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Assessing translucent environmental water release in the Murrumbidgee River below Burrinjuck Dam 1999-2002

Report 2 – Water quality

Regulated and unregulated rivers of the Murrumbidgee catchment and the effect of translucent releases – an Integrated Monitoring of Environmental Flows report

www.dpi.nsw.gov.au

Publisher

NSW Department of Primary Industries, a division of NSW Department of Trade and Investment, Regional Infrastructure and Services.

Assessing translucent environmental water releases in the Murrumbidgee River below Burrinjuck Dam 1999-2002. Report 2 – Water quality. Regulated and unregulated rivers of the Murrumbidgee catchment and the effect of translucent releases – an Integrated Monitoring of Environmental Flows Report

This publication may be cited as: 'Hardwick, L., Chessman B., Westhorpe D., Mitrovic S. (2012). Assessing translucent environmental water releases in the Murrumbidgee River below Burrinjuck Dam 1999-2002. Report 2 – Water quality. Regulated and unregulated rivers of the Murrumbidgee catchment and the effect of translucent releases – an Integrated Monitoring of Environmental Flows Report, NSW Department of Primary Industries, Published: Sydney, March 2012'.

ISBN 978-0-7313-3511-4

© State of New South Wales through Department of Trade and Investment, Regional Infrastructure and Services 2012.

This publication is copyright. You may download, display, print and reproduce this material in an unaltered form only (retaining this notice) for your personal use or for non-commercial use within your organisation. To copy, adapt, publish, distribute or commercialise any of this publication you will need to seek permission from the Department of Trade and Investment, Regional Infrastructure and Services.

Disclaimer The information contained in this publication is based on knowledge and understanding at the time of writing (March 2012). However, because of advances in knowledge, users are reminded of the need to ensure that information on which they rely is up to date and to check the currency of the information with the appropriate officer of the Department of Primary Industries or the user’s independent advisor.

Publication number NOW 12_030

Assessing translucent environmental water releases in the Murrumbidgee River below Burrinjuck Dam 1999-2002. Report 2

Contents

Summary ............................................................................................................................................... 4

Introduction............................................................................................................................................ 4

The effect of dams......................................................................................................................... 5

The Murrumbidgee catchment ...................................................................................................... 5

Hydrology of the Murrumbidgee River ................................................................................ 5

Characterisation of the Murrumbidgee catchment.............................................................. 6

Aims and objectives of this study .......................................................................................................... 7

Objectives...................................................................................................................................... 7

Aims ............................................................................................................................................ 7

The hypotheses................................................................................................................... 8

Methods................................................................................................................................................. 8

Collection....................................................................................................................................... 8

Field sampling ..................................................................................................................... 8

Processing .......................................................................................................................... 9

Data handling and analysis................................................................................................. 9

Results................................................................................................................................................... 9

Nutrients ........................................................................................................................................ 9

Physical water quality attributes.................................................................................................. 12

Discussion ........................................................................................................................................... 18

Management implications............................................................................................................ 19

References .......................................................................................................................................... 21

Bibliography......................................................................................................................................... 21

Tables

Table 1 Nested analysis of variance of nutrients. ........................................................................ 11

Table 2. Analysis of variance of temporal differences in nutrient concentrations......................... 11

Table 3 Multiple regression of water temperature in regulated rivers against their reference rivers, 2000-02................................................................................................ 15

Table 4 Stepwise multiple regression of physical water quality attributes, 2000-2002.Significant R values highlighted............................................................................. 16

ii | NSW Office of Water, June 2012


iii | NSW Office of Water, June 2012

Figures

Figure 1 Map of the monitoring sites............................................................................................... 6

Figure 2 Nutrients in regulated and unregulated rivers of the Murrumbidgee catchment 2000-2002... .................................................................................................................... 10

Figure 3 Water quality parameters measured over time in each of the four rivers...................... 12

Figure 4 Temperature for the Murrumbidgee, Goodradigbee, Goobarragandra and the Tumut rivers, 2000-2003................................................................................................. 16

Figure 5 Principal components analysis of water quality across river catchments. ...................... 17

Figure 6 Types of physical and chemical stressors on inland rivers (redrawn from ANZECC 2000). .............................................................................................................. 19


Summary

Environmental flows in the Murrumbidgee River commenced in 1999. These were developed using river flow objectives to guide release rules. One of the river flow objectives was to increase small

scale variability downstream of regulatory dams. The solution to this lack of variability was the development of the ‘translucency and transparency’ environmental flow rules. Monitoring of these environmental flow rules was performed between 1999 and 2001.

