Water Quality Status and Trends: Bay of Plenty - DairyNZ · PDF fileWater Quality Status and...

Water Quality Status and Trends:

Bay of Plenty

Reviewed by Approved for

DairyNZ publication by

Name: Dr. Mike Scarsbrook

Position: Environment Policy Manager

Organisation: DairyNZ Ltd.

Date: 30/06/2014

Name: Dr. Rick Pridmore

Position: Strategy and Investment Leader

Organisation: DairyNZ Ltd.

Date: 30/06/2014

Authors/Contributors:

Tom Stephens (DairyNZ)

For any information regarding this report please contact:

Tom Stephens PhD Water Quality Specialist Policy and Advocacy Department

DairyNZ

Cnr Ruakura & Morrinsville Roads | Newstead | Private Bag 3221| Hamilton 3240 | NEW ZEALAND Ph +64 7 858 3750 | Mob +64 027 702 5665 | Fax +64 7 858 3751 Web www.dairynz.co.nz

Report prepared by DairyNZ Ltd (30/06/2014).

Recommended citation:

DairyNZ Ltd. 2014. Water Quality Status and Trends: Bay of Plenty

© 2014 DairyNZ

This document and accompanying data may contain information that is confidential and subject to

privilege. Any use, dissemination, distribution or copying of this document or data is prohibited without

consent from DairyNZ. DairyNZ will not accept liability for any loss or damage caused by using any

material or data contained in this report. While every best practice has been taken, no warranty is

made that this material is free from error. DairyNZ's entire liability will be limited to resupplying the

material.

http://www.dairynz.co.nz/

Water Quality Status and Trends (2004-2013): Bay of Plenty i

Executive Summary

Spatial patterns and temporal trends in twelve water quality indicators have been analysed for 25

sites in the Bay of Plenty region using non-parametric statistical methods (seasonal Kendall slope

estimator and trend test, hierarchical clustering, principal components analysis). At 20 sites, monthly

records exist for the period 2004-2013 and at 5 sites, monthly records exist for the period 2009-2014.

To prevent a step-change in 2008 from biasing trend analyses (arising from a change to methodology

in July), all DRP records were filtered to test only the period 2009-2014. All records were tested for

absolute trends in concentration and flow-adjusted trends in loading.

Clustering of average annual water quality in 2013 (across 12 indicators) demonstrated that

geographic location appeared to exert a substantial effect on expected water quality. For instance, the

four meaningful clusters isolated the East Central, Eastern and Western rivers regions from each

other. The Tauranga Streams region exhibited considerable variability across the 12 indicators,

meaning several Tauranga streams were isolated in unique clusters (e.g., Waimapu, Kopurererua at

SH29 and Wairoa at SH2). Remaining Tauranga streams were spread between East Central, Eastern

and Western Rivers clusters. The importance of geographic location on water quality state might

indicate the underlying control of climate and geology on water quality, or indicate that resource use

(and its effects on water quality) varies between the four regions (and widely within the Tauranga

Streams region).

Inspection of annualised statistics for water quality indicators of “ecosystem health” and “human

health” in the National Objectives Framework, highlighted that median E.coli concentrations, 1-day

minimum DO availability, median and 95th% NO3-N concentration as well as median and 95

th% NH4-

N concentration would classify all 25 stations into grades A (“no stress”) or B (“minor stress”).

However, the absence of periphyton estimates precludes determination of whether current in-stream

nutrient concentration would breach or support community or Regional Council specified limits on

algal biomass. Likewise, measures of water clarity (TSS, turbidity) are hard to draw conclusions from

in the absence of specific information on which native or exotic fauna are managed within each river

(i.e., a turbidity of 20 NTU is recognised as a limit to protect migratory banded kokopu in New Zealand

but without knowledge on their distribution or that of other fish, let alone invertebrates, it is difficult to

determine if present day turbidity or TSS would pose a threat to “ecosystem health”). However, non-

compulsory guidelines for pH and temperature are highly likely to result in D scores across several

sites (i.e., exceed non-compulsory national bottom-line). The absence of continuous diel

measurement precludes much certainty in this inference. Presuming the spot measurements are

robust, sites where thermal stress is likely (i.e., Cox-Rutherford Index >25°C averaged over 5 hottest

days from 1 December to 30 March [Davies-Colley et al., 2013]) include:

Waioeka (max 23.4°C), Nukuhou (max 24.6°C) and Whakatane River (max 23.1°C) in the

Eastern Rivers region; and

Tarawera River at its outlet from Lake Tarawera (max 22.4°C) in the East Central Rivers

region.

Assuming the spot measurements are robust, sites where pH stress is likely (i.e., pH <6 or >9 from

diel continuous measurement [Davies-Colley et al., 2013]) include:

Water Quality Status and Trends (2004-2013): Bay of Plenty ii

Wairoa River at SH2 (pH 6.1-7.2), Omanawa River (pH 5.9-7.3), Kopurererua Stream at SH2

(6.1-7.4) within the Tauranga Streams;

Waioeka River (pH 6.2-8.4), Nukuhou River (pH 5.8-7.2) and Whakatane River (pH 6.7-8.8) in

the Eastern Rivers;

Puarenga Stream (pH 4.6-6.9), Ohau Channel (pH 5.9-7.9), Kaituna River at Paengaroa (pH

6.2-6.9) in the Western Rivers.

The result of ordinations (PCA) suggest that changes in water quality over the last 5 years vary

between clusters, although marked improvement of water clarity (TSS and turbidity) predominates in

all. Within the Tauranga Streams and Eastern Rivers, changes to NH4-N, NO3-N and TN are also

marked whilst in East Central and Western Rivers, changes to DRP and NH4-N are obvious.

Examination of trend results by region also highlights a picture of stable or improving water quality

across most indicators (in most instances since 2004), with the exception of DRP and TP in Tauranga

Streams (since 2009):

Tauranga Streams: largely stable or improving across the suite of nutrient, sediment and

bacterial indicators, with the exception of DRP and TP concentrations and flow-corrected

loadings that are rising (worsening) at most sites for DRP and a third of sites for TP. The Te

Mania Stream has improved markedly and significantly since 2004 for NH4-N, TN, turbidity

and TSS. The Omanawa River has worsened significantly since 2004 for NO3-N (but not TN)

and worsened significantly since 2009 for DRP and TP.

Eastern Rivers: all five sites on the Motu, Waioeka, Nukuhou and Whakatane Rivers have

recorded stable or improving water quality for the uncorrected suite of nutrient, sediment and

bacterial indicators, since 2004. Both the Nukuhou and Whakatane Rivers have improved

meaningfully and significantly for faecal bacterial concentration/loading, DO concentration,

NO3-N concentrations (but not loads), NH4-N concentration/loading and TN

concentration/loading, as well as for turbidity and TSS concentration.

East Central Rivers: all seven monitoring sites observed stable or improving significant and

meaningful trends for E.coli, DO, NH4-N, temperature, pH and TSS. Only the Rangitaiki River

at Murupara observed a rising (worsening) trend for TN concentration or loading (+6.7%/yr,

p<0.001 and +4.0%/yr, p<0.001 respectively). Although no sites exhibited a trend for TP

concentration, the Tarawera River at Boyce Park exhibited a meaningful and significant trend

for increased TP and DRP flow-corrected concentration or loading (+1.6%/yr, p<0.002 and

+4.0%/yr, p<0.004 respectively). In addition, the Tarawera River has exhibited a trend for

rising turbidity at two of four monitoring stations (its outlet and furthest downstream at

Awakaponga).

Western Rivers: all six monitoring stations exhibited a stable or improving significant and

meaningful trend for E.coli, DO, TN, DRP, temperature, pH, turbidity and TSS concentration.

Although, DRP and TP flow-corrected concentration (loading) has worsened on the Puarenga

Stream (+5.6%/yr, p<0.03 and +1.8%/yr, p<0.01 respectively). That said, the Ohau Channel

and Kaituna River at its outlet from Lake Rotoiti and Paengaroa have undergone meaningful

and significant improvements to TP loading, ranging from -3.0%/yr to -9.3%/yr. Most

impressively, all Western River sites have undergone meaningful and significant

improvements to turbidity, ranging from -2.0%/yr (Puarenga Stream since 2004) to -19.4%/yr

(Kaituna River at Paengaroa since 2009).

Water Quality Status and Trends (2004-2013): Bay of Plenty iii

Table of Contents

1.0 Introduction ........................................................................................................................................... 10

1.1 Context ............................................................................................................................................. 10

1.2 Aim of Study ..................................................................................................................................... 10

2.0 Methodology ......................................................................................................................................... 12

2.1 Original dataset ................................................................................................................................ 12

2.2 Water quality data preparation ......................................................................................................... 12

2.3 Parameters analysed ....................................................................................................................... 15

2.4 Monthly series .................................................................................................................................. 20

2.5 Flow data .......................................................................................................................................... 20

2.6 DRP correction ................................................................................................................................. 20

2.7 Data analysis .................................................................................................................................... 21

3.0 Water Quality in the Bay of Plenty Rivers ............................................................................................ 23

3.1 Water Quality Status (2013) ............................................................................................................. 24

3.2 Water Quality Trends (2004-2013)................................................................................................... 28

3.3 Water Quality Clusters (2013) .......................................................................................................... 36

3.4 Water Quality Patterns (2009-2013) ................................................................................................ 46

4.0 Discussion of Trends in Water Quality ................................................................................................. 52

4.1 Faecal bacteria (E.coli) .................................................................................................................... 53

4.2 Dissolved Oxygen ............................................................................................................................ 53

4.3 Nitrate-Nitrogen (NO3-N) .................................................................................................................. 53

4.4 Ammoniacal-Nitrogen (NH4-N) ......................................................................................................... 54

4.5 Total Nitrogen (TN) .......................................................................................................................... 55

4.6 Dissolved Reactive Phosphorus (DRP) ........................................................................................... 56

4.7 Total Phosphorus (TP) ..................................................................................................................... 56

4.8 Temperature ..................................................................................................................................... 57

4.9 pH ..................................................................................................................................................... 57

4.10 Turbidity ............................................................................................................................................ 57

4.11 Total Suspended Solids ................................................................................................................... 58

5.0 Water Quality Conclusions ................................................................................................................... 59

6.0 References ........................................................................................................................................... 62

Appendix A Standardised CUSUM .......................................................................................................... 63

Water Quality Status and Trends (2004-2013): Bay of Plenty iv

Appendix B Annual water quality statistics (2009-2013) ......................................................................... 76

Water Quality Status and Trends (2004-2013): Bay of Plenty v

List of Figures

Figure 1. Bay of Plenty Regional Council River Monitoring Sites ......................................................... 14

Figure 2. Fusion level plot of the “average” linkage dendrogram for the 25 monitoring stations in the

BoPRC dataset (using 2013 averaged geochemical and bacterial characteristics). Note: the marked

reductions in cophenetic distance (node height) at 4 clusters (k = 4). .................................................. 36

Figure 3. Pruned agglomerative, hierarchical dendrogram of 25 BoPRC monitoring stations, clustered

by “average” linkage for geochemical and bacterial characteristics for 2013 (i.e., each site is

represented by the annual average of monthly observations for the year 2013). T = Tauranga; ER =

Eastern Rivers; WR = Western Rivers; and ECR = East Central Rivers regions. ................................ 37

Figure 4. Performance measures of PCA on clusters A and B (annual averages 2009-2013). ........... 46

Figure 5. PCA of water quality (annual average) for the period 2009-2013, at monitoring stations in

clusters A and B (scaling = 2 to ensure vectors are drawn to approximate correlation between

indicators).Sites correspond to annual average scores for variables at each monitoring station. (The

four letters of each site label correspond to the location and digits correspond to year).Colours

correspond to Tauranga Streams and Eastern Rivers. ........................................................................ 47

Figure 6. Performance measures of PCA on clusters C and D (annual averages 2009-2013). .......... 49

Figure 7. PCA of water quality (annual average) for the period 2009-2013, at monitoring stations in

clusters C and D (scaling = 2 to ensure vectors are drawn to approximate correlation between

indicators).Sites correspond to annual average scores for variables at each monitoring station. (The

four letters of each site label correspond to the location and digits correspond to year). Colours

correspond to Tauranga Streams, Eastern Rivers, Eastern Central Rivers and Western Rivers. ....... 50

Figure A1 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at

BOP110014 (Whirinaki River) ............................................................................................................... 63


BOP110015 (Rangitaiki River) .............................................................................................................. 63


BOP110018 (Rangitaiki River) .............................................................................................................. 64


BOP110020 (Tarawera River) .............................................................................................................. 64








BOP110093 (Motu River) ...................................................................................................................... 66


BOP110003 (Motu River) ...................................................................................................................... 67


BOP160102 (Waioeka River) ................................................................................................................ 67

Figure A11 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP

110007 (Nukuhou River) ....................................................................................................................... 68

Water Quality Status and Trends (2004-2013): Bay of Plenty vi


BOP110011 (Whakatane River) ........................................................................................................... 68


BOP110013 (Ngongotaha Stream) ....................................................................................................... 69


BOP110058 (Puarenga Stream) ........................................................................................................... 69


BOP110025 (Ohau Channel) ................................................................................................................ 70


BOP110026 (Kaituna River).................................................................................................................. 70






BOP160121 (Waimapu Stream) ........................................................................................................... 72


BOP110088 (Wairoa River) .................................................................................................................. 72


BOP110034 (Wairoa River) .................................................................................................................. 73


BOP110036 (Omanawa River) ............................................................................................................. 73


BOP710008 (Kopurererua Stream) ...................................................................................................... 74


BOP710009 (Kopurererua Stream) ...................................................................................................... 74


BOP710022 (Te Mania Stream) ........................................................................................................... 75

Water Quality Status and Trends (2004-2013): Bay of Plenty vii

List of Tables

Table 1 The National Objective Framework – values and related attributes for rivers (summarised

from MfE, 2013b). ................................................................................................................................. 11

Table 2 Parameters analysed for state, trend and patterns across the 25 sites monitored regularly by

BoPRC. ................................................................................................................................................. 15

Table 3 Summary of monitoring stations analysed for water quality status and trends in the East

Central Rivers region of the Bay of Plenty. ........................................................................................... 16

Table 4 Summary of monitoring stations analysed for water quality status and trends in the Eastern

Rivers region of the Bay of Plenty. ........................................................................................................ 17

Table 5 Summary of monitoring stations analysed for water quality status and trends in the Western


Table 6 Summary of monitoring stations analysed for water quality status and trends in the Tauranga


Table 7 Water quality status during 2013 for stations in the Tauranga Streams region of the Bay of

Plenty. Red cells indicate failure to meet proposed NOF bottom-lines and blue cells indicate top (Band

A) water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates

worst performing of sub-region. Non-compulsory NOF attribute scores have been highlighted for

temperature (using recommended bands for “Eastern Dry” regions as per Davies-Colley et al., 2013)

and pH. .................................................................................................................................................. 24

Table 8 Water quality status during 2013 for stations in the Eastern Rivers region of the Bay of Plenty.

Red cells indicate failure to meet proposed NOF bottom-lines and blue cells indicate top (Band A)

water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates worst

performing of sub-region. Non-compulsory NOF attribute scores have been highlighted for


and pH. .................................................................................................................................................. 25

Table 9 Water quality status during 2013 for stations in the East Central Rivers region of the Bay of


A) water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates worst



and pH. .................................................................................................................................................. 26

Table 10 Water quality status during 2013 for stations in the Western Rivers region of the Bay of


A) water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates worst



and pH. .................................................................................................................................................. 27

Table 11 Absolute (uncorrected for flow) water quality trends for stations in the Tauranga Streams

region of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by

* where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically

meaningful in bold (>1.0%/yr). ............................................................................................................. 28

Table 12 Flow-corrected water quality trends for stations in the Tauranga Streams region of the Bay of

Plenty. Trends (RSKE) presented for period 01/01/2004-31/12/2013, unless indicated by * where

Water Quality Status and Trends (2004-2013): Bay of Plenty viii

trends presented for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Those in

bold are ecologically meaningful (>1.0%/yr). ....................................................................................... 29

Table 13 Absolute (uncorrected for flow) water quality trends for stations in the Eastern Rivers region

of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by *

where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically


Table 14 Flow-corrected water quality trends for stations in the Eastern Rivers region of the Bay of




Table 15 Absolute (uncorrected for flow) water quality trends for stations in the East Central Rivers

region of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by

* where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically


Table 16 Flow-corrected water quality trends for stations in the East Central Rivers region of the Bay

of Plenty. Trends (RSKE) presented for period 01/01/2004-31/12/2013, unless indicated by * where



Table 17 Absolute (uncorrected for flow) water quality trends for stations in the Western Rivers region

of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by *

where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically


Table 18 Flow-corrected water quality trends for stations in the Western Rivers region of the Bay of




Table 19 Gower (1982) distances for hierarchical agglomerative clustering of the BoP dataset (n = 25)

– the smaller the estimate the better the clustered or cophenetic correlation to the initial dissimilarity

matrix (i.e., better the clustering at replicating the initial data pattern). Gower distances are calculated

as the sum of squared distances between the original Euclidean and cophenetic distances. ............. 36

Table 20 Agglomerative, hierarchical “average” linkage cluster results for the 25 monitoring stations

included in trend analyses, reporting summary statistics for the period 01/01/2013 to 31/12/2013.

