero in a five-yearstart-up period, then was allowed to remainat zero for a further 15 years of simulation.

The time course of head changes is notshown for the starting period up until thepresent, but only for the next 20 years, andonly in the O’Briens Creek section (Figure 30). Heads in this arm of thecatchment responded favourably to therecharge reduction, for both the five-yearrecharge reduction section and the 15 yearsof simulation thereafter. The effect is still quitelocalised however, with no effect on headsfurther downstream than 25 km from thecatchment outlet.

Figure 29. Land capability mapping of suitability for plantation of (a) softwood and (b) hardwood, where Class 1 ismost suitable for commercial returns, and 6 is not suitable for forestry. No area of Class 1 was mapped; it wasassumed that these areas would already be forested.


23

TABLE 2. Input parameters for combined fractured and alluvial aquifers in O’Briens and Kyeamba creeks

O'Briens Creek section

GW Surf Width THK Base K Length Por Idc

270 284.77 2900 20 264 5 1000 0.02 2

250 263.98 7050 20 243 5 2000 0.02 3

239 252.97 10800 20 232 5 2000 0.03 4

234 238.98 8750 20 218 5 2000 0.03 5

229 231.73 5750 20 211 5 2000 0.04 6

224 226.54 4650 20 206 5 2000 0.04 19

Kyeamba Creek section

350 395.17 5500 50 335 3 2000 0.01 8

325 353.87 9500 50 293 3 2000 0.01 9

300 316.55 10500 55 256 3 2000 0.01 10

280 296.20 11250 55 236 2.5 2000 0.02 11

265 280.85 12000 60 220 2.5 2000 0.02 12

256 268.53 12700 60 208 2 2000 0.02 13

251 260.25 12000 65 195 2 2000 0.03 14

246 251.68 11300 65 186 2 2000 0.03 15

241 245.01 10600 65 180 2 2000 0.03 16

235 237.76 9900 70 167 2 2000 0.04 17

228 230.89 9200 70 160 2.5 2000 0.04 18

222 224.01 8400 70 154 2.5 2000 0.04 19

217 219.34 12400 75 144 2 2000 0.05 20

joint section to Murrumbidgee

212 214.05 11,000 75 139 5 2000 0.05 21

208 210.15 10,300 75 135 5 2000 0.05 22

203 205.88 9600 80 125 5 2000 0.05 23

198 201.00 8950 80 121 5 2000 0.05 24

193 199.09 8250 80 119 5 2000 0.05 25

188 194.16 7550 80 114 5 2000 0.05 26

184 189.66 6900 80 109 5 2000 0.05 27

180 182.81 6200 80 102 5 2000 0.05 28

177 179.98 5500 80 99 5 1000 0.05 29

175 177.71 5150 80 97 5 -1 0.05 -1


24

A localisation of effectiveness was also foundin the main Kyeamba Creek arm of thesimulation. In this area there was nodifference in head distribution in thedischarge areas, but a lesser amount ofdischarge occurred due to zero rechargeassumed under this zone. In the upper partsof the recharge area heads did drop by asmuch as one centimetre per year, but thiseffect is unlikely to continue into the future,and produce the desired level of water levelcontrol expected of such a large area ofafforestation.

It has been common practice to simulate ageneral reduction in recharge of 50% and90% in similar work for the NLWRA (Short etal. 2000, Stauffacher et al. 2000, Baker et al.2001, Hekmeijer et al. 2001). The formerreduction is assumed to be possible usingonly changes to cropping and grazingpractice, while the latter usually requiresextensive land use change to trees anddeep-rooted perennial plants. The capacity ofthe aquifer towards the Murrumbidgee Rivervaries between 2.2 and 5.5 mm/year overthe range of aquifer parameterisations usedin this report. This represents a total variationof only a factor of 2.5, which is probablycommensurate with the level of confidence inthe individual values that generate this result,i.e. aquifer width, thickness, conductivity andhydraulic gradient. In terms of the rechargeestimated across the catchment, this is afactor of between four and 20 less than whatis entering the system. This has seriousimplication for broad-scale rechargereduction strategies.

