This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Status of Cold Water Releases from Victorian Dams

TABLE OF CONTENTS

LIST OF FIGURES ...... II

EXECUTIVE SUMMARY ...... III

INTRODUCTION ...... 1

THERMAL POLLUTION – CHANGES IN THE TEMPERATURE REGIME OF NATURAL WATERS ...... 1 EFFECTS OF DAMS ON RIVER TEMPERATURES IN SOUTH-EASTERN AUSTRALIA...... 1 BIOLOGICAL EFFECTS OF THERMAL POLLUTION...... 2 Reduced temperature variability...... 3 Removal of rapid Spring - Summer increases and delay of peak temperatures...... 4 Rapid changes in temperature ...... 4 Effects of dams on stream biodiversity ...... 4 ASSOCIATED EFFECTS OF HYPOLIMNIAL DISCHARGES ...... 5 THIS STUDY ...... 5 METHODS...... 7

ASSESSMENT OF DAMS ...... 7 COMPILATION OF TEMPERATURE DATA ...... 8 RESULTS ...... 9

CLASSIFICATION OF PRIORITY RESEARCH DAMS...... 9 INVESTIGATION OF MAXIMUM PRIORITY RESEARCH DAMS ...... 11 Lake Dartmouth ...... 11 Hume Dam and Murray River ...... 14 Mt. Beauty Regulating Pondage and the Kiewa River...... 16 Lake William Hovell ...... 18 Lake Nillahcootie and Loombah Weir ...... 20 Lake Eildon...... 22 Malmsbury Reservoir...... 24 Lake Eppalock ...... 26 Cairn Curran Reservoir...... 28 Tullaroop Reservoir and Laanecoorie Reservoir ...... 28 Lake Bellfield ...... 31 Glenmaggie Reservoir ...... 31 Cardinia Reservoir ...... 34 Upper Yarra Valley (O’Shannassy Reservoir, Upper Yarra Reservoir, Silvan dams)...... 34 Pykes Creek, Merrimu and Melton reservoirs ...... 37 Bostock Reservoir ...... 39 West Barwon Dam ...... 39 Rocklands Reservoir ...... 39 INVESTIGATION OF MEDIUM PRIORITY DAMS ...... 42 Lake Buffalo...... 42 Barkers Creek Reservoir...... 42 Newlyn Reservoir...... 42 Blue Rock Reservoir and Lake Narracan ...... 44 Moondarra Reservoir ...... 44 Tarago Reservoir ...... 46 Maroondah Reservoir...... 46 Expedition Pass Reservoir ...... 46 Moorabool Reservoir and Lal Lal Reservoir...... 48 DISCUSSION...... 50

LOCATION OF MONITORING SITES ...... 50 TEMPORAL RESOLUTION OF SAMPLES ...... 51 IMPROVING TEMPERATURE MONITORING...... 52 RESEARCH AND MONITORING PROTOCOL...... 52

i Status of Cold Water Releases from Victorian Dams

Water temperature monitoring...... 52 Biological Monitoring...... 53 ASSESSMENT CRITERIA...... 54 MANAGEMENT OF COLD WATER POLLUTION...... 55 Operational constraints ...... 55 RECOMMENDATIONS...... 56 CONCLUSION...... 59

ACKNOWLEDGEMENTS...... 60

REFERENCES...... 61

PERSONAL CONTACTS ...... 67

Appendix A: Dams greater than 5 m and associated temperature research priority level...... 68 Appendix B: Summary Statistic for all sites presented in report ...... 71

LIST OF FIGURES

Figure 1: Flow chart to decide research priority for dams in Victoria ...... 9 Figure 2: Location of Research Priority Dams...... 10 Figure 3: Temperature data and location of Lake Dartmouth and sites within basin 1...... 13 Figure 4: Temperature data and location of Hume dam and sites in the Murray River ...... 15 Figure 5: Temperature data and location of reservoirs and sites within basin 2 ...... 17 Figure 6: Temperature data and location of Lake William Hovell and sites within basin 7 ...... 19 Figure 7: Temperature data and location of Lake Nillahcootie and sites within basin 4...... 21 Figure 8: Temperature data and location of Lake Eildon and sites within basin 5...... 23 Figure 9: Temperature data and location of Malmsbury Reservoir and sites within basin 6 ...... 25 Figure 10: Temperature data and location of Lake Eppalock and sites within basin 6 ...... 27 Figure 11: Temperature data and location of Cairn Curran Reservoir and sites within basin 7...... 29 Figure 12: Temperature data and location of Tullaroop Reservoir and Laanecoorie Reservoir...... 30 Figure 13: Temperature data and location of Lake Bellfield and sites within basin 15 ...... 32 Figure 14: Temperature data and location of Lake Glenmaggie and sites within basin 25...... 33 Figure 15: Temperature data and location of Cardinia Reservoir and sites within basin 28 ...... 35 Figure 16: Temperature data and location of Upper Yarra dams and sites within basin 29...... 36 Figure 17: Temperature data and location of Pykes Creek, Merrimu and Melton Reservoirs ...... 38 Figure 18: Temperature data and location of West Barwon Dam and sites within basin 33...... 40 Figure 19: Temperature data and location of Rocklands Reservoir and sites within basin 38...... 41 Figure 20: Temperature data and location of Lake Buffalo and sites within basin 3 ...... 43 Figure 21: Temperature data and location of Lake Narracan and sites within basin 26...... 45 Figure 22: Temperature data and location of Tarago Reservoir and sites within basin 28 ...... 47 Figure 23: Temperature data and location of Lal Lal Reservoir and sites within basin 32 ...... 49 Figure 24: Research steps required to determine the extent and impact of cold water pollution in Victoria ...... 57

ii Status of Cold Water Releases from Victorian Dams

EXECUTIVE SUMMARY

Alteration to natural temperature regimes has been listed as a threatening process in Victoria since 1992 but little has been done to address the issue. The problem arises when water contained in deep impoundments thermally stratifies, resulting in a layer of cold water within the hypolimnion, on the bottom of the dam. As most dams are fitted with low level outlet structures, water from hypolimnion is released downstream. When these releases are outside the 20th to 80th percentile of natural stream temperatures, cold water pollution is deemed to have occurred and further monitoring is recommended (ANZECC & ARMCANZ 2000). Impacts of cold water pollution include the lowering of summer temperatures, elevated winter temperatures, reduced seasonal and diel amplitude, delay of the summer peak and rapid temperature reductions. The issues of thermal pollution can be more easily managed than other perturbations associated with river regulation (Lugg 1999), and should therefore be addressed as a matter of high priority.

The aims of this study were to assess the prevalence of thermal pollution in Victoria and to determine where additional monitoring sites and information is required. An investigation of the dam wall size, capacity, release structures and release patterns was undertaken to determine the number of Victorian dams that have the potential to contribute to thermal pollution. Dam management authorities were surveyed to obtain information on the release structures and strategies of those dams extracted from the Victorian Dams Database. Available water temperature and flow information upstream and downstream from each dam were sort to determine if there was sufficient evidence to implicate dams as cold water polluters.

Draft findings from this report were presented at the Thermal Pollution Workshop held in Albury on June 18 - 19, 2000. This was a national workshop convened by the Inland Rivers Network and the World Wildlife Fund for Nature. A set of recommendations from the workshop was developed and approved by almost all participants. This report has undertaken many of the recommendations that were developed at this workshop and has greatly improved our knowledge of the extent of cold water pollution in Victoria.

Of the 411 dams over 5 metres in height extracted from the Victorian Dams Database, 160 were privately managed and were not considered in this study. Of the remaining 251 dams, 202 were noted to be offstream storages with no discharges to natural streams, or had surface release capabilities only (i.e. spillway releases). The 49 dams that were included as potential contributors to cold water pollution were categorised by maximum priority (24), medium priority (11) and minimum priority (14) for additional research and monitoring action. This ranking provided the direction of focus for this for this study. Those ranked as maximum and medium priority were investigated further (included in this report) to determine if there is information available to assess the magnitude and extend of cold water pollution. Maximum priority dams include Hume, Dartmouth, Mt. Beauty, William Hovell, Nillahcootie, Loombah, Eildon, Malmsbury, Eppalock, Tullaroop, Cairn Curran, Laanecoorie, Bellfield, Glenmaggie, Cardinia, Upper Yarra, O’Shannassy, Silvan, Pykes Creek, Merrimu, Melton, Bostock, West Barwon and Rocklands. Medium priority dams include Buffalo, Newlyn, Barkers Creek,

iii Status of Cold Water Releases from Victorian Dams

Expedition Pass, Narracan, Moondarra, Blue Rock, Tarago, Maroondah, Lal Lal and Moorabool.

The monthly water temperature data available through the Victorian Water Resources Data Warehouse (http://www.vicwaterdata.net) was in most cases the only information available to assess the downstream impact of dams. The ability of this study to assess the impact of dams on downstream thermal regimes was constrained by the amount and type of temperature data available around ‘candidate’ dams. Data was deficient in terms of the number and location of monitoring sites, as well as the temporal resolution of available data was deficient. Of all the maximum (24) and medium (11) priority dams investigated, only four have sufficient evidence to indicate a downstream impact on the thermal regime. These four are Lake Dartmouth, Lake Hume, Lake Eildon and Lake Eppalock, all of which have been previously identified as cold water polluters.

Future monitoring programs need to be standardised and developed in a scientifically rigorous manner to ensure that the downstream impacts of dams can be confidently detected against potential background influences. This information will not only determine the magnitude and downstream extent of cold water releases, but will also provide feedback to ensure better management of release water. Moreover, this information could help guide decisions on future amelioration options. Suggestions will be made for the next stage of research and monitoring programs and recommendations provided are based on those generated from the findings of this study and from the June 2000 workshop.