This report typifies the water quality of the regulated rivers impacted by translucency and transparency rules and their unregulated tributaries. Results indicated that water quality in the regulated rivers differed substantially from unregulated rivers and water released from Burrinjuck Dam

in particular was affected by upstream catchment development as well as the influence of the dam itself. These affects are likely to mitigate any environmental improvement expected to result from flow restoration in the Murrumbidgee River downstream of Burrinjuck Dam.

Introduction

Water quality is a major driver structuring aquatic communities. Components of water quality include suspended particles from erosional processes as well as nutrients, organic and inorganic carbon, (Thorp and Delong 1994) salinity and a range of naturally derived chemicals and anthropogenic

toxicants. In naturally flowing rivers in forested catchments with pool riffle sequences, water is often highly oxygenated and oligotrophic that may lead to nutrient limitation for aquatic communities. But in more cleared agricultural catchments water may be highly productive and turbid along with

heightened temperature due to lack of shading (Boulton and Brock 1999, Harris 2001).

Physical processes such as erosion increase concentrations of suspended particulate material in running water. Depending on particle size, this material might fall out in areas of low flow or may

persist in the water column for long periods of time. Suspended particles contribute to turbidity in rivers and may impact on aquatic ecosystems by reducing light intensity. This will affect plant growth, altering aquatic biofilm composition to more bacterial and fungal communities and reducing algal

growth on rocks and other aquatic surfaces. These particles may also act physically to clog gills and other respiratory organs of invertebrates and fish. Concentrations of transported sediments increase with discharge and stream bank erosion that in turn are related to catchment clearing and stream

naturalness (Boulton and Brock 1999). In the Murrumbidgee catchment, 90% of suspended sediment load is derived from stream banks and gully erosion (Wallbrink et al. 1996). Other components of turbidity include particulate and dissolved organic carbon and tannins. These are derived from plant

and other organic material from smaller tributaries and from the river bank.

Electrical conductivity, pH and water temperature are also affected by upstream catchment conditions. Pristine forested catchments tend to produce water low in conductivity and temperature

due to high levels of shading. Depending on the surrounding vegetation or source of water, the pH can be variable. Low pH levels are associated with runoff from peaty swamps and high levels of tannic acids, while high pH levels can be associated with limestone geology (Boulton and Brock 1999

as an example).

Nutrient runoff is usually a feature of catchment clearing and subsequent agricultural development. Use of fertilisers, grazing runoff and sewage outfall all contribute to additions of nitrogen and

phosphorus into streams (Fellows et al. 2007). While nitrogen is quite labile, moving between gaseous, oxidised and reduced forms (NO2, NO3, NH3 and N2) phosphorus tends to adsorb to soil particles and depending on flow velocity be transported or settle into the sediments. The dynamics of

nutrient movement and transformations in aquatic environments is complex (Bormans et al. 2007;

4 | NSW Office of Water, June 2012


Baldwin and Williams 2007; Ryder and Vink 2007) and aquatic systems can exhibit either nitrogen or phosphorus limitation at varying levels and temporal scales (Boulton and Brock 1999).

The effect of dams

Dams may alter downstream water quality in various ways. By reducing the magnitude and frequency of flood events (Pinay et al. 2002) they may have an influential role in both chemical and physical

processes in rivers (Ward and Stanford 1995).

Sediments and organic material tend to settle in the bottom of dams, leading to internal loading of phosphorus and anoxic respiration at the sediment water interface (Boulton and Brock 1999). Water

released from bottom release valves, such as those in the major storages in the Murrumbidgee, may affect water quality such that in the warmer months releases would be expected to be both lower in dissolved oxygen and temperature and have higher concentrations of reduced nutrients such as

ammonia and soluble phosphorus (Boulton and Brock 1999). Thermal stratification within a dam in the warmer months would be expected to lead to unnaturally cold hypolimnetic water being released from bottom release valves (Ryder and Vink 2007, Olden and Naiman 2009). This effect interacts with

nutrient concentrations altering nutrient cycling dynamics and timing. These impacts are known to affect instream ecology with changes in food chain dynamics (Biggs 1995; Stelzer and Lamberti 2001; Stelzer et al.. 2003; Sekar et.al. 2002) and resultant ecological effects.