The simulation with vegetation belts and areduction to zero recharge over 13% of the

catchment (see Figure 30) demonstratedthat very localised management is required.Recharge must locally be reduced to a levelsuch that the bottlenecks created by thebedrock topography can still transmit all thegroundwater. The major problem with thealluvial system, from a managementperspective, is that upstream of aconstriction the amount of discharge isapproximately equal to the amount ofrecharge. A 50% recharge reduction, that isassumed to be possible from bettermanagement alone, is unlikely to changethe location of the current discharge areas,but will reduce the volume of discharge withfeedbacks to the stream salt load into thefuture. The local nature of the flow promisesto show changes in water levels in theshort-term, e.g. less than 20 years. Greaterrecharge reductions will require massiveland use changes with serious socio-economic implications.

4.7 CATSALT modelling

The CATSALT model has been developedwithin the NSW DLWC (Tuteja et al. 2002).CATSALT simulates water flow and streamsalinities for medium sized catchments from500 to 2000 km2 under current conditions.Its three main components are:

• rainfall-runoff water balance model

• salt mobilisation and wash-offcomponent

• Fourier Transform estimator for in-stream salt exported at the catchmentoutlet.

The water balance component is a lumpedconceptual model for which there are nineparameters (five for water balance, and four forrouting) that are fitted to a time series ofobserved stream flow data with acorresponding sequence of daily rainfall andevaporation. The five water balanceparameters relate to a crop factor, a run-offcoefficient, the infiltration capacity, the soilmoisture storage in root zone and anevaporation function. Since these parametersrelate to physical factors, it is feasible toestimate how these parameters, once fitted,may change under certain conditions. Forexample, whole catchment rainfall run-offrelationships (for details, see Zhang et al. 2001)

Figure 30. Modelled heads in O’Briens Creekfollowing the establishment of plantation trees overfive years, then an additional 15 years of zerorecharge in their immediate vicinity.

150

200

250

300

350

0 5 10 15 20 25 30

Distance (km)

Ele

vati

on

(mA

HD

)

Surface

Year 2000

Trees Established,2005Year 2020


25

between forest cover and long-term water yieldcan be used to help recalibrate runoffparameters for an afforestation scenario. Thefour routing parameters simulate a streamresponse for the groundwater and shallow flowcomponents to a rainfall event.

The salt balance is achieved throughcalibration with stream salinity data andprocess modelling. Three parameters arefitted. The first is the fraction of base flowthat is groundwater, i.e. ratio of base flow togroundwater salinity. The other twoparameters control an adsorption isothermrelating soil salt storage and salinity of run-off. Effectively, the salinity of the shallow flow(quick flow) processes is calibrated to thestream data. This is not an unreasonableassumption for larger flow events if the saltdischarge is almost linear with respect tostream discharge, as occurs in many of thestreams. The adsorption isotherm thenallows the aggregation of salt loads fromvarious parts of the catchment according totheir soil salt content. Those areas withhigher salt content produce higher salinityflows and contribute a higher fraction of thesalinity at the catchment outlet.

Whilst most gauging stations have goodrecords of flow, the same is not necessarilytrue for stream salinity. Frequently, grabsamples are taken every two to six weeks.To obtain estimates of salt balances,interpolation is required between thesesampling times. Such interpolation requirescorrelation with flow and time from the lastlarge event. The Fourier Transform stochasticmodel used in CATSALT is a relativelysystematic and objective method for doingthis, and can provide error estimates.

Daily stream flow was recorded in KyeambaCreek at a gauging station at Ladysmith from1975 to 1987, after which the gaugingstation was moved upstream to Book Book.Discrete electrical conductivity samples atLadysmith were available from 1993 to 1997,with a total of 117 samples. The modelcalibration suggested that processes relatingto evapotranspiration, soil moisture storageand saturation excess run-off in response toclimate variability are the most importantfactors in determining run-off. This led to thefollowing estimates for the water balance ofKyeamba Creek (see also Figure 17):

• average annual rainfall 683 mm

• routed groundwater run-off 10 mm

• surface run-off comprising saturatedthrough flow and saturation excess run-off with no infiltration run-off 84 mm

• actual evapotranspiration 600 mm.