It is recommended that monitoring commence as soon as possible for those dams identified as maximum priority, and amelioration options should be considered at the earliest opportunity. Dams ranked as medium priority for future research should also be monitored and additional information should be sourced to assess the downstream effects. Monitoring of these sites is also essential, as the classification criteria used in this report are broadly based and may not be sensitive enough to detect significant downstream physical and biological impacts. Those dams listed as minimum priority should be considered for future monitoring programs, particularly those releasing significant downstream Spring - Summer flows (see following diagram).

iv Status of Cold Water Releases from Victorian Dams

11 MEDIUM PRIORITY DAMS + 24 MAXIMUM PRIORITY DAMS

ESSENTIAL MONITORING PROGRAM ADDITIONAL ASSESSMENTS

G Review operational constraints for each dam G Install preliminary monitoring program G Assess hydrodynamic stratification potential (loggers in reservoir, at least one upstream and G Compile other information from databases and reports at least one downstream site) G Determine biological significance of downstream rivers6

Stratification and cold Cold water releases water releases? likely to be an issue? NO NO

YES

Review monitoring program Encourage greater monitoring and operation procedures (see following recommendations)

FURTHER MONITORING AND ASSESSMENT

G Instigate large scale temperature monitoring program G Undertaken risk assessment of dam releases G Instigate mitigation investigations and works

Future research and monitoring strategies need to consider the physical and biological implications of cold water releases. In order to measure the downstream response to an altered temperature regime, it is important to investigate the biological consequences of cold water releases. Where mitigation works appear likely, it is important to commence physical and biological monitoring as soon as possible. It is necessary to determine the current physical and biological characteristics of the downstream reach to enable a comparison when warmer water discharges are established. Mitigation works are very expensive, therefore it is essential that monitoring programs are scientifically rigorous and logistically feasible. A multi-disciplinary approach is required to grasp the full biological consequences of cold water pollution and changes associated with increased release temperatures. It is important to note that the cost of installing and maintaining water temperature monitoring equipment and undertaking biological monitoring is relatively inexpensive in relation to the cost involved in mitigation works. This report also provides cost estimates associated with establishing a biological monitoring program.

Once monitoring programs are established it is important to consider how this information will be used to assess the impacts and subsequent improvements if and when mitigation works are introduced. The assessment process needs to provide continuous feedback to dam management and to monitoring programs in place. As more information is collected, a greater understanding of the cause and effect relationships will be developed, which should ultimately improve water release management strategies and help refine monitoring programs. The assessment criteria also need to be flexible enough to be applicable to all situations. The specific issues within each catchment need to be considered in the overall management and monitoring approach.

v Status of Cold Water Releases from Victorian Dams

It is also recommended that one or two case study dams be undertaken in Victoria to demonstrate benefits of the amelioration of cold water discharges. It will be important to demonstrate with these case studies the downstream improvement in the temperature regime and the improvement in biological diversity and viability over time.

Following on from this report, the next research directions in Victoria should incorporate the following recommendations: ¾ Undertake mitigation works on one or two case study dams from the 24 maximum priority list to demonstrate the ecological benefits of warmer water release strategies ¾ Develop and gain consensus on a monitoring strategy and assessment criteria to be adopted for all maximum and medium priority dams (national coordination may be required) ¾ Encourage additional monitoring effort for all maximum and medium research priority dams, including the installation of continuous water temperature loggers at least at one site upstream, and three sites downstream ¾ Encourage a greater monitoring program within dams, including depth profiles and stratification measurements for all maximum and medium priority dams ¾ Investigate the relationship between releases and the extent of cold water pollution for all maximum and medium priority dams ¾ Attempt to minimise current impacts by alterations to water release management without compromising water supply to other downstream users ¾ Develop a decision tree to help define the best mitigation options for dams releasing cold water ¾ Develop an agreed approach to prioritise mitigation works on dams in relation to the social, economic and environmental risks and consequences ¾ Encourage a greater community understanding and ownership of the biological consequences of cold water pollution

vi Status of Cold Water Releases from Victorian Dams

INTRODUCTION

Thermal Pollution – Changes in the temperature regime of natural waters An alteration to the temperature regime of natural waters can be referred to as ‘thermal pollution’ and can include increases and decreases of the water temperature. A number of factors have been identified that can lead to thermal pollution, including heated industrial discharges, the release of power station cooling waters, returning irrigation waters, changes in riparian vegetation, inter-basin transfer of water and river regulation (Pusey et al. 1998). The extent of downstream thermal pollution is affected by a number of factors. These include the size of the impoundment, the origin and volume of release waters, the contribution of downstream tributaries, the form of the channel and the differences between air and water temperatures (Crisp 1987). The release of cold water from large dams causes the greatest change to stream water temperatures in south-east Australia. Releases made from impoundments, with no surface water release strategies, commonly cause a decrease in summer temperatures and an increase in winter temperatures in waters downstream of dams (Baxter 1977). The effect occurs because of the tendency of standing water bodies to become thermally stratified during spring and summer (Hutchinson and Maness 1979). Thermal stratification occurs when solar energy heats the surface layer of water. Warm water is less dense than cooler water, and therefore ‘floats’ above denser cooler water (Bayly and Williams 1973). When stratification occurs, the cooler bottom layer is known as the hypolimnion, while the warmer layer on top is known as the epilimnion. This change in temperature with depth is known as the thermocline (Bayly and Williams 1973). Research of dams in the United States of America suggests that any impounded water body over 5 metres (m) in depth can undergo thermal stratification, except those reservoirs where average yearly inflow volume exceeds the reservoir volume by a factor of 10 or more (Harlemann 1982). The retention time of water is also a major influence of thermal regime, as are other factors such as elevation, riparian shading, water depth, substrate composition and water clarity (Ward 1985). More detailed examinations of the causes of thermal stratification can be found in the literature (Goodling and Arnold 1972, Harleman 1982). In thermally stratified reservoirs, water released from below the thermocline (hypolimnial release), can cause downstream temperatures to be depressed. This effect is termed ‘cold water pollution’. Conversely, when stratification breaks down during winter (due to decreased radiant heat and increased inflow of water) the released water may be warmer than would be expected for an unregulated river, due to the thermal buffering of the large body of water (Baxter 1977). When these releases are outside the 20th to 80th percentile of natural stream temperatures, it is regarded as cold water pollution, and it is recommended that further monitoring be undertaken (ANZECC & ARMCANZ 2000).

Effects of dams on river temperatures in south-eastern Australia There are a number of dams in Australia that appear to be altering the downstream thermal regimes. For example, Lugg (1999) identified 17 dams in NSW where cold water pollution was likely to be affecting riverine biota. There are perhaps two main explanations for this. Firstly, many Australian dams were built at a time when public concern for the environment was not paramount. The consequences of altered thermal regimes were not understood and it is only now that we are beginning to grasp the potential implications of the effects. Secondly, the high variability seen in annual discharge of Australian waterways means that larger impoundments are necessary in order to guarantee a minimum supply level from each impoundment. Larger dams are more expensive to build, and so less money is likely to be spent on provision of multi- level offtake structures designed to protect the downstream environment (McMahon and Finlayson 1995). In hindsight, it is now obvious that if multi-level offtake structures were

1 Status of Cold Water Releases from Victorian Dams installed at the time of dam construction much money would have been saved given the current estimates for retro-fitting existing dams. And thirdly, the consequences of altered thermal regimes were not understood and it is only now that we are beginning to grasp the potential implications of the effects. There have been relatively few studies undertaken in south-eastern Australia that examine the effects of dams on river thermal regimes. Whittington and Hillman (1999) reported changes to the thermal regimes of a number of river stretches within the Murray-Darling Basin. These conclusions, however, were based upon expert opinion rather than upon measured water temperatures. Walker (1979) reported thermal impacts 200 km downstream of Lake Hume, and Gippel et al. (1992) noted thermal effects over 5 km downstream of the Thomson Dam. Dams and river systems predominantly in New South Wales and Victoria that have been the subjects of specific studies include the Macquarie downstream of Burrendong Dam (Acaba et al. 2000; Harris 1997), the Hunter downstream of Glenbawn Dam (Acaba et al. 2000), the Mitta Mitta downstream of Dartmouth Dam (Blyth et al. 1984; Doeg 1984; Koehn et al. 1995), the Goulburn downstream of Lake Eildon (Gippel and Finlayson 1993), the Campaspe downstream of Lake Eppalock (Growns 1998), the Cudgegong downstream of Windamere Dam (Acaba et al., 2000), the Murray downstream of Lake Hume (Walker 1985), the Thomson downstream of Thomson Dam (Gippel et al. 1992; Marchant 1989), and the Gordon downstream of Gordon Dam (Coleman 1978). In addition, (Lugg 1999) lists another ten river stretches in NSW that are ‘known’ to be affected by cold water pollution. The most commonly reported effect of the dams has been a lowering of summer temperatures (Acaba et al. 2000; Blyth et al. 1984; Doeg 1984; Gippel et al. 1992; Harris 1997; Growns 1998; Marchant 1989; Coleman 1978). Elevated winter temperatures have also been recorded (Acaba et al. 2000; Gippel et al. 1992), as are reduced seasonal amplitudes of temperatures are a commonly reported effect (Acaba et al. 2000; Walker 1985). Reduced diel amplitudes of temperature have been reported in the Campaspe River (Growns 1998), but the study by Marchant (1989) found no evidence of this effect downstream of the Thomson Dam. Delays in the summer temperature peak have been found in several studies (Acaba et al. 2000; Walker 1985; Growns 1998), but no studies have specifically addressed the rate of change of river temperatures during spring. In addition to the depression of seasonal temperature amplitude, four other major changes are associated with altered thermal regimes. First, there is a reduced thermal amplitude in streams, both on a seasonal and daily basis (Saltveit et al. 1994). Secondly, the rapid rise in temperature that naturally occurs in spring is reduced, and sometimes become non-existent (Lugg 1999). Thirdly, the summer temperature peak may be delayed by weeks or months (Jaske and Goebel 1967; Ward 1976a, b; Walker 1980). Finally, temperatures downstream of dams may drop suddenly with the release of large volumes of water for hydroelectric or irrigation purposes (Ward and Stanford 1979; Mackay and Shafron 1998).