Values ±1 standard deviation of the cluster mean. Key dissimilarities are shaded. ............................. 38

Table 21 Summary of statistically significant (p<0.05) and ecologically meaningful trends (≥1%/yr) by

cluster A. ............................................................................................................................................... 42


cluster B. ............................................................................................................................................... 43


cluster C. ............................................................................................................................................... 43


cluster D. ............................................................................................................................................... 44

Table 25 PCA statistics for ordination on centred and standardised variables in Cluster A and B. Only

the first two axes are likely to be meaningful. ....................................................................................... 47

Table 26 PCA statistics for ordination on centred and standardised variables in Cluster A and B. Only

the first three axes are likely to be meaningful...................................................................................... 49

Water Quality Status and Trends (2004-2013): Bay of Plenty ix

Table 27 Summary trend output for all 25 sites included for analysis in this report. Only significant

(p<0.05) and ecologically meaningful trends are reported. Trends reported for period 2004-2013

except for * where period is 2009-2013. ............................................................................................... 52

Water Quality Status and Trends (2004-2013): Bay of Plenty 10

1.0 Introduction

1.1 Context

The National Objectives Framework (within the National Policy Statement for Freshwater

Management) has stipulated that several numeric water quality values and associated attributes are

of universal importance to all riverine systems in New Zealand (MfE, 2013a).

Thresholds for numeric attributes, ranked into four bands (A-D), define water quality for “human” and

“ecosystem” health (MfE, 2013b) (Table 1).

This report analyses routinely monitored data on rivers in the Bay of Plenty to determine recent water

quality status under the NOF and decadal temporal trends in water quality.

1.2 Aim of Study

The aim of this report is to analyse recent state (2013) and long-term trends in the Bay of Plenty’s

monitored river networks (varying from 2004-2013 to 2009-2013 as records permit).

Combined, state and trend analysis can determine which catchments currently, or in the near future,

will likely experience degraded water quality (i.e., which should be prioritised for management).

At degraded or degrading sites, the relationships between numeric attributes are also analysed, to

make recommendations for water resource management. The information is therefore of use to land

users and resource managers (e.g., Bay of Plenty Regional Council, Iwi governance groups).


Table 1 The National Objective Framework – values and related attributes for rivers (summarised from MfE, 2013b).

Value Attributes Numeric Attribute Band

A B C (Bottom-line) D

Ecosystem health and general protection for indigenous species*

• Nitrate (toxicity)

• Ammonia (toxicity)

• Dissolved oxygen (DO)

• Periphyton

• Temperature**

• pH**

• Sediment**

• Invertebrates**

• Fish**

99% protection from toxicants (nitrate, ammoniacal-nitrogen)

No stress due to hypoxia (DO)

Rare blooms indicative of limited nutrient enrichment or modification of flows and habitat (periphyton)


Occasional minor stress from hypoxia

Occasional blooms of plants reflecting minor alteration of flow or nutrient availability (periphyton)


Moderate stress on sensitive fish and macroinvertebrate taxa

Periodic short-duration nuisance blooms reflecting moderate nutrient enrichment and/or alteration of flow regime or habitat (periphyton)

Impacts on the growth of multiple species that approach acute toxicity levels for sensitive species (nitrate, ammoniacal-nitrogen)

Significant, persistent stress on a range of aquatic fauna with loss of ecological integrity (DO)

Regular and/or extended-duration nuisance blooms reflecting significant nutrient enrichment and/or flow alteration (periphyton)

Human health for secondary* contact

• Escherichia coli (E.coli)

• Planktonic cyanobacteria

• Benthic cyanobacteria**

Very low risk of

gastroenteritis (<0.1%)

from secondary

exposure (E.coli)

Low risk of

gastroenteritis (0.1-

1.0%) from secondary

exposure (E.coli)

Moderate risk of

gastroenteritis (1.0-

5.0%) from secondary

exposure (E.coli)

High risk of

gastroenteritis (>5.0%)

from secondary

exposure (E.coli)

*These two ‘objectives’ are enshrined as national values under the NOF; **These numeric attributes are not compulsory in the NOF (MfE, 2013b) but are under consideration for inclusion for 2016-2019.


2.0 Methodology

2.1 Original dataset

River water quality data in the Bay of Plenty region has been routinely monitored by the Bay of Plenty

Regional Council (BoPRC) and National Institute of Water and Atmospheric Research (NIWA) since

1990.

A complete extract of the BoPRC’s water quality database for the Bay of Plenty region, partitioned

into sub-regional catchments, was obtained from BoPRC’s Water Quality and Ecology teams

(26/03/2014).

The records for a total of 55 monitoring stations were supplied. Of these, 20 contain complete or near-

complete monthly records covering the period 2004 to 2013 and a further 5 contain complete or near-

complete monthly records covering the period 2009-2013 (Figure 1).

At the combined total of 25 sites included for analysis here, average flow on the day of sampling was

obtained, either by direct measurement or by correlation with a flow recorded site (data supplied by

BoPRC Hydrology team).

2.2 Water quality data preparation

The dataset contained a small proportion of “non-detectable” or “less than detection limit”

observations for several numeric attributes.

To conduct reliable statistical analyses, non-detectable observations were “censored” or replaced by

a value of ½ the lowest detection limit during the period of analysis (2004-2013 or 2009-2013) (i.e., as

per the recommendations of Scarsbrook and McBride, 2007).

Corresponding limits of detection (and altered value for trend analyses) are:

Suspended solids = 0.1 mg/L (0.05 mg/L)

Turbidity = 0.1 NTU (0.05 NTU)

TP = 0.005 mg/L (0.0025 mg/L)

DRP = 0.001 mg/L (0.0005 mg/L)

TN = 0.01 mg/L (0.005 mg/L)

NH4-N = 0.001 (0.0005 mg/L)

NOx-N = 0.001 (0.0005 mg/L)

No two observations were taken on the same day at the same site.

The dataset contained two indicators for bacteriological water quality: faecal coliform (FC) and

Escherichia coli (E.coli) count. As per the recommendations of the NOF report on bacteriological risk

(McBride, 2012) and the national microbiological water quality guidelines (MfE and MoH, 2003), E.coli

concentration was selected as the numeric attribute for water quality determined by “human” health.


Both TN and TP samples were further filtered, to exclude samples where either TN was greater than

the sum of N-fractions monitored or TP was greater than DRP.


Figure 1. Bay of Plenty Regional Council River Monitoring Sites


2.3 Parameters analysed

Parameters selected for analysis here are those included with the NOF (Table 1) as well as additional

non-statutory numeric attributes for aspects of “ecosystem” health (Table 2).

Descriptions for the 25 monitoring stations analysed in this report are listed in Tables 3-6, including

notes on the monitoring record length and water quality data available.

Table 2 Parameters analysed for state, trend and patterns across the 25 sites monitored regularly by BoPRC.

NOF/Additional parameter

Numeric Attribute Indicator Units of measurement

Human health E.coli MPN/100ml

Ecosystem health Chlorophyll-a (Chl-a) mg/m3

Dissolved Oxygen (DO) % or mg/L

Nitrate-Nitrogen (NO3-N) mg/L

Ammoniacal-Nitrogen (NH4-N) mg/L

Additional ecosystem health numeric

attributes

Total Nitrogen (TN) mg/L

Soluble Inorganic Nitrogen (SIN) mg/L

Dissolved Reactive Phosphorus (DRP) mg/L

Total Phosphorus (TP) mg/L

Temperature °C

pH SI

Turbidity & Total Suspended Solids (TSS) NTU & mg/L

Conductivity mS/cm-1

Flow m3/s

-1


Table 3 Summary of monitoring stations analysed for water quality status and trends in the East Central Rivers region of the Bay of Plenty.

Sub-region

Monitoring Station

BoPRC

Site ID

Water Quality Attributes n (% monthly median of 10-yr/5-yr series)

Flow Data (record

available)

Record comments

Physico-chemical

Nutrients Bacterio-logical

East

Cen

tral

Riv

ers

Whirinaki River BOP110014 √ √ √ 120 (100%) √ (2004-13) 2004-2013 @ Galatea Bridge

Rangitaiki River BOP110015 √ √ √ 120 (100%) √ (2004-13) 2004-2013 @ Old Bridge (Murupara)

Rangitaiki River BOP110018 √ √ √ 120 (100%) √ (2004-13) 2004-2013 @ Te Teko Bridge

Tarawera River BOP110020 √ √ √ 120 (100%) √ (2004-13) 2004-2013 @ Lake Outlet

Tarawera River BOP110021 √ √ √ 100 (83%) √ (2004-13) 2004-2013 @ Kawarau Bridge

(Boyce Park)

Tarawera River BOP110023 √ √ √ 52 (87%) √ (2009-13) 2009-2013 @ SH30 Bridge

Tarawera River BOP110052 √ √ √ 120 (100%) √ (2004-13) 2004-2013 @ Awakaponga


Table 4 Summary of monitoring stations analysed for water quality status and trends in the Eastern Rivers region of the Bay of Plenty.

Sub-region

Monitoring Station

BoPRC

Site ID


Flow Data (record

available)

Record comments

Physico-chemical


Easte

rn R

ivers

Motu River BOP110093 √ √ √ 120 (100%) √ (2004-13) 2004-2013 @ Waitangirua

Motu River BOP110003 √ √ √ 119 (99%) √ (2004-13) 2004-2013 @ SH35 Bridge

Waioeka River BOP160102 √ √ √ 115 (96%) √ (2004-13) 2004-2013 @ Gorge mouth

Nukuhou River BOP110007 √ √ √ 117 (98%) √ (2004-13) 2004-2013 @ Old Quarry

Whakatane River BOP110011 √ √ √ 115 (96%) √ (2004-13) 2004-2013 @ Pekatahi Bridge


Table 5 Summary of monitoring stations analysed for water quality status and trends in the Western Rivers region of the Bay of Plenty.

Sub-region

Monitoring Station

BoPRC

Site ID


Flow Data (record

available)

Record comments

Physico-chemical


Weste

rn R

ivers

Ngongotaha Stream

BOP110013 √ √ √ 109 (91%) √ (2004-13) 2004-2013 @ Town Bridge (SH5 Bridge 24/09/08-

14/03/11)

Puarenga Stream BOP110058 √ √ √ 116 (97%) √ (2004-13) 2004-2013 @ FRI

Ohau Channel BOP110025 √ √ √ 118 (98%) √ (2004-13) 2004-2013 @ Ohau Channel

Kaituna River BOP110026 √ √ √ 112 (93%) √ (2004-08; 2011-13)

2004-2013 @ Lake Rotoiti outlet

(Okere)

Kaituna River BOP110027 √ √ √ 52 (87%) √ (2009-13) 2009-2013 @ Maungarangi

Bridge (Paengaroa)

Kaituna River BOP120000 √ √ √ 56 (93%) √ (2009-13) 2009-2013 @ Te Matai Bridge*


Table 6 Summary of monitoring stations analysed for water quality status and trends in the Tauranga Rivers region of the Bay of Plenty.

Sub-region

Monitoring Station

BoPRC

Site ID


Flow Data (record

available)

Record comments

Physico-chemical


Tau

ran

ga R

ive

rs

Waimapu Stream BOP160121 √ √ √ 59 (98%) √ (2009-13) 2009-2013 @ SH29 bridge

(Greerton Park 09/01/08-07/09/10)

Wairoa River BOP110088 √ √ √ 71 (59%) √ (2004-08; 2010-13)

2004-2013 @ Ruahihi power

station*

Wairoa River BOP110034 √ √ √ 60 (100%) √ (2010-13) 2009-2013 @ SH2 Bridge

Omanawa River BOP110036 √ √ √ 115 (96%) √ (2004-13) 2004-2013 @ SH29 Bridge

Kopurererua Stream

BOP710008 √ √ √ 60 (100%) √ (2009-13) 2009-2013 @ SH29 Bridge

Kopurererua Stream

BOP710009 √ √ √ 98 (82%) √ (2004-13) 2004-2013 @ SH2 Bridge

Te Mania Stream BOP710022 √ √ √ 100 (83%) √ (2004-13) 2004-2013 @ SH2 Bridge*


2.4 Monthly series

Monitoring frequency varies between sites and over record intervals, depending on the parameter

(i.e., in accordance with state of the environment [SOE] protocols and compliance programmes). For

example, SOE monitoring is now monthly but was quarterly during the period 1999 to 2004, whilst

bacteriological monitoring for primary contact recreation is conducted at weekly intervals during the

bathing season (1st November-31

st April).

To consolidate datasets into consistent temporal envelopes, all time-series analyses were conducted

on representative monthly statistics. Two considerations were made, when:

Multiple observations were available for a parameter in one month, the result included was

the median of all; unless

An observation was recorded within 7 days of the start or finish of a month lacking an

observation. In which case, the latter observation was used to represent the month lacking

information and a monthly median calculated from remaining samples for the alternate month.

2.5 Flow data

All flow data used in this report was supplied by BoPRC’s Hydrology Team as daily average flow.

River flow data was obtained either from direct flow gauging or correlation with gauged recording sites

in the respective river system. Flow records varied in resolution and length (recorded in Table 3) but

were filtered as before (2.4 Monthly series) to include a single monthly statistic for time-series

analyses.

2.6 DRP correction

Scholes (2013) acknowledged that a change in detection methodology for dissolved reactive

phosphorus (DRP) since July 2008, caused a noted shift in baseline DRP concentration irrespective

of environmental conditions (i.e., a step-change in the long-term time-series for DRP is evident since

July, 2008). The change in methodology has resulted in greater sensitivity to lower concentrations

whereas the older laboratory approach possessed a higher upper range.

To test the likelihood of a step change, all DRP series were tested graphically in TimeTrends (v.3.02)

for a step change (using the CUSUM function – cumulative sum of differences from the series mean).

The CUSUM variable (Ci) is the sum of the deviations from the long-term mean, so that the CUSUM

Value for the rth datapoint is:

Ci = Σ(xr-ẋ)

Where xr is the observation and ẋ is the series mean. Ci can be standardised by dividing by the

standard error of the series (i.e., square root of the sum of the squares divided by 2[N-1]).

Step-change results are displayed in Appendix A by site. From these, it is clear that a step-change

(>10 mg/L) in DRP occurred in many time-series, coeval with the change in methodology (July, 2008).

In the absence of paired observations of DRP using both available methodologies and to avoid any

likelihood of an arbitrary change in methodology distorting inferences of long-term DRP trends, only

trends for the period 2009-2013 have been examined in this report.


2.7 Data analysis

2.7.1 State and trend analysis

Descriptive statistics (percentiles, mean, median) listed in this report were calculated from Microsoft

Office Excel, for comparison to proposed NOF guidelines, for the year 2013.

Monthly water quality statistics were also analysed for long-term temporal trends using NIWA’s

TimeTrends software (v.3.2; Jowett, 2011).

Seasonally-adjusted non-parametric time-series analysis can demonstrate the statistical significance

and magnitude of changes to numeric attributes (e.g., as per Smith et al., 1996; Larned et al., 2004).

The seasonal Kendall slope estimator (SKSE), which reports the magnitude of trend, and seasonal

Kendall trend test, which reports the statistical significance of the trend, were reported for all attributes

listed in Table 2 by site.

The SKSE estimates the slope (rate) and direction of change in an attribute over a time-series (as the

median of all possible within-month combinations of slopes [i.e., all possible slopes between January

observations, repeated within all months, and the median of all within-month slopes reported in

corresponding units – mg/L for instance]).

Positive SKSE (slopes) record an increase in an attribute and negative vice-versa.

Standardisation of slopes, by dividing the SKSE by the series-median, yields the relative slope or

relative SKSE (RSKSE) (as relative change per unit time; %/yr). Here, changes >1.0%/yr are believed

to be ecologically meaningful (Scarsbrook and McBride, 2007) but bear in mind that the % change

depends on how units are reported. For instance, an increase in temperature of 1°C on a median of

15°C is approximately 7%/yr whereas when reported in K, the same change is 0.3%/yr (i.e.,

100*1K/[273+15]) (see Vant, 2013). Relative changes are nonetheless valuable in determining the

impact of change at a site and permit reliable comparison of changes between sites.

The seasonal Kendall trend test then assigns a statistical significance to an SKSE value by

determining the likelihood of a trend arising by chance. Here, significant trends are those reported by

p<0.05 (5% chance of trend arising from random variation). Importantly, only trends that are

ecologically meaningful (>1.0%/yr) and statistically significant (p<0.05) are reported herein.

Changes in flow can concentrate or dilute numeric attributes regardless of changes to input (i.e.,

irrespective of changes to land use or point-source discharge).

Trends are reported for observed concentrations and, following flow-correction. Flow-adjustment

followed the recommendations of Ballantine and Davies-Colley (2009) (i.e., using a locally weighted

scatterplot smoother with 30% span).

Flow-adjustment routines involve identifying the effect of flow on concentration, standardising all

observations to identical flow and analysing the residuals of standardised numeric attribute

concentrations for long-term trends.

Note: By removing the potential for changes in concentration due to arbitrary changes in flow, flow-corrected trends offer a more direct measure of changes in the input of a chemical or bacterial contaminant. Hence, flow-corrected trends offer a more reliable measure of changes in nutrient loading from land-use.