The Murrumbidgee catchment

Hydrology of the Murrumbidgee River

The Murrumbidgee River lies in the temperate zone of south east Australia that experiences peaks in

rainfall and runoff in winter and spring with dry hot summers. This sets the template for flows in western flowing rivers out of the New South Wales Alps. The Murrumbidgee, draining 84,000 km2 (Wallbrink et al.1996) and 1,609 km long, is one of the largest of these rivers.

There are several major tributaries upstream of Wagga Wagga. The largest, the Tumut River, provides water for irrigation diverted by the Snowy Mountains hydroelectric scheme into Blowering Dam including 1,026 GL per year of which 550 GL is diverted from upper Murrumbidgee tributaries at

Tantangara Reservoir and numerous aqueducts throughout the Australian Alps. Blowering Dam has a storage capacity of 1,628 GL.

Major tributaries upstream of Burrinjuck Dam include the Cotter, Queanbeyan, Molonglo, Yass and

Goodradigbee rivers. The majority of these rivers are highly regulated, providing water supply to Canberra, the ACT generally and surrounding towns. In addition, the Molonglo sewage treatment plant releases treated waste water back into the Murrumbidgee just upstream of Burrinjuck Dam.

Mean annual diversion between 1996-2009 to ACT is 58,758 ML/year (ACTEWGL 2011).

Major tributaries downstream of Burrinjuck and Blowering storages include Tarcutta Creek (MAF 133.4 GL), Jugiong Creek (MAF 82.2 GL), Adelong Creek (MAF 38.5 GL) and Muttama Creek (MAF

36.5 GL). Ecologically important natural tributaries to the regulated river include the Goodradigbee River (MAF 303.3 GL) that flows into Burrinjuck Dam and the Goobarragandra River (MAF 291.3 GL) also flowing into the Tumut River.

The hydrology of the Murrumbidgee River is highly altered with Burrinjuck Dam having a storage of 1,026 ML and a mean annual inflow of 1,350 ML/annum (Parliament of NSW 2000 – Question 1152). This storage capacity, used primarily for summer irrigation, means that seasonality of flows

downstream of Burrinjuck Dam are skewed by around four months. Peak flows in the Murrumbidgee are now during summer rather than the spring snow melt peak.



Rainfall exhibits a winter spring peak that generally varies between 600 and 1000 mm increasing with altitude into the Australian Alps.

Characterisation of the Murrumbidgee catchment

While the Murrumbidgee River has a large and developed catchment, the Tumut River is largely

forested above Blowering Dam. Water entering Blowering Reservoir runs from tributaries from within Kosciusko National Park. The major source of water into Blowering comes by upstream storages managed by Snowy Hydro. These in turn receive water by pipeline from more montane storages. It

would be expected that this water would be cold and oligotrophic and severely nutrient limited. Only the bottom release of deposited and degraded litter and other organic matter would provide a source of nutrients and energy (carbon) downstream in the Tumut River.

Figure 1 Map of the monitoring sites

The unregulated rivers, the Goodradigbee and Goobarragandra Rivers, are semi natural catchments

with some clearing but relatively intact riparian zones. A small proportion of natural flow is diverted from the head of the Goodradigbee River into the Snowy hydroelectric scheme. Both of these rivers exhibit upland boulder/cobble pool riffle geomorphology with relatively high slope. Water quality would

be expected to reflect this with relatively low levels of nutrients derived mostly from riparian vegetation and litter washed in from forested tributaries.

The Murrumbidgee River, on the other hand, has a comparatively larger catchment, comprising high

levels of clearing and urbanisation. Canberra and the ACT extract water from the river and return treated effluent and stormwater upstream of Burrinjuck Dam. Instream sources or erosion of stream



banks contribute phosphorus and sediments to the upper Murrumbidgee (Pengelly 1998) and water quality downstream of Canberra may often be poor (ACT Environment Commissioner 2007).

Nutrients are known to have a significant effect on growth rates and abundance of both periphyton and invertebrate grazers (Rosemond et al. 1993; Kiffney and Richardson 2001) and interact with other instream drivers such as light, temperature and indirectly with predation pressures (Vannote et al.

1980).

Therefore flow and regulation in rivers interact to define the physical and chemical constitution of water that in turn drives aquatic ecological communities (Stelzer and Lamberti 2001).