Some detailed water balance studies at thenearby Wagga Wagga research station werecompared with the SMAR modelling results.The water balance model HYDRUS-2D wasused to interpret the very detailed fieldmeasurements. This suggested that of the 84mm run-off, 27 to 37 mm occurs throughsaturated throughflow and 47 to 57 mmthrough shallow subsurface flow. From thesalt balance analysis, the fraction of baseflowthat was directly sourced from groundwateris around seven percent. For comparison, theratio of salt load in the stream flow relative tothat entering in rainfall is approximately 9:1.

5. Discussion and conclusions

The Kyeamba Creek catchment covers anarea of 602 km2 in central New South Wales,south of the city of Wagga Wagga. Salinity inthe catchment is expressed as a scatteringof local areas of surface soil salinity, localisedshallow and saline groundwater tables, and ahigh stream salt load relative to thecatchment area. This behaviour is consistentwith the expectations of Coram et al. (2000)for this type of catchment.

Areas of shallow water levels extrapolatedfrom two-point bore water level rises suggestthat approximately two-thirds of thecatchment could suffer from shallow waterlevels by the Year 2100. Bore hydrographsand groundwater modelling, however,indicate that water levels have remained highand stable for up to 25 years, and that adynamic equilibrium may exist. Salt load datafor Kyeamba Creek and other catchments inthe region indicate that stream EC appearsto have stabilised.

Harvey and Jones (pers. comm. 2001) havedescribed the collection and analysis ofstream electrical conductivity in fourcatchments within the mid-Murrumbidgee,including Kyeamba Creek. The data availableat Kyeamba Creek was much less than forthe other catchments studied, but allcatchments show similar behaviour. Animportant trend evident form the data is thatthe EC of the streams peaked in the earlynineties and now appears to have stabilised.In combination with the bore hydrographevidence and responsiveness of FLOWTUBEsimulations, we might infer that catchmentwater levels are in a dynamic equilibrium, andthe stream flow and salt load trends arefollowing a longer-term climatic signal. Sucha situation implies that the application of theCATSALT model to current data shouldprovide a robust estimate of the catchmentprocesses and bulk water balance terms.

Using three different interpretations of theavailable bore lithology and soils mappingdata, the aquifers within Kyeamba Creekhave been identified and modelled using theFLOWTUBE groundwater model. The results

have consistently indicated the dominance inthe surface system of an alluvial aquiferwithin the main creek channels as thedelivery mechanism for salt to the stream.Local regions are defined by variable depthto the bedrock topography, and each mustbe managed on a case-by-case basis. Thedeeper and more extensive fractured rockaquifer still shows high hydraulic headsacross large areas and can deliver stored saltto the surface alluvial zone.

Simulations of past and present head trendssupport the bore hydrograph data, and theconcept of a catchment in dynamicequilibrium. Future tree-planting scenarios,based on current plans for plantation forestry,show a quick response of the KyeambaCreek water levels, and reinforce thelocalised nature of near-surface flows andthus the management implications.Successful plantings of trees and perennialswithin the catchment to date encouragemore widespread use of this strategy.


26

6. Future directions

Further monitoring of the Kyeamba Creekcatchment is required. A permanent streamflow and conductivity recording station in thenorthern part of the catchment aroundLadysmith would help in further constrainingthe response of this high salt yieldingcatchment. In light of the anticipated treeplanting in the central to upper catchment,such data collection would add greatly to ourunderstanding of this catchment. Periodicmonitoring of individual local flow cells withsaline outbreaks would also assist fine-tuningmanagement of these areas. Continuingimprovements to modelling, remote sensingand GIS technologies promise to yielddeeper understandings of catchments suchas Kyeamba Creek. Application of the currentsuite of models and techniques to othermonitored catchments within the mid-Murrumbidgee would also help tie togetherour overall understanding of this region.

Monitoring of water levels in the north of thecatchment is also important, with thegroundwater pumping at Gumly Gumly likelyto have a local influence. Possible workthrough manipulation of pumping times andvolumes would allow an accuratecharacterisation of aquifer properties, andbetter describe the influence of the pumpingscheme. Future management of shallowwater levels through pumping would benefitfrom such a study.

