Temperature monitoring of dam releases in Victorian river s 2002 - 2004

Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Report produced for Environmental Flows and River Health Division, Department of Sustainability and Environment

Acknowledgments The project partners gratefully acknowledge the assistance of the individuals from organisations that own / operate dams who
kindly provided information for this study.

Prepared by: Sinclair Knight Merz

Published by the Victorian Government Department of Sustainability and Environment

Melbourne, September 2005

© The State of Victoria Department of Sustainability and Environment 2005

This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968 .

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ISBN 1 74152 246 3

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Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

September 2005

REPORT PREPARED BY SINCLAIR KNIGHT MERZ

Sinclair Knight Merz ABN 37 001 024 095 590 Orrong Road, Armadale 3143 PO Box 2500 Malvern VIC 3144 Australia Tel: +61 3 9248 3100 Fax: +61 3 9248 3400 Web: www.skmconsulting.com

Page i Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Page ii Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Contents

1 Introduction 1

2 Method 3 2.1 Data availability 3 2.2 Data validation 8 2.3 Analysis 9 2.3.1 Storage levels 9 2.3.2 Temperature patterns 9 2.3.3 Relationships between flow and temperature 11 3 Thermal impacts associated with controlled releases from Victorian dams 12 3.1 Cairn Curran Reservoir 12 3.1.1 Comparison upstream and downstream of Cairn Curran Reservoir 14 3.1.2 Diurnal temperature patterns 17 3.1.3 Relationship between flow and temperature 18 3.1.4 Summary 20 3.2 Laanecoorie Reservoir 21 3.2.1 Comparison between sites upstream and downstream of the reservoir 23 3.2.2 Diurnal temperature patterns 26 3.2.3 Relationship between flow and temperature 27 3.2.4 Summary 28 3.3 Tullaroop Reservoir 30 3.3.1 Comparison upstream and downstream of Tullaroop Reservoir 32 3.3.2 Diurnal temperature patterns 35 3.3.3 Relationship between flow and temperature 36 3.3.4 Summary 38 3.4 Lake Eildon 39 3.4.1 Temperature differences between Lake Eildon inlet streams 41 3.4.2 Comparison between water temperatures upstream and downstream of Lake Eildon 42 3.4.2.1 Howqua River and Jamieson River vs Goulburn River at Molesworth 42 3.4.2.2 Big River at Jamiesons Rd, Goulburn River at Doherty’s and Goulburn River at Molesworth 44 3.4.3 Diurnal temperature patterns 47 3.4.4 Relationship between flow and temperature 48 3.4.5 Summary 51 3.5 Lake Eppalock 52 3.5.1 Temperature differences between Lake Eppalock inlet streams 54

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Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.5.2 Comparison between Lake Eppalock inlet streams and sites at various distances downstream of Lake Eppalock. 56 3.5.3 Diurnal temperature patterns 59 3.5.4 Relationship between flow and temperature 60 3.5.5 Summary 63 3.6 Lake Nillahcootie 64 3.6.1 Comparison between sites upstream and downstream of Lake Nillahcootie 66 3.6.2 Diurnal temperature patterns 70 3.6.3 Relationship between flow and temperature 71 3.6.4 Summary 73 3.7 Lake William Hovell 74 3.7.1 Comparison between upstream and downstream sites 76 3.7.2 Diurnal temperature patterns 80 3.7.3 Relationship between temperature and flow 80 3.7.4 Summary 83 3.8 Thomson Reservoir 84 3.8.1 Comparison between sites upstream and downstream of Thomson Reservoir 85 3.8.2 Diurnal temperature patterns 89 3.8.3 Relationship between flow and temperature 90 3.8.4 Summary 92 3.9 Upper Yarra Reservoir 93 3.9.1 Comparison between the upstream and all downstream monitoring sites 94 3.9.2 Diurnal temperature patterns 98 3.9.3 Relationship between flow and temperature 99 3.9.4 Summary 100 3.10 Lake Glenmaggie 102 3.10.1 Comparison upstream and downstream of Lake Glenmaggie 104 3.10.2 Diurnal temperature patterns 107 3.10.3 Relationship between flow and temperature 108 3.10.4 Summary 110 3.11 Blue Rock Dam 111 3.11.1 Comparison between upstream and downstream sites 112 3.11.2 Diurnal temperature patterns 115 3.11.3 Relationship between flow and temperature 116 3.11.4 Summary 118 3.12 Narracan Reservoir 119 3.12.1 Comparison upstream and downstream of Lake Narracan 121 3.12.2 Diurnal temperature patterns 124 3.12.3 Relationship between flow and temperature 125 3.12.4 Summary 127 3.13 Pykes Creek Reservoir 128 3.13.1 Comparison between monitored sites 130

Page iv Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.13.2 Diurnal temperature patterns 133 3.13.3 Relationship between flow and temperature 134 3.13.4 Summary 136 3.14 Melton Reservoir 137 3.14.1 Comparison between all sites 139 3.14.2 Diurnal temperature patterns 142 3.14.3 Relationship between flow and temperature 143 3.14.4 Summary 145 3.15 Mt. Beauty regulating pondage and the Kiewa River 146 3.15.1 Comparison between sites upstream and downstream of Mt. Beauty regulating pondage 148 3.15.2 Diurnal temperature patterns 151 3.15.3 Relationship between flow and temperature 152 3.15.4 Summary 154 4 Conclusion and monitoring recommendations 155 4.1 Summary and conclusion 155 4.2 Monitoring design recommendations 158 5 References 159

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Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Page vi

1 Introduction

Many large dams have been designed with bottom or low release points so that water releases can be made independent of storage levels. However, thermal stratification commonly occurs in deep water bodies and creates a cold water layer near the bottom. Dams that have low level outlets may deliver cold water to downstream waterways and can substantially change the thermal characteristics of receiving waters.

Releases from thermally stratified storages can lower summer temperatures, increase winter temperatures, reduce seasonal and diurnal amplitudes, delay summer peaks and may cause rapid temperature changes in downstream waterways (Ryan et al. 2002). Endemic species, particularly fish, are adapted to warm summer and cold winter water temperatures. Some species migrate away from areas that have unsuitable thermal conditions and others may use temperature cues to trigger spawning (Schiller and Harris 2001). Low summer temperatures may also affect the growth and survival of some native fish species (Astles et al. 2000). Egg, larval and juvenile stages are particularly susceptible to temperature changes and cold water pollution may severely impact native fish recruitment in some areas (Astles et al. 2000). Temperature changes associated with cold water dam releases may also favour exotic species such as trout, which may then compete with or prey on native fauna. Cold water pollution is also likely to affect native invertebrate species that have an aquatic larval stage and a terrestrial adult stage. Many macroinvertebrate larvae require warm summer temperatures to complete their development and water temperature has been shown to be an effective predictor of macroinvertebrate distribution patterns (Chessman and Royal 2004). Changes to the natural temperature regime may determine whether particular species are able to persist or recruit to certain areas and therefore alter macroinvertebrate community composition in some waterways.