2.7.2 Cluster and Ordination analyses (PCA)

Cluster and ordination analyses are tools to discern underlying patterns in multivariate data, which are

widely used in water quality analyses (e.g., Borcard et al., 2011). Given the continuous nature of

geochemical and bacteriological abundance data from the BoPRC monitoring dataset, clustering is

well-suited to partitioning the 25 monitoring stations into groups of similar water quality. Thereafter,

ordination analyses can be performed to identify the dominant gradient(s) of change in geochemistry

and bacteriological characteristics over time (i.e., reinforce earlier trend analyses).

Note: clustering is not a typical statistical method in that it does not test any hypothesis but requires inspection by the analyst for useful structures (i.e., clustering is a heuristic procedure).

Agglomerative hierarchical clustering was performed in the statistical programme “R” using the

HCLUST function of the Stats package (R Core Team, 2013). A Euclidean dissimilarity matrix for all

25 monitoring stations was generated from their corresponding 2013 average estimates for

parameters listed in Table 2 (using the same filtered dataset of prior trend analyses – i.e., excluding

anomalous samples and correcting for non-detectable observations; and omitting Chl-a, flow and

conductivity). The “average” linkage coefficient (UPGMA) was selected to create compact clusters of

similar size that minimise cophenetic correlation. Agglomerative clustering whilst more rigid than “k-

means” is sufficient to identify the underlying structure of similarity or dissimilarity between monitoring

stations based on their bacteriological and geochemical characteristics by sequentially building

clusters from two stations initially, to a final cluster containing all stations.

Following cluster analysis, the underlying gradient of changes amongst the 25 monitoring stations has

been analysed by ordination analysis (over the period 2009-2013 to test findings from earlier trend

analyses). To simplify ordination analyses, all sites identified in similar clusters have been analysed

together for their similar geochemistry and bacterial properties.

Note: The Wairoa River at Ruahine Power Stations [BoP110088) has been excluded from ordinations

for insufficient data in 2009 and 2012 – all other stations were included).

Given the non-ecological, continuous nature of bacterial and geochemical data, principal components

analysis was conducted (e.g., Scarsbrook and McBride, 2007). PCA isolates the underlying gradient

as a combination of changes to any parameters included in Table 2. The combination of changes to

numeric attributes maximises the variance (difference) between observations along the first axis, then

the second and so on (i.e., identifies the maximum gradient of changes between monitoring stations

based on their attributes, and then determines which attribute contributes most strongly to this

‘maximised’ change) (e.g., Legendre and Legendre, 1998). PCA ordination is therefore a useful tool to

determining the dominant gradients of change across a suite of indicators, whose patterns can be

indicative of the underlying cause of observed trends.

PCA was performed on averaged annual observations for the period 2009-2013.

Averaged annual observations were standardised to zero mean, unit variance prior to ordination – to

neutralise the effect of any one attribute dominating an axis simply because it is recorded in units of

greatest absolute, rather than relative, change.

Ordinations were performed in the statistical programme “R” using the DECORANA function of the

Vegan package (Oksanen, 2013). Broken-stick and Kaiser-Guttman statistics were generated for

ordinations of clusters to determine how many meaningful axes were present in each corresponding

PCA.


3.0 Water Quality in the Bay of Plenty

Rivers

The NOF has proposed a series of bottom-lines for rivers throughout New Zealand, including (MfE,

2013b):

NO3-N – annual median ≤6.9 mg/L and annual 95th% ≤9.8 mg/L;

NH4-N – annual median ≤1.30 mg/L and annual 95th% ≤2.20 mg/L;

DO – 7-day min (1 Nov-30 Apr) ≥5.0 mg/L and 1-day min (1 Nov to 30 Apr) ≥4.0 mg/L;

Periphyton - <200 mg/m2 Chl-a;

Cyanobacteria – biovolume equivalent of <1.8 mm3/L (potentially toxic cyanobacteria) or 0.5

to <10 mm3/L (total biovolume of cyanobacteria);

E.coli – annual median ≤1000 MPN/100 ml.

Additional non-compulsory guidelines have been recommended for temperature and pH (Davies-

Colley et al., 2013):

Temperature – Cox-Rutherford Index ≤24°C in maritime regions or ≤25°C in eastern dry

regions (including Bay of Plenty) (1 Dec to 30 March, averaged over five hottest days,

continuous record); or CRI no more than 3°C greater than reference site (1 Dec to 30 March,

averaged over five hottest days, continuous record);

pH – pH <6 or pH >9 (summer monitoring data, upper 95th%, continuous record).

The above recommended bottom-lines (and equivalent thresholds for Grades A, B and C under the

NOF) are compared to each of the 25 monitoring stations’ physico-chemistry and bacterial properties

as recorded at monthly resolution over 2013 in Tables 7--10. Implications of this comparison are

reserved for 5.0 Water Quality Conclusions.


3.1 Water Quality Status (2013)

Table 7 Water quality status during 2013 for stations in the Tauranga Streams region of the Bay of Plenty. Red cells indicate failure to meet proposed NOF bottom-lines and

blue cells indicate top (Band A) water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates worst performing of sub-region. Non-compulsory

NOF attribute scores have been highlighted for temperature (using recommended bands for “Eastern Dry” regions as per Davies-Colley et al., 2013) and pH.

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli

(median MPN/

100ml)

DO (1-day min mg/L)

NO3-N (median/95

th%

mg/L)

NH4-N (median/95

th%

mg/L)

TN (median/95

th%

mg/L)

DRP (median/95

th%

mg/L)

TP (median/95

th%

mg/L)

Temp. (max °C)

pH (min/ max)

Turb (median

NTU)

TSS (median mg/L)

Cond. mS/cm

Ta

ura

ng

a S

tre

am

s

Waimapu Stream

BOP160121 365 8.36 0.829/ 0.960

0.015/ 0.025

0.919/ 1.367

0.012/ 0.017

0.029/ 0.050

19.1 6.2-7.4 2.6 6.2 7.0

Wairoa River BOP110088 17 9.5 0.310/ 0.421

0.009/ 0.011

0.386/ 0.492

0.009/ 0.014

0.019/ 0.025

15.6 7.0-7.3 0.9 4.0 4.7

Wairoa River BOP110034 70 8.3 0.444/ 0.517

0.013/ 0.019

0.555/ 0.592

0.011/ 0.015

0.024/ 0.044

19.4 6.1-7.2 3.0 6.1 43.8

Omanawa River

BOP110036 65 9.0 1.280/ 1.315

0.006/ 0.009

1.280/ 1.370

0.023/ 0.026

0.037/ 0.042

16.7 5.9-7.3 2.8 8.6 7.1

Kopurererua Stream

BOP710008 225 8.6 1.005/ 1.044

0.011/ 0.022

1.050/ 1.525

0.017/ 0.022

0.038/ 0.071

16.1 6.3-7.2 4.6 14.0 6.8

Kopurererua Stream

BOP710009 160 7.5 0.961/ 1.145

0.044/ 0.176

1.090/ 1.765

0.015/ 0.019

0.042/ 0.120

18.9 6.1-7.4 6.2 13.0 17.4

Te Mania Stream

BOP710022 195 8.67 0.266/ 0.694

0.014/ 0.060

0.375/ 0.765

0.005/ 0.013

0.016/ 0.083

18.2 6.4-7.4 3.2 2.4 7.0


Table 8 Water quality status during 2013 for stations in the Eastern Rivers region of the Bay of Plenty. Red cells indicate failure to meet proposed NOF bottom-lines and blue

cells indicate top (Band A) water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates worst performing of sub-region. Non-compulsory NOF

attribute scores have been highlighted for temperature (using recommended bands for “Eastern Dry” regions as per Davies-Colley et al., 2013) and pH.

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli

(median MPN/

100ml)

DO (1-day min mg/L)

NO3-N (median/95

th%

mg/L)

NH4-N (median/95

th%

mg/L)

TN (median/95

th%

mg/L)

DRP (median/95

th%

mg/L)

TP (median/95

th%

mg/L)

Temp. (max °C)

pH (min/ max)

Turb (median

NTU)

TSS (median mg/L)

Cond. mS/cm

Ea

ste

rn R

ive

rs

Motu River BOP110093 60 8.30 0.113/ 0.400

0.005/ 0.011

0.279/ 0.606

0.010/ 0.016

0.026/ 0.057

20.7 7.4-8.1 3.2 2.1 8.8

Motu River BOP110003 15 8.90 0.029/ 0.108

0.002/ 0.006

0.079/ 0.214

0.010/ 0.014

0.013/ 0.118

20.4 7.7-8.2 2.2 2.6 9.5

Waioeka River

BOP160102 6 9.51 0.009/ 0.124

0.001/ 0.004

0.061/ 0.230

0.015/ 0.023

0.018/ 0.062

23.4 6.2-8.4 0.7 0.8 7.0

Nukuhou River

BOP110007 120 8.25 0.259/ 0.647

0.013/ 0.112

0.414/ 1.070

0.019/ 0.042

0.048/ 0.156

24.6 5.8-7.5 2.6 1.9 9.6

Whakatane River

BOP110011 31 9.33 0.046/ 0.294

0.003/ 0.011

0.115/ 0.490

0.024/ 0.035

0.031/ 0.127

23.1 6.7-8.8 1.4 1.7 8.7


Table 9 Water quality status during 2013 for stations in the East Central Rivers region of the Bay of Plenty. Red cells indicate failure to meet proposed NOF bottom-lines and blue cells indicate top (Band A) water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates worst performing of sub-region. Non-compulsory NOF attribute scores have been highlighted for temperature (using recommended bands for “Eastern Dry” regions as per Davies-Colley et al., 2013) and pH.

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli

(median MPN/

100ml)

DO (1-day min mg/L)

NO3-N (median/95

th%

mg/L)

NH4-N (median/95

th%

mg/L)

TN (median/95

th%

mg/L)

DRP (median/95

th%

mg/L)

TP (median/95

th%

mg/L)

Temp. (max °C)

pH (min/ max)

Turb (median

NTU)

TSS (median mg/L)

Cond. mS/cm

Ea

st

Ce

ntr

al

Riv

ers

Whirinaki River

BOP110014 22 9.2 0.020/ 0.155

0.003/ 0.006

0.100/ 0.208

0.018/ 0.023

0.028/ 0.035

20.4 7.7/8.4 1.9 1.4 9.46

Rangitaiki River

BOP110015 12 9.6 0.995/ 1.086

0.007/ 0.011

1.060/ 1.154

0.021/ 0.023

0.028/ 0.032

17.3 7.7/8.1 1.2 3.2 9.45

Rangitaiki River

BOP110018 10 9.7 0.405/ 0.508

0.011/ 0.019

0.521/ 0.616

0.013/ 0.023

0.033/ 0.048

20.0 6.9/7.3 2.0 3.3 9.89

Tarawera River

BOP110020 0.5* 8.9 0.001*/ 0.002

0.001*/ 0.004

0.101/ 0.118

0.002/ 0.005

0.009/ 0.011

22.4 7.7/8.3 0.8 0.9 51.2

Tarawera River

BOP110021 29 9.5 0.262/ 0.336

0.005/ 0.009

0.299/ 0.315

0.057/ 0.062

0.068/ 0.075

17.4 6.9/7.8 1.7 4.0 30.7

Tarawera River

BOP110023 34 8.0 0.279/ 0.318

0.086/ 0.231

0.492/ 0.549

0.081/ 0.093

0.113/ 0.126

18.6 7.0/8.1 3.2 7.3 36.7

Tarawera River

BOP110052 22 6.7 0.404/ 0.432

0.042/ 0.055

0.577/ 0.706

0.065/ 0.074

0.099/ 0.124

18.8 7.1/7.5 3.5 8.1 35.6


Table 10 Water quality status during 2013 for stations in the Western Rivers region of the Bay of Plenty. Red cells indicate failure to meet proposed NOF bottom-lines and blue

cells indicate top (Band A) water quality for E.coli, DO, NO3-N and NH4-N.*Indicates below detection limit. Bold indicates worst performing of sub-region. Non-compulsory NOF

attribute scores have been highlighted for temperature (using recommended bands for “Eastern Dry” regions as per Davies-Colley et al., 2013) and pH.

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli

(median MPN/

100ml)

DO (1-day min mg/L)

NO3-N (median/95

th%

mg/L)

NH4-N (median/95

th%

mg/L)

TN (median/95

th%

mg/L)

DRP (median/95

th%

mg/L)

TP (median/95

th%

mg/L)

Temp. (max °C)

pH (min/ max)

Turb (median

NTU)

TSS (median mg/L)

Cond. mS/cm

We

ste

rn R

ive

rs

Ngongotaha Stream

BOP110013 99 9.55 0.813/ 0.862

0.013/ 0.018

0.861/ 0.901

0.029/ 0.035

0.055/ 0.067

14.1 6.5-7.7 2.2 7.40 6.32

Puarenga Stream

BOP110058 52 8.78 0.735/ 0.922

0.072/ 0.088

0.890/ 1.090

0.037/ 0.045

0.080/ 0.091

18.2 4.6-6.9 4.4 6.20 23.00

Ohau Channel

BOP110025 6 6.63 0.105/ 0.152

0.017/ 0.043

0.316/ 0.412

0.004/ 0.005

0.020/ 0.035

19.5 5.9-7.9 1.4 2.85 18.39

Kaituna River

BOP110026 3 7.66 0.053/ 0.147

0.013/ 0.030

0.256/ 0.329

0.004/ 0.005

0.018/ 0.021

21.5 6.7-7.5 1.1 1.75 17.22

Kaituna River

BOP110027 21 9.17 0.298/ 0.366

0.005/ 0.009

0.415/ 0.504

0.018/ 0.029

0.034/ 0.044

20.1 6.2-6.9 1.4 8.25 15.71

Kaituna River

BOP120000 26 7.66 0.614/ 0.765

0.038/ 0.087

0.716/ 0.911

0.026/ 0.051

0.046/ 0.061

18.6 6.3-7.0 2.0 7.1 13.07


3.2 Water Quality Trends (2004-2013)

Table 11 Absolute (uncorrected for flow) water quality trends for stations in the Tauranga Streams region of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by * where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically meaningful in bold (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Waimapu Stream

BOP160121 +1.1% (0.033)

-10.0% (0.029)

+8.7% (0.003)

-3.3% (0.038)

-5.3% (0.026)

Wairoa River BOP110088 +2.0% (0.048)

Wairoa River*

BOP110034 +10.0% (0.021)

Omanawa River

BOP110036 +2.1% (<0.000)

+4.8% (0.007)

+3.1% (<0.000)

-0.2% (0.001)

Kopurererua Stream*

BOP710008 +6.3% (0.015)

Kopurererua Stream

BOP710009 +7.1% (0.002)

+2.6% (0.048)

-0.2% (0.025)

Te Mania Stream

BOP710022 -5.6% (0.028)

-3.6% (0.009)

+20.0% (0.002)

-5.5% (0.001)

-6.6% (0.006)

Meaningful and

Significant Trends

Worsening 0 0 1 0 0 6 2 1 0 0 0

Stable 7 6 6 5 6 1 5 5 7 5 6

Improving 0 1 0 2 1 0 0 1 0 2 1


Table 12 Flow-corrected water quality trends for stations in the Tauranga Streams region of the Bay of Plenty. Trends (RSKE) presented for period 01/01/2004-31/12/2013,

unless indicated by * where trends presented for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Those in bold are ecologically meaningful (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Waimapu Stream

BOP160121 -11.0% (0.001)

-4.0% (0.029)

+5.9% (0.025)

-3.4% (0.022)

Wairoa River BOP110088 +3.2% (0.034)

+1.7% (0.018)

Wairoa River*

BOP110034 -28.4% (0.004)

Omanawa River

BOP110036 -9.9% (0.026)

+1.6% (0.000)

+4.2% (0.006)

+1.6% (0.006)

-0.1% (0.049)

-5.0% (0.034)

-7.3% (0.038)

Kopurererua Stream*

BOP710008 -16.7% (0.005)

-25.7% (0.002)

-32.3% (0.000)

Kopurererua Stream

BOP710009 +5.7% (0.047)

-10.7% (0.001)

Te Mania Stream

BOP710022 -3.5% (0.000)

+14.6% (0.023)

-5.6% (0.001)

-6.9% (0.012)

Meaningful and

Significant Trends

Worsening 0 0 1 0 0 4 2 1 0 0 0

Stable 6 7 6 5 5 3 5 5 7 4 2

Improving 1 0 0 2 2 0 0 1 0 3 5


Table 13 Absolute (uncorrected for flow) water quality trends for stations in the Eastern Rivers region of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by * where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically meaningful in bold (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

ste

rn R

ive

rs

Motu River BOP110093 -0.7% (0.040

Motu River BOP110003 +0.1% (0.032)

Waioeka River

BOP160102 -9.6% (0.007)

+0.9% (0.004)

-4.7% (0.009)

Nukuhou River

BOP110007 -8.4% (0.011)

+1.3% (0.001)

-2.7% (0.010)

-8.6% (0.001)

-4.3% (0.000)

-6.4% (0.001)

-6.6% (0.000)

Whakatane River

BOP110011 -10.0% (0.000)

-3.2% (0.023)

-16.7% (0.000)

-6.4% (0.000)

+0.9% (0.020)

-0.2% (0.037)

-6.2% (0.013)

-7.7% (0.010)