This report is one of a series identifying the effect of introducing environmental flows to the Murrumbidgee River downstream of Burrinjuck Dam. Translucent flows, related to natural inflows, were designed to scour periphyton from rocky riffles in the flow altered Murrumbidgee River (Report

1). This was expected to lead to a long term improvement in river health, moving ecology more towards that of natural tributaries such as the Goodradigbee and Goobarragandra rivers. The Tumut River, a large regulated tributary of the Murrumbidgee, did not receive translucent releases.

While flow is a determining factor in aquatic ecosystems, there are other influences that may interact directly or indirectly with river regulation to impact on river health (Thoms 2006). Water quality is one of those influences and the report will document the differences between the rivers investigated. The

implications for periphyton communities (Report 3), aquatic invertebrates (Report 4) and instream productivity (Report 5) will be discussed.

Aims and objectives of this study

Objectives

A flow monitoring study was designed to assess the ecological effects of flow change brought about by the introduction of translucent environmental water releases downstream of Burrinjuck Dam with

the objective:

to assess the change in the ecology of the Murrumbidgee River as a result of translucent

environmental water releases and to compare these changes against comparative reference and control rivers.

Aims

To identify the ecological effect of introduction of translucent environmental flows in the Murrumbidgee River downstream of Burrinjuck Dam on:

riffle periphyton communities

riffle invertebrate communities particularly invertebrate scrapers and their predators

to measure rehabilitation trajectory of riffle periphyton and invertebrate communities as a response of the introduction of translucent environmental flows in the Murrumbidgee River.

Rehabilitation is to be measured against the natural unregulated tributaries of the Goodradigbee and the Goobarragandra rivers. The regulated Tumut River, that does not receive translucent releases, is to be a control

to identify importance of multiple stressors including water quality that impact on the ability for

restoration of the Murrumbidgee River.

The premise of the study was that translucent (Chessman and Jones 2001) environmental flows

would reset periphyton communities on rocky riffles of the Murrumbidgee River downstream of



Burrinjuck. This would lead to early successional stages of ecological community development, resulting in more palatable food sources and healthier aquatic communities, in turn leading to a long

term improvement in the ecology of riffle aquatic communities in the Murrumbidgee River downstream of Burrinjuck Dam. Water quality was measured to identify its importance in controlling or driving ecological condition.

This report provides background information to inform the ecological response of translucent flow releases on periphyton and invertebrate communities.

The null hypotheses

The null hypotheses for this study are:

There is no significant difference in water quality attributes:

water temperature (oC)

electrical conductivity (µS/cm)

pH

dissolved oxygen (mg/L and % saturation)

total suspended solids (mg/L)

nitrogen oxides (mg/L), ammoniacal nitrogen (mg/L) and filterable reactive phosphorus (mg/L).

between the Murrumbidgee (test river) the Goodradigbee and Goobarragandra Rivers (reference rivers) and the Tumut River (control river).

There is no significant change over time in water quality attributes:

water temperature (oC)

electrical conductivity (µS/cm)

pH and dissolved oxygen (mg/L and % saturation)

total suspended solids (mg/L)

nitrogen oxides (mg/L), ammoniacal nitrogen (mg/L) and filterable reactive phosphorus (mg/L)

between the Murrumbidgee (test river) the Goodradigbee and Goobarragandra Rivers (reference

rivers) and the Tumut River (control river).

Methods

Collection

Field sampling

Water quality data was collected on twelve occasions at the monitoring sites (Table 4). Sampling was undertaken at the same time as data was collected for periphyton, invertebrates and productivity. Triplicate measurements of water temperature (oC), electrical conductivity (µS/cm), pH and dissolved

oxygen (mg/L and % saturation) were taken in flowing water using a calibrated Hydrolab Minisonde multi probe water quality instrument.

Daily time series water temperature data was collected from the following gauging stations:

410068 – Murrumbidgee River at Glendale

410024 – Goodradigbee River at Wee Jasper

410057 – Goobarragandra River at Lacmalac

410073 – Tumut River at Oddys Bridge.



Two water samples were taken for laboratory analysis of total suspended solids (mg/L) using prewashed one litre PET sample bottles that were chilled before transport to the laboratory.

Water samples for soluble nutrient analysis (nitrogen oxides (mg/L), ammoniacal nitrogen (mg/L) and filterable reactive phosphorus (mg/L)) were collected for sampling events 6 to 11 (September 2000 - November 2001). These were filtered on site through 0.45µm filters attached to plastic syringes and

frozen.