Biological effects of thermal pollution It has been recognised at least as early as 1974, that large dams situated on natural waterways in Australia can have significant ecological impacts on downstream biota (Koehn et al. 1995). The presence of an impounded water body can result in environmental changes that include alterations to flow regimes, changes in sediment transport patterns, changes in chemical properties of released water, reductions in the level of oxygen in released water and changes to the temperature regimes of streams below the dam wall (Baxter 1977; Boon 1988; Ward and Stanford 1979; Finlayson et al. 1994). In addition, dam walls represent a barrier to fish migration and prevent the colonisation of downstream sections by drifting invertebrates (Baxter 1977; Finlayson et al. 1994; Marchant 1989) and fish eggs and larvae.

2 Status of Cold Water Releases from Victorian Dams

It has been stated that ambient temperature is the single environmental variable that exerts the greatest biological influence on in-stream biota (Coutant 1987; Armour 1991; Ward and Stanford 1979). In general, natural stream temperatures increase with an increase in distance from the source (Crisp 1987). The different aspects of thermal pollution outlined above all have the potential to affect riverine flora and fauna. The impacts of cold water releases can have direct and indirect effects on riverine biota. Direct effects may include the exceedence of tolerances or reproduction requirements, while indirect effects may include the exclusion of species based on thermal preference, reduced resilience to other potential stressors, reduced metabolic and physiological abilities and reduced stream productivity overall. In Australia, the most widely recognised effect of thermal pollution is that of depressed summer temperatures on native fish populations. Most native species breed over the warmer months and require relatively warm temperatures to induce spawning (Rowland 1983; Cadwallader and Gooley 1985; Lake 1967; Llewellyn 1971). Lugg (1999) demonstrated that temperatures in the Murrumbidgee River, downstream of Burrinjuck Dam, seldom approached the levels required for spawning of key native species. Other impacts of cold water releases may be more subtle and it may take longer for the symptoms to become obvious. Embryos and larvae of fish species tend to be the most sensitive life-history stages to the effects of temperature (Elliot 1981; Alabaster and Lloyd 1980). This suggests that estimates of spawning inhibition may underestimate the effects of depressed summer water temperatures on native fish. Reduced temperatures during these early life-history stages will extend the development time of eggs (Lake 1967, Llewellyn 1973), reduce growth rates of juvenile fish (Clarkson and Childs 2000; Hokanson et al. 1977) and render young fish less resistant to additional environmental stresses. A shift in the thermal regime may mean that riverine species are required to live outside their thermal optimum, thereby affecting all physiological processes. Another effect of reduced summer water temperature is that overall biotic production in the river will be lower than in a warmer stream (Alabaster and Lloyd 1980; Thoms et al. 1998), which may result in broader scale impacts at the community level.

Reduced temperature variability Overall, the depression of temperature amplitude can be expected to reduce biotic diversity in river systems. Seasonal variation in water temperature is an important cue for gonad development and spawning in many freshwater fish species (Milton and Arthington 1983; 1984; 1985; Koehn and O’Connor 1990). Large seasonal temperature variations allow species with different biological cues and thermal optimums to coexist by providing temporal separation of major resource use periods (Vannote et al. 1980). Spatial variation in water temperature is also known to influence fish species occurrence (Coon 1987, Cech et al. 1990, Matthews 1998, Pusey et al. 1997, Llewellyn 1973, Moyle 1976). High species diversity of aquatic insects is generally associated with areas that experience wide annual temperature fluctuations (Ward and Stanford 1982). It has also been found that some invertebrates cease to grow altogether below certain threshold temperatures, such as the caenid mayfly (Tasmanocoenis tonnoiri), whose threshold temperature is 8oC (Marchant et al. 1984). The elevation of winter temperatures is likely to extend the period of emergence of some invertebrate species and increase winter production of rivers as a whole (Ward 1976b). However, adults emerging from these artificially warmed streams are likely to be smaller in size than might otherwise be the case (Vannote and Sweeney 1980). On a finer temporal scale, studies have indicated that species exposed to depressed diel thermal amplitudes are less resilient than those exposed to more natural daily temperature fluctuations (Konstantinov et al. 1989). Moreover, in environments subjected to diel temperature fluctuations, a greater number of species will be exposed to thermally optimum temperatures

3 Status of Cold Water Releases from Victorian Dams each day (Sweeney and Vannote 1978). It is therefore not surprising that lowered biotic diversity has generally been found in rivers below dams that exhibit reduced seasonal and diel temperature fluctuations (Saltveit et al. 1994; Comargo and Voelz 1998; Pozo et al. 1997).

Removal of rapid Spring - Summer increases and delay of peak temperatures The elimination of the rapid rise in water temperature seen in unregulated rivers in spring affects the timing of reproduction of river fauna, along with other cues such as increased photoperiod, change in flow, and increase in food availability. The rate of temperature change can be an important cue for spawning and emergence of some species. The delay in the peak summer temperature downstream of dams can also affect patterns of reproduction in streams below dams. To spawn, some species of native fish require minimum temperatures to be reached within a certain period each year (Koehn and O’Connor 1990). Delayed summer peak temperatures may occur after this time period. In such a situation, spawning will be prevented even if the theoretical minimum spawning temperature is reached. Similarly, timing of reproduction and emergence of many invertebrate species is based on water temperature (Vannote and Sweeney 1980; Hynes 1970; Precht et al. 1973; Wieser 1973). Delays caused by the lag in water temperature could result in the emergence of adults into environmental conditions to which they are not adapted (Ward and Stanford 1979). If temperature releases are consistently impacting on the reproductive success of downstream populations, the viability of this population is threatened. Natural variations in population biomass dynamics may often result in the loss of reproductive success of occasional seasons. However repeated loss of reproductive success over a number of years may result in the collapse of resident populations. If temperature releases are consistently impacting on the reproductive success of downstream populations, the viability of this population is threatened.

Rapid changes in temperature Sudden changes to the temperature regime of a river can occur with the sudden release of large volumes of water from dams (Ward and Stanford 1979). Similarly, biota may be exposed to sudden changes in water temperature at the confluence of a regulated river with a non- regulated tributary (Clarkson and Childs 2000). Sudden changes in temperature have immediate physiological effects on fish (Crawshaw 1979; Tanck et al. 2000). Moreover, a rapid drop in temperature may result in ‘cold coma’, a condition that effectively renders fish unconscious (Elliot 1981), thereby exposing them to greater dangers of physical damage and predation (Clarkson and Childs 2000). Such impacts can be immediately obvious, such as a fish kill, however they may also be more subtle and be reflected by a reduced biological diversity, with the dominance of thermally adaptable species. Massive fish kills have been associated with reduced temperatures in the Finke River (Langdon et al. 1985) and in streams of North Queensland during winter (Pusey et al. 1998). These fish kills were thought to be related to increases in susceptibility of particular native fish (as a result of cold water stress) to protozoan diseases.

Effects of dams on stream biodiversity In general, dams of widely differing discharge volumes, and with widely differing discharge patterns, have had remarkably similar effects on in-stream biota. Invertebrate assemblages immediately downstream of dams are generally much simpler than those upstream or further downstream, and absolute densities are also typically reduced (Doeg 1984; Céréghino and Lavandier 1998; Pozo et al. 1997; Comargo and Voelz 1998; Saltveit et al. 1994; Coleman 1978; Chessman and Robinson 1986). Fish assemblages downstream of dams are generally dominated by exotic cold water species (Koehn et al. 1995; Martinez et al. 1994),

4 Status of Cold Water Releases from Victorian Dams and many native species have become locally extinct downstream of large impoundments (Koehn et al. 1995; Walker 1980). Conversely an increased density of macrophytes has been found below dams following alterations in thermal regimes (Saddlier and Doeg 1997; Brizga and Finlayson 1992). This is likely to be due to the reduction in the frequency of channel-forming floods and the long-term reduction in turbidity and domination by cold water tolerant species. It is difficult to unequivocally ascribe effects of dams on river biota solely to altered temperature regimes. The persistence of cold water tolerant invertebrate assemblages can be explained by the reduced thermal amplitudes (Vannote et al. 1980). However, it is apparent that one cause of the depauperate invertebrate assemblages found downstream from most dams and weirs is the lack of recolonisation by drifting invertebrates from upstream (Doeg 1984; Boles 1981; Marchant 1989). The poor water quality of hypolimnial release dams has also been cited as a factor leading to downstream effects on invertebrate assemblages (Coleman 1978). Similarly, while modified thermal regimes from dams may prevent the reproduction of native fish populations and give a competitive advantage to exotic cold water species (Lugg 1999), other aspects of damming rivers have also been shown to affect native fish populations. These include the effects of altered flow regimes (Humphries and Lake 2000; Almodóvar and Nicola 1999), alteration of habitat (Walker 1980; Finlayson et al. 1994), and prevention of migration both upstream and downstream (Martinez et al. 1994).