Meaningful and

Significant Trends

Worsening 0 0 0 0 0 0 0 0 0 0 0

Stable 2 4 3 3 2 5 5 5 5 3 3

Improving 3 1 2 2 3 0 0 0 0 2 2


Table 14 Flow-corrected water quality trends for stations in the Eastern Rivers region of the Bay of Plenty. Trends (RSKE) presented for period 01/01/2004-31/12/2013, unless

indicated by * where trends presented for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Those in bold are ecologically meaningful (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

ste

rn R

ive

rs

Motu River BOP110093 +5.9% (0.031)

Motu River BOP110003 +0.1% (0.037)

-4.2% (0.012)

Waioeka River

BOP160102 -29.1% (0.017)

+0.8% (0.026)

-17.3% (0.028)

-22.6% (0.001)

-6.6% (0.000)

Nukuhou River

BOP110007 -8.8% (0.008)

+1.3% (0.000)

-7.7% (0.001)

-3.1% (0.002)

-5.3% (0.007)

Whakatane River

BOP110011 -22.1% (0.001)

-17.8% (0.000)

-5.4% (0.004)

-9.4% (0.000)

-9.6% (0.003)

Meaningful and

Significant Trends

Worsening 0 0 0 0 0 0 0 0 0 1 0

Stable 3 1 1 3 3 5 5 5 5 2 2

Improving 2 4 4 2 2 0 0 0 0 2 3


Table 15 Absolute (uncorrected for flow) water quality trends for stations in the East Central Rivers region of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by * where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically meaningful in bold (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Whirinaki River

BOP110014 -6.3% (0.000)

-4.0% (0.000)

+0.3% (0.002)

-8.2% (0.001)

Rangitaiki River

BOP110015 +4.1% (0.000)

+6.7% (0.000)

+0.1% (0.021)

-9.1% (0.000)

Rangitaiki River

BOP110018 -12.1% (0.000)

Tarawera River

BOP110020 -0.2% (0.002)

+4.4% (0.001)

Tarawera River

BOP110021 -7.8% (0.013)

+2.7% (0.000)

-12.5% (0.002)

-1.5% (0.015)

-0.4% (0.000)

Tarawera River*

BOP110023 -23.0% (0.010)

-6.7% (0.000)

-14.3% (0.001)

Tarawera River

BOP110052 -14.2% (0.000)

+0.6% (0.019)

+0.7% (0.016)

-5.6% (0.000)

-1.4% (0.000)

-1.8% (0.000)

-0.3% (0.016)

+4.8% (0.003)

Meaningful and

Significant Trends

Worsening 0 0 2 0 1 0 0 0 0 2 0

Stable 4 7 4 5 2 7 6 7 7 4 4

Improving 3 0 1 2 4 0 1 0 0 1 3


Table 16 Flow-corrected water quality trends for stations in the East Central Rivers region of the Bay of Plenty. Trends (RSKE) presented for period 01/01/2004-31/12/2013,

unless indicated by * where trends presented for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Those in bold are ecologically meaningful (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Whirinaki River

BOP110014 -2.8% (0.022)

-2.6% (0.006)

Rangitaiki River

BOP110015 -0.3% (0.008)

+4.2% (0.000)

+4.0% (0.000)

+3.6% (0.014)

Rangitaiki River

BOP110018 -13.1% (0.000)

Tarawera River

BOP110020 +0.8% (0.012)

+5.3% (0.002)

Tarawera River

BOP110021 -14.3% (0.002)

-1.5% (0.028)

+4.0% (0.004)

+1.6% (0.002)

+0.7% (0.016)

-0.3% (0.000)

-8.3% (0.000)

-11.6% (0.000)

Tarawera River*

BOP110023 -4.7% (0.002)

-3.5% (0.008)

-8.4% (0.008)

Tarawera River

BOP110052 -24.8% (0.000)

-4.7% (0.000)

-1.5% (0.000)

-1.8% (0.002)

+3.5% (0.003)

-5.0% (0.003)

Meaningful and

Significant Trends

Worsening 0 0 1 0 1 1 1 0 0 3 0

Stable 6 7 5 5 2 6 4 7 7 2 4

Improving 1 0 1 2 4 0 2 0 0 2 3


Table 17 Absolute (uncorrected for flow) water quality trends for stations in the Western Rivers region of the Bay of Plenty. Trends (RSKE) presented for 01/01/2004-31/12/2013, unless indicated by * where trends for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Ecologically meaningful in bold (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Chl-a (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Ngongotaha Stream

BOP110013 -7.6% (0.001)

-1.1% (0.014)

NA -0.4% (0.000)

-5.0% (0.002)

-4.3% (0.012)

Puarenga Stream

BOP110058 -8.6% (0.001)

-1.8% (0.000)

-3.5% (0.000)

+1.3% (0.0006)

NA -0.34% (0.001)

-2.0% (0.031)

-2.2% (0.021)

Ohau Channel

BOP110025 -3.5% (0.036)

+8.6% (0.018)

-4.1% (0.001)

-9.4% (0.000)

-26.6% (0.000)

-0.2% (0.41)

-7.0% (0.001)

-5.2% (0.013)

Kaituna River

BOP110026 -7.0% (0.028)

-0.4% (0.023)

+12.9% (0.000)

+7.7% (0.026)

-2.0% (0.035)

-8.7% (0.000)

-26.4% (0.000)

-0.5% (0.000)

-5.4% (0.001)

-5.2% (0.003)

Kaituna River*

BOP110027 +9.2% (0.036)

-8.6% (0.001)

-19.4% (0.006)

Kaituna River*

BOP120000 +7.8% (0.000)

-6.25% (0.007)

-19.0% (0.003)

-14.1% (0.040)

Meaningful and

Significant Trends

Worsening 0 0 4 1 0 0 1 0 0 0 0 0

Stable 2 6 1 5 2 6 1 1 6 6 0 2

Improving 4 0 1 0 4 0 4 3 0 0 6 4


Table 18 Flow-corrected water quality trends for stations in the Western Rivers region of the Bay of Plenty. Trends (RSKE) presented for period 01/01/2004-31/12/2013, unless

indicated by * where trends presented for period 01/01/2009-31/12/2013. Only significant (p<0.05) trends shown. Those in bold are ecologically meaningful (>1.0%/yr).

Sub-region

Monitoring Station

BoPRC

Site ID

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP* (mg/L)

TP (mg/L)

Chl-a (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Ngongotaha Stream

BOP110013 -7.5% (0.002)

-1.1% (0.006)

NA -0.26% (0.000)

-5.8% (0.000)

-4.8% (0.001)

Puarenga Stream

BOP110058 -10.9% (0.004)

-1.8% (0.000)

-3.2% (0.000)

+5.6% (0.029)

+1.8% (0.007)

NA -0.4% (0.000)

-2.9% (0.005)

-6.2% (0.000)

Ohau Channel

BOP110025 -3.9% (0.000)

-9.3% (0.000)

-24.6% (0.002)

-9.0% (0.006)

-5.7% (0.012)

Kaituna River

BOP110026 -0.6% (0.011)

+14.6% (0.025)

-2.3% (0.016)

-8.2% (0.000)

-0.3% (0.002)

-7.8% (0.000)

-6.6% (0.000)

Kaituna River*

BOP110027 -38.7% (0.021)

-3.0% (0.043)

-3.0% (0.043)

Kaituna River*

BOP120000 +5.2% (0.000)

-3.74% (0.037)

-21.4% (0.010)

Meaningful and

Significant Trends

Worsening 0 0 2 0 0 1 1 0 0 0 0 0

Stable 4 6 3 4 2 5 2 1 6 6 2 2

Improving 2 0 1 2 4 0 3 3 0 0 4 4


3.3 Water Quality Clusters (2013)

Inspection of Gower (1982) distances demonstrated that the “average” linkage outperformed “Ward”,

“single” and “complete” linkages for maximising correlation between the initial dissimilarity and

clustered (cophenetic) matrix (Table 19). Inspection of chord distances attached to the “average”

linkage (UPMGA) approach demonstrates that there are likely to be 4-5 meaningful clusters amongst

the 25 monitoring stations (Figure 2).

0 100 200 300 400

51

01

52

02

5

Fusion levels - Chord - UPGMA

h (node height)

k (

nu

mb

er

of clu

ste

rs)

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

Figure 2. Fusion level plot of the “average” linkage dendrogram for the 25 monitoring stations in the BoPRC dataset (using 2013 averaged geochemical and bacterial characteristics). Note: the marked reductions in cophenetic distance (node height) at 4 clusters (k = 4).

Table 19 Gower (1982) distances for hierarchical agglomerative clustering of the BoP dataset (n = 25) – the smaller the estimate the better the clustered or cophenetic correlation to the initial dissimilarity matrix (i.e., better the clustering at replicating the initial data pattern). Gower distances are calculated as the sum of squared distances between the original Euclidean and cophenetic distances.

Cluster Linkage Gower Distance Rank (1 = best; 4 = worst performing)

Average 1513314 1

Single 8522937 2

Complete 10688523 3

Ward 22930890 4


Accordingly, a dendrogram was created following the UPMGA linkage procedure and pruned to 4

clusters (Figure 3). Summary statistics for each cluster of stations are presented in Table 20.

Figure 3. Pruned agglomerative, hierarchical dendrogram of 25 BoPRC monitoring stations, clustered by “average” linkage for geochemical and bacterial characteristics for 2013 (i.e., each site is represented by the annual average of monthly observations for the year 2013). T = Tauranga; ER = Eastern Rivers; WR = Western Rivers; and ECR = East Central Rivers regions.


Table 20 Agglomerative, hierarchical “average” linkage cluster results for the 25 monitoring stations included in trend analyses, reporting summary statistics for the period

01/01/2013 to 31/12/2013. Values ±1 standard deviation of the cluster mean. Key dissimilarities are shaded.

Cluster Monitoring stations and region

Region Annual summary statistics (2013)

DO

(mg/L)

Temp

(°C)

TSS

(mg/L)

Turb

(NTU)

pH

(SI)

DRP

(mg/L)

TP

(mg/L)

NH4-N

(mg/L)

NO3-N

(mg/L)

TN

(mg/L)

E.coli

(MPN/100 ml)

A

Kopurererua Stream @ SH2 (BOP710009)

Te Mania Stream @ SH2 (BOP710022)

Wairoa River @ Ruahihi station (BOP110088)

Omanawa River @ SH29 (BOP110036)

Tauranga Streams

10.4

±0.6

14.7

±1.6

14.4

±15.0

9.4

±7.3

7.12

±0.32

0.016

±0.007

0.040

±0.017

0.020

±0.022

0.472

±0.422

0.615

±0.427

462

±48

Whakatane River (BOP110011)

Nukuhou River (BOP110007)

Motu @ Waitangirua (BOP110093)

Eastern Rivers

B

Waimapu Stream @ SH29 (BOP160121)

Kopurererua Stream @SH29 (BOP710008)

Tauranga Streams

10.2

±0.3

13.2

±0.4

25.1

±20.0

10.4

±9.4

6.91

±0.01

0.015

±0.004

0.037

±0.009

0.014

±0.003

0.881

±0.114

1.036

±0.117

637

±76

C Wairoa River @ SH2 (BOP110034)

Tauranga Streams

10.0 14.8 8.5 3.6 6.82 0.011 0.027 0.011 0.431 0.539 201

D

Waioeka River @ Gorge (BOP160102)

Motu River @ SH35 (BOP110003)

Eastern Rivers

9.9

±1.0

15.2

±1.3

6.1

±2.8

4.9

±6.9

7.22

±0.55

0.027

±0.023

0.047

±0.031

0.023

±0.031

0.332

±0.307

0.456

±0.313

54

±41


Whirinaki River @ Galatea (BOP110014)

Rangitaiki River @ Murupara (BOP110015)

Rangitaiki River @ Te Teko (BOP110018)

Tarawera River @ Outlet (BOP110020)

Tarawera River @ Kawarau (BOP 110021)

Tarawera River @SH30 (BOP110023)

Tarawera River @ Awakaponga (BOP110052)

East Central Rivers

Ngongotaha Stream @ SH5 (BOP110013)

Puarenga Stream @ FRI (BOP110058)

Ohau Channel (BOP 110025)

Kaituna River @ Outlet (BOP 110026)

Kaituna River @ Paengaroa (BOP110027)

Kaituna River @ Te Matai (BOP120000)

Western Rivers


Several features are noteworthy from the average-linkage dendrogram of water quality in 2013:

Cluster A contains most Tauranga Streams (n=4) and several Eastern Rivers (n=3)

Cluster B contains only Tauranga Streams (n=2)

Cluster C contains only a single Tauranga Stream (Wairoa River @ SH2 – downstream of the

Ruahine power station)

Cluster D contains all Western Rivers (n= 6), all Eastern Central Rivers (n=7) and two Eastern

Rivers (Waioeka River and Motu River at SH35 downstream of the other Motu River station

at Waitangirau)

Clusters A and B are highly similar whilst clusters C and D are themselves highly similar.

Clusters A+B are highly dissimilar from clusters C+D (i.e., greater cophenetic distances

between clusters than amongst).

Clearly, annual average water chemistry and bacterial characteristics in 2013 varies in a pattern that

mirrors that of underlying physical location (i.e., the clusters discriminate between Western, East

Central and Tauranga Rivers whilst Eastern Rivers appear more varied and shared by highly

dissimilar clusters A and D). Processes governing water quality likely therefore vary between districts,

resulting in the changes to geochemistry and bacterial characteristics apparent between clusters.

Clusters A and B, that include most of the Tauranga Streams and Eastern Rivers, are distinguished

by their lower clarity (high turbidity and suspended solids), low DRP, greater TN and E.coli

concentrations. The Waimapu Stream and Kopurererua Stream at SH29 (cluster B) are distinguished

from other Tauranga streams in cluster A, by their markedly lower temperature and NH4-N

concentration and greater E.coli, NO3-N and TN concentrations. For instance, the Kopurererua

Stream at SH2 (cluster A) is cooler, more clear and possesses greater E.coli and NH4-N

concentrations than further upstream at SH29 (cluster B). However, the clustering routine has not

effectively captured that NO3-N and TN concentrations are actually similar between both sites on the

Kopurererua Stream (see Appendix B for annual average by site in 2013).

The two Wairoa River monitoring stations (in the Tauranga Streams region) are split between clusters

A and C. The Wairoa at SH2 is the only site in cluster C, which is distinguished from other clusters by

lower E.coli, DRP and TP concentrations (annual mean of 201 MPN/100 ml, 0.011 mg/L and 0.027

mg/L respectively, in 2013) as well as relatively low levels of suspended solids and greater water

clarity. Notably, this indicates an improvement in water quality downstream by SH2 compared to the

upstream monitoring station at the Ruahihi power station, which was classified in cluster A (i.e., into a

grouping of stations with lesser clarity and greater DRP, TP). Clusters A, B and C all share similar

NO3-N and TN concentrations, as well as similar levels of DO, temperature and pH.

The Western Rivers and East Central Rivers, as well as two Eastern Rivers, that sit in cluster D share

similar DO, temperature and pH with other clusters. Cluster D sites are distinguished by their greater

concentration of DRP, TP and NH4-N as well as lower NO3-N and TN concentrations. As with Cluster

C, cluster D monitoring stations possess high clarity and lower suspended solid concentrations than

clusters A and B. Given the two Motu River sites are split into clusters A and D, which are markedly

dissimilar by water chemistry and bacterial characteristics, this suggests a wide gradient of water

quality in the same waterway. For instance, upstream at SH35 the Motu River possesses lower NH4-

N, NO3-N and TN as well as lower E.coli concentration (x7 less) than upstream at Waitangirua.

However, clarity is actually better further upstream at Waitangirua (lower TSS and turbidity).


A summary of statistically significant (p<0.05) and ecologically meaningful trends (≥1%/yr) is

presented by cluster in Tables 21-24. As before, clusters A and B are distinguished from C and D by

their lesser clarity (greater TSS and turbidity) and greater E.coli concentrations. Long-term trends

indicate continuing stable or improving clarity and E.coli concentrations amongst all sites in clusters A

and B.

Note: both the Waimapu Stream and Kopurererua Stream @SH29 in cluster B have maintained

relatively high E.coli concentrations since 2004.

Likewise, although NH4-N concentrations are moderately high in cluster A, nearly half of sites

improved (reduced) upon these since 2004 (remaining sites in cluster A exhibited no trend in NH4-N).

Both sites in cluster B maintained relatively low NH4-N concentrations (no trend). Notably, the

Waimapu Stream and Kopurererua Stream @ SH29 were distinguished by greater NO3-N

concentrations in 2013, which have remained elevated although stable since 2004. Worsening (rising)

trends for DRP were expressed in nearly half of cluster A and both sites in cluster B since 2004,

though background DRP-concentrations in 2013 were low-moderate (~0.015 mg/L). Hence, a priority

for cluster B might be to target E.coli reductions whilst cluster A could prioritise arresting trends for

increasing DRP concentration.

Clusters C and D are distinguished by their greater clarity (lower TSS and turbidity) and lower E.coli

concentrations in 2013. Reassuringly, nearly half of sites in clusters C and D exhibited significant and

meaningful trends for further improvements to turbidity – with the exception of the Tarawera River (@

outlet) and Tarawera River (@ SH30) (the remainder being stable). No sites in clusters C or D

exhibited worsening trends for suspended solids – indeed seven exhibited meaningful and significant

improvements to current levels of great clarity. Likewise, all sites in clusters C or D exhibited stable or

improving trends to E.coli concentration leading to their low levels in 2013 (over half improving).