Consistent and reliable data within KyeambaCreek has only been collected for the last 25years, a period that appears to be under aquasi-equilibrium flow regime. As such thisdata is most useful in modelling andanalysing the current state, rather thanproviding insight into historical or futuretrends. With the planned introduction of amajor plantation forestry project, thisprovides an excellent opportunity to observechanges in both surface and groundwaterflows within a realistic time frame, in acatchment with a good baseline set of data.


27

References

Baker, P, Please, P, Coram, J, Dawes, W, Bond, W, Stauffacher, M, Gilfedder, M, Probert, M, Huth, N, Gaydon, D,Keating, B, Moore, A, Simpson, R, Salmon, L & Stefanski, A 2001, Assessment of salinity managementoptions for Upper Billabong Creek catchment, NSW: Groundwater and farming systems water balancemodelling. National Land and Water Resources Audit, Canberra.

Beale, GTH, Beecham, R, Harris, K, O’Neill, D, Schroo, H, Tuteja, NK & Williams, RM 2000, Salinity prediction forNSW rivers in the Murray-Darling Basin. Centre for Natural Resources Report 99.048, NSW Department ofLand and Water Conservation, Wagga Wagga.

Chen, XY & McKane, DJ 1996, Soil Landscapes of the Wagga Wagga, 1:100,000 Sheet. NSW Department of Landand Water Conservation, Wagga Wagga.

Coram, JE (ed.) 1998, National Classification of Catchments for land and river salinity control. RIRDC PublicationNo. 98/78, Rural Industries Research and Development Corporation, Canberra.

Coram, JE, Dyson, PR, Houlder, PA & Evans, WR 2000, Australian groundwater flow systems contributing todryland salinity. Report by Bureau of Rural Science for the Dryland Salinity Theme of the National Land andWater Resources Audit, Canberra (CD contains report, maps, and spatial data).

Dawes, WR, Stauffacher, M & Walker, GR 2000, Calibration and modelling of groundwater processes in theLiverpool Plains. Technical Report 5/00, CSIRO Land and Water, Canberra, 41p.

Dawes, WR, Walker, GR & Stauffacher, M 1997, Model building: Process and practicality. In Proceedings ofMODSIM 97 Volume 1, 8-11 December 1997, Hobart, A McDonald & M McAleer (eds.). Modelling andSimulation Society of Australia and New Zealand, Canberra, pp.317-322.

Dawes, WR, Walker, GR & Stauffacher, M 2001, Practical modelling for management in data-limited catchments.Mathematical and Computer Modelling, 33, 625-633.

Hekmeijer, P, Dawes, W, Bond, W, Gilfedder, M, Stauffacher, M, Probert, M, Huth, N, Gaydon, D, Keating, B, Moore,A, Simpson, R, Salmon, L & Stefanski, A 2001, Assessment of salinity management options forKamarooka, Victoria: Groundwater and crop water balance modelling. National Land and Water ResourcesAudit, Canberra.

Hekmeijer, P & Dawes, WR 2003, Assessment of Salinity Management Options for Axe Creek, Victoria: DataAnalysis and Groundwater Modelling. CSIRO Land and Water Technical Report 22/03, Murray-Darling BasinCommission Publication 08/03, Canberra.

Lapsevic, PA, Novakowski, KS & Sudicky, EA 1999, Groundwater flow and solute transport in fractured media. InThe Handbook of Groundwater Engineering. JW Delleur (ed.), CRC Press, New York.

Love, A & Cook, PG 1999, The importance of fractured rock aquifers. PIRSA Report Book 99/23, Primary Industriesand Resources SA, Adelaide, 12p.

Page, KJ & Carden, YR 1998, Channel adjustment following the crossing of a threshold: Tarcutta Creek,Southeastern Australia. Australian Geographical Studies, 36, 289-311.

Short, R, Salama, RB, Pollock, D, Hatton, TJ, Bond, W, Paydar, Z, Cresswell, H, Gilfedder, M, Moore, A, SimpsonR, Stefanski, A, Probert, M, Huth, N, Keating, B, Coram, J & Please, P 2000, Assessment of salinitymanagement options for Lake Warden Catchments, Esperance, WA: Groundwater and crop water balancemodelling. Technical Report 20/00, CSIRO Land and Water, Canberra.