Associated effects of hypolimnial discharges Along with the changes in temperature regime outlined above, hypolimnial waters differ from those of unregulated streams in several aspects. Firstly, dissolved oxygen levels may be severely reduced compared to surface waters. This occurs due to the oxidation of plant matter and other organic material at the base of the dam (Baxter 1977). In some cases the sudden mixing of dam waters has been linked to massive fish kills within impounded waters (Ellis 1941). Downstream of dams, the level of oxygen saturation usually rises quite quickly. For example, waters immediately downstream of Lake Hume in Victoria have been found to be around 50% saturated with oxygen, but are 70% saturated 37 km downstream and 100% saturated 100 km downstream (Walker 1980). To control this problem it has been shown that active re- oxygenation of the discharge waters can virtually eliminate the effect (Pozo et al. 1997). Hypolimnial waters are also generally higher in nutrients than waters of unregulated rivers (Baxter 1977; Fearnside 1989), due to the release of absorbed compounds via the decomposition processes mentioned above. This can affect standing algal crop downstream of discharges, which in turn may affect all trophic levels within the system. The effects can be likened to those caused by organic pollution in other systems (Blyth 1980). Similarly, toxicant adsorbed to bottom sediments can be released, resulting in high toxicant loads in waters released from within the hypolimnion (Rosenberg et al. 1997; Krenkel et al. 1979).

This study The release of cold water releases from large dams has been listed as a threatening process in Victoria since 1992 (Victorian Flora and Fauna Guarantee Act 1988) but little has been done to address the problem. The aims of this study were to assess the prevalence of thermal pollution in Victoria and to identify sites where further information is required below dams suspected of discharging cold water. To achieve this we surveyed dam management authorities for information regarding Victorian dams. On the basis of this information, dams were assigned a level of priority for further research, based on the likelihood that the dams were altering

5 Status of Cold Water Releases from Victorian Dams downstream thermal regimes. We then gathered available information on water temperatures in the vicinity of these dams in order to assess their effects on thermal regimes. This information was used to determine if there was sufficient evidence to implicate dams as cold water polluters and, where it was insufficient, identify recommendations for further assessments. Draft findings from this report were presented at Thermal Pollution Workshop held in Albury on June 18 to 19, 2000. This was a national workshop convened by the Inland Rivers Network and the World Wildlife Fund for Nature (sponsored by a number of organisations including the Murray-Darling Basin Commission, NSW Fisheries, NSW Land and Water Conservation, Victorian Department of Natural Resources and Environment, Queensland Department of Natural Resources and Mines, the Natural Heritage Trust and Environment Australia). A set of recommendations from the workshop was developed and accepted by almost all participants (IRN 2001) (also see www.wwf.org.au/content/). These recommendations will be incorporated into the final recommendations of this report.

6 Status of Cold Water Releases from Victorian Dams

METHODS

Assessment of Dams A list of potential problem dams in Victoria was assembled from a dam database held by the Catchment and Water Division of Natural Resources and Environment (Siraj Perera, DNRE, pers. comm.). All dams with a listed weir height of 5 m or greater were included and are provided in Appendix A. Research suggests that any impounded water body over 5 m in depth has the potential to become thermally stratified during summer (Harleman 1982). This depth was therefore adopted as the minimum depth of dam that should be investigated. Dams in need of further investigation, and priorities for assessment were assigned using the decision criteria outline in Figure 1. The procedure of investigating each dam as potential cold water polluters was as follows. The managing authorities for each dam were surveyed to provide further data on each of the dams under their control. Any dams that did not discharge to natural stream or river systems and/or release from the water surface level were removed from consideration, as we considered that these dams were not likely to be impacting on downstream thermal regimes. This included all overshot weirs, dams that discharged only to pipelines, some domestic supplies, and dams that had been decommissioned since the last update of the database. Following this screening, 48 dams were marked for further investigation (Appendix A). For these dams we sought information regarding the types and heights of offtake structures, flow regimes that had been implemented in the past, and operational constraints of the dams. Firstly, it was necessary to standardise the cold water pollution potential of each dam regardless of current storage volumes. Currently, most of the storages are well below full capacity, therefore additional offtake height and water levels would need to be considered in future risk assessment procedures. However, for this report we considered the impact standardised to the Full Supply Level (FSL). Dams that were artificially destratified or had surface release strategies (releasing water from less than 6 m from FSL), but were still of sufficient size and had the potential to release cold water were considered as being of minimum priority for further research. At this level we did not undertake further investigations, but recognised that they should receive some attention at a later date. The next group of dams was those that had multiple releases that could release from 6 m to 10 m below FSL, or were releasing only occasionally and not as a regular bulk entitlement flow. These dams were considered to be of medium priority level and were worthy of further investigations. The third group of dams were those that were discharging regularly with offtakes greater than 10 m below FSL. These were considered a maximum priority level and were investigated further in this report. The 10 m cut-off was assigned after the study by Acaba et al. (2000) found that water drawn from a constant 10 m below the surface of Glenbawn Dam in NSW, had significantly different thermal properties than water at an off-stream reference site. This pattern is also seen at Dartmouth Dam (P. Liepkalins, Goulburn-Murray Water, pers. comm.). Also included within this classification were those dams (such as Lake Eildon, Lake Dartmouth, Lake Hume and Lake Eppalock) where previous research had found evidence of cold water pollution. Dams that were the last in a closely linked series (such as Mt. Beauty Regulating Pondage) were classified as maximum priority regardless of offtake structures. These dams may receive cold water from upstream dams, resulting in a cumulative effect of cold water.

7 Status of Cold Water Releases from Victorian Dams

Compilation of temperature data The Department of Natural Resources and Environment operates an online database of river monitoring data (DNRE 2000; URL http://www.vicwaterdata.net). From this database, we obtained temperature data that existed above, below and nearby to the dams that had been marked for further investigation. Temperature measurements were taken at approximately one month intervals for most sites, and so potentially a great deal of information concerning peak and trough temperatures were not recorded. In most cases, it was found that there was limited additional data available via other biological databases (such as AusRivas) and datasets maintained by the water authorities. Several types of site comparisons were used to assess the effects of dams on river temperatures. In the simplest case, monitoring sites existed both upstream and downstream of the dam in question, and there was only a single major tributary flowing into the dam. For such cases, we were able to directly compare the temperature regimes at the two sites. Where upstream reference sites were not available, sites on adjacent rivers (referred to as off-stream comparisons) were sometimes used. Thermal variation in rivers is partly a function of the volume of water flowing through the river (Ward 1985), and so average discharge volumes were recorded for comparison sites. Where regular temperature data were available, several parameters were used to describe the thermal regime of the river. The maximum summer and minimum winter temperatures, and their month of occurrence were recorded for each seasonal cycle. The summer season was defined as the months from November to April inclusive and the winter season was defined as the months from May to October inclusive. In the case where two or more readings of the same maximum or minimum temperature were recorded within the same season, the date of first occurrence was recorded. The thermal range was computed from these figures. The numbers of readings above 18oC and 20°C in each summer season were also recorded. The summer maxima and minima were plotted, and summary statistics were computed from the data. Statistics included in this report were average and median summer maximum temperature, the median date of the summer maximum, average and median winter minimum temperature, average and median temperature range for the site, and the proportion of total readings that exceeded 18oC and 20°C.

8 Status of Cold Water Releases from Victorian Dams

RESULTS

Classification of Priority Research Dams Of the 411 dams over 5 m extracted from the Victorian Dams Database, 251 dams were controlled by public authorities or by private water supply companies, and 160 dams were privately managed and were considered to be farm dams (Figure 1). Farm dams were not surveyed for the current report, however a list of all registered onstream structures over 5 m in height is attached (Appendix A). The majority of farm dams are fitted with a small gauge compensation pipe at the base of the dam wall. Unless dams are spilling, this is typically the only water released from the structures. Future investigations of the downstream impact of these privately owned dams should be undertaken.

411 dams > 5m Extracted from NRE Dams Database

Farm dam ? YES 160 NO NO Discharge to natural streams ? YES 202 Surface releases for all flows? YES NO (49)

14 MINIMUM PRIORITY Destratification OR surface release DAMS (< 6m below FSL) strategies in place YES OR shallow regulating pondage? NO

11 MEDIUM PRIORITY Releases from 6m to 10m below FSL DAMS OR occasional release only ? YES

24 MAXIMUM PRIORITY Releases from > 10m below FSL DAMS AND regular releases ? YES Figure 1: Flow chart to decide research priority for dams in Victoria

Of the 251 water authority managed dams, 202 were noted to be offstream storages with no discharges to natural streams or had surface release capabilities only (i.e. spillway releases). The 49 dams that were included as potential contributors to cold water pollution were categorised (Figure 1), with 24, 11 and 14 dams being ranked as maximum, medium and minimum priority for further research respectively (Appendix A). This ranking provided a direction for this study. Those ranked as maximum and medium priority were investigated

9 Status of Cold Water Releases from Victorian Dams further (included in this report) to determine if there is information available to assess the magnitude and extend of cold water pollution. The location of all research priority dams is also provided (Figure 2). The numbering of sites is based on the locality within each drainage basin, starting from Lake Dartmouth in Basin 1. The priority research dams are scattered across the state and are managed by 15 different water authorities. Within the Murray-Darling Basin there are 11 maximum, 4 medium and 5 minimum priority dams, while in the Upper Yarra and Gippsland catchments there are 5 maximum, 4 medium and 3 minimum research priority dams.