Changes to natural temperature regimes in waterways is listed as a threatening process under the Victorian Flora and Fauna Guarantee Act (1988) and studies to assess and manage cold water pollution are a high priority. The Victorian Department of Sustainability and Environment (DSE) commissioned Arthur Rylah Institute to investigate potential cold water pollution impacts from priority dams throughout Victoria. Twenty-four maximum priority dams were identified for further study. All of these dams released water to natural streams from more than 10 m below their full supply level and therefore have the potential to cause thermal pollution in receiving waters. Water temperature has been monitored in streams upstream and downstream of 18 of these maximum priority dams over the last 12-18 months. The Murray-Darling Basin Commission is analysing data from two of these dams (Lake Hume and Dartmouth Dam) but data from the remaining 16 dams requires analysis.

Page 1 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

In this report, we analyse temperature data from the cold water pollution monitoring program to assess temperature changes in rivers and streams downstream of 15 high priority dams throughout Victoria and review the current monitoring program design.

Page 2 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

2 Method

2.1 Data availability Temperature Water temperature data loggers were installed for the temperature monitoring program in one or more major inlet streams upstream of high priority reservoirs and in receiving waters at various distances downstream of the reservoir dam walls. Hourly temperature monitoring commenced at most of these sites in November 2002 or April 2003 and is ongoing, but equipment failure means that some sites have an interrupted data record. At the time of reporting, data was available from most sites up until June or September 2004 (Table 2-1).

Table 2-1 List of temperature monitoring sites including the available data record analysed in the current report.

Number First Last Continuous Reservoir Site US / DS of data record record Record * days Cairn Curran Loddon River at US Nov 2002 June 2004 499 r Reservoir Newstead Cairn Curran Tail DS Nov 2002 June 2004 507 r Gauge Loddon River at Mullins DS Nov 2002 June 2004 499 r Rd

Laanecoorie Tullaroop Creek at US Nov 2002 June 2004 498 r Reservoir Mullins Rd Loddon River at Mullins US Nov 2002 June 2004 499 r Rd Loddon River at DS June 2003 June 2004 374 b Newbridge

Tullaroop Tullaroop Creek at US Nov 2002 June 2004 498 r Reservoir Clunes Tullaroop Reservoir DS Nov 2002 June 2004 499 r Tail Gauge Tullaroop Creek at DS Nov 2002 June 2004 499 r Carisbrook Tullaroop Creek at DS Nov 2002 June 2004 498 r Mullins Rd

Lake Eildon Big River at Jamiesons US Nov 2002 June 2004 542 r Rd Jamieson River at US Nov 2002 June 2004 504 r Gerrans Howqua River at US Nov 2002 June 2004 570 r Glenesk

Page 3 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Number First Last Continuous Reservoir Site US / DS of data record record Record * days Goulburn River at US Nov 2002 June 2004 571 r Dohertys Goulburn River at DS Nov 2002 May 2004 549 r Molesworth

Lake Campaspe River at US Nov 2002 June 2004 469 r Eppalock Redesdale Coliban River at Lyell US Nov 2002 June 2004 538 r Rd Campaspe River at DS Nov 2002 June 2004 552 r Lake Eppalock Tail Gauge Campaspe River at DS Nov 2002 June 2004 552 r Axedale Campaspe River at DS Nov 2002 June 2004 421 r Barnadown

Lake Broken River US US Nov 2002 June 2004 529 r Nillahcootie Nillahcootie Immediately DS of DS Nov 2002 June 2004 592 b Nillahcootie

Broken River at DS Nov 2002 June 2004 593 b Swanpool Broken River at DS Nov 2002 June 2004 591 b Moorngag

Lake William King River US William US Nov 2002 April2004 462 r Hovell Hovell

King River DS William DS Feb 2003 June 2004 505 b Hovell King River at Cheshunt DS Nov 2002 June 2004 379 r King River at Edi DS Nov 2002 June 2004 606 b

Thomson Thomson River at US May 2003 Sept 2004 523 b Reservoir Whites Rd Thomson River DS of DS May 2003 Sept 2004 524 b dam Thomson River at DS May 2003 Sept 2004 523 b Narrows Track Thomson River at DS May 2003 Sept 2004 523 b Coopers Creek Track Thomson River US of DS May 2003 Sept 2004 526 b Cowwarr Weir

Page 4 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Number First Last Continuous Reservoir Site US / DS of data record record Record * days

Upper Yarra Yarra US Yarra US April 2003 Oct 2004 533 b Reservoir Reservoir Yarra DS Doctors DS April 2003 Oct 2004 474 r Creek Yarra DS McMahons DS April 2003 Oct 2004 559 b Creek Yarra at Warburton DS June 2003 Oct 2004 489 b Yarra at Millgrove DS April 2003 Oct 2004 476 r

Lake Macalister River at US Oct 2002 Sept 2004 691 b Glenmaggie Stringybark

Macalister River at DS Oct 2002 Sept 2004 693 b Glenmaggie Tail Gauge

Macalister River at DS Oct 2002 June 2004 600 b Hagans Rd Macalister River at DS Oct 2002 Oct 2004 742 b Manson Rd

Lake Latrobe River at Becks US Nov 2002 Oct 2004 720 b Narracan Bridge Latrobe River at DS Nov 2002 Oct 2004 641 r Yallourn Power Latrobe River US DS Nov 2002 Oct 2004 704 b Morwell River Latrobe River at Thoms DS Nov 2002 Oct 2004 720 b Bridge

Blue Rock Tanjil River at Tanjil US Nov 2002 Oct 2004 721 b Dam Junction Tanjil River DS Blue DS Nov 2002 Oct 2004 681 r Rock Dam

Tanjil River at Tanjil DS Nov 2002 Oct 2004 721 b South Latrobe River at Becks DS Nov 2002 Oct 2004 720 b Bridge

Pykes Creek Pykes Creek Reservoir DS Nov 2002 July 2004 629 b Reservoir Tail Gauge Werribee River at DS Nov 2002 July 2004 575 r Bacchus Marsh Falls Werribee River at DS Nov 2002 July 2004 629 b Bacchus Marsh

Page 5 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Number First Last Continuous Reservoir Site US / DS of data record record Record * days

Melton Werribee River at US Nov 2002 July 2004 629 b Reservoir Bacchus Marsh Pyrites Creek DS US Nov 2002 July 2004 629 b Merrimu Reservoir Melton Reservoir Tail DS Nov 2002 July 2004 625 b Gauge Werribee River at DS Nov 2002 July 2004 384 r Werribee Tunnel Werribee River at DS Nov 2002 July 2004 576 r Droomers

Mt Beauty West Kiewa Diversion US May 2004 April 2005 336 b Pondage

Mt Beauty Pondage DS May 2004 April 2005 336 b discharge

Kiewa River at DS May 2004 April 2005 336 b Mongans Bridge

* Refer to average daily temperature time series plots in Section 3 to see specific missing data periods.