Although a significant and meaningful increase of +10%/yr DRP occurred in the Wairoa River (@

SH2) this was on low background levels and resulted in a low annual average concentration in 2013

(0.011 mg/L). Likewise, nearly half of sites in cluster D exhibited worsening trends for NO3-N

concentrations since 2004 though many resulted in relatively low NO3-N levels overall in 2013 (cluster

average of 0.332 mg/L NO3-N). TN concentrations in both clusters C and D are low-moderate overall,

and associated with meaningful, significant reductions since 2004 in 9 of 16 sites (the remaining 7

sites exhibiting stable TN concentration). TP concentrations for cluster D included the greatest of all

clusters and reassuringly, only one site exhibited a worsening trend (Ngongotaha Stream) whilst five

others underwent marked improvement since 2004. Hence, a priority for management would be to

arrest NO3-N increases and ensure continued improvement of TP concentrations.


Table 21 Summary of statistically significant (p<0.05) and ecologically meaningful trends (≥1%/yr) by cluster A. Trends reported for period 01/01/2004-31/12/2013 unless

where indicated by * (01/01/2009-31/12/2013).


Region RSKE of significant (p<0.05) trends ≥1%/yr

DO Temp TSS Turb pH DRP* TP NH4-N NO3-N TN E.coli

A

Kopurererua Stream @ SH2 (BOP710009)

Te Mania Stream @ SH2 (BOP710022)

Wairoa River @ Ruahihi station (BOP110088)

Omanawa River @ SH29 (BOP110036)

Tauranga Streams

+1.3%/yr

+2.0%/yr

-6.6%/yr

-7.7%/yr

-6.6%/yr

-5.5%/yr

-6.2%/yr

-6.4%/yr

+6.3%/yr

+20%/yr

+4.8%/yr

+3.1%/yr

-5.6%/yr

-16.7%/yr

-8.6%/yr

-3.6%/yr

+2.1%/yr

-3.2%/yr

-2.7%/yr

-6.4%/yr

-4.3%/yr

-10%/yr

-8.4%/yr



Motu @ Waitangirua (BOP110093)

Eastern Rivers

Number of statistically significant and ecologically meaningful trends

Improving 1 0 3 3 0 0 0 3 3 2 2

Stable 6 6 4 4 7 4 6 4 3 5 5

Worsening 0 1 0 0 0 3 1 0 1 0 0


Table 22 Summary of statistically significant (p<0.05) and ecologically meaningful trends (≥1%/yr) by cluster B. Trends reported for period 01/01/2004-31/12/2013 unless



Region RSKE of significant (p<0.05) and meaningful trends (≥1%/yr)


B

Waimapu Stream @ SH29 (BOP160121)

Kopurererua Stream @SH29 (BOP710008)

Tauranga Streams

+1.1%/yr

-3.3%/yr

-5.3%/yr

+8.7%/yr

+7.1%/yr

+2.6%/yr

-10.0%/yr


Improving 1 1 0 1 0 0 0 1 0 0 0

Stable 1 1 2 1 2 0 1 1 2 2 2

Worsening 0 0 0 0 0 2 1 0 0 0 0

Table 23 Summary of statistically significant (p<0.05) and ecologically meaningful trends (≥1%/yr) by cluster C.



DO Temp TSS Turb pH DRP TP NH4-N NO3-N TN E.coli

C

Wairoa River @ SH2 (BOP110034)

Tauranga Streams

+10%/yr


Improving 0 0 0 0 0 0 0 0 0 0 0

Stable 1 1 1 1 1 0 1 1 1 1 1

Worsening 0 0 0 0 0 1 0 0 0 0 0


Table 24 Summary of statistically significant (p<0.05) and ecologically meaningful trends (≥1%/yr) by cluster D. Trends reported for period 01/01/2004-31/12/2013 unless





D

Waioeka River @ Gorge (BOP160102)

Eastern Rivers

-4.7%/yr -9.6%/yr

Motu River @ SH35 (BOP110003)

Whirinaki River @ Galatea (BOP110014)

East Central Rivers

-8.2%/yr -6.3%/yr -4.0%/yr

Rangitaiki River @ Murupara (BOP110015)

-9.1%/yr +4.1%/yr +6.7%/yr

Rangitaiki River @ Te Teko (BOP110018)

-12.1%/yr

Tarawera River @ Outlet (BOP110020)

+4.4%/yr

Tarawera River @ Kawarau (BOP 110021)

-12.5%/yr +2.7%/yr -1.5%/yr -7.8%/yr

Tarawera River @SH30 (BOP110023)

-14.3%/yr -6.7%/yr -23.0%/yr

Tarawera River @ Awakaponga (BOP110052)

+4.8%/yr -1.8%/yr -5.6%/yr -1.4%/yr -14.2%/yr


Ngongotaha Stream @ SH5 (BOP110013)

Western Rivers

-4.3%/yr -5.0%/yr -1.1%/yr -7.6%/yr

Puarenga Stream @ FRI (BOP110058)

-2.2%/yr -2.0%/yr +1.3%/yr -1.8%/yr -3.5%/yr -8.6%/yr

Ohau Channel (BOP 110025)

-5.2%/yr -7.0%/yr -9.4%/yr +8.6%/yr -4.1%/yr -3.5%/yr

Kaituna River @ Outlet (BOP 110026)

-5.2%/yr -5.4%/yr -8.7%/yr +7.7%/yr +13%/yr -2.0%/yr -7.0%/yr

Kaituna River @ Paengaroa (BOP110027)

-19.4%/yr -8.6%/yr +9.2%/yr

Kaituna River @ Te Matai (BOP120000)

-14.1%/yr -6.3%/yr +7.8%/yr


Improving 0 0 7 7 0 0 5 2 2 9 8

Stable 15 15 8 6 15 15 9 12 8 5 7

Worsening 0 0 0 2 0 0 1 1 6 1 0


3.4 Water Quality Patterns (2009-2013)

3.4.1 Cluster A + B

The PCA performed on standardised, annual averages for water quality at monitoring stations located

in cluster A and B from 2009 to 2013, demonstrated that axes 1 and 2 (λ1 and λ2) explained 54% of

total variance amongst water quality indicators and sites (Table 25). A corresponding broken stick

model demonstrated that only axes 1 and 2 explained more variance than would be expected by

change (i.e., are of interest – although axis 3 is approximately equal) (Figure 4).

PC

1

PC

2

PC

3

PC

4

PC

5

PC

6

PC

7

PC

8

PC

9

PC

10

PC

11

PC

12

Eigenvalues

0.00.51.01.52.02.53.03.5

Average eigenvalue

PC

1

PC

2

PC

3

PC

4

PC

5

PC

6

PC

7

PC

8

PC

9

PC

10

PC

11

PC

12

% variance

05

1015202530

% eigenvalue

Broken stick model

Figure 4. Performance measures of PCA on clusters A and B (annual averages 2009-2013).


Table 25 PCA statistics for ordination on centred and standardised variables in Cluster A and B. Only the first two axes are likely to be meaningful.

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

Eigenvalue 3.798 2.745 1.657 1.215 0.909 0.702 0.444 0.234 0.156 0.090 0.046 0.005

Proportion explained

0.317 0.229 0.138 0.101 0.076 0.058 0.037 0.020 0.013 0.007 0.004 0.000

Cumulative proportion

0.317 0.545 0.683 0.785 0.860 0.919 0.956 0.975 0.988 0.996 0.999 1.000

Figure 5. PCA of water quality (annual average) for the period 2009-2013, at monitoring stations in clusters A and

B (scaling = 2 to ensure vectors are drawn to approximate correlation between indicators).Sites correspond to

annual average scores for variables at each monitoring station. (The four letters of each site label correspond to

the location and digits correspond to year).Colours correspond to Tauranga Streams and Eastern Rivers.

Inspection of the PCA biplot for clusters A and B (2009-2013) reveals that over the past 5 years at the

10 sites in the Tauranga Streams and Eastern Rivers regions (Figure 5):


Turbidity, TSS, E.coli, TP and DRP concentrations are positively correlated and co-vary

meaning lower clarity water is associated with greater phosphorus and faecal bacterial

concentrations as well as greater temperature.

Note: The similarity in responses amongst turbidity, TSS, E.coli, TP and DRP variables indicates the

likelihood of a shared pathway or controlling mechanism, possibly through the effects of riparian

management. For instance, effective riparian management would reduce livestock access, overland

runoff of sediment/bacteria/phosphorus and reduce in-stream temperature by greater shading as

riparian vegetation is allowed to regenerate.

TN and NO3-N are negatively correlated with DO (mg/L). Higher nitrogen concentrations are

associated with lesser dissolved oxygen. Although unlikely to be directly linked, higher

nitrogen availability appears associated with another process resulting in reduced oxygen

availability (i.e., excessive periphyton or macrophyte growth under high NO3-N that causes

diel DO minima) and/or a shared pathways (i.e., lower DO associated with hypoxic/anoxic

groundwater contributions to a stream and greater NO3-N contributions in baseflow).

Curiously, DO appears uncorrelated with temperature (i.e., vectors are orthogonal). Whereas

in theory, temperature is a key determinant of absolute DO (mg/L rather than relative or %

DO). As above, if riparian management is a key driver of the positive correlation between

TSS, turbidity, TP, DRP and temperature, then improved shading to reduce temperature

would be expected to result in DO becoming linked once more to in-stream temperature.

The primary axis is driven by changes primarily to TSS and turbidity (higher to lower turbidity

from left to right) as well as DO (lower to higher from left to right). The secondary axis is a

response to changes in DRP and turbidity (lower to higher, top to bottom) as well as NO3-N

and TN (higher to lower, top to bottom). Combined, this suggests that the most marked

differences over the last five years at monitoring stations in clusters A and B have been to

water clarity (turbidity, TSS) and nutrient availability (DRP, NO3-N).

The ordination confirms the clustering of sites with two clear (coloured) groupings. Eastern

Rivers (Whakatane, Nukuhou and Motu at Waitangirua) possess greater DO and lesser

NO3-N than Tauranga streams (Te Mania, Omanawa, Waimapu, Kopurererua at SH2 and

SH29).

The inter-annual pattern also highlights 2011 as a year of higher turbidity, TSS, TP and DRP

concentrations (many stations shift to the bottom left of the PCA biplot in 2011), followed by a

recovery at most stations in clusters A and B by 2013. The exception being the Kopurererua

Stream at SH2 which suffered a marked deterioration in NH4-N concentration during 2013 on

already elevated DRP and TP concentrations (as well as highly turbid water). The Nukuhou

and Whakatane Rivers both underwent quite marked changes in turbidity and phosphorus

concentration (TP, DRP) over the 5-year period from 2009-2013, although both have most

recently returned to lower phosphorus availability and greater clarity in 2013.

Overall, the ordination underscores the earlier classification into clusters A and B between

Tauranga and Eastern Rivers, with changes to water clarity (turbidity and TSS) and

phosphorus availability (DRP, TP) dominating the period 2009-2013 (amongst and between

stations). Curiously, absolute DO appears to be unrelated to in-stream temperature or

phosphorus availability and is instead highly inversely correlated with NO3-N and TN, which

might suggest instream productivity/respiration is associated with DIN-availability.


3.4.2 Cluster C + D

The PCA performed on standardised, annual averages for water quality at monitoring stations located

in cluster C and D from 2009 to 2013, demonstrated that axes 1 and 2 (λ1 and λ2) explained 71% of

total variance amongst water quality indicators and sites (Table 26). A corresponding broken stick

model demonstrated that only axis 1 explained more variance than would be expected by change

(i.e., is of interest – although axes 2 and 3 are approximately equal) (Figure 6). P

C1

PC

2

PC

3

PC

4

PC

5

PC

6

PC

7

PC

8

PC

9

PC

10

PC

11

PC

12

Eigenvalues

0123456

Average eigenvalue

PC

1

PC

2

PC

3

PC

4

PC

5

PC

6

PC

7

PC

8

PC

9

PC

10

PC

11

PC

12

% variance

0

10

20

30

40

50% eigenvalue

Broken stick model

Figure 6. Performance measures of PCA on clusters C and D (annual averages 2009-2013).

Table 26 PCA statistics for ordination on centred and standardised variables in Cluster C and D. Only the first three axes are likely to be meaningful.

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

Eigenvalue 6.337 2.192 1.647 0.728 0.529 0.259 0.108 0.089 0.052 0.025 0.020 0.012

Proportion explained

0.528 0.183 0.137 0.061 0.044 0.022 0.009 0.007 0.004 0.002 0.002 0.001

Cumulative proportion

0.528 0.711 0.849 0.909 0.953 0.974 0.983 0.991 0.995 0.997 0.999 1.000


Figure 7. PCA of water quality (annual average) for the period 2009-2013, at monitoring stations in clusters A and

B (scaling = 2 to ensure vectors are drawn to approximate correlation between indicators).Sites correspond to

annual average scores for variables at each monitoring station. (The four letters of each site label correspond to

the location and digits correspond to year). Colours correspond to Tauranga Streams, Eastern Rivers, Eastern

Central Rivers and Western Rivers.

Inspection of the PCA biplot for clusters C and D (2009-2013) reveals that over the past 5 years at the

16 sites in the Tauranga Streams (Wairoa River at SH2), Eastern Rivers (Waioeka and Motu River at

SH35), Eastern Central Rivers and Western Rivers regions (Figure 7):

A principle axis (λ1) exists of positively correlated changes to nutrient availability (DRP, TP,

NO3-N, NH4-N, TN), temperature and DO. The length of this primary gradient is heavily

influenced by the Wairoa River at SH2, whose nutrient concentration, temperature and DO

are all very low. Removing the latter station would likely result in changes to the secondary

axis becoming more dominant amongst remaining sites in clusters C and D.

Turbidity and TSS are positively correlated and co-vary, driving the secondary axis (λ2). Hene,

the second most marked differences in water quality amongst monitoring stations, between

2009 and 2013, within clusters C and D is water clarity.


Note: low absolute DO (mg/L) is a concern in the Wairoa at SH2 – possible causes could include high

in-stream plant growth (reducing nutrient availability but taking-up available DO) and/or contributions

of low-DO groundwater (reducing in-stream temperatures). The lower in-stream temperature at the

Wairoa (@SH2) would tend to imply limited in-stream plant growth, as the latter would be associated

with greater direct insolation and solar heating.

Curiously, TSS and turbidity appear uncorrelated with TP or DRP (i.e., vectors are

orthogonal), suggesting mechanisms governing water clarity are not strongly linked to

nutrient losses.

The Motu and Waioeka Rivers (Eastern Rivers) both exhibited the most marked variations

along λ2 (water clarity) between 2009 and 2013, with similar temporal patterns exhibited by

both sites (including degradation of clarity in 2011 and 2012 followed by a recovery to

reduced annual mean TSS and turbidity in 2013). In both systems, limited change to nutrient

availability, faecal bacterial concentrations and temperature occurred – stressing the

sediment management is a priority therein.

Absolute variation in water physicochemistry and faecal bacterial concentrations was less

marked between 2009 and 2013 amongst Eastern Central and Western Rivers (Whirinaki,

Rangitaiki, Tarawera Ngongotaha, Puarenga and Kaituna Rivers and Ohau Channel),

although typified by greater overall nutrient availability (compared to Tauranga Stream and

Eastern River stations in clusters C and D). However, note this is contrasted by earlier

indications of marked relative (RSKE) change in clarity (turbidity, TSS) TN, E.coli

concentrations.


4.0 Discussion of Trends in Water Quality

In total, 279 water quality records were analysed with results reported earlier in Tables 11-18, where statistically significant (p<0.05) and ecologically

meaningful (>1% per year RSKSE). Table 27 summarises all ecologically meaningful and statistically significant trends over the period 2004-2013 for 20 sites

and 2009-2013 at 5 sites.

Note: in this report, trends with p-values ≥0.05 are insignificant and labelled ‘stable’.

Table 27 Summary trend output for all 25 sites included for analysis in this report. Only significant (p<0.05) and ecologically meaningful trends are reported. Trends reported for period 2004-2013 except for * where period is 2009-2013.

Number of ecologically meaningful & statistically

significant trends

Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP * (mg/L)

TP (mg/L)

Chl-a * (mg/L)

Temp. (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Uncorrected Worsening 0 0 7 1 1 6 3 0 1 0 2 0

Stable 15 23 14 18 12 19 17 1 10 25 12 15

Improving 10 2 4 6 12 0 5 3 1 0 11 10

Stable or improving 25 25 18 24 24 19 22 4 11 25 23 25

Flow-corrected

Worsening 0 0 4 0 1 6 4 0 1 0 4 0

Stable 19 21 15 17 12 19 16 1 23 25 10 10

Improving 6 4 6 8 12 0 5 3 1 0 11 15

Stable or improving 25 25 21 25 24 19 21 4 24 25 21 25


4.1 Faecal bacteria (E.coli)

All 25 sites across the four regions exhibited stable or statistically significant and ecologically

meaningful improvements in E.coli concentrations and flow-corrected loading.