40 36 2 37 1 12 27 6 3 11 28 9 5 25 42 4 10 24 13 41 8 39 38 7 47 26 43 46 45 22 19 20 33 35 21 17 16 44 34 48 18 14 15 32 31 30 29 49 23

Figure 2: Location of Research Priority Dams Priority symbols represented include maximum priority as black stars with white numbers, medium priority as dark grey diamonds and minimum priority as light grey squares. Numbered maximum priority dams include: (1) Dartmouth, (2) Hume, (3) Mt. Beauty, (4) William Hovell, (5) Nillahcootie, (6) Loombah, (7) Eildon, (8) Malmsbury, (9) Eppalock, (10) Tullaroop, (11) Cairn Curran, (12) Laanecoorie, (13) Bellfield, (14) Glenmaggie, (15) Cardinia, (16) Upper Yarra, (17) O’Shannassy, (18) Silvan, (19) Pykes Creek, (20) Merrimu, (21) Melton, (22) Bostock, (23) West Barwon and (24) Rocklands. Numbered medium priority dams include: (25) Buffalo, (26) Newlyn, (27) Barkers Creek, (28) Expedition Pass, (29) Narracan, (30) Moondarra, (31) Blue Rock, (32) Tarago, (33) Maroondah, (34) Lal Lal and (35) Moorabool. Numbered minimum priority dams included: (36) Yarrawonga, (37) Mokoan, (38) Eildon Pondage, (39) Sunday Creek, (40) Torrumbarry, (41) Hepburn Lagoon, (42) Wartook, (43) Nicholson, (44) Thompson, (45) Rosslyne, (46) Korweinguboora, (47) Gong Gong and (48), Upper Stoney Creek, (49) West Gellibrand.

10 Status of Cold Water Releases from Victorian Dams

Investigation of Maximum Priority Research Dams All dams within the maximum priority level are discussed in this section. The listing of dams was undertaken in order of the basin number in which they occur. Three of the dams within this category were rated as maximum priority because they were the last in a series. None of these dams (Malmsbury Reservoir, Mt. Beauty Regulating Pondage and Loombah Weir) are very large, and two are fitted with multi-level offtake facilities to reduce cold water releases. However, the temperatures of released waters are not monitored at either of the dams and, as stated above, dams in a series may be more likely to release cold water from lower stratified layers than solitary dams of a similar size.

Lake Dartmouth The effect of Lake Dartmouth on the thermal regime of the Mitta Mitta River downstream has received previous attention (Doeg 1984; Blyth et al. 1984; Koehn et al. 1995, Mitchell 1999). The dam has two outlet structures that are situated at 62 m and 122 m below FSL (Koehn et al. 1995), and with releases of up to 15 000ML, effects of released waters on the downstream temperature regime are almost inevitable. Irrigation releases have been estimated to lower downstream summer water temperatures by 8 to 10°C (Blyth et al. 1984). Most discharges are made through the power generation plant and are constrained to releasing water from a significant depth beneath the surface to prevent the generation of vortices and the subsequent cavitation of the turbines (P. Liepkalins, Goulburn-Murray Water, pers. comm.) For the purpose of this report, downstream data was recorded at Coleman’s (401211, Figure 3), which is approximately 7 km downstream from the dam wall at the lower pondage. Upstream data were taken from the monitoring station at Hinnomunjie (401203, Figure 3), which lies around 50 km upstream of Lake Dartmouth on the Mitta Mitta River. For both of these sites, data were available from 1976 to 1999, but comparisons were made for the period since the first irrigation release in summer 1980 to 1981 (Doeg 1984). Off-stream data were available for 1980 – 1988 for Snowy Creek, which was insufficient to provide an adequate comparison. For the upstream-downstream comparison, the summary statistics suggest that the effect of the dam is not as severe as widely believed. However, if the last 10 years of data are examined, the effect on maximum summer temperature, in particular, is more pronounced. This change in thermal effect around 1990 is apparent from the plot of maximum and minimum temperatures for the two sites (Figure 3), and highlights the information that may be missed if the summary figures are simply taken at face value. It is probable that a change in operating procedure, or a change in demand for irrigation water, has led to the greatly lowered summer maxima of the last decade. Examination of discharge data would reveal whether or not the discharge patterns/volumes changed around 1990. Maximum temperatures downstream at Tallandoon, which is approximately 70 km downstream (401204, Figure 3), demonstrate that after 1991 summer maximums are affected, and are greater than 25 oC less often than far upstream on the Mitta Mitta River at Hinnomunjie (401203, Figure 3). Despite the lack of overlapping monthly data for the adjacent stream (Snowy Creek) and the downstream site (Tallandoon), the effects of Lake Dartmouth on downstream temperature regimes, are effectively demonstrated at least over the last ten years. The main assumption is that the upstream site at Hinnomunjie is representative of other tributaries such as the Gibbo River and the Dart River. The majority of inflowing water into Lake Dartmouth is derived from the Gibbo and the Dart rivers and therefore this information would be better indicators of upstream water temperatures. Other assumptions relate to using monthly temperature data, as will be detailed in the Discussion.

11 Status of Cold Water Releases from Victorian Dams

A more comprehensive monitoring program is recommended to include sites on the Gibbo and Dart rivers as well as at Hinnomunjie for the upstream sites, in addition to a site on Snowy Creek. Downstream sites should be spaced at regular intervals and would for example include sites at Coleman’s, Mitta Mitta, Eskdale and Tallandoon to determine the downstream extent of the cold water influences.

12 Status of Cold Water Releases from Victorian Dams

401211

Mitta Mitta River

Dartmouth Dam

401204

401203

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key Upstream - 401203 15 Downstream - 401211 Downstream - 401204 10 Summer max. Winter min.

Water Temperature (°C) 5

0 8183 85 87 89 91 93 95 97 99 Year Figure 3: Temperature data and location of Lake Dartmouth and sites within basin 1 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in dark blue and light blue, while upstream site is plotted in red (see key).

13 Status of Cold Water Releases from Victorian Dams

Hume Dam and Murray River The comparison of maximum temperatures for Jingellic (approximately 170 km upstream), Hume Dam and Heywoods (approximately 1 km downstream from Lake Hume) (Figure 4) demonstrates the released water from Lake Hume is significantly colder than water upstream at Jingellic. Releases made from 34.3 m below FSL results in maximum average temperatures of between 5 oC and 7 oC colder than at Jingellic. Maximum surface temperatures at Jingellic are greater than 25 oC for most years, whereas at Heywoods, the maximum average temperature was 22 oC. Additionally, when looking at the temperature time series data, there appears to be a delay in the peak summer temperatures downstream from Lake Hume from January (at Jingellic) to March (at Heywoods). It is important to note that Jingellic is potentially impacted by cold water releases from the Snowy Mountain Scheme, which together with cold water releases from Lake Dartmouth may be contributing to cold water releases at Hume Dam. The seasonal maximum temperatures at the Hume Dam (surface measurement) are generally 2 to 3 oC higher than at Jingellic, which may indicate a gradual warming of the water, at least at the surface (Figure 4). Impacts further downstream have not been detected, however in 1995, temperatures at Yarrawonga (at a site below Lake Mulwala, approximately 200 km downstream) were noted to be significantly depressed (Figure 4) due to large releases from Lake Dartmouth and Hume Dam. Normally Lake Mulwala would be expected to warm passing waters due to its being relatively wide and shallow and due to inflows from the Ovens River. While such releases are uncommon, this impact demonstrates the potential extent downstream of cold water impacts from Lake Hume. The biological consequences of this release were detected by native fish monitoring surveys downstream from Yarrawonga, which indicated a significant gap in recruitment in the 1994/95 season (S. Nicol, DNRE, pers. comm.). Continuous water temperature loggers at sites further downstream in the Murray River would determine the extent of the cold water releases and would demonstrate the link between temperature and the magnitude of releases from Hume Dam. Similarly, additional monitoring is required to determine the water circulation patterns and linkages between water entering from the upper Murray River and the Mitta Mitta River and the releases at Hume Dam.

14 Status of Cold Water Releases from Victorian Dams

Yarrawonga

Lake Hume

Jingellic

Heywoods

Modified from RWC (1990) and DNRE (2000)

Downstream - Upstream comparison

20 Key Upstream - Jingellic 15 Surface - Hume Dam Downstream - Heywoods

10 Downstream- Yarrawonga Summer max.

Water Temperature (°C) 5 Winter min.

0 8587 89 91 93 95 97 99 Year

Figure 4: Temperature data and location of Hume dam and sites in the Murray River Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in light blue and grey, the Hume dam surface is plotted in dark blue and the upstream site is plotted in red (see key).

15 Status of Cold Water Releases from Victorian Dams

Mt. Beauty Regulating Pondage and the Kiewa River A series of pipes, channels and short stretches of river link five dams in the Southern Hydro system. As such, discharges from the lowest pondage, the Mt. Beauty Regulating pondage were of greatest concern. There is an environmental flow requirement of 100 ML d-1 (or discharge equivalent to inflow if less than this) from this pondage into the West Branch of the Kiewa River. This can rise to 840 ML d-1 during periods of power generation. The storages are not particularly deep and the rapid turnover of impounded waters means that stratification is not common (D. Connors, Southern Hydro Group, pers. comm.). However, significant cooling of river waters due to inflow from a high altitude hydropower storage is likely, as has been observed elsewhere (Céréghino and Lavandier 1998). The existing monitoring stations are poorly placed to assess potential thermal pollution impacts. The downstream monitoring site (402203, Figure 5) is around 20 km downstream of the Mt Beauty pondage. There are two comparison sites on adjacent streams. However, they both have substantially smaller discharge volumes (402223, 402206, Figure 5), making the comparison less valid. It is not surprising therefore, that the summary statistics and maxima / minima plot do not appear to show temperature impacts in the West Branch of the Kiewa River. However, given the nature of the releases from the hydropower generation, it may be that river temperatures are only intermittently affected. Statistics and plots based on seasonal maxima and minima will not detect such an effect. Future monitoring should be aimed at examining variability within seasonal temperatures, as this would also have consequences for spawning of native fish and survival of offspring. Continuous temperature loggers should be installed immediately above and below the point on the West Branch of the Kiewa River where discharges from Mt Beauty pondage enter the river.