Processing

Water samples for laboratory analysis of total suspended solids were analysed according to APHA-AWWA-WEF standard methods (2001).

Oxidised nitrogen, ammoniacal nitrogen and filterable reactive phosphorus were determined by APHA (1998) methods 4500-NO3 F (automated cadmium reduction), 4500-NH3 H (automated phenate) and 4500-P F (automated ascorbic acid reduction) respectively. All analyses were performed at the NSW

Office of Water NATA registered laboratory at Wolli Creek.

Data handling and analysis

All water quality data were added to the NSW Office of Water database (TRITON) and quality coded.

Spatial and temporal variations in nutrient concentrations in water were assessed by analysis of

variance (ANOVA). Because not all sites were sampled on each occasion, separate analyses were conducted comparing sites for each occasion between sites and within each site with the multiple samples taken within a site on a sampling occasion treated as replicates. In the comparisons between

sites, a nested ANOVA design was used to match the sampling design with sites nested within rivers and rivers nested within river types (regulated and unregulated). Before analysis, nutrient concentrations in water that were below detection limits (0.01 mg/L for nitrogen forms and 0.005 mg/L

for phosphorus) were converted to half the detection level and all nutrient concentrations were transformed to log10 in order to reduce skewness for each variable and to homogenise variances.

Water quality data were matched by sample number to hydrological and biological data for

multivariate analyses in PRIMER 5 for Windows (Clarke and Warwick 2000). Water quality data were log transformed (Jongman et al. 1995) prior to analysis.

Further analysis of continuous water temperature data was performed using time series analysis with

general stepwise regression and significance testing using the Wald statistic to test the significance of the regression coefficient and chi squared probability.

Results

Nutrients

Differences in nutrient concentrations indicated that the Murrumbidgee River had significantly greater oxidized N than both the unregulated rivers and the regulated Tumut River (Figure 1). This was also

true for the Tumut River compared to its tributary, the Goobarragandra River. Ammonium and filterable reactive phosphorus downstream of Burrinjuck Dam on the Murrumbidgee both reflected the nutrients flowing into the dam from the Goodradigbee River. Patterns of nutrients over time in the

Tumut River indicated that water discharged from Blowering was both more nutrient rich (Figure 2) and more variable over time.



Figure 2 Nutrients in regulated and unregulated rivers of the Murrumbidgee catchment 2000-2002...

Concentrations in water of oxidised nitrogen (○), ammoniacal nitrogen (∆) and filterable reactive

phosphorus (●) at each site on each sampling occasion in 2000-2001. Some data points overlap.

Regulated Unregulated

Murrumbidgee R site 1

0.001

0.010

0.100

1.000

01-Jan-00 01-Jul-00 01-Jan-01 01-Jul-01 01-Jan-02

Co

nce

ntr

atio

n (

mg

/L)

Goodradigbee R site 1

0.001

0.010

0.100

1.000


Tumut R site 2

0.001

0.010

0.100

1.000


Date

Co

nce

ntr

atio

n (

mg

/L)

Goobarragandra R site 2

0.001

0.010

0.100

1.000


Tumut R site 1

0.001

0.010

0.100

1.000


Co

nce

ntr

atio

n (

mg

/L)

G o o b arrag an d ra R s ite 1

0 .001

0 .010

0 .100

1 .000

01-Jan -00 01 -Ju l-00 01-Jan-01 01-Ju l-01 01 -Jan-02

Murrumbidgee R site 2

0.001

0.010

0.100

1.000


Co

nce

ntr

atio

n (

mg

/L)

.

Goodradigbee R site 2

0.001

0.010

0.100

1.000


Date



Table 1 Nested analysis of variance of nutrients.

F-values from nested ANOVA of spatial variation in log-transformed concentrations in water of

oxidised nitrogen, ammoniacal nitrogen and filterable reactive phosphorus for each sampling occasion. *, P < 0.05; **, P < 0.01; ***, P < 0.001; others not significant. ANOVA was not possible for ammoniacal nitrogen for November 2001 because all measured concentrations were identical.

Comparisons between unregulated and regulated river types within regulated and unregulated rivers and within sites in each river.