Flow Stream flow was not specifically measured as part of the temperature monitoring program and therefore flow data was not available for many of the temperature monitoring sites. Where possible, average daily flow data from established gauging sites (Table 2-2) was used to assess the relationship between flow and temperature upstream and downstream of each dam. It should be noted that this study primarily focussed on thermal impacts of Victorian dams and therefore a detailed assessment of flow changes due to each dam is not provided.

Table 2-2 List of flow monitoring sites with available data that was used in this project to compare flow patterns upstream and downstream of each dam and to assess relationships between flow and temperature. Data records were continuous at all sites and this table indicates the period of data that was analysed in this study.

Reservoir Site First record Last record Cairn Curran Reservoir Loddon at Newstead April 2003 June 2004 Cairn Curran Tail Gauge April 2003 June 2004

Laanecoorie Reservoir Laanecoorie Tail Gauge April 2003 June 2004 * No upstream monitoring site

Page 6 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Reservoir Site First record Last record Tullaroop Reservoir Tullaroop Creek at April 2003 June 2004 Clunes Tullaroop Tail Gauge April 2003 June 2004

Lake Eildon Jamieson River at April 2003 June 2004 Gerrans Goulburn River at April 2003 June 2004 Doherty’s Lake Eildon Tail Gauge April 2003 June 2004

Lake Eppalock Campaspe River at April 2003 June 2004 Redesdale Coliban River at Lyell Rd April 2003 June 2004 Lake Eppalock Tail April 2003 June 2004 Gauge

Lake Nillahcootie Nillahcootie Tail Gauge April 2003 June 2004 Broken River at April 2003 June 2004 Moorngag * No upstream monitoring site

Lake William Hovell William Hovell Tail April 2003 June 2004 Gauge King River at Cheshunt April 2003 June 2004 * No upstream monitoring site

Thomson Reservoir Thomson River at May 2003 October 2004 Whites Thomson Tail Gauge May 2003 October 2004 Thomson River at May 2003 October 2004 Narrows Track

Upper Yarra Reservoir Yarra River at Millgrove April 2003 August 2004 * No upstream monitoring site

Lake Glenmaggie Macalister River at November 2002 October 2004 Stringybark Glenmaggie Tail Gauge November 2002 October 2004

Blue Rock Dam Tanjil River at Tanjil November 2002 September 2004 Junction

Page 7 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Reservoir Site First record Last record Tanjil River at Tanjil November 2002 September 2004 South

Lake Narracan Latrobe River at November 2002 October 2004 Yallourn Latrobe River at Thoms November 2002 October 2004 Bridge * No upstream monitoring site

Pykes Creek Reservoir Pykes Creek Reservoir November 2002 July 2004 Tail Gauge Werribee River at November 2002 July 2004 Bacchus Marsh * No upstream monitoring site

Melton Reservoir Werribee River at November 2002 July 2004 Bacchus Marsh Melton Reservoir Tail November 2002 July 2004 Gauge

Mt Beauty Pondage West Kiewa Diversion November 2002 July 2004 Power Station discharge November 2002 July 2004 Mt Beauty Pondage November 2002 July 2004 discharge Kiewa River at Mongans November 2002 July 2004 Bridge

Storage level Average monthly storage volume and water levels were obtained for 14 out of the 15 dams studied in this project. Storage level data was not available for Lake Narracan and Merrimu Reservoir and therefore could not be included in this report.

2.2 Data validation Any Theiss supplied data with a quality code greater than 150 (indicating lost or unreliable data) were excluded from data sets prior to analysis. In addition, all data was visually inspected to identify potential errors. Data before and after sudden temperature shifts was scrutinised to determine whether the pattern could have been due to measurement error. Flow records were also scrutinised to see if temperature spikes could be explained by sudden changes in flow. Most abnormal temperature records occurred on days when temperature probes were installed, removed

Page 8 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

or checked. Data records that were suspected of being incorrect were excluded from subsequent analyses. Zero temperatures were occasionally recorded at some sites, but checks of temperature and flow records immediately before, after and during these events indicated that they were not likely to have been accurate measures and were therefore excluded from subsequent analyses.

2.3 Analysis Separate analyses were conducted for each dam. We examined storage level fluctuations and assessed mean temperature patterns, temperature variability, diurnal temperature ranges and the relationship between flow and temperature upstream and downstream of each dam.

2.3.1 Storage levels Dam storage levels can have a substantial effect on water temperatures in the dam and the temperature of water that is released further downstream. If water levels are very low, then the whole reservoir may be heated in summer and contribute to elevated temperatures further downstream.

Thermal stratification can occur when there is poor or no mixing between surface water layers and water at depth. Stratified waters have a thermocline that marks the boundary between the mixed surface layer and generally cooler bottom layers. Stratification can occur in relatively shallow water, but is more common in deep storages. The depth of the mixed surface layer will vary between storages due to differences in physical characteristics and meteorological conditions, but for most large storages it will usually range between 5 and 20 metres (Astles 2001). Cold water pollution will only occur in downstream waters when the reservoir outlet is below the mixed surface layer. Most Victorian dams have fixed outlets, therefore the relative difference between the water surface and the outlet depth will determine whether cold water pollution is likely to be a problem in downstream waterways.

Average monthly storage volumes throughout the monitoring period and the relative difference between water surface levels and outlet levels were plotted for each dam. These plots were used to determine the likelihood of thermal impacts to downstream waters during the monitoring period and to assess whether the patterns observed during this study reflect normal conditions or are confounded by the drought.

2.3.2 Temperature patterns Individual hourly temperature records do not accurately characterise conditions at a particular site as the high degree of variation between instantaneous records makes it difficult to assess and interpret temperature differences between readings over successive time periods at individual sites or between sites. We therefore aggregated the available hourly data and calculated daily average, daily minimum and daily maximum temperatures at each site. Differences between daily minimum

Page 9 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

and maximum temperatures were used to calculate the diurnal range at each site and differences in daily averages between consecutive days were calculated at each site to describe short-term temperature fluctuations.