16 Status of Cold Water Releases from Victorian Dams

402206 402203

Mt Beauty Pondage Clover Dam 406223 Junction Dam

Pretty Valley Pondage Rocky Valley Storage

Modified from DNRE (2000)

Downstream - Adjacent stream comparison 30

15 Key 10 Adjacent stream - 402223 Adjacent stream - 402206

Water Temperature (°C) Temperature Water 5 Downstream - 402203 Summer max. 0 Winter min. 76 7880 82 84 86 88 90 92 94 96 98 Year

Figure 5: Temperature data and location of reservoirs and sites within basin 2 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue, while adjacent stream sites are plotted in dark green and light green (see key).

17 Status of Cold Water Releases from Victorian Dams

Lake William Hovell It is also difficult to demonstrate a cold water release from Lake William Hovell (Figure 6). Lake William Hovell has a dam wall 37 m high with a capacity of 13 500 ML and discharges water from low level bellmouth release at 18.4 m below FSL. The release capability alone indicates that Lake William Hovell has the potential for cold water impact under higher release conditions. Releases are relatively large with a daily average of 381 to 916 ML (W. Francisco, G-MW, pers. comm.). Algal blooms have been noted in Lake William Hovell and therefore would provide some constraints against surface release strategies in summer periods. Sampling periods at sites immediately downstream (403228) and approximately 30 km downstream (403240) do not coincide, making it impossible to assess the impact of potential cold water releases. The increase in temperature at the site approximately 50 km downstream (403223) by as much as 10 oC, demonstrates that the cold water impacts do not appear to be significant this far down the King River. An offstream site on the Ovens River at Harrietville (403244, Figure 6) is presented as a comparison with the temperatures being releases from Lake William Hovell (403228). The site at Harrietville is at a higher altitude (484 m Above Sea Level (ASL) compared to 373 m ASL) and has a median monthly discharge (over the period from 1990 to 2000) less than a third compared to the site at Lake William Hovell. The altitude should cool the stream in summer, but the smaller discharge would allow it to heat more than the King River. It therefore appears that discharges from Lake William Hovell are maintaining comparatively lower temperatures than would naturally occur at this section of the river.

18 Status of Cold Water Releases from Victorian Dams

403223

403240

403228 403244

Lake William Hovell

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key Adjacent stream - 403244

15 Downstream - 403228 Downstream - 403240 Downstream - 403223 10 Summer max.

Water Temperature (°C) 5 Winter min.

0 7779 81 83 85 87 89 91 93 95 97 99 01 Year

Figure 6: Temperature data and location of Lake William Hovell and sites within basin 7 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in dark blue, light blue and grey and the adjacent stream site is plotted in green (see key).

19 Status of Cold Water Releases from Victorian Dams

Lake Nillahcootie and Loombah Weir Lake Nillahcootie has a dam wall height of 34 m, and a capacity of 40 000 ML. Releases are made from 16 m below FSL, with a average daily releases of 388 to 50 ML d-1 based on 1990 to 2000 discharges (W. Francisco, G-MW, pers. comm.). Again algal blooms have been detected in the lake and therefore may represent constraints to surface releases downstream. The depressed maximum temperatures below Lake Nillahcootie are demonstrated in the comparison between the site downstream (404206) and an adjacent stream (Moonee Creek, 404208) during the period between 1985 and 1987 (Figure 7). Temperatures are 2oC to 5oC colder downstream from Lake Nillahcootie than the adjacent Moonee Creek. However, caution should be shown with this interpretation, as significantly less discharge occurs in Mooney Creek (404208), with an average daily discharge of 10 to 20 ML less than the downstream site (404206). The downstream extent of cold water releases from Nillahcootie is also difficult to assess given the location of site 404216, approximately 70 km downstream and with a number of other possible influences such as releases from Ryans Creek and from Lake Mokoan. Loombah Weir, which is 13.5 m high, has a capacity of 677 ML and has a multi-level offtake tower. However, it lies immediately downstream of the 23 m high McCall-Say Reservoir, which discharges water from the base to fill Loombah Weir. McCall-Say Reservoir has a capacity of 1133 ML and may therefore significantly impact temperatures within it and may consequently result in cold water releases from Loombah Weir. At present there are no temperature monitoring sites near the weirs. Flow data are collected at two stations upstream of McCall-Say Reservoir on Whiskey Creek and Ryan’s Creek, and it would be a simple matter to fit these stations with temperature loggers. Downstream of Loombah Weir, the nearest temperature monitoring site lies on Holland Creek after the confluence of Holland and Ryan’s creeks. Temperature data at this site are unlikely to show any effect of the weirs. Additional monitoring is required downstream of Lake Nillahcootie and immediately downstream from Loombah Weir and McCall-Say Reservoir, to confirm whether cold water releases were occurring, and to measure the downstream extent of thermal effects of these dams. Biological monitoring of introduced Macquarie perch populations may also be warranted and may provide a biological indication of temperature impacts downstream from Lake Nillahcootie. Biological monitoring sites with a number of sampling occasions (AusRivas) also exist upstream.

20 Status of Cold Water Releases from Victorian Dams

401211

Mitta Mitta River

Dartmouth Dam 404207 4012

404216 Loombah 401210 Weir

404208 404206 401203

Lake Nillacootie

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key

15 Adjacent stream - 404208 Downstream - 404206 10 Downstream - 404216 Downstream - 404207

Water Temperature (°C) 5 Summer max. Winter min.

0 7779 81 83 85 87 89 91 93 95 97 99 Year

Figure 7: Temperature data and location of Lake Nillahcootie and sites within basin 4

Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in dark blue, light blue and grey while the adjacent stream site is plotted in green (see key).

21 Status of Cold Water Releases from Victorian Dams

Lake Eildon Gippel and Finlayson (1993) have previously studied the effects of Lake Eildon on downstream temperatures in the Goulburn River. They found that summer temperatures were reduced by approximately 7°C and winter temperatures were raised by around 2°C. The bulk of water released from Lake Eildon is for irrigation purposes. Waters are released via a single offtake at 52 m depth (Gippel and Finlayson 1993). Average discharges in 1999/2000 were 2586 ML d-1 from the Eildon Pondage. Temperature data were available downstream of the dam at Eildon (405203, Figure 8) for the period 1975 to 1999. Temperature data were available for at least some years on ten different tributaries entering the reservoir. Three of the major upstream tributaries flowing into Lake Eildon were considered (Big River, 405227; Goulburn River, 405219; Jamieson River, 405218, Figure 8). The upstream sites did not have coinciding periods of had temperature data, therefore four sets of summary statistics appear in Appendix B. We can see from this table that the numbers of days that the river temperature directly below the lake were not greater than 20 oC for the past 25 years. The effect shown in the comparison is similar, with reductions in median summer maxima of between 5 oC and 9 °C, and increases in the median winter minima of 2 oC to 3 °C. The peak summer temperature also appears to be delayed with downstream maxima occurring in March, whereas upstream maxima were seen in January or February. The results accord closely with those of Gippel and Finlayson (1993). It is interesting to note that recent summer maxima have been rising, and this coincides with the dam being at historically low levels. It is likely that waters were not being discharged from any considerable depth during summer 1998 to 1999. Water temperature was also recorded further downstream at Seymour (approximately 90 km downstream) from 1977 to 1990 (Figure 8). During this time the impacts of cold water releases can be observed by the lowered maximum temperatures, an impact that would be likely to have occurred at least as far as Lake Nagambie, approximately 120 km downstream from Lake Eildon. The effects of Lake Eildon on the temperature of the Goulburn River are well known. This river section is now dominated by introduced trout populations, having replaced the once healthy native populations of Trout cod and Macquarie perch. The question that should now be addressed is whether ameliorative works should be carried out, or as recommended by Gippel and Finlayson (1993), the river should be managed as a cold-water fishery, and the money collected from fishing licences be used in the rehabilitation of other stretches of degraded river. This is currently a topical issue and will continue to remain so for some time. While there is little doubt that Lake Eildon releases cold water, it is still unclear how far the impact reaches downstream. Continuous monitoring is recommended at regular distance downstream, including below Goulburn Weir (at Lake Nagambie), to determine the downstream extent of cold water pollution in the Goulburn River.

22 Status of Cold Water Releases from Victorian Dams

405218 405202

405219

Goulburn River 405203 405227 Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key Upstream - 405227 15 Upstream - 405219 Upstream - 405218 10 Downstream - 405203 Downstream - 405202

Water Temperature (°C) 5 Summer max. Winter min. 0 7779 81 83 85 87 89 91 93 95 97 99 Year

Figure 8: Temperature data and location of Lake Eildon and sites within basin 5

Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in dark blue and light blue, while upstream sites are plotted in red, purple and orange (see key).