Sampling occasion

Oxidised N Ammoniacal N Filterable reactive P

Between river types

Between rivers within types

Between sites within rivers

Between river types



Between river types



September 2000

13124.3 *** 2179.7 *** 471.0 *** 2.7 2.2 3.5 10.0 * 2.2 1.0

October 2000

984.0 *** 215.4 *** 0.5 0.3 23.5 *** 1.9 22.9 ** 39.4 *** 0.0

February 2001

341.8 *** 31.8 *** 1.2 3.4 2.6 1.2 11.0 * 13.0 ** 1.7

May 2001 310.5 *** 61.8 *** 0.5 2.0 10.0 ** 0.0 2.5 7.2 * 0.9 August 2001

418.0 *** 148.2 *** 6.1 * 25.0 ** 1.0 5.0 * 62.1 *** 45.2 *** 5.2 *

November 2001

1329.3 *** 13.5 * 9.0 * - - - 1.6 0.5 1.9

Results indicated that there were significant differences between unregulated and regulated rivers particularly for oxidised nitrogen but also between the Murrumbidgee and Tumut rivers that illustrated the difference in water source. Significant differences were also apparent at some sampling events

between rivers (Table 1). Variability in oxidised nitrogen decreased with scale, indicating that river sites were generally homogeneous compared to different rivers and between unregulated and regulated rivers. For ammoniacal nitrogen, variability did not decrease with scale generally and little

difference was found across river types, within river types and between riffles. Filterable reactive phosphorus was more often significantly different between rivers within type than between river types and variability indicated inconclusive patterns (Table 2).

Table 2. Analysis of variance of temporal differences in nutrient concentrations.

F-values from ANOVA of differences over sampling events (temporal variation) in log-transformed

concentrations in water of oxidised nitrogen, ammoniacal nitrogen and filterable reactive phosphorus for each site. *, P < 0.05; **, P < 0.01; ***, P < 0.001; others not significant.

Site oxidised nitrogen (mg/L)

ammoniacal

nitrogen (mg/L)

filterable reactive phosphorus (mg/L)

Murrumbidgee R site 1 14.3 ** 123.5 *** 73.0 ***

Murrumbidgee R site 2 43.5 *** 10.5 ** 39.0 ***

Tumut R site 1 12.1 ** 35.1 *** 2.2

Tumut R site 2 1.3 13.1 ** 20.0 **

Goobarragandra R site 1 6.2 * 37.0 *** 4.6 *

Goobarragandra R site 2 9.2 ** 3.0 7.0 *

Goodradigbee R site 1 48.5 *** 22.3 *** 35.0 ***

Goodradigbee R site 2 66.0 *** 30.1 *** 9.2 **



Physical water quality attributes

Field measured water quality results (Figure 3) indicated that over all times and rivers, electrical

conductivity, total suspended solids and turbidity were significantly different in the Murrumbidgee (general stepwise regression analysis with Walds statistic chi pr <0.01).

These results reflect the relatively elevated conductivity of water from the Murrumbidgee River as

inflows into Burrinjuck Dam compared to all other rivers. Other physical water parameters exhibited significant differences at some sampling times and in some rivers, but not as an overall pattern.

Graphical representation of each of the physical attributes illustrated the contribution of not only

catchment influences but natural seasonal influences complicated by those created by regulation such as temperature alteration (Figure 3) and release of bottom, highly turbid water (Table 4).

Time series data of temperature (Table 4) illustrates the effect of regulation on downstream river

temperatures where there are skews to the natural temperature regime by several months, reduction in amplitude, reduction of summer temperatures and elevated temperatures in autumn.

Temperature depression can be as much as 22 degrees colder during summer in the Tumut River

and five degrees colder in the Murrumbidgee River. During the study, water samples from the Murrumbidgee and Tumut rivers regularly exceeded the default Australian and New Zealand Environment Conservation Council (ANZECC 2000) trigger values for upland streams for NOx and

NH4. Turbidity, pH and EC levels also approached or exceeded the trigger values in the Murrumbidgee River.

Figure 3 Water quality parameters measured over time in each of the four rivers

Electrical conductivity (µS/cm), turbidity (NTU), pH, water temperature (Deg C), dissolved oxygen (% saturation) and total suspended solids (mg/L).