Separate analyses were conducted for each monitored reservoir. Average daily temperature, short term temperature variation and diurnal temperature range at sites downstream of individual reservoirs were compared against conditions at upstream reference sites to determine whether releases from the dams were having a detectable effect on downstream water temperature. Many of the monitored reservoirs had multiple sites at varying distances downstream of the dam wall and where possible temperature differences between these sites were compared to determine the spatial extent of any thermal change. A small number of reservoirs had monitoring stations on multiple inlet streams and temperature conditions at these sites were compared to estimate the overall inputs to downstream waterways.

Under normal conditions, water temperatures are expected to increase with distance downstream and therefore sites downstream of the reservoir are likely to have warmer temperatures than upstream reference sites. No data was available to estimate temperature differences that would be expected at monitoring sites in the absence of dams. Therefore we adopted a conservative approach whereby dam releases are only considered to have cooled downstream waters if temperatures at downstream sites are lower than at upstream reference sites.

Time series plots Average daily temperatures vary substantially within and between seasons and seasonal patterns can vary between years, therefore data from replicate seasons is required to statistically contrast temperature between sites. The temperature monitoring program is only in its early stages and the available data set it too short for seasonal replication. In this report, we use time series plots to describe average daily temperature patterns at each site. As more data is collected, future analyses will be able to use data from replicate seasons to more comprehensively compare conditions upstream and downstream of reservoirs.

In most cases we produce two time series plots to compare average daily temperature patterns between specific sites. The first plot shows a moving daily average, calculated over 14 days, for each site. The moving daily average is the average temperature recorded for seven days either side of the nominated date. This measure hides most of the day to day temperature fluctuations and makes specific temperature comparisons between sites much clearer. This plot is used to describe the magnitude of temperature differences between sites, to assess temporal lags in summer peak or winter minimum temperatures between sites and to identify sudden temperature changes at particular sites. The second plot shows the actual daily average temperature at each site and is used to highlight short-term variation between specific sites. These short term temperature fluctuations are more formally assessed by calculating the difference in average daily temperatures on every

Page 10 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

consecutive day at each site. Average daily temperature fluctuations are calculated for the entire data record and individually for each season at each site.

Diurnal temperature patterns Diurnal temperature ranges were calculated by subtracting the daily minimum temperature from the corresponding daily maximum temperature at every site. Boxplots were used to show median diurnal ranges and associated variation at individual sites.

2.3.3 Relationships between flow and temperature Time series plots showing average daily flow at individual gauging stations were used to highlight differences in flow magnitude and seasonal patterns upstream and downstream of each dam. Where flow and temperature data was available for the same site, the timing of specific flow events and temperature changes were compared to determine whether sudden flow changes were affecting downstream temperatures. More general associations between temperature and flow were assessed by plotting average daily temperature against average daily flow at one site upstream and one site downstream of each dam. Water temperature was expected to vary between seasons regardless of flow, therefore data was plotted separately for each season so that the effect of flow on temperature could be more reliably assessed.

Page 11 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3 Thermal impacts associated with controlled releases from Victorian dams

3.1 Cairn Curran Reservoir Cairn Curran Reservoir has a storage capacity of 148,000 ML and is impounded by a 44 m high dam wall. Releases are made from a wet tower with a single outlet 19 m below the full supply level (FSL) and a spillway. Hourly temperature data was collected from the Loddon River at Newstead immediately upstream of the reservoir, at the Cairn Curran Tail Gauge and at Mullins Rd, approximately 10 km downstream of the reservoir (Figure 3-1). No major tributaries enter the Loddon River between any of the monitoring sites. Storage levels were very low and ranged between 4% and 18% of capacity throughout the monitoring period (Figure 3-2).

Mullins Rd

Cairn Curran TG

Newstead

Figure 3-1 Cairn Curran Reservoir temperature monitoring sites. Map adapted from DSE (2005).

Page 12 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Monthly Storage Level for Cairn Curran Reservoir

160,000 140,000 120,000 100,000 80,000 60,000 40,000 20,000 0 Storage Volume (ML) Volume Storage Jul-03 Jan-04 Jan-03 Nov-03 Nov-02 Mar-04 Mar-03 Sep-03 May-04 May-03

Capacity Storage

Figure 3-2 Plot of Cairn Curran Storage volume and total capacity between November 2002 and June 2004. Due to the relatively low storage levels, releases from Cairn Curran Reservoir were made relatively close to the water surface rather than at depth throughout the monitoring period. At FSL, releases from Cairn Curran Reservoir may be made from up to 19 m below the water surface, but releases during the monitored period were made from 0 m to 8 m below the water surface (Figure 3-3). Thermal stratification increases with depth. Therefore thermal patterns reported downstream of Cairn Curran Reservoir during this current monitoring period may not reflect conditions when storage levels are higher. Thermal pollution downstream of Cairn Curran Reservoir is likely to be more severe when storage levels are closer to FSL.

210.0 205.0 200.0 Storage level 195.0 Outlet 190.0

AHD (m) AHD FSL 185.0 180.0 175.0

3 03 0 03 04 04 04 04 - t- - - t- c an c Oct-02 Jan Apr-03 Jul- O J Apr Jul- O

Figure 3-3 Plot showing the relationship between mean storage level, FSL and the main outlet at Cairn Curran Reservoir between October 2002 and October 2004.

Page 13 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.1.1 Comparison upstream and downstream of Cairn Curran Reservoir 24 N ew stead

22 Cairn Curran TG

Mulllins 20

18

16

14

12

10

8

6 T emperature (D egrees Celcius)

4

2

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-4 Average daily temperature (smoothed over 14 days) in the Loddon River upstream and at two sites downstream of Cairn Curran Reservoir from November 2002 to June 2004. Average daily temperatures in the Loddon River downstream of Cairn Curran Reservoir were higher than the upstream site throughout the monitoring period, although this difference is most pronounced during summer and least noticeable in spring. Summer temperatures in the Loddon River immediately downstream of Cairn Curran Reservoir are approximately 1.5-3.0 °C higher than the upstream site at Newstead, the site further downstream at Mullins Road is another 1 °C warmer indicating a general increase in water temperature downstream of the dam (Figure 3-4). Winter temperatures at the tail gauge site were approximately 1 °C warmer than the Loddon River at Newstead (Figure 3-4). Autumn and winter temperatures further downstream at Mullins Road were in between the upstream and tail gauge sites. This difference is probably due to the greater variation in daily water temperature at the Mullins Road site compared to the Cairn Curran Tail Gauge site. Temporal patterns in water temperature however are similar at all sites suggesting that the reservoir (at the low levels experienced over the monitoring period) does not substantially affect the timing or duration of summer peaks and winter lows. There is also no evidence that releases from Cairn Curran Reservoir cause sudden temperature changes at any of the Loddon River sites downstream of the dam.