Stauffacher, M, Bond, W, Bradford, A, Coram, J, Cresswell, H, Dawes, W, Gilfedder, M, Huth, N, Keating, B, Moore,A, Paydar, Z, Probert, M, Simpson, R, Stefanski, A & Walker, G 2000, Assessment of salinity managementoptions for Wanilla, Eyre Peninsula: Groundwater and crop water balance modelling. Technical Report01/00, CSIRO Land and Water, Canberra.

Summerell, GK 2001, Exploring mechanisms of salt delivery to stream within the Kyeamba valley catchment NewSouth Wales, Australia. In Proceedings of MODSIM 2001, F Ghassemi, P Whetton, R Little & M Littleboy(eds.). Modelling and Simulation Society of Australia and New Zealand, Canberra, 627-631.


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Freeze, RA & Cherry, JA 1979, Groundwater. Prentice-Hall, Englewood Cliffs, New Jersey.

Harvey, F & Jones, H 2003, Maximising the information from discrete electrical conductivity samples in the third ordercatchments. CNR 2001.054. NSW Department of Infrastructure Planning & Natural Resources, Parramatta.


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Tuteja, NK, Beale, GTH, Summerell, G & Johnston, WH 2002, Development and validation of the Catchment ScaleSalt Balance Model—CATSALT (Version 1). Technical Report, Centre for Natural Resources, NSWDepartment of Land and Water Conservation, Wagga Wagga.

Woolley, D 1991, Kyeamba Landcare Area Groundwater. Unpublished DLWC report to Kyeamba Landcare Group.

Zhang, L, Dawes, WR & Walker, GR 2001, Response of mean annual evapotranspiration to vegetation changes atcatchment scale. Water Resources Research, 37, 701-708.


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Integrated catchment management in the Murray-Darling BasinA process through which people can develop a vision, agree on shared values and behaviours, make informeddecisions and act together to manage the natural resources of their catchment: their decisions on the use of land,water and other environmental resources are made by considering the effect of that use on all those resources and onall people within the catchment.

Our valuesWe agree to work together, and ensure that our behaviour reflects that following values.

Courage

• We will take a visionary approach, provide leadershipand be prepared to make difficult decisions.

Inclusiveness

• We will build relationships based on trust andsharing, considering the needs of futuregenerations, and working together in a truepartnership.

• We will engage all partners, including Indigenouscommunities, and ensure that partners have thecapacity to be fully engaged.

Commitment

• We will act with passion and decisiveness, takingthe long-term view and aiming for stability indecision-making.

• We will take a Basin perspective and a non-partisan approach to Basin management.

Respect and honesty

• We will respect different views, respect each otherand acknowledge the reality of each other’s situation.

• We will act with integrity, openness and honesty, be fairand credible and share knowledge and information.

• We will use resources equitably and respect theenvironment.

Flexibility

• We will accept reform where it is needed, be willingto change, and continuously improve our actionsthrough a learning approach.

Practicability

• We will choose practicable, long-term outcomesand select viable solutions to achieve theseoutcomes.

Mutual obligation

• We will share responsibility and accountability, andact responsibly, with fairness and justice.

• We will support each other through the necessarychange.

Our principlesWe agree, in a spirit of partnership, to use the followingprinciples to guide our actions.

Integration

• We will manage catchments holistically; that is,decisions on the use of land, water and otherenvironmental resources are made by consideringthe effect of that use on all those resources and onall people within the catchment.

Accountability

• We will assign responsibilities and accountabilities.

• We will manage resources wisely, beingaccountable and reporting to our partners.

Transparency

• We will clarify the outcomes sought.

• We will be open about how to achieve outcomesand what is expected from each partner.

Effectiveness

• We will act to achieve agreed outcomes.

• We will learn from our successes and failures andcontinuously improve our actions.

Efficiency

• We will maximise the benefits and minimise thecost of actions.

Full accounting

• We will take account of the full range of costs andbenefits, including economic, environmental, socialand off-site costs and benefits.

Informed decision-making

• We will make decisions at the most appropriate scale.

• We will make decisions on the best availableinformation, and continuously improve knowledge.

• We will support the involvement of Indigenouspeople in decision-making, understanding the valueof this involvement and respecting the livingknowledge of Indigenous people.

Learning approach

• We will learn from our failures and successes.

• We will learn from each other.

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