Multiple regression of continuous daily temperature using the regulated rivers as dependent variables indicated that the Murrumbidgee River absolute deviation in water temperature from its unregulated

tributary the Goodradigbee, (June 2000- April 2003) was 2.84+/- 0.065 degrees Celsius. That of the Tumut River was 3.42 +/- 0.08 degrees colder than its tributary, the unregulated Goobarragandra River (Table 3). Regression relationships of Murrumbidgee water temperature was highly correlated

with that of the Goodradigbee (R=0.858) compared to the Tumut River, where Goobarragandra River temperatures correlated at R= 0.516. This indicates that the Tumut River was more severely affected by temperature deviation particularly as the Goobarragandra River runs into the Tumut River

downstream of Blowering Dam.

Table 3 Multiple regression of water temperature in regulated rivers against their reference rivers, 2000-02.

regulated vs. unregulated

Multiple R and R2

df p absolute deviation (June

2000-April 2003)

S.E of absolute

deviation

Murrumbidgee vs. Goodradigbee

0.858/0.737 1,1743 0.000 2.838 0.065

Tumut vs. Goobarragandra 0.516/0.266 1,1910 0.000 3.418

0.087



Figure 4 Temperature for the Murrumbidgee, Goodradigbee, Goobarragandra and the Tumut rivers, 2000-2003.

Table 4 Stepwise multiple regression of physical water quality attributes, 2000-2002.Significant R values highlighted.

Significant p = 0.05. The beta coefficients are the regression coefficients obtained when variables are standardised to a mean of 0 and a standard deviation of 1. Thus, the advantage of beta coefficients is

that their magnitudes allow you to compare the relative contribution of each independent variable in the prediction of the dependent variable – refer to Statistica (Statsoft 2005).

Attribute results Between

rivers

Between

sampling

Between river

types (reg/unreg)

Between riffles

within river types

EC

F = 17.6, p=0.000

Beta = -0.55* Beta = -0.01 Beta = -0.86 Beta = 0.490

Temperature

F = 2.31, p=0.07

Beta =-0.19 Beta = -0.22 Beta =0.62 Beta = -0.70

Turbidity

F = 18.7, p=0.00

Beta = -0.59* Beta = 0.26* Beta = -0.59 Beta = 0.27

pH

F = 6.0, p=0.00

Beta = -0.48* Beta =-0.10 Beta = -0.63 Beta = 0.59

DO % Saturation

F = 2.1, p = 0.09

Beta = -0.18 Beta = -0.23* Beta =-1.3 Beta = 1.26

Stepwise multiple regression of the most commonly sampled water quality attributes indicated a range of significant differences between rivers particularly the Murrumbidgee compared to all other rivers, and between sampling where significant regression results were returned on just one or two sampling events (dissolved oxygen - November 2000 and February 2001 and turbidity -August 2001) in the Murrumbidgee River (Table 4).



Figure 5 Principal components analysis of water quality across river catchments.

P ro ject ion of t he v ariables on the f ac tor- plane ( 1 x 2)

E C

DO M G L

DO P E RS AT

TE M P

T URB

P T

M E A NO X M E A NNH3

pH

TS S

P RD

A LK CA A LKB I C

NKJ E LD

- 1. 0 -0.5 0. 0 0.5 1. 0

F ac tor 1 : 47. 12%

- 1. 0

- 0. 5

0. 0

0. 5

1. 0

Fa

ctor 2 : 23

.69

%

Principal components analysis of the four rivers with respect to water quality suggested that the

attributes indicative of disturbance (EC, NH3, NOx, turbidity and TSS) were grouped and this group made the Murrumbidgee River considerably different in terms of its water quality from the other rivers. The first principal components axis (PC1) contributes 47% of the difference between the rivers. These

attributes were all indicative of catchment alteration such as clearing, agricultural and urban runoff and erosion.



Discussion

Analysis of water quality in the Murrumbidgee River and its three tributaries between 1999 and 2001 indicated that there were significant differences in chemical and physical attributes of dam release

water. There were also major differences in water released from the two major dams and unregulated river water quality. High levels of oxidised nitrogen from Burrinjuck Dam reflected both catchment inflow status but also the effect of water releases. In contrast, ammoniacal nitrogen did not show

significant differences across all rivers. Release of hypolimnetic water form Burrinjuck Dam would be expected to be high in ammoniacal nitrogen, however oxygenation of release water, and distance to the sampling sites of 20 km downstream mean that nitrogen transformations would be expected. The

intervening reach comprises bedrock and boulder gorge with areas of cascades, runs and riffles that would allow oxygenation of ammonia in released water. Nitrogen dynamics in freshwater are complex but much studied (Hart and Grace 2001) with interactions between physical and biological processes