Page 14 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Newstead Ave 25 Curran TG Ave Mullins Ave

20

15

10 T emperature (D egrees Celcius) 5

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-5 Average daily temperature in the Loddon River upstream and at two sites downstream of Cairn Curran Reservoir from November 2002 to June 2004. Variation in average daily temperatures were similar in the Loddon River at Newstead upstream of Cairn Curran Reservoir and at the Cairn Curran Tail Gauge, but was substantially higher at Mullins Road further downstream (Figure 3-5). Average fluctuations in daily temperatures were higher upstream of Cairn Curran Reservoir compared to the tail gauge site in autumn, but were lower than the tail gauge site in spring (Table 3-1). Average daily temperature fluctuations downstream of Cairn Curran Reservoir at Mullins Road were substantially higher than either the upstream or tail gauge site in all seasons and were nearly twice as variable as other sites over the year (Table 3-1).

Page 15 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Table 3-1 Summary statistics for the daily temperature fluctuation at each site. Average and standard deviations are provided for differences between temperatures on successive days assessed over the entire monitoring period and separately for each season.

Loddon River Cairn Curran Loddon River Statistic at Newstead Tail Gauge at Mullins Overall Mean 0.39 0.39 0.74 Stand Dev. 0.36 0.31 1.00 Summer Mean 0.38 0.38 0.91 Stand Dev. 0.29 0.31 0.66 Autumn Mean 0.52 0.38 0.56 Stand Dev. 0.66 0.32 0.51 Winter Insufficient data to calculate winter statistics Mean NA NA NA Stand Dev. NA NA NA Spring Mean 0.33 0.42 0.90 Stand Dev. 0.25 0.30 1.86

Page 16 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.1.2 Diurnal temperature patterns

Autumn Spring

10 10 9 9 8 8 7 7

e e

g g

n 6 n 6

a a

R R

l 5 l 5

a a

n n r 4 r 4

u u

i i

D 3 D 3 2 2 1 1 0 0 d e e d e e a g g a g g te au s te au s s G lin s G lin ew il ul ew il ul N Ta M N Ta M Summer Winter

10 10 9 9 8 8 7 7

e e

g g

n 6 n 6

a a

R R

l 5 l 5

a a

n n r 4 r 4

u u

i i

D 3 D 3 2 2 1 1 0 0 d e e d e e a g g a g g te au s te au s s G lin s G lin ew il ul ew il ul N Ta M N Ta M

Figure 3-6 Boxplots showing the diurnal temperature range ( °°°C) in the Loddon River at one site upstream and two sites downstream of Cairn Curran Reservoir. Diurnal temperature ranges are shown separately for each season. Diurnal temperature ranges at all sites were highest in autumn and lowest in winter, but differences between sites were not consistent between seasons (Figure 3-6). Diurnal temperature ranges in the Loddon River upstream of Cairn Curran Reservoir at Newstead were significantly higher and more variable than downstream sites in autumn (Tukeys pairwise comparison P<0.001). However, at other times diurnal ranges were slightly higher at the Cairn Curran Tail Gauge site and were highest further downstream at Mullins Road, indicating a trend for diurnal temperature ranges in the Loddon River to increase with downstream distance (Figure 3-6). The high variation in diurnal temperature ranges at Newstead in autumn may reflect very low flow in the Loddon River at this time as shallow, slow flowing water is strongly influenced by ambient air temperature.

This pattern suggests that releases from Cairn Curran Reservoir had little effect on diurnal temperature ranges in the Loddon River during the monitored period.

Page 17 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.1.3 Relationship between flow and temperature Flow data was available for the upstream reference site at Newstead and for the Cairn Curran Tail Gauge. This data was plotted to highlight the effect of Cairn Curran Reservoir on downstream flow patterns and relationships between flow and temperature at each site were also analysed.

N ew stead 1600 T ail Gauge

1400

1200

1000

800 Flow (ML/d) 600

400

200

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-7 Average daily flow in the Loddon River at Newstead upstream of Cairn Curran Reservoir and in the Loddon River immediately downstream of Cairn Curran Reservoir between April 2003 and June 2004.

Page 18 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

25

Summ er 20

15 A utumn

10 W inter

Spring

Average daily temperature 5

0 0 50 100 150 200 250 300 350 400 Flow (ML/d)

Figure 3-8 Plot of average daily flow vs average daily temperature ( °°°C) in the Loddon River at Newstead, upstream of Cairn Curran Reservoir, between April 2003 and Sept 2003. (Note flows > 400 ML/day have been excluded to better illustrate seasonal patterns).

24 22

20 Sum m er 18 16 A utum n 14 12

10 W inter 8 6 Spring Average daily temperature 4 2 0 0 20 40 60 80 100 120 140160180 200 220 Flow (ML/d)

Figure 3-9 Plot of average daily flow vs average daily temperature in the Loddon River at Newstead, upstream of Cairn Curran Reservoir, between April 2003 and Sept 2003.

Page 19 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Average daily flow in the Loddon River immediately downstream of Cairn Curran Reservoir was substantially lower than flow at the Loddon River at Newstead in winter and spring, but was higher in summer and autumn (Figure 3-7). There was no relationship between temperature and flow upstream of Cairn Curran Reservoir for most of the year, but warmer temperatures were recorded at low flows in spring (Figure 3-8). There was no relationship between water temperature and flow in the Loddon River downstream of Cairn Curran Reservoir (Figure 3-9).

3.1.4 Summary The two monitored sites in the Loddon River downstream of Cairn Curran Reservoir had higher average daily temperatures than the single upstream reference site at Newstead throughout the monitoring period. In the absence of major tributary inputs, water temperatures would normally be expected to increase with distance downstream. However, the temperature difference between the Cairn Curran Tail Gauge site and the upstream reference site was much greater than the difference between the two downstream sites, which suggests that if anything, releases from Cairn Curran Reservoir may be warming downstream waters.