Ten sites exhibited a significant and meaningful improvement in observed E.coli concentrations (all

bar one for the period 2004-2013). Improvements for E.coli concentration varied from -3.5%/yr (Ohau

Channel) to -23.0%/yr (Tarawera River at SH30) on the series median.

Within the Eastern Rivers region, the Waioeka, Nukuhou and Whakatane Rivers observed significant

and ecologically meaningful reductions in E.coli concentration and loads. Within the East Central

region, the Tarawera River observed significant and ecologically meaningful reductions in E.coli

concentrations at all three monitoring stations downstream of its outlet (including the only site noted

above as possessing a record from 2009-2013). Within the Western Rivers region, the Ngongotaha

and Puarenga stream that feed Lake Rotorua observed significant and meaningful declines in E.coli

concentrations and flow-corrected loads (-7.6 to -10.9%/yr 2004-2013). The Ohau Channel from Lake

Rotorua and outlet of the Kaituna River from Lake Rotoiti, both also observed significant and

meaningful declines in E.coli concentrations (2004-2013), whereas faecal bacterial concentrations

and flow-corrected loadings were stable downstream on the further two sites of the Kaituna River.

Note: by correcting and normalising for changes in flow that otherwise could dilute or concentrate contaminants, flow-corrected concentrations are a direct proxy for catchment loading. As such, this report infers changes to catchment loading from flow-corrected trends (so-called “flow-corrected loading”).

Trends for E.coli concentrations and loading within the Tauranga Streams region were all stable

(2004-2013) except a significant and meaningful decline in faecal loading (-9.9%/yr) at Omanawa

River.

4.2 Dissolved Oxygen

Trends in dissolved oxygen concentrations are all stable or improving across the Bay of Plenty

stations with the exception of the Kaituna River at its outlet from Lake Rotoiti (-0.4%/yr, p<0.023).

Note: The decline in DO at the outlet from Lake Rotoiti is not “ecologically-meaningful” – but the cause for this reduction in DO should be investigated and arrested prior to further reductions in oxygen availability (i.e., to avoid the risk of harm to ecosystem health).

Two sites observed ecologically meaningful and statistically significant improvements in oxygenation

(Waimapu Stream +1.1%/yr, p<0.033 and Nukuhou River +1.3%/yr, p<0.001). (All values correspond

to uncorrected DO data as flow-correction would be inappropriate, given the effects of DO are

instantaneous and also not a consequence of loading from the land).

Note: the limited resolution of DO records and basis on instantaneous or spot measurement, results in uncertainty for DO trend inferences as diurnal minima are unlikely to be repeatedly captured without higher-resolution, continuous sampling (e.g., Davies-Colley et al., 2013).

4.3 Nitrate-Nitrogen (NO3-N)

Trends in NO3-N concentrations varied markedly between regions. Within the Eastern Rivers, all five

sites exhibited a stable or improving (reducing) trend for observed and flow-corrected NO3-N

concentrations. That is, no significant or meaningful increases in NO3-N concentrations or flow-


corrected loads occurred over the period 2004-2013 within the Motu, Waioeka, Nukuhou and

Whakatane Rivers. Indeed, the Nukuhou and Whakatane Rivers observed a meaningful and

significant decline in NO3-N concentrations (-2.7%/yr, p<0.01 and -3.2%yr, p<0.03 respectively).

When corrected for flow and amongst these, only the Waioeka River observed a decline in NO3-N

loading albeit a very large improvement (-17.3%/yr, p<0.03).

The pattern for changes to NO3-N concentrations and flow-corrected loads since 2004 within the

Western Rivers region is complex. For instance, of the 6 monitoring stations, the Ngongataha stream

expressed no trend (stable) for NO3-N concentration or loading. The Puarenga stream underwent a

decline of -1.8%/yr (p<0.001) and -1.8%/yr (p<0.001) in NO3-N concentrations and flow-corrected

loading, respectively. However, the Ohau Channel and entirety of the Kaituna River expressed rising

trends in uncorrected NO3-N trends (from +7.8%/yr [p<0.001] to +12.9 %/yr [p<0.001]). Curiously, the

greatest relative increase in NO3-N concentration occurred at the outlet from Lake Rotoiti and lowest

increase, furthest downstream on the Kaituna River at Te Matai. When corrected for flow, only the

Kaituna River at its outlet (+14.6%/yr, p<0.025) and furthest downstream at Te Matai (+5.2%/yr,

p<0.001) experienced increasing NO3-N loads.

Note: the increase in uncorrected NO3-N concentrations of +8.6%/yr (p<0.018) at the Ohau Channel (from Lake Rotorua) is lower than the increased NO3-N concentration of +12.9%/yr (p<0.001) at the outlet of Lake Rotoiti, which the Ohau channel feeds (although note that trends in TN are markedly different, being stable or reducing at the Ohau Channel and throughout the Kaituna River).This suggests both lakes are experiencing a rise in NO3-N concentration, although it should be noted that trends in TN markedly differ, reducing significantly (p<0.05) at the Ohau Channel and outlet to the Kaituna River (both uncorrected and flow-corrected). A plausible hypothesis to explain the combination of increased NO3-N and decreased TN concentrations is of reduced assimilation of NO3-N either on existing or increasing DIN loads (i.e., decreased phytoplankton growth and uptake of NO3-N leaving more in solution). Evidence for this includes the trends for decreasing Chl-a (algal biomass) at the Ohau Channel (uncorrected [-26.6%/yr, p<0.001] and flow-corrected [-24.6%/yr, p<0.002]) and the outlet to the Kaituna River (uncorrected only [-26.4%/yr, p<0.001], flow-corrected are insignificant but also of a negative magnitude).

Within the Tauranga Streams region, all sites bar one (Omanawa River) exhibited no meaningful or

significant trend in NO3-N concentrations or flow-corrected loads. Loading to the Omanawa River has

increased by +1.6%/yr (p<0.001), driving increased NO3-N concentrations of +2.1%/yr (p<0.001).

Within the East Central Rivers region, the majority of water quality stations recorded stable (no trend)

NO3-N concentrations and flow-corrected loads since 2004. The Whirinaki River underwent a

meaningful and significant improvement (decline) in NO3-N concentrations (-2.8%/yr, p<0.03) and

loading (-6.3%/yr, p<0.00). By contrast, the Rangitaiki River at Murupara exhibited meaningful,

significant increases to NO3-N concentration (+4.1%/yr, p<0.001) and flow-corrected load (+4.2%/yr,

p<0.001). Further downstream at Te Teko bridge, no apparent trend in NO3-N concentration or

loading is apparent (2004-2013), suggesting any increase upstream has been matched by a decrease

downstream or the flux of NO3-N is readily uptaken. Flow-corrected NO3-N concentrations have

remained stable on the Tarawera River at all four monitoring stations (since 2004 at three stations

and 2009 at the third) although an meaningful, significant increase of +2.7%/yr (p<0.001) was

expressed in uncorrected NO3-N concentrations at Kawarau Bridge.

4.4 Ammoniacal-Nitrogen (NH4-N)

With the exception of the Kaituna River at its outlet from Lake Rotoiti, all sites experienced either no

trend (stable) or a significant, meaningful trend for improving (decreasing) NH4-N concentrations and


flow-corrected loads. Reductions are therefore widespread and are of a higher magnitude compared

to most other water quality attributes tested.

At the outlet from Lake Rotoiti, the Kaituna River experienced a rise in absolute and flow-corrected

NH4-N concentrations of +7.7%/yr (p<0.03) and +14.6%/yr (p<0.03) (2004-2013). These changes are

not evident further downstream on the Kaituna River at Paengaroa (BOP110027) and Te Matai

(BOP120000) where absolute NH4-N concentrations exhibited a stable trend since 2009, but flow-

corrected NH4-N concentrations (loading) decreased by -38.7%/yr (p<0.03) and -3.7%/yr (p<0.04)

respectively.

Note: the increase in NH4-N and NO3-N concentrations at the Kaituna River’s source in Lake Rotoiti are further evidence of either increased inputs and/or reduced uptake of DIN (i.e., continued ammonification of organic carbon from the lake benthos but limited assimilation due to reduced phytoplankton biomass). As before, the trends for decreasing Chl-a at the Ohau Channel (uncorrected and flow-corrected) and the outlet to the Kaituna River (uncorrected only; flow-corrected is insignificant) are evidence for decreasing phytoplankton biomass and therefore, a contributing factor to rising DIN availability in both Lake Rotorua and Lake Rotoiti.

All regions reported meaningful and significant reductions in absolute NH4-N concentration, ranging -

5.6%/yr to -16.7%/yr. In particular, the Tarawera River has undergone marked reductions in NH4-N

concentrations (2004-2013) nearest Boyce Park (-12.5%/yr, p<0.002) and furthest downstream at

Awakaponga (-5.6%/yr, p<0.001).

Flow-corrected trends display a similar pattern with 8 of the 25 sites exhibiting improved water quality

(reduced NH4-N), ranging from –3.7%/yr to -38.7%/yr (note: the min and max improvements were

recorded on the Kaituna River from 2009-2013). No site exhibited any significant and meaningful

trend to worsening flow-corrected NH4-N concentration (i.e., the Kaituna River at its outlet was

actually stable when corrected for changes in flow).

In total therefore, 7 different rivers of the 15 tested - 16 including the Ohau Channel - demonstrated

meaningful and significant reductions in flow-corrected NH4-N loading including the Tarawera River at

Boyce Park (-14.35%/yr, p<0.002) and Awakaponga (-4.7%/yr, p<0.001) (2004-2013) and Kaituna

River at Paengaroa and Te Matai (-38.7%/yr, p<0.03 and -3.7%/yr, p<0.04 respectively).

4.5 Total Nitrogen (TN)

Patterns of significant and meaningful trends in TN largely mirrored those of NH4-N and NO3-N, with

only a single site on the Rangitaiki River (at Murupara) observing a deterioration (increase) in

concentration of TN (+6.7%/yr, p<0.001) or flow-corrected TN load (+4.0%/yr, p<0.001). Of the

remaining 24 sites (15 rivers and Ohau Channel), half (12) exhibited significant and meaningful

improvements (decrease) in TN concentration and flow-corrected loading, distributed throughout the

four regions. Reductions in absolute TN concentration varied -1.1%/yr to -6.7%/yr whilst significant

and meaningful declines in flow-corrected TN concentration varied -1.1%/yr to -6.6%/yr.

Curiously, the Kaituna River at its outlet from Lake Rotoiti exhibited a reduction in TN concentration of

-2.0%/yr despite significant (p<0.05) increases in NO3-N and NH4-N concentrations of +12.9%/yr and

+7.7%/yr, respectively. Although this may correspond to instrument or laboratory error, inspection of

the monitoring record for 2004-2013 suggests that on average, only 23.3% of TN is comprised of

NO3-N and NH4-N. Consequently, organic-N is a major component of TN in the Kaituna River at its

outlet from Lake Rotoiti and a decline in the latter appears highly likely to explain the trend for -

2.0%/yr (p<0.04) in TN concentration (2004-2013). For instance, phytoplankton Chl-a records are only


available on the Kaituna River and Ohau Channel, where they mirror changes to TN (see Tables 17-

18). The reduction in uncorrected TN concentrations at the outlet from Lake Rotoiti is matched by a

significant (p<0.001), meaningful reduction in Chl-a of -26.4%/yr (with a similar reduction from the

Ohau Channel of -26.6%/yr, p<0.001)

Note: the Kaituna River at its outlet was the only site to exhibit an unusual pattern of reducing TN but

increasing NO3-N and NH4-N (although as noted, the Ohau Channel experienced a rise in the

concentration of NO3-N coupled to a decrease in TN, but no or an insignificant change to NH4-N).

4.6 Dissolved Reactive Phosphorus (DRP)

Significant and meaningful worsening (increasing) trends in absolute DRP concentrations were only

apparent, albeit widely, in the Tauranga Stream region. For instance, 6 sites on 5 rivers in the latter,

exhibited significant (p<0.05) rising (worsening) trends of +4.8%/yr (Omanawa River) to +20.0%/yr

(Te Mania Stream). The remaining 18 sites on 11 rivers and streams in the Western, Eastern and

Eastern Central regions exhibited stable DRP concentrations over the period 2009-2013. Hence,

increased DRP concentrations since 2009 appear limited to the Tauranga Streams (Waimapu Stream,

Wairoa River, Omanawa River, Kopurererua Stream and Te Mania Stream).

Flow-corrected DRP trends varied somewhat, with worsening (rising) corrected DRP concentrations

(loads) in 4 of the Tauranga Streams sites (Waimapu Stream, Omanawa River, Kopurererua Stream

at SH2 and Te Mania Stream [2009-2013]). Increased flow-corrected DRP concentrations (loading)

were evident from 2009-2013 in middle reaches of the Tarawera River at Boyce Park (+4.0%/yr,

p<0.005), though not further upstream at the outlet from Lake Rotoiti nor downstream at SH30 or

Awakaponga. In the Western Rivers region, only the Puarenga Stream exhibited a trend for rising

flow-corrected DRP concentrations from 2009-2013 (+5.6%/yr, p<0.03), which is unusual given the

recent alum-dosing programme implemented on the Puarenga.

4.7 Total Phosphorus (TP)

Significant and meaningful worsening (increasing) trends in absolute TP concentration occurred in

only 3 of the 25 sites. These were restricted largely to the Tauranga Streams region, including the

Omanawa River (+3.1%/yr, p<0.001) and Kopurererua Stream at SH2 (+2.6%/yr, p<0.05). (Note: no

significant trend for worsening TP concentration was noted further upstream on the Kopurererua

Stream at the SH29 bridge [2004-2013]). The Puarenga Stream was the remaining site to exhibit a

reliable trend for worsening (increased) TP concentration since 2004 (+1.3%/yr, p<0.001).

With the exception of the Puarenga Stream, the western rivers region exhibited widespread

improvements in absolute TP concentration throughout the Kaituna River (3 sites, ranging from -

8.7%/yr [p<0.001] at the outlet from Lake Rotoiti to -6.3%/yr furthest downstream [p<0.01]). This

pattern is mirrored by the decrease in absolute TP concentrations within the Ohau Channel since

2004 (-9.4%/yr, p<0.001). Examination of flow-corrected trends in TP reveals a similar pattern of

reduced TP loading through the Ohau Channel (-9.3%/yr, p<0.001) and in the Kaituna River at its

outlet from Lake Rotoiti (-8.2%/yr, p<0.001) and middle reach at Paengoroa (-3.0%/yr, p<0.05).

In the East Central Rivers region, the Tarawera River at Boyce Park exhibited a significant and

meaningful rise in flow-corrected TP concentration since 2004 (+1.6%/yr, P<0.01), whereas improving

flow-corrected trends were evident on the Tarawera River further downstream at the SH30 road


bridge since 2009 (-3.5%/yr, p<0.01) and also since 2004, furthest downstream at Awakaponga (-

1.8%/yr, p<0.002).

Note: although 6 of 7 monitoring stations in the Tauranga Streams region exhibited significant,

meaningful increased absolute DRP concentration over the last 5-10 years, only two sites observed

similar increased absolute TP. Discrepancies between the two could be the consequence of

reductions in organic-P off-setting increased DRP, and/or minimal contributions of DRP to TP.

4.8 Temperature

Only two sites exhibited a significant and meaningful trend for changing stream temperature, both in

the Tauranga Streams region. The Waimapu Stream is improving with a decline in stream

temperature of -3.3%/yr (p<0.04) since 2009 whilst the Wairoa River at Ruahihi power station

exhibited a worsening (warming) trend since 2004 for temperature of +2.0%/yr (p<0.05) that was not

evident further downstream in the Wairoa River at the SH2 Bridge.

Note: instantaneous temperature measurements, even spread over 10 years at monthly resolution

can fail to note trends for increasing or decreasing maxima (e.g., Davies-Colley et al., 2013), limiting

the faith in inferences attached to the regional water quality monitoring information.

4.9 pH

None of the 25 sites analysed here exhibited a significant and meaningful trend in pH, suggesting

limited change to this aspect of stream geochemistry throughout the Bay of Plenty.

Note: as with temperature, continuous monitoring of pH is recommended at fine-temporal resolution

to reveal trends in maxima and minima.

4.10 Turbidity

Only two sites - both on the Tarawera River in the East Central Rivers region - observed a significant

and meaningful deterioration in absolute turbidity (note: flow-corrected turbidity is not recommended

for analysis as effects on ecosystem health attached to visual clarity are instantaneous). A worsening

(increase) in turbidity was recorded since 2004 at its outlet (+4.4%/yr, p<0.001) which was not

expressed further downstream at Boyce Park, nor the SH30 road-bridge (where turbidity actually

improved by -14.3%/yr [p<0.001]). However, a significant and meaningful trend for rising turbidity

since 2004 was recorded furthest downstream on the Tarawera River at Awakaponga (+4.8%/yr,

p<0.003).

All 7 sites in the Tauranga Streams region observed either stable or improving trends for absolute

turbidity over the last decade. Here, the Waimapu (-5.3%/yr, p<0.03) and Te Mania stream (-5.5%/yr,

p<0.001) markedly improved since 2004. Likewise, all 5 sites in the Eastern Rivers exhibited reliable

stable or improving trends for absolute turbidity since 2004 with both the Nukuhou River (-6.4%/yr,

p<0.001) and Whakatane River (-6.2%/yr, p<0.01) improving significantly. All 6 sites in the Western

Rivers region, also exhibited significant (p<0.05) and meaningful (>1%/yr) trends for improving

(reducing) turbidity. On the Kaituna River, improvements to absolute turbidity ranged from -5.4%/yr

(p<0.001) at its outlet to -14.1%/yr (p<0.04) furthest downstream.