23 Status of Cold Water Releases from Victorian Dams

Malmsbury Reservoir Malmsbury Reservoir lies downstream of Upper Coliban and Lauriston reservoirs. No data were collected on the discharge capabilities of these reservoirs, however data supplied by Coliban Water indicated that Lauriston Reservoir stratifies annually. The potential for the accumulation of cold water in Malmsbury from low-level releases from the Upper Coliban and Lauriston reservoirs, requires it be considered as a maximum priority. Historically, there have been no releases of sub-surface water from Malmsbury Reservoir to Coliban River, other than winter / spring flood releases (Bruce Duncan, Coliban Water, pers. comm.). However, during 2000, an environmental flow requirement of a minimum of 8 ML d-1 (or the natural inflow) was introduced. Temperature information for 2000 was not available, therefore the monitoring data from a site on the Coliban River some 50 km downstream of Malmsbury Reservoir (406215, Figure 9) and a site on the adjacent Campaspe (406213, Figure 9) river suggest no differences in thermal regime (Figure 9, Appendix B). Discharges are made via a multi-level tower, reducing the chances that cold water will be released. While discharges from the dam appear to be relatively low, future monitoring of temperatures is recommended to assess the effects and downstream extent of the recently introduced environmental flows on summer water temperatures.

24 Status of Cold Water Releases from Victorian Dams

406215 406213

Coliban River

Malmsbury Res. Lauriston Res. Upper Coliban Res. Campaspe River

Modified from DNRE (2000)

Downstream - Adjacent stream comparison 35

20 Key Adjacent stream - 406213 15 Downstream - 406215 Summer max. 10 Winter min. Water Temperature (°C) 5

0 78 80 82 84 86 88 90 92 94 96 98 Year

Figure 9: Temperature data and location of Malmsbury Reservoir and sites within basin 6 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue, while adjacent stream site is plotted in green (see key).

25 Status of Cold Water Releases from Victorian Dams

Lake Eppalock Lake Eppalock has a dam wall that is 45 m high and a capacity of 312 000 ML. Releases are mostly for irrigation purposes and averaged 137 to 349 ML d-1 between 1990 and 2000, with the majority occurring from August 15 to May 15 (Wayne Francisco, G-MW, pers. comm). Water is released through a free-standing wet tower that discharges from seven offtakes from 4 m to 30.5 m below FSL. There may be other operational constraints that were not recorded, however annual stratification has been observed. In a previous study of Lake Eppalock, Growns (1998) found that summer temperatures were depressed by about 4 to 5 °C relative to the nearby Broken River. It was also observed that below Lake Eppalock summer maximum temperatures were delayed and diel temperature variation during summer was reduced by around one degree. Temperature data were available immediately downstream of the dam (406207), 90 km downstream (406202) and on four tributaries entering the reservoir (Coliban River, Campaspe River, Wild Duck Creek, Mt Ida Creek). For this report only temperatures for the two streams contributing the majority of flow were included (Coliban River, 406215 and Campaspe River, 406215, Figure 10). Collectively, these two streams discharged to the lake over 65% of the volume of water recorded at site 406201, some 20 km downstream of Lake Eppalock (Figure 10). The summary statistics show that downstream summer maxima were depressed by around 6 °C (but occasionally by more than 10 oC) compared to temperatures on the Coliban and Campaspe rivers. Temperatures appear to have recovered at site 406202 (approximately 70 km downstream), and are generally similar and often higher than those of the upper tributaries. However, the maximum temperatures at 406202 appear to mimic the pattern at 406207 and therefore may still be significantly influenced by Eppalock releases (Figure 10). Winter minima were less affected by the dam, but all comparisons show an increase of average winter minima by around 2 to 3 °C (Appendix B). Appendix B also shows a significant depression in the median maximum temperatures downstream of the dam compared to those at upstream sites. The overall result is a compression of the annual thermal amplitude below the dam of between 5 oC and 10 °C when compared to the upstream sites. All comparisons also show a delay in the date of maximum summer temperature, similar to the result found by Growns (1998). There appears to be adequate evidence to suggest that Lake Eppalock is releasing cold water that is impacting on the downstream thermal regime. The infrastructure appears to be capable of augmenting such impacts, however there may be additional operational constraints preventing releases from higher in the water column. Further monitoring is highly recommended, particularly to determine the downstream extent of the cold water releases and to provide real-time feedback to dam managers with regards to release strategies.

26 Status of Cold Water Releases from Victorian Dams

406202

406201

Campaspe River Lake Eppalock 406207

406215

406213

Modified from DNRE (2000)

Downstream - Upstream comparison 35

20 Key Upstream - 406215 15 Upstream - 406213 Downstream - 406207 10 Downstream - 406202 Summer max. Water Temperature (°C) 5 Winter min.

0 78 80 82 84 86 88 90 92 94 96 98 Year

Figure 10: Temperature data and location of Lake Eppalock and sites within basin 6 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites is plotted in dark blue and light blue, while upstream sites are plotted in red and purple (see key).

27 Status of Cold Water Releases from Victorian Dams

Cairn Curran Reservoir Cairn Curran Reservoir has a dam wall that is 44 m high and a capacity of 148 800 ML. It releases water from a free-standing wet tower from one outlet 19 m below FSL and from a spillway. Average daily releases of 60 to 398 ML d-1 for the period from 1990 to 2000, are mostly made between August 15 and May 15 (W. Francisco, G-MW, pers. comm.). Limited data were available to assess the thermal impact of Cairn Curran Reservoir. While the discharges in the adjacent stream (Jim Crow Creek, 407221, Figure 11) are 20 to 40% less than discharges in the upstream Loddon River site (407215), the summer maxima and winter minima temperatures correlate very well. Water temperature information immediately downstream from Cairn Curran Reservoir (site 407210), was available from 1977 to 1989 only. In that period there appears to have been two episodes (from 1981 to 1982 and from 1987 to 1990) where the downstream maximum temperatures were 3 to 5oC colder than the upstream site at 407215 and the adjacent site 407221 (Figure 11). More monitoring is required downstream from Cairn Curran Reservoir, as it has a high potential to impact on the downstream thermal regime. Cold water discharges from Cairn Curran may add to the downstream impacts of Laanecoorie Reservoir and thereby impact on larger section of the Loddon River.

Tullaroop Reservoir and Laanecoorie Reservoir Tullaroop Reservoir has a dam wall that is 42 m high and a capacity of 74 000 ML, while Laanecoorie Reservoir has a dam wall that is 22 m high and a capacity of 8000ML. Releases from Tullaroop are made from a free-standing dry tower with one outlet 12.8 m below FSL, while Laanecoorie Reservoir releases are made via outlet pipes within the spillway approximately 10 m below FSL. Average daily releases between 1990 and 2000 range from 19 to 382 ML d-1 for Tullaroop Reservoir and from 94 to 1327 ML d-1 for Laanecoorie Reservoir. As is the case for Cairn Curran Reservoir, there is limited monthly temperature information available to assess the downstream thermal impact of Laanacoorie and Tullaroop reservoirs (Figure 12). It is impossible to detect a downstream impact of Tullaroop Reservoir due to the lack of downstream temperatures. Upstream temperatures at site 407222 were available from 1978 to 1987, but without a downstream comparison, little can be done with this information. Comparison of the upstream site on Bet Bet Creek (407220) with the site downstream from Laanecoorie Reservoir (407203) suggests that releases from Laanecoorie are not impacting maximum temperatures in the lower Loddon River (Figure 12). The summer maxima were generally higher and the winter minima slightly higher as would be expected naturally for a downstream site. Tullaroop and Laanecoorie reservoirs attract maximum priority, together with Cairn Curran Reservoir, due to the potential to impact on the temperature regime of upper Loddon River system. An integrated monitoring approach is required to investigate the respective and collective temperature impacts.

28 Status of Cold Water Releases from Victorian Dams

407210

Cairn Curran Reservoir 407215

407221

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key Upstream - 407215 15 Upstream - 407221 Downstream - 407210 10 Summer max.

Water Temperature (°C) 5 Winter min.

0 7779 81 83 85 87 89 91 93 95 97 99 01 Year

Figure 11: Temperature data and location of Cairn Curran Reservoir and sites within basin 7 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue, while upstream sites are plotted in red and purple (see key).

29 Status of Cold Water Releases from Victorian Dams

407229

407203 Laanecoorie Reservoir

407220 Tullaroop Reservoir

407222

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key U/s of Laanecoorie - 407220 15 U/s of Tullaroop - 407222 D/s of Laanecoorie - 407203 10 Downstream - 407229 Summer max.

Water Temperature (°C) 5 Winter min.

0 7779 81 83 85 87 89 91 93 95 97 99 01 Year

Figure 12: Temperature data and location of Tullaroop Reservoir and Laanecoorie Reservoir Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in dark blue and light blue and upstream sites are plotted in red and purple (see key).

30 Status of Cold Water Releases from Victorian Dams

Lake Bellfield Lake Bellfield has a 36 m wall and a capacity of 78 500 ML, with a release outlet at 36.3 m below FSL. Discharges can range from 100 to 250 ML d-1 into Fyans Creek to maintain environmental flows. Typically, water levels are well below FSL, as has been the case for a number of years, therefore releases may not be from the hypolimnion. Monthly temperature measurements from the upstream site (415217) and the downstream site (415214) did not indicate a cold water release impact (Figure 13). However, Appendix B shows that the numbers of days where water temperatures have been recorded above both 18oC and 20oC are markedly fewer just downstream of the dam compared to sites upstream of the impoundment. The upstream discharges are approximately 43% of the discharges at the downstream site. Downstream summer maxima and winter minima are often 3 to 5oC higher than the upstream seasonal temperatures. This suggests a minimal effects on downstream water temperature and is probably related to the low water level maintained within the dam. The prospect of increased environmental flows, and the possibility of higher lake levels combined with the outlet structure still classifies Lake Bellfield as a maximum priority based on the criteria for this report. Additional monitoring is required to confirm the pattern detected by monthly temperature measurements.