The results presented above indicate that Cairn Curran Reservoir had little effect on water temperatures, daily temperature fluctuations and diurnal temperature ranges in the Loddon River. However, the data analysed in this study was collected during a drought period when Cairn Curran storage levels were very low. It is not possible to extrapolate these results to assess potential downstream temperature impacts associated with releases when the reservoir is full and it is recommended that the monitoring program be continued to collect data when storage levels are higher.

Page 20 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.2 Laanecoorie Reservoir Laanecoorie Reservoir is impounded by a 22 m high dam wall and has a storage capacity of 8,000 ML, which represents only 3.5% of mean annual flow in the Loddon River at this point. Releases are made from outlet pipes within the spillway at approximately 10 m below FSL (Ryan et al. 2001). Temperature was recorded hourly in the Loddon River and Tullaroop Creek at Mullins Road upstream of Laanecoorie Reservoir and approximately 12 km downstream of the reservoir at Newbridge (Figure 3-10). Bradford Creek joins the Loddon River downstream of Laanecoorie Reservoir and may influence temperature patterns at Newbridge. Storage levels varied between 35% and 98% capacity during the monitoring period, but were at or less than 50% for most of this time (Figure 3-11).

Newbridge

Laanecoorie Reservoir

Tullaroop Creek Loddon River at at Mullins Rd Mullins Rd

Figure 3-10 Laanecoorie Reservoir temperature monitoring sites. Map adapted from DSE (2005).

Page 21 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

10,000 8,000 6,000 4,000 2,000 0 Storage Volume (ML) Jul-03 Jan-04 Jan-03 Nov-03 Nov-02 Mar-04 Mar-03 Sep-03 May-04 May-03

Capacity Storage

Figure 3-11 Plot of Laanecoorie Storage volume and total capacity between November 2002 and June 2004. Despite relatively low storage volumes, water levels remained well above the outlet point throughout the monitoring period (Figure 3-12). This suggests that Laanecoorie Reservoir has a large surface to volume relationship and that the reservoir is relatively shallow except near the dam wall. Water levels may be higher in other years, but higher levels are not likely to lead to a significant increase in thermal stratification and will not substantially increase the distance between the water surface and outlet. Therefore temperature patterns reported downstream of Laanecoorie Reservoir in this study are likely to reflect patterns in most years.

162.0 160.0 158.0 156.0 Storage level 154.0 Outlet 152.0

AHD (m) AHD 150.0 FSL 148.0 146.0 144.0

3 4 0 0 t-02 - r-04 -04 c ct-03 n- O Jan-03 Apr-03 Jul O Ja Ap Jul-04 Oct

Figure 3-12 Plot showing the relationship between mean storage level, FSL and the main outlet in Laanecoorie Reservoir between October 2002 and October 2004.

Page 22 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.2.1 Comparison between sites upstream and downstream of the reservoir 24 Loddon Mullins 22 Tulla Mullins Loddon Newbridge 20

18

16

14

12

10

8

6 T emperature (D egrees Celcius)

4

2

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-13 Average daily temperature (smoothed over 14 days) in the Loddon River and Tullaroop Creek upstream and at two sites downstream of Laanecoorie Reservoir from November 2002 to June 2004. The smoother function fitted to average daily temperature data reduces the noise that is associated with short term variation and allows specific temperature differences between sites to be more clearly assessed. This plot indicates a slight temperature difference between the two monitoring sites on the Loddon River and Tullaroop Creek upstream of Laanecoorie Reservoir. Average daily temperatures in the Loddon River at Mullins were 1-2 °C higher than Tullaroop Creek at Mullins in summer but were only slightly higher or comparable in winter and spring (Figure 3-13). Autumn temperatures in Tullaroop Creek were slightly higher than the Loddon River at Mullins in 2004 (Figure 3-13), but there is no data from autumn 2003 and therefore it is not possible to say whether this is a normal autumn pattern. The Tullaroop Creek site at Mullins is downstream of Tullaroop Reservoir and therefore temperature patterns at this site are likely to be affected by releases from that reservoir and may vary from year to year.

Temperature monitoring downstream of Laanecoorie Reservoir at Newbridge was only conducted between June 2003 and June 2004. Average daily temperatures in the Loddon River at Newbridge downstream of Laanecoorie Reservoir were up to 1 °C higher than temperatures at the upstream monitoring sites throughout the year, but mirrored the temporal fluctuations at both upstream sites (Figure 3-13). There were no sudden temperature changes at the downstream site compared to either of the upstream monitoring sites (Figure 3-13). One of the main reasons for the lack of any

Page 23 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

substantial thermal impact downstream of Laanecoorie Reservoir is the relatively small size of the Reservoir. When full, Laanecoorie Reservoir holds an equivalent of 3.5% of the mean annual flow in the Loddon River at this point. Therefore, water held in the reservoir will be regularly flushed through, which reduces the probability of thermal stratification.

Loddon Mullins 25 Tulla Mullins Loddon Newbridge

20

15

10 T emperature (D egrees Celcius) 5

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-14 Average daily temperature in the Loddon River and Tullaroop Creek upstream and in the Loddon River downstream of Laanecoorie Reservoir from November 2002 to June 2004. Average daily temperatures fluctuated most in summer and were more variable in 2002/03 compared to 2003/04 (Figure 3-14). Average daily temperatures were more variable in the Loddon River than Tullaroop Creek upstream of Laanecoorie Reservoir (Table 3-2) and temperatures at both sites were slightly more variable than in the Loddon River at Newbridge (Table 3-2). Temperature fluctuations in all river sites were higher than in Laanecoorie Reservoir and these results suggest that reduced variability associated with releases from the reservoir do not persist far beyond Newbridge.

Page 24 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Table 3-2 Summary statistics for the daily temperature fluctuation at each site. Average and standard deviations are provided for differences between temperatures on successive days assessed over the entire monitoring period and separately for each season.