Clearly, there are widespread patterns for improving turbidity which should drive a consequent

improvement in water quality through increased water clarity.

4.11 Total Suspended Solids

No significant and meaningful trend for worsening (increasing) total suspended solid (TSS)

concentration was noted at any of the 25 monitoring sites over the past decade. Reassuringly, this

supports the inferences above that improving or stable water clarity has been expressed since 2004

across 20 sites and since 2009 at 5 additional sites.

Indeed, 10 of the 25 sites analysed here exhibited improving (reduced) absolute TSS concentrations.

These included:

Te Mania Stream in the Tauranga Streams region (-6.6%/yr, p<0.006) (since 2004);

Nukuhou River (-6.6%/yr, p<0.001) and Whakatane River (-7.7%/yr, p<0.01) in the Eastern

Rivers region (since 2004);

Whirinaki River (-8.2%/yr, p<0.001) and Rangitaiki River (-9.1%/yr and -12.1%/yr, p<0.001) in

the East Central Rivers region (since 2004);

Ngongataha Stream (-4.3%/yr, p<0.01), Puarenga Stream (-2.2%/yr, <0.02), Ohau Channel (-

5.2%/yr, p<0.01) and Kaituna River at its outlet (-5.2%/yr, <0.01) in the Western Rivers

region (since 2004).

Following flow correction, significant and meaningful trends for improved TSS occurred in 14 sites

distributed throughout the four Bay of Plenty regions (note: no flow-corrected, significant trends for

worsening TSS were noted in the 25 records). This is further evidence for widespread improvement to

sediment management in the Bay of Plenty over the past decade, alongside trends in turbidity.

Note: the Kaituna River exhibited improving meaningful and significant trends for turbidity throughout

the three monitoring stations, whereas only the upper Kaituna River at its outlet from Lake Rotoiti

recorded a significant and meaningful decline in TSS (-5.2%/yr, p<0.003).


5.0 Water Quality Conclusions

Water quality has been analysed for 25 stations in the Bay of Plenty, across 12 indicators, from 2004-

2013 (n = 20) and 2009-2013 (n = 5). Hierarchical clustering by average-linkage (UPGMA)

demonstrated that water quality across the 12 indicators, averaged from monthly sampling in 2013,

exhibited a pattern that mirrored geographical locations. For instance, only four clusters appeared

meaningful, of which the Eastern Rivers possessed distinctly different water quality to the Western

and East Central Rivers regions. The latter possessed similar water quality whilst the Tauranga

Streams exhibited the greatest diversity of water quality, with sites distributed mostly in Cluster A (with

the Eastern Rivers) but also comprising Clusters B and C in their entirety. Notably, the Wairoa River

at SH2 behaves distinctly from its headwaters and also from other Tauranga streams for its greater

clarity (lower TSS and turbidity) and lower E.coli concentrations downstream (in 2013).

Ordination (PCA) demonstrated a complex pattern of water quality change within and between each

cluster, over the past five years (2009-2013). In most sites across clusters A, B, C and D, water

quality has varied most markedly in terms of clarity (e.g., turbidity, TSS) followed thereafter by nutrient

availability (varying between clusters - primarily NH4-N, NO3-N and TN amongst Tauranga Streams

and Eastern Rivers; and primarily DRP and NH4-N amongst East Central and Western Rivers).

Additional findings from ordinations include that, within:

Clusters A and B: turbidity, TSS, E.coli, TP and DRP co-vary indicating a likely shared

pathway (i.e., ineffective riparian management, which would otherwise reduce livestock

access and overland runoff contributing sediment/bacteria/phosphorus). Also, of note is that

TN and NO3-N negatively co-vary with absolute DO (and unusually, that DO is uncorrelated

to temperature). This might be a consequence of increased in-stream productivity/respiration

driven by increased DIN-availability; and/or that lower DO is associated with dominant

contributions of hypoxic/anoxic groundwater enriched in NO3-N to stream baseflow.

Clusters C and D: turbidity and TSS co-vary but are uncorrelated with TP, DRP, NO3-N, NH4-

N or TN, meaning mechanisms governing water clarity are different from Clusters A and B

(i.e., are not strongly linked to nutrient losses). Also of note is that the Wairoa River at SH2

observed the lowest nutrient concentrations, temperature and DO of sites in Clusters C and

D. The lower DO is of concern for fish health and possible causes include high in-stream

plant growth (reducing nutrient availability and DO through respiration) and/or contributions of

hypoxic/anoxic groundwater (thereby reducing in-stream temperature). The lack of higher

temperatures would indicate the latter over the former (i.e., insufficient direct insolation to

heat waters would also restrict light availability and plant growth).

In-keeping with the patterns expressed in clustering, quantitative trend analysis amongst the 12 water

quality indicators by region, indicates:

Tauranga Streams: largely stable or improving across the suite of nutrient, sediment and

bacterial indicators, with the exception of DRP and TP concentrations and flow-corrected

loadings that are rising (worsening) at most sites for DRP and a third of sites for TP. The Te

Mania Stream has improved markedly and significantly since 2004 for NH4-N, TN, turbidity

and TSS. The Omanawa River has worsened significantly since 2004 for NO3-N (but not TN)

and worsened significantly since 2009 for DRP and TP.


Eastern Rivers: all five sites on the Motu, Waioeka, Nukuhou and Whakatane Rivers have

recorded stable or improving water quality for the uncorrected suite of nutrient, sediment and

bacterial indicators, since 2004. Both the Nukuhou and Whakatane Rivers have improved

meaningfully and significantly for faecal bacterial concentration/loading, DO concentration,

NO3-N concentrations (but not loads), NH4-N concentration/loading and TN

concentration/loading, as well as for turbidity and TSS concentration.

East Central Rivers: all seven monitoring sites observed stable or improving significant and

meaningful trends for E.coli, DO, NH4-N, temperature, pH and TSS. Only the Rangitaiki River

at Murupara observed a rising (worsening) trend for TN concentration or loading (+6.7%/yr,

p<0.001 and +4.0%/yr, p<0.001 respectively). Although no sites exhibited a trend for TP

concentration, the Tarawera River at Boyce Park exhibited a meaningful and significant trend

for increased TP and DRP flow-corrected concentration or loading (+1.6%/yr, p<0.002 and

+4.0%/yr, p<0.004 respectively). In addition, the Tarawera River has exhibited a trend for

rising turbidity at two of four monitoring stations (its outlet and furthest downstream at

Awakaponga).

Western Rivers: all six monitoring stations exhibited a stable or improving significant and

meaningful trend for E.colil, DO, TN, DRP, temperature, pH, turbidity and TSS concentration.

Although, DRP and TP flow-corrected concentration (loading) has worsened on the Puarenga

Stream (+5.6%/yr, p<0.03 and +1.8%/yr, p<0.01 respectively). That said, the Ohau Channel

and Kaituna River at its outlet from Lake Rotoiti and Paengaroa have undergone meaningful

and significant improvements to TP loading, ranging from -3.0%/yr to -9.3%/yr. Most

impressively, all Western River sites have undergone meaningful and significant

improvements to turbidity, ranging from -2.0%/yr (Puarenga Stream since 2004) to -19.4%/yr

(Kaituna River at Paengaroa since 2009). Similar patterns are evident in improved TSS

concentrations and flow-corrected loading, reinforcing the likelihood that allochthonus and

autochthonus particulate matter supplies have been markedly reduced throughout the

Western Bay of Plenty.

By comparison to provisional NOF guidelines on ecosystem and human health water quality

attributes, annualised statistics for 2013 at all sites rest above the Band C/D bottom-lines for E.coli,

DO (1-day minimum [mg/L]), NO3-N (median and 95th%) and NH4-N (median and 95

th%) (see

McBride, 2012; Davies-Colley et al., 2013). Although limited by their non-continuous status,

comparison of spot measurements to recommended temperature attributes for “Eastern Dry” rivers in

Davies-Colley et al (2013), demonstrates that although no single site is likely to breach the Band C/D

bottom-line, maximum spot temperatures in Eastern Rivers (Cluster A) were considerably greater than

any other region, with maximum in the Waioeka (23.4°C), Nukuhou (24.6°C) and Whakatane Rivers

(23.1°C) likely to be within the Band C Cox-Rutherford Index (≤25°C) (note: the CRI is calculated as

the average of Tmax+Tmean for a 5-day continuous period in summer). Temperatures in these

systems would likely reduce invertebrate diversity and ecosystem health (e.g., Quinn and Hickey,

1990 reported the absence of stonefly and mayfly in waters >19°C and >21.5°C respectively). The

only other site to observe a maximum temperature >21.5°C in 2013 was the Tarawera River at its

outlet, which might be linked to the discharge of warm surface waters from Lake Tarawera, especially

as maximum temperatures at three sites further downstream are less (e.g., max of 17.4 to 18.8°C).

Comparison to recommended pH attributes for ecosystem health values, whilst again non-

compulsory, highlight wider potential breaches of bottom-lines for Band C/D (i.e., pH <6 or >9) at


which “significant, persistent stress [is] caused by intolerable pH on a range of aquatic organisms

[including] local extinction of keystone species” (Davies-Colley et al., 2013:69). Continuous summer

sampling should be conducted to determine the causes for exceedance of Band C/D diel variability

and whether this is a natural (“baseline”) characteristic of geothermal inputs or consequence of

resource use. However, those rivers likely to fall in Band D include (values in brackets refer to min-

max for 2013, bold highlights concern):

Wairoa River at SH2 (pH 6.1-7.2), Omanawa River (pH 5.9-7.3), Kopurererua Stream at SH2

(6.1-7.4) within the Tauranga Streams;

Waioeka River (pH 6.2-8.4), Nukuhou River (pH 5.8-7.2) and Whakatane River (pH 6.7-8.8) in

the Eastern Rivers; and

Puarenga Stream (pH 4.6-6.9), Ohau Channel (pH 5.9-7.9), Kaituna River at Paengaroa (pH

6.2-6.9) in the Western Rivers.


6.0 References

Ballantine, D., and Davies-Colley, R. 2009. Water quality trends at National River Water Quality Network sites for 1989-2007. NIWA Client Report CHC2010-038 for the Ministry for the Environment. Pp.61.

Borcard, D., Gillet, F., and Legendre, P. 2011. Numerical Ecology with R. Springer, Amsterdam. Pp.306.

Davies-Colley, R., Franklin, P., Wilcock, B., Clearwater, S., and Hickey, C. 2013. National Objectives Framework - Temperature, Dissolved Oxygen and pH. Proposed thresholds for discussion. Prepared for Ministry for the Environment. NIWA Client Report No. HAM2013-056.

Gower, J. 1982. Euclidean distance geometry. Mathematical Scientist, 7: 1-14. Jowett, I. 2011. Time Trends: Analysis of trends and equivalence in water quality data. Version 3.20

(2011). Prepared by NIWA. Funded by FRST Envirolink with sponsorship of Northland and Hawke’s Bay Regional Councils (Diagnostic Manual).

Larned, S., Scarsbrook, M., Snelder, T., Norton, N., and Biggs, B. 2004. Water quality in low-elevation streams and rivers of New Zealand: recent state and trends in contrasting land-cover classes. New Zealand Journal of Marine and Freshwater Research, 38: 347-366.

Legendre, P., and Legendre, L. 1998. Numerical Ecology. Elsevier, Amsterdam. Pp.852. Ministry for the Environment. 2013a. Freshwater reform 2013 and beyond. Wellington, Ministry for the

Environment. Pp.52. Ministry for the Environment. 2013b. Proposed amendments to the National Policy Statement for

Freshwater Management 2011-2012. Wellington, Ministry for the Environment. Pp.76 Ministry for the Environment and Ministry of Health. 2003. Microbiological Water Quality Guidelines for

Marine and Freshwater Recreational Areas. Wellington, Ministry for the Environment and Ministry of Health. Pp.159.

McBride, G. 2012. Issues in setting secondary contact recreation guidelines for New Zealand freshwater. Pp.12.

Oksanen, J. 2013. Multivariate Analysis of Ecological Communities in R: Vegan. Quinn, J., and Hickey, C. 1990. Characterisation and classification of benthic invertebrate

communities in 88 New Zealand rivers in relation to environmental factors. Journal of Marine and Freshwater Research, 24: 287-409.

Scarsbrook, M. and McBride, G. 2007. Best practice guidelines for the statistical analysis of freshwater quality data. NIWA client report HAM2007-088.

Smith, D., McBride, G., Bryers, C., Wisse, J., and Mink, D. 1996. Trends in the New Zealand’s national river water quality network. New Zealand Journal of Marine and Freshwater Research, 23: 139-146.

Vant, B. 2013. Trends in river water quality in the Waikato region, 1993-2012. Environment Waikato Technical Report 2013/20. Hamilton, Waikato Regional Council.


Appendix A Standardised CUSUM

Standardised CUSUM graphical output presents the statistical likelihood of a step-change in the

concentration of a numeric attribute – an instantaneous vertical change of >5 units is significant at

p<0.05 (>10 is the standard cut-off for hydro-chemical attributes). Those titles in bold demonstrate a

strong likelihood of a step-change at the time of methodological change in DRP-analysis (July 2008)

(>10). CUSUM graphs can be used to demonstrate no trend (straight line), a step-change (abrupt

change >5 vertical units), an increasing trend (downwards parabola) or increasing trend (upwards

parabola) (Jowett, 2011).

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

Figure A1 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP110014

(Whirinaki River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-8

-6

-4

-2

0

2

4


(Rangitaiki River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

15


(Rangitaiki River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-15

-10

-5

0

5

10

15

20


(Tarawera River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-10

-8

-6

-4

-2

0

2


(Tarawera River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/02/2009 1/02/2010 1/02/2011 1/02/2012 1/02/2013

-8

-6

-4

-2

0

2

4

6


(Tarawera River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-10

0

10

20

30

40


(Tarawera River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-4

-2

0

2

4

6

Figure A8 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP110093 (Motu

River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-4

-2

0

2

4

6

8

10

Figure A9 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP110003 (Motu

River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-6

-4

-2

0

2

4

6

8


(Waioeka River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-10

0

10

20

30

40

Figure A11 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP 110007

(Nukuhou River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10


(Whakatane River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

15

20

25


(Ngongotaha Stream)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

0

10

20

30

40

50

60


(Puarenga Stream)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

15


(Ohau Channel)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

15

20

25

Figure A16 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP110026 (Kaituna

River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/03/2009 1/02/2010 1/01/2011 1/12/2011 1/11/2012 1/10/2013

-12

-10

-8

-6

-4

-2

0

2


(Kaituna River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2009 1/01/2010 1/01/2011 1/01/2012 1/01/2013 1/01/2014

-8

-6

-4

-2

0

2

4

6

Figure A18 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP120000 (Kaituna

River)


Sta

ndard

ised C

US

UM

of

Am

mN

Date

1/01/2009 1/01/2010 1/01/2011 1/01/2012 1/01/2013 1/01/2014

0

2

4

6

8

10

12


(Waimapu Stream)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

15

Figure A20 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP110088 (Wairoa

River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2009 1/01/2010 1/01/2011 1/01/2012 1/01/2013 1/01/2014

-15

-10

-5

0

5

Figure A21 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP110034 (Wairoa

River)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

15

20

25


(Omanawa River)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2009 1/01/2010 1/01/2011 1/01/2012 1/01/2013 1/01/2014

-20

-15

-10

-5

0

5


(Kopurererua Stream)

Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-5

0

5

10

15

20

25


(Kopurererua Stream)


Sta

ndard

ised C

US

UM

of

DR

P

Date

1/01/2004 1/01/2006 1/01/2008 1/01/2010 1/01/2012 1/01/2014

-0

10

20

30

40

Figure A25 Standardised Cumulative Sum (CUSUM) graph of DRP concentration (mg/L) at BOP710022 (Te

Mania Stream)


Appendix B Annual water quality statistics (2009-2013)

Table B1 Annual water quality statistics (median unless indicated) for Waimapu Stream in the Tauranga Streams region.

Sub-region

Monitoring Station (BoPRC Site ID)

Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s Waimapu Stream

(BOP160121) 2009 270 7.19 0.864 0.024 1.064 0.008 0.025 20.9 6.95 3.9 6.40

2010 200 8.52 0.788 0.020 0.963 0.009 0.028 19.1 7.05 3.0 6.25

2011 600 7.78 0.948 0.023 1.080 0.012 0.032 20.4 6.90 3.7 8.40

2012 390 9.15 0.796 0.019 0.937 0.012 0.027 17.7 7.00 2.4 8.70

2013 365 8.36 0.828 0.015 0.919 0.012 0.029 19.1 7.00 2.6 6.20


Table B2 Annual water quality statistics (median unless indicated) for Wairoa River at the Ruahihi Power Station in the Tauranga Streams region.