creating rapid moving fluxes (Boulton and Brock 1999). It is likely that transformation of ammonia into nitrogen oxide and nitrogen dioxide occurs rapidly downstream of Burrinjuck Dam. High levels of both nitrogen and phosphorus downstream of dams is well known (Growns and Growns 2001) and

extensive biostimulation of periphyton a common effect of release of nutrient rich water. Filterable reactive phosphorus levels showed dynamic variability and significant differences across unregulated and regulated rivers indicating that filterable reactive phosphorus may be variable across spatial and

temporal scales. In natural upland streams it is likely that phosphorus limits productivity if there are sufficient carbon inputs from forested catchments (Boulton and Brock 1999). More developed catchments, such as the Murrumbidgee, export more phosphorus but dams may store it in sediments

with high rates of adsorption.

Seasonality and thermal modifications may also play a part in release of elevated soluble nutrients (Olden and Naiman 2009). In summer during periods of thermal stratification, anoxic hypolimnetic

water is released through bottom release valves in a dam. Nutrient levels are characteristically high. In cooler weather when a dam is fully mixed, one would expect lower concentrations (Bowling pers. comm.). The results don’t fully concur with expectations, so other factors, such as inflow effects,

summer mixing and rainfall events must also play a part. Similarities in concentrations of filterable reactive phosphorus between the Murrumbidgee and the Goodradigbee rivers suggest that either the filterable reactive phosphorus was travelling through the dam and into release waters or was being

released at the same rate as adsorption onto sediments within the dam. These fluxes in nutrients are both dynamic and complex (Harris 2001).

Water quality may be as important in determining ecosystem condition as flow. Water quality

downstream of Burrinjuck in the Murrumbidgee River has all of the attributes of a river impacted by, not only regulation such as with temperature deviation and deoxygenated nutrients, but also catchment influences such as elevated concentrations of nutrients and comparatively high turbidity

and suspended sediments. Periphyton and invertebrate responses to flow and other drivers of ecological structure and function will be further investigated in later reports in this series.



Figure 6 Types of physical and chemical stressors on inland rivers (redrawn from ANZECC 2000).

Direct effect Indirect effect

Types of physical and chemical stressors

Stressors that can modify effects of other stressors e.g.

pH – release metals temperature –

increase physiological rates

DO – change redox conditions and release P

Stressors directly toxic to biota e.g

heavy metals ammonia salinity pH DO temperature

Stressors not directly toxic but can directly affect ecosystems and biota e.g.

nutrients turbidity flow alien species

Changes to water quality create stress on aquatic ecosystems (Figure 6) and may alter conditions for biota. If flows are not dominant enough to become stronger drivers of ecological condition, then water

quality is likely to play a governing role in ecological condition in the regulated rivers in particular in the Murrumbidgee River downstream of Burrinjuck.

So even if restoration of natural hydrology is managed in rivers such as the Murrumbidgee River,

altered nutrient status may still lead to biostimulation and taxa replacement of periphyton communities. Resultant alteration of grazing invertebrate community structure and food web structure is inevitable.

These responses would not be expected to be deterministic in nature but rather would follow stochastic trajectories based on dynamics in water quality, flow and seasonality as well as internal ecosystem processes such as competition, grazing and predation.

Management implications

Partially restoring small scale variability in the hydrograph during April to October in the

Murrumbidgee may not significantly affect water quality although it is likely to have an impact on amount of deposited fine sediment that generally tends to accumulate in pools downstream of dams. Flushing at higher flows will increase this effect. This would be expected to rehabilitate instream

habitat. However, water high in nutrients, total suspended solids and with unnatural temperature regimes would be expected to mitigate any flow improvement. It is therefore important that catchment restoration in the Murrumbidgee be a long term goal to reduce inputs of nutrients, sediment and

organic material into Burrinjuck dam.

Management of temperature regimes is also important with temperature data collection and modelling necessary to build a natural temperature regime for releases into the Murrumbidgee. Thermal

pollution mitigation forms a necessary long term objective to aid rehabilitation of the Murrumbidgee River downstream of Burrinjuck. Cold water pollution mitigation must be a major management goal for



the Tumut River downstream of Blowering where water temperatures can be as much as eight degrees colder or warmer than nearby naturally flowing streams. Management of temperature

regimes within environmental flow management is a goal both locally and internationally (Olden and Naiman 2010).



References

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