Tullaroop Ck. Loddon River Laanecoorie Loddon River Statistic at Mullins Rd. at Mullins Rd. Head Gauge at Newbridge Overall Mean 0.55 0.70 0.36 0.48 Stand Dev. 0.45 0.58 0.45 0.37 Summer Mean 0.72 0.91 0.38 0.70 Stand Dev. 0.50 0.66 0.55 0.49 Autumn Mean 0.55 0.56 0.31 0.43 Stand Dev. 0.46 0.51 0.31 0.31 Winter Mean 0.30 0.47 0.24 0.34 Stand Dev. 0.22 0.36 0.19 0.22 Spring Mean 0.53 0.72 0.50 0.48 Stand Dev. 0.38 0.56 0.54 0.34

Page 25 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.2.2 Diurnal temperature patterns

Autumn Spring

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0 0 li r li r u ul op b u ul op b t M M t w t M M t w a G e a G e la on H N la on H N ll d n on ll d n on Tu od aa d Tu od aa d L L od L L od SummerL WinterL

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0 0 u lli p br u lli p br M u to w M u to w t M G e t M G e a n H N a n H N llla do n n llla do n n u d a do u d a do T Lo La d T Lo La d Lo Lo

Figure 3-15 Boxplots showing the diurnal temperature range ( °°°C) in Tullaroop Creek and the Loddon River upstream and downstream of Laanecoorie Reservoir. Diurnal temperature ranges are shown separately for each season and are plotted on a Log 10 scale. Diurnal ranges at all sites were highest in summer and lowest in winter (Figure 3-15), but average diurnal ranges were significantly lower downstream of Laanecoorie Reservoir compared to the two upstream reference sites (Tukeys pairwise comparisons P<0.001). Diurnal temperature ranges averaged over the whole monitoring period in the Loddon River and Tullaroop Creek upstream of Laanecoorie Reservoir were 2.1 °C and 1.9 °C respectively, but diurnal ranges at the Laanecoorie Head Gauge and further downstream at Newbridge were 1.4 °C and 1.5 °C respectively. Diurnal ranges were consistently higher at sites upstream of Laanecoorie Reservoir than the downstream sites in all seasons, but the magnitude of these differences varied and was most pronounced in summer (Figure 3-15).

Page 26 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.2.3 Relationship between flow and temperature No streamflow data was available from any of the temperature monitoring sites upstream or downstream of Laanecoorie Reservoir, therefore a direct assessment of flow temperature relationships is not possible. The only site close to Laanecoorie Reservoir with flow data is the Laanecoorie Tail Gauge site immediately downstream of the dam wall. The closest temperature monitoring site was at Newbridge, approximately 10-15 km further downstream. In this section we compare flow at the Laanecoorie Tail Gauge with temperature at Newbridge, but emphasise that the distance between these sites substantially reduces the value of this comparison. No flow data was available from sites upstream of Laanecoorie Reservoir.

Laan TG flow 160

140

120

100

80 Flow (ML/d) 60

40

20

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-16 Average daily flow in the Loddon River immediately downstream of Laanecoorie Reservoir between March 2003 and June 2004.

Page 27 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

25

Summ er 20

A utumn 15

W inter 10

Spring

Average daily temperature 5

0 0 20 40 60 80 100 120 140 160 Flow (ML/d)

Figure 3-17 Plot of average daily flow immediately downstream of Laanecoorie Reservoir against average daily temperatures ( °°°C) at Newbridge. Results for individual seasons are plotted separately. Flow immediately downstream of Laanecoorie Reservoir peaked in summer as a result of irrigation releases (Figure 3-16). There was a positive relationship between flow at the Laanecoorie Tail Gauge and water temperature further downstream at Newbridge in autumn and spring, but there was no relationship between flow and temperature at these sites in summer and winter (Figure 3-17). Given the distance between the Laanecoorie Tail Gauge and Newbridge, little inference can be drawn from these patterns.

3.2.4 Summary Overall, Laanecoorie Reservoir did not appear to have a great effect on downstream water temperatures in the Loddon River during the monitoring period. Average daily temperatures in the Loddon River at Newbridge were up to 1 °C higher than at the upstream reference sites, which is the type of difference that may be expected if the dam were not present. Daily temperature fluctuations were also reasonably similar upstream and downstream of Laanecoorie Reservoir. The most noticeable effect of the dam is likely to be changes to diurnal temperature ranges, with the Loddon River downstream of Laanecoorie Reservoir having slightly lower diurnal ranges than the upstream reference sites, however the magnitude of these differences was not great.

Laanecoorie Reservoir storage levels were close to or less than 50% of capacity for most of the monitoring period. There is no indication that thermal impacts downstream of the reservoir were

Page 28 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

any more severe in spring 2003, when storage levels were higher. Higher water levels are not likely to substantially increase thermal stratification or the vertical distance between the water surface level and outlet point. Therefore, thermal patterns downstream of Laanecoorie Reservoir are not expected to vary greatly with changes in storage levels and the patterns reported in this study are therefore likely to be a reliable indication of impacts associated with controlled releases from this reservoir.

Page 29 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.3 Tullaroop Reservoir Tullaroop Reservoir is impounded by a 42 m high dam wall and a storage capacity of 74,000 ML. Releases are made from an outlet in a dry tower that is 12.8 m below FSL. Water temperature was monitored hourly at four sites within the Tullaroop catchment. The upstream reference site was in Tullaroop at Clunes, which is approximately 15 km upstream of Tullaroop Reservoir. The three downstream monitoring sites were at Tullaroop Tail Gauge, Tullaroop Creek at Calisbrook and Tullaroop Creek at Mullins Road (Figure 3-18). Storage levels varied between 10% and 35% capacity during the monitoring period (Figure 3-19).

Mullins Rd

Carisbrook

Tullaroop TG

Clunes

Figure 3-18 Tullaroop Reservoir temperature monitoring sites. Map adapted from DSE (2005).

Page 30 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 Storage Volume (ML) Jul-03 Jan-03 Jan-04 Nov-02 Nov-03 Mar-03 Mar-04 Sep-03 May-03 May-04

Capacity Storage

Figure 3-19 Plot of Tullaroop Reservoir storage volume and total capacity between November 2002 and June 2004. At FSL, releases from Tullaroop Reservoir may be made from up to 19 m below the water surface. However, low storage levels meant that releases during the monitoring period were made from no more than 2 m below the water surface (Figure 3-20). For some of the monitored period, water levels were below the outlet (Figure 3-20) and therefore flow from the reservoir at these times would have been at or close to zero. Some thermal stratification may have occurred in Tullaroop Reservoir during the monitoring period, but it is unlikely that water would have been released from below the thermocline. Therefore the thermal patterns reported in this study do not necessarily reflect impacts that may occur when storage levels are higher.

225.0

220.0

215.0 Storage level Outlet 210.0

AHD (m) AHD FSL 205.0

200.0

3 3 3 4 0 0 0 0 t-02 t- l-04 t-04 n- pr- c n- u c Oc Ja A Jul-03 O Ja Apr-04 J O

Figure 3-20 Plot showing the relationship between mean storage level, FSL and the main outlet in Tullaroop Reservoir between October 2002 and October 2004.