Table B3 Annual water quality statistics (median unless indicated) for Wairoa River at the SH2 bridge in the Tauranga Streams region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Wairoa River at the Ruahihi

Powerstation (BOP110088)

2009 NA

2010 62 9.71 0.317 0.009 0.390 0.008 0.018 17.3 7.05 0.9 1.45

2011 345 8.92 0.411 0.011 0.497 0.009 0.021 19.6 6.90 1.6 3.15

2012 NA

2013 17 9.53 0.310 0.008 0.385 0.009 0.019 15.6 7.05 0.9 4.00

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Wairoa River at the SH2 bridge

(BOP110034)

2009 74 9.10 0.431 0.013 0.586 0.007 0.020 22.1 7.00 4.9 9.20

2010 44 8.97 0.429 0.015 0.581 0.007 0.025 20.6 7.00 3.3 8.55

2011 600 8.79 0.484 0.014 0.629 0.011 0.033 20.9 6.75 4.8 12.00

2012 220 9.13 0.413 0.017 0.558 0.010 0.026 18.7 6.90 3.9 7.60

2013 70 8.34 0.444 0.013 0.555 0.010 0.024 19.4 6.90 3.0 6.10


Table B4 Annual water quality statistics (median unless indicated) for Omanawa River in the Tauranga Streams region.

Table B5 Annual water quality statistics (median unless indicated) for Kopurererua River at the SH29 bridge in the Tauranga Streams region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Omanawa River (BOP110036)

2009 178 9.16 1.103 0.005 1.190 0.018 0.030 17.9 7.00 4.3 20.00

2010 63 9.30 1.140 0.009 1.240 0.020 0.033 17.1 7.05 3.0 11.00

2011 280 8.48 1.045 0.011 1.075 0.022 0.044 17.4 7.00 5.4 13.00

2012 87 8.90 1.240 0.008 1.260 0.021 0.037 16.8 7.05 4.0 11.00

2013 65 8.98 1.280 0.006 1.280 0.023 0.036 16.7 7.00 2.8 8.60

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Kopurererua River at the SH29 bridge

(BOP710008)

2009 230 9.08 0.923 0.013 1.060 0.013 0.035 17.7 7.00 9.4 35.00

2010 185 9.36 0.927 0.009 1.030 0.013 0.039 16.8 7.00 4.2 11.00

2011 575 8.37 0.977 0.020 1.030 0.017 0.046 17.9 6.85 8.6 25.50

2012 215 8.58 0.950 0.009 1.030 0.016 0.040 16.5 7.00 5.2 16.00

2013 225 8.55 1.005 0.011 1.050 0.017 0.038 16.1 6.95 4.6 14.00


Table B6 Annual water quality statistics (median unless indicated) for Kopurererua River at SH2 bridge in the Tauranga Streams region.

Table B7 Annual water quality statistics (median unless indicated) for Te Mania Stream in the Tauranga Streams region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Kopurererua River at SH2 bridge (BOP710009)

2009 170 5.63 0.983 0.065 1.245 0.011 0.029 21.5 7.00 8.2 14.00

2010 75 7.89 0.975 0.033 1.090 0.013 0.037 20.0 6.95 5.4 9.20

2011 340 7.14 0.922 0.068 1.216 0.016 0.051 21.8 6.80 8.7 24.00

2012 175 7.13 0.965 0.053 1.110 0.015 0.038 18.9 6.85 5.2 9.00

2013 160 7.46 0.961 0.044 1.090 0.015 0.042 18.9 6.95 6.2 13.00

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ta

ura

ng

a S

tre

am

s

Te Mania Stream (BOP710022)

2009 200 8.63 0.229 0.017 0.410 0.002 0.013 21.8 6.80 5.0 8.20

2010 170 8.86 0.221 0.017 0.372 0.003 0.017 19.9 6.95 5.8 5.15

2011 305 8.54 0.282 0.018 0.501 0.005 0.021 18.9 6.80 3.6 9.90

2012 193 8.58 0.254 0.018 0.329 0.005 0.015 17.9 6.90 3.0 3.00

2013 195 8.67 0.266 0.014 0.374 0.005 0.016 18.2 6.85 3.2 2.40


Table B8 Annual water quality statistics (median unless indicated) for Motu River at Waitangirua in the Eastern Rivers region.

Table B9 Annual water quality statistics (median unless indicated) for Motu River at the SH35 bridge in the Eastern Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

ste

rn R

ive

rs

Motu River at Waitangirua

(BOP110093)

2009 200 8.90 0.079 0.006 0.306 0.006 0.026 18.4 7.70 2.9 2.15

2010 112 8.70 0.047 0.009 0.354 0.009 0.031 19.7 7.59 3.7 6.00

2011 195 8.70 0.146 0.009 0.280 0.009 0.027 19.1 7.61 3.6 12.00

2012 83 8.80 0.199 0.009 0.373 0.009 0.035 18.9 7.58 12.2 6.75

2013 60 8.30 0.113 0.005 0.279 0.005 0.026 20.7 7.74 3.2 2.10

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

ste

rn R

ive

rs

Motu River at the SH35 bridge

(BOP110003)

2009 12 8.70 0.031 0.003 0.095 0.011 0.017 21.6 7.73 2.9 NA

2010 40 9.00 0.042 0.003 0.088 0.012 0.016 20.5 7.78 1.8 2.20

2011 77 8.70 0.065 0.003 0.137 0.012 0.025 20.6 7.79 7.0 4.70

2012 30 8.80 0.064 0.003 0.125 0.012 0.029 19.2 7.77 10.5 7.10

2013 15 8.90 0.029 0.002 0.079 0.010 0.013 20.4 7.93 2.2 2.60


Table B10 Annual water quality statistics (median unless indicated) for Waioeka River in the Eastern Rivers region.

Table B11 Annual water quality statistics (median unless indicated) for Nukuhou River in the Eastern Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

ste

rn R

ive

rs

Waioeka River (BOP160102)

2009 23 8.54 0.033 0.005 0.129 0.015 0.019 20.4 7.20 1.3 1.15

2010 12 8.60 0.010 0.008 0.080 0.018 0.022 21.0 7.00 1.2 1.10

2011 25 8.13 0.035 0.004 0.079 0.020 0.030 22.4 7.15 2.1 5.50

2012 14 9.08 0.042 0.002 0.066 0.019 0.024 19.5 7.30 1.6 1.90

2013 6 9.51 0.008 0.001 0.061 0.015 0.018 23.4 7.35 0.7 0.80

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

ste

rn R

ive

rs


2009 515 6.49 0.373 0.032 0.782 0.016 0.072 21.5 7.00 6.2 5.80

2010 340 8.08 0.519 0.042 0.795 0.019 0.078 24.5 7.20 6.9 4.25

2011 610 7.95 0.601 0.028 0.837 0.018 0.064 21.9 6.90 6.9 9.20

2012 270 8.72 0.373 0.021 0.565 0.016 0.052 23.0 7.00 3.3 5.55

2013 120 8.25 0.259 0.013 0.414 0.019 0.048 24.6 7.10 2.6 1.90


Table B12 Annual water quality statistics (median unless indicated) for Whakatane River in the Eastern Rivers region.

Table B13 Annual water quality statistics (median unless indicated) for Whirinaki River in the East Central Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

ste

rn R

ive

rs


2009 56 8.64 0.082 0.005 0.188 0.022 0.029 24.0 7.20 2.2 2.40

2010 59 9.14 0.043 0.007 0.157 0.022 0.035 23.1 7.35 2.9 5.50

2011 83 7.85 0.128 0.007 0.205 0.027 0.043 23.4 7.25 6.5 9.60

2012 28 8.94 0.061 0.004 0.138 0.024 0.035 23.0 7.30 1.6 3.60

2013 31 9.33 0.045 0.003 0.115 0.024 0.030 23.1 7.20 1.4 1.65

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Whirinaki River (BOP110014)

2009 36 9.10 0.096 0.004 0.181 0.020 0.032 21.0 7.99 1.4 NA

2010 54 9.50 0.032 0.004 0.145 0.019 0.031 17.6 8.02 1.1 NA

2011 80 8.90 0.100 0.003 0.185 0.022 0.031 19.8 7.85 1.7 4.15

2012 16 10.0 0.105 0.005 0.195 0.022 0.034 17.2 7.81 2.2 5.15

2013 26 9.20 0.020 0.004 0.105 0.018 0.028 20.4 8.21 1.5 2.40


Table B14 Annual water quality statistics (median unless indicated) for Rangitaiki River at Murupara in the East Central Rivers region.

Table B15 Annual water quality statistics (median unless indicated) for Rangitaiki River at Te Teko in the East Central Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Rangitaiki River at Murupara

(BOP110015)

2009 23 8.30 0.942 0.007 0.994 0.021 0.030 17.5 7.84 1.1 NA

2010 30 9.90 0.908 0.008 0.989 0.019 0.029 16.0 7.72 1.0 NA

2011 29 9.50 1.208 0.007 1.277 0.022 0.030 17.5 7.71 1.5 9.05

2012 22 10.00 1.077 0.006 1.142 0.022 0.031 15.8 7.75 2.0 5.45

2013 12 9.60 0.995 0.007 1.060 0.021 0.028 17.3 7.90 1.2 3.20

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Rangitaiki River at Te Teko

(BOP110018)

2009 38 9.90 0.379 0.013 0.532 0.013 0.037 22.3 7.14 1.8 NA

2010 22 10.00 0.431 0.013 0.540 0.018 0.037 20.1 7.07 1.3 NA

2011 40 9.70 0.530 0.011 0.677 0.020 0.041 19.7 7.12 3.0 10.00

2012 55 9.80 0.498 0.010 0.620 0.014 0.037 18.0 7.07 2.5 4.55

2013 10 9.70 0.405 0.011 0.521 0.013 0.033 20.0 7.13 2.0 3.30


Table B16 Annual water quality statistics (median unless indicated) for Tarawera River at the outlet from Lake Tarawera in the East Central Rivers region.

Table B17 Annual water quality statistics (median unless indicated) for Tarawera River at Kawerau Bridge in the East Central Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Tarawera River at the outlet from Lake

Tarawera (BOP110020)

2009 <1 9.20 <0.001 <0.001 0.104 0.003 0.009 23.2 8.07 NA 0.87

2010 1 8.70 <0.001 <0.001 0.092 0.004 0.008 22.0 8.14 NA 0.42

2011 1 8.90 <0.001 <0.001 0.091 0.004 0.009 22.7 8.09 NA 0.50

2012 <1 9.50 <0.001 <0.001 0.093 0.002 0.009 20.3 8.00 0.7 0.70

2013 <1 8.90 <0.001 <0.001 0.101 0.002 0.009 22.4 8.07 0.8 0.90

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Tarawera River at Kawerau Bridge

(BOP110021)

2009 56 8.91 0.273 0.005 0.353 0.046 0.063 18.7 7.30 2.1 4.80

2010 60 7.43 0.265 0.009 0.330 0.048 0.064 18.0 7.30 1.7 4.65

2011 110 8.67 0.323 0.011 0.351 0.052 0.070 19.5 7.20 3.3 14.00

2012 31 9.43 0.300 0.005 0.331 0.050 0.066 17.0 7.20 2.2 7.00

2013 29 9.47 0.262 0.005 0.299 0.057 0.068 17.4 7.05 1.7 3.95


Table B18 Annual water quality statistics (median unless indicated) for Tarawera River at the SH30 bridge in the East Central Rivers region.

Table B19 Annual water quality statistics (median unless indicated) for Tarawera River at Awakaponga in the East Central Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Tarawera River at the SH30 bridge

(BOP110023)

2009 88 7.45 0.278 0.090 0.633 0.086 0.130 20.4 7.20 3.8 8.65

2010 71 7.53 0.275 0.148 0.625 0.077 0.120 19.3 7.20 5.0 9.60

2011 117 7.63 0.325 0.087 0.576 0.066 0.112 20.9 7.20 5.8 22.50

2012 48 8.05 0.311 0.111 0.556 0.076 0.109 18.2 7.20 4.4 12.00

2013 34 8.04 0.279 0.086 0.492 0.081 0.113 18.6 7.10 3.2 7.30

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

Ea

st

Ce

ntr

al

Riv

ers

Tarawera River at Awakaponga

(BOP110052)

2009 61 6.80 0.402 0.045 0.668 0.067 0.112 22.1 7.32 3.0 NA

2010 82 6.40 0.434 0.061 0.694 0.076 0.119 19.6 7.30 3.6 NA

2011 140 6.40 0.425 0.033 0.666 0.047 0.087 19.5 7.30 4.1 23.00

2012 80 7.80 0.434 0.052 0.639 0.059 0.094 18.4 7.30 5.9 12.50

2013 22 6.69 0.404 0.042 0.577 0.065 0.098 18.8 7.31 3.4 8.05


Table B20 Annual water quality statistics (median unless indicated) for Ngongotaha River in the Western Rivers region.

Table B21 Annual water quality statistics (median unless indicated) for Puarenga River in the Western Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Ngongotaha River (BOP110013)

2009 125 9.29 0.862 0.015 0.870 0.022 0.046 14.6 6.95 3.6 9.80

2010 165 9.08 0.821 0.016 0.918 0.026 0.048 15.8 6.80 3.0 8.00

2011 285 8.94 0.888 0.018 0.977 0.024 0.057 14.8 6.90 4.2 9.75

2012 72 8.63 0.842 0.016 0.914 0.025 0.054 15.3 6.80 2.4 6.20

2013 99 9.55 0.813 0.013 0.861 0.029 0.055 14.1 6.90 2.2 7.40

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Puarenga River (BOP110058)

2009 170 8.47 0.950 0.074 1.205 0.027 0.079 19.3 6.50 6.0 7.10

2010 135 7.38 0.859 0.067 1.065 0.033 0.075 20.4 6.60 5.8 6.50

2011 125 7.26 0.947 0.074 1.135 0.030 0.096 20.7 6.65 6.5 8.60

2012 50 8.52 0.817 0.067 0.943 0.031 0.069 18.8 6.70 4.7 5.70

2013 52 8.78 0.734 0.072 0.890 0.036 0.080 18.2 6.50 4.4 6.20


Table B22 Annual water quality statistics (median unless indicated) for Ohau Channel in the Western Rivers region.

Table B23 Annual water quality statistics (median unless indicated) for Kaituna River at the outlet from Lake Rotoiti in the Western Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Ohau Channel (BOP110025)

2009 23 7.64 0.009 0.013 0.418 0.002 0.037 23.5 6.70 5.8 8.50

2010 25 8.38 0.008 0.005 0.353 0.002 0.033 23.3 6.85 4.1 8.90

2011 22 8.32 0.027 0.029 0.372 0.002 0.022 22.6 6.80 2.3 7.00

2012 9 7.64 0.180 0.018 0.372 0.003 0.015 19.8 6.90 1.1 3.40

2013 6 6.63 0.104 0.017 0.316 0.004 0.020 19.5 6.80 1.4 2.85

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Kaituna River at the outlet from Lake

Rotoiti (BOP110026)

2009 16 8.10 0.007 0.010 0.371 0.002 0.034 24.4 6.90 2.7 6.40

2010 6 8.27 0.021 0.010 0.338 0.003 0.028 23.4 6.75 2.6 4.90

2011 5 8.38 0.039 0.016 0.278 0.003 0.019 23.0 6.90 1.7 3.20

2012 6 8.00 0.102 0.023 0.287 0.003 0.015 20.4 6.80 1.2 2.20

2013 3 7.66 0.053 0.013 0.256 0.004 0.018 21.5 6.90 1.1 1.75


Table B24 Annual water quality statistics (median unless indicated) for Kaituna River at Paengaroa in the Western Rivers region.

Table B25 Annual water quality statistics (median unless indicated) for Kaituna River at Te Matai in the Western Rivers region.

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Kaituna River at Paengaroa

(BOP110027)

2009 17 9.33 0.236 0.005 0.474 0.009 0.038 19.9 6.80 3.5 10.00

2010 17 8.75 0.244 0.008 0.460 0.019 0.042 21.3 6.65 2.6 6.30

2011 29 8.47 0.261 0.015 0.433 0.014 0.035 21.8 6.70 2.9 9.65

2012 19 9.25 0.308 0.008 0.427 0.016 0.029 20.4 6.80 1.4 4.50

2013 21 9.17 0.298 0.005 0.415 0.018 0.034 20.1 6.70 1.4 8.25

Sub-region


Year Human health

Ecosystem health

E.coli (MPN/ 100ml)

DO min (mg/L)

NO3-N (mg/L)

NH4-N (mg/L)

TN (mg/L)

DRP (mg/L)

TP (mg/L)

Temp max (°C)

pH (SI) Turb (NTU)

TSS (mg/L)

We

ste

rn R

ive

rs

Kaituna River at Te Matai (BOP120000)

2009 54 9.03 0.498 0.054 0.762 0.021 0.049 22.5 6.80 3.3 7.60

2010 77 8.66 0.530 0.065 0.765 0.030 0.054 20.2 6.85 3.0 13.50

2011 57 8.20 0.551 0.060 0.720 0.025 0.052 21.1 6.80 2.8 11.00

2012 43 9.52 0.615 0.025 0.739 0.027 0.042 18.9 6.80 1.4 5.15

2013 26 7.66 0.614 0.038 0.715 0.026 0.046 18.6 6.80 2.0 7.10


Date post:	06-Feb-2018
Category:	Documents
Upload:	vonhi
View:	216 times
Download:	3 times

Water Quality Status and Trends: Bay of Plenty - DairyNZ · PDF fileWater Quality Status and...

Documents