Page 31 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.3.1 Comparison upstream and downstream of Tullaroop Reservoir 24 Clunes

22 Tullaroop TG

Carisbrook 20 Mullins 18

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8

6 T emperature (D egrees Celcius)

4

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0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-21 Average daily temperature (smoothed with a moving average over 14 days) at one site upstream and three sites downstream of Tullaroop Reservoir between November 2002 and June 2004. Differences in average daily temperatures between the monitoring sites were most apparent in summer 2003/04, but the general trend between upstream and downstream sites was different to that observed in 2002/03. Average daily temperatures in Tullaroop Creek 7 km and 25 km downstream of Tullaroop Reservoir were slightly lower than the upstream reference site in summer 2002/03 (Figure 3-21). However, in summer 2003/04 average daily temperatures at all downstream sites were 1.5 – 3.5 °C warmer than in Tullaroop Creek upstream of the reservoir (Figure 3-21). Temperatures at the Tullaroop Reservoir Tail Gauge were higher than at sites further downstream in summer 2003/04, which suggests that warm water released from the reservoir is probably cooling in the river channel after release. Average daily temperatures in winter were very similar at the upstream site and two furthest downstream sites, but were about 1 °C warmer at Tullaroop Tail Gauge (Figure 3-21). There was no difference in the timing of specific temperature changes between upstream and downstream sites, nor was there any indication of sudden temperature changes at downstream sites due to releases from the reservoir (Figure 3-21).

Page 32 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

25 Clunes Tullaroop TG

20

15

10 T emperature (D egrees Celcius) 5

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-22 Average daily temperature in Tullaroop Creek upstream and immediately downstream of Tullaroop Reservoir between November 2002 and June 2004. Average daily temperatures at the Tullaroop Reservoir Tail Gauge were less variable than the upstream reference site (Figure 3-22), but temperatures 7 km further downstream at Calisbrook were more variable than the upstream reference site in all seasons (Table 3-3). Daily temperature fluctuations at Calisbrook were particularly high in summer and autumn (Table 3-3). Daily fluctuations further downstream at Mullins Road were slightly higher than the upstream reference site in summer and autumn, but less variable than the reference site in winter and spring (Table 3-3).

Page 33 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Table 3-3 Summary statistics for the daily temperature fluctuation at each site. Average and standard deviations are provided for differences between temperatures on successive days assessed over the entire monitoring period and separately for each season.

Tullaroop Tullaroop Tullaroop Tullaroop Statistic Creek at Reservoir at Creek at Creek at Clunes Tail Gauge Carisbrook Mullins Overall Mean 0.53 0.43 0.80 0.55 Stand Dev. 0.50 0.41 0.61 0.45 Summer Mean 0.56 0.56 0.99 0.72 Stand Dev. 0.55 0.44 0.69 0.50 Autumn Mean 0.49 0.38 0.78 0.55 Stand Dev. 0.49 0.34 0.56 0.46 Winter Mean 0.36 0.27 0.55 0.30 Stand Dev. 0.28 0.45 0.43 0.22 Spring Mean 0.72 0.41 0.76 0.53 Stand Dev. 0.52 0.30 0.59 0.38

Page 34 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.3.2 Diurnal temperature patterns

Autumn Spring

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0 0 s b in s G b in ne TG ris ll ne T ris ll lu a a u lu a a u C ll C M C ll C M a Tu la lla a Tu la lla ll ul u ll ul u Tu T T Tu T T Summer Winter

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0 0 s G b in s G b in ne T ris ll ne T ris ll lu la a u lu la a u C ul C M C ul C M a T la lla a T la lla ll ul u ll ul u Tu T T Tu T T

Figure 3-23 Boxplots showing the diurnal temperature range ( °°°C) in Tullaroop Creek at one site upstream and three sites downstream of Tullaroop Reservoir. Diurnal temperature ranges are shown separately for each season. Diurnal temperature ranges at all monitored sites in Tullaroop Creek were high in spring and summer and were lowest in winter (Figure 3-23). Overall, the average diurnal range at Clunes upstream of the reservoir was 0.4-0.6 °C less than at all monitored downstream sites (Tukeys HSD test P<0.001), but the magnitude of site differences varied between seasons and were highest in autumn (Figure 3-23). Summer diurnal temperature ranges upstream of Tullaroop Reservoir were also more variable than at downstream sites (Figure 3-23).

Diurnal temperature ranges in Tullaroop Creek at Mullins Road were slightly lower than the other downstream sites, but this difference was small compared to the difference between sites upstream and downstream of the reservoir (Figure 3-23). This pattern suggests that releases from Tullaroop Reservoir increase the diurnal temperature range in Tullaroop Creek and that this effect persists for at least 25 km downstream.

Page 35 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

3.3.3 Relationship between flow and temperature Daily flow data was available for Tullaroop Creek at Clunes upstream of Tullaroop Reservoir and at the Tullaroop Tail Gauge. Flow data from each site was compared to assess the effect of Tullaroop Reservoir on downstream flow patterns and relationships between flow and temperature at each site were also assessed.

550 Clunes flow

Tulla TG flow 500

450

400

350

300

250 Flow (ML/d) 200

150

100

50

0 D ec02 Feb03 A pr03 Jun03 A ug03 Oct03 D ec03 Feb04 A pr04 Jun04

Figure 3-24 Average daily flow in Tullaroop Creek at Clunes (upstream of Tullaroop Reservoir) and at Tullaroop Tail Gauge between April 2003 and June 2004.

Page 36 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

25

Clunes Summer 20

Clunes Autumn 15

10 Clunes Winter

5 Clunes Spring Average daily temperature (celcius) 0 0 20 40 60 80 100 120 140 160 180 200 Flow (ML/d)

Figure 3-25 Plot of average daily flow vs average daily temperature in Tullaroop Creek at Clunes, 15 km upstream of Tullaroop Reservoir, between April 2003 and June 2004. (Note flows greater than 200 ML/day have been excluded to better illustrate seasonal patterns).

25

Tulla TG Summer 20

Tulla TG Autumn 15

10 Tulla TG Winter

5 Tulla TG Spring Average daily temperature (celcius) 0 0 5 10 15 20 25 30 35 40 45 50 Flow (ML/d)

Figure 3-26 Plot of average daily flow vs average daily temperature at the Tullaroop Reservoir Tail Gauge between April 2003 and June 2004.

Page 37 Temperature monitoring of dam releases in Victorian rivers 2002 - 2004

Flow seasonality and magnitude at Tullaroop Tail Gauge differed markedly from flow patterns at Clunes upstream of Tullarooop Reservoir. Average daily flow in the Tullaroop Creek at Clunes was much larger than flow at the Tullaroop Tail Gauge in spring 2003, but was less than flow at the Tullaroop Tail Gauge site in summer and autumn (Figure 3-24). There was a slight negative asso