Glenmaggie Reservoir Glenmaggie Reservoir has a dam wall of 37 m and a capacity of 190 400 ML. It is fitted with two low level outlets which discharge to irrigation channels. Fourteen radial gates fitted to the crest allow flood discharge to the river whilst the storage level is within 3.5 m of FSL. Normal discharge to the river for environmental flows is via one of the low level outlets located 16 m below FSL, and through a conduit, hydro-turbine and out to the river. Releases to the river are up to 400 ML d-1 during irrigation season with 40-50 ML d-1 being made for environmental purposes all year round. Monthly temperature data were available at the tail gate of Glenmaggie Reservoir (225204) and a site some 25 km upstream on the Macalister River (225209) from 1976 to 1999, and at a site on Glenmaggie Creek around 10 km upstream (225230) from 1977 to 1987 (Figure 14). Summer maxima and winter minima temperatures appear to indicate some minor effects of the dam (Figure 14, Appendix B). Results indicate that the elevation of winter minimum temperatures is a more predictable effect of the dam than the lowering of summer temperatures (Figure 14), although in some years the difference between upstream temperature maxima range from 2 to 10oC. Several peaks of high temperature in the early 1980s coincide with very low storage levels (Ian Kitchenn, Southern Rural Water, pers. comm.). Low lake levels may also provide some explanation for the years where little downstream impact is observed, as has been the case in recent years (G. Harris, Southern Rural Water, pers. comm.). On average, the summer maximum temperatures are slightly lower downstream of the dam in the comparison with the major tributary, the Macalister River, and the winter maximum is higher for both comparisons. As a result, annual thermal amplitude is reduced. The temperature data available for Glenmaggie Reservoir is good compared to the general standard of data available. Nevertheless, temperature monitoring at the upstream sites closest to the reservoir (e.g. 225230, 225221), or at closer sites, should be undertaken. This would allow a better assessment of effects of the reservoir on the thermal regime of the Macalister River than is possible with the upstream data currently available.

31 Status of Cold Water Releases from Victorian Dams

415214 Lake Bellfield

415217 Modified from DNRE (2000)

Downstream - Upstream comparison 35

25 Key 20 Upstream - 415217 Downstream - 415214 15

Summer max. 10 Winter min.

Water Temperature (°C) 5

0 7576 77 78 79 80 81 82 83 84 85 86 87 88 89 Year Figure 13: Temperature data and location of Lake Bellfield and sites within basin 15 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue and upstream site is plotted in red (see key).

32 Status of Cold Water Releases from Victorian Dams

225209

225204

225221

225230

Glenmaggie Reservoir

Modified from DNRE (2000)

Downstream - Upstream comparison 35

25 Key 20 Adjacent stream - 225230 Upstream - 225209 15 Downstream - 225204 Summer max. 10 Winter min.

Water Temperature (°C) 5

0 7779 81 83 85 87 89 91 93 95 97 99 Year

Figure 14: Temperature data and location of Lake Glenmaggie and sites within basin 25 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue, the upstream site is plotted in red and the adjacent site in plotted in green (see key).

33 Status of Cold Water Releases from Victorian Dams

Cardinia Reservoir

Cardinia Reservoir has a dam wall of 86 m and a capacity of 286 911 ML. Releases are made from an outlet approximately 1/3 of the FSL height with an average discharge of 18.9 ML d-1. There were no suitable water quality monitoring sites and available information to adequately demonstrate cold water releases from Cardinia Reservoir. Immediately downstream from the dam only two water temperatures were recorded, providing the estimation of just only one minimum temperature (Figure 15). Approximately 20 km downstream, there appears to be no significant pattern suggesting cold water impacts compared to the adjacent stream at site 228217 (Figure 15). The potential of cold water releases from Cardinia Reservoir are significant based on the size and releases structure. Additional monitoring sites are recommended as a maximum priority.

Upper Yarra Valley (O’Shannassy Reservoir, Upper Yarra Reservoir, Silvan dams) The Upper Yarra Reservoir has a dam wall 89 m high, a maximum capacity of 204 985 ML and a maximum release of 10 ML d-1 from an outlet 15 m below FSL. O’Shannassy Reservoir has a dam wall 34 m high, a capacity of only 3123 ML and a maximum release of 3 ML d-1 which in summer can consist entirely of low level releases. Silvan Dam has a dam wall 40 m high, a capacity of 40 581 ML and a maximum release of 2 ML d-1 from offtake approximately 2/3 of the way from the bottom of the reservoir. Based on the infrastructure of these dams each was assigned a maximum priority. A lack of temperature monitoring made the assessment of downstream water temperature impacts impossible. The site downstream from the Upper Yarra Reservoir (229212, Figure 16) provides over 20 years of monthly temperature information. However, without other monitoring sites for comparison it is difficult to assess the impact. Temperatures at this site rarely reach greater than 20oC and therefore appear to be impacted, especially during 1987 when maximum summer temperatures were below 15 oC. Saddlier and Doeg (1997) indicated that cold water releases may have been responsible for poor blackfish recruitment and encouraged higher level releases from the Upper Yarra Dam. One site downstream from O’Shannassy Reservoir (229653, Figure 16) recorded monthly temperature for two years, but with little data from sites in the vicinity, comparisons were difficult. There were no temperature monitoring sites near Silvan Dam. The current daily release from these dams is relatively small, and therefore the downstream impact is likely to be minimal. However, if additional environmental releases are required for any streams downstream from these dams, the possibility of extensive cold water pollution is likely. It is essential that the current extent of cold water releases be assessed for each of these Upper Yarra Valley dams.

34 Status of Cold Water Releases from Victorian Dams

Cardinia Reservoir

228230

228228

228217

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key Adjacent Stream - 228217

15 Downstream - 228230 (1) Downstream - 228228 10 Summer max. Winter min.

Water Temperature (°C) Temperature Water 5

0 75 76 7778 79 80 81 82 83 84 85 86 87 88 89

Figure 15: Temperature data and location of Cardinia Reservoir and sites within basin 28 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in dark blue and light blue and the offstream site is plotted in green (see key).

35 Status of Cold Water Releases from Victorian Dams

229653 O’Shannassy Reservoir

Upper Yarra 229108 Reservoir

229212

Silvan Dam

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key

Downstream - 229212 15 D/s Upper Yarra - 229108

10 Summer max. Winter min.

Water Temperature (°C) 5

0 7678 80 82 84 86 88 901 92 94 96 98

Figure 16: Temperature data and location of Upper Yarra dams and sites within basin 29

Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in dark blue, light blue and grey (see key).

36 Status of Cold Water Releases from Victorian Dams

Pykes Creek, Merrimu and Melton reservoirs Pykes Creek Reservoir has a dam wall 39 m high, a capacity of 24 500 ML and a single outlet 20 m below FSL. Pykes Creek flows into the Werribee River 2 km downstream from the dam with a seasonal release of 10 to 200 ML d-1 made from August to May. Temperature data were available at a site immediately downstream of the reservoir (231203, Figure 17) over the period 1977 to 1990. Comparison data were available from the adjacent Werribee River (231225, Figure 17) over the same period. The comparison does not appear to show any effects of the dam, although there was a large difference between maximum temperatures reached during 1989 of 7 to 10oC. The downstream impact on the Werribee River was not possible to assess, but it is likely to be considerable. Additional monitoring is recommended in conjunction with Merrimu and Melton reservoirs. Merrimu Reservoir is a domestic water storage with a surface area of 310 ha and a capacity of 35 000 ML. The height of the dam wall is 34 m, and the dam releases an average of 50 MLd-1 The dam is fitted with a multi-level outlet, with offtakes at 6 m intervals over the full depth of the dam. The dam flows via Pyrites Creek into Melton Reservoir, and therefore could be influencing on the thermal gradient of this downstream impoundment. The only temperature data available from this Merrimu was from 1978-1984 at a monitoring station just above the dam (231224, Figure 17). Due to the location of the dam, any further investigations should also include Pykes Creek and Melton Reservoirs. Melton Reservoir is fitted with a single offtake at the base of the 35 m high dam, which has a capacity of 17 150 ML. The outlet is approximately 15 m below FSL and between 50 and 270 ML/d are released between August and May. Temperature data were available for a 13-year period at a site immediately downstream of the reservoir (231205, Figure 17). However, of the five major tributaries entering the reservoir, concurrent temperature data existed only for a 4-year period (1986 – 1990) on the Lerderderg River (231211, Figure 17). Temperature data were available for Parwan Creek upstream of the reservoir, but only for a period after the downstream monitoring had ceased. The available data suggest a slight effect of the reservoir on downstream temperature regimes, with lower summer maxima, higher winter minima and reduced seasonal thermal amplitude occurring. However, it should be noted that the Lerderderg River contributes only around one third of the flow that is discharged from Melton Reservoir. The upstream temperature of the Werribee River, which contributes around half of the flow that leaves the reservoir, should also be monitored. Moreover, conclusions should not be based on data from only 4 years. The plot of maximum and minimum temperatures shows how few data points exist. Concurrent monitoring of the Werribee River upstream and downstream of Melton Reservoir (including Pykes Creek and Merrimu reservoirs) and of the Lerderderg River upstream of Melton Reservoir would be a minimum requirement to properly assess the effects of this dam on downstream thermal regime.

37 Status of Cold Water Releases from Victorian Dams

Pykes Creek Reservoir 231224

Merrimu Reservoir

231225 231211

231203 Melton Reservoir

231205

Modified from DNRE (2000)

Downstream - Upstream comparison 30 Key 25 Adjacent stream - 231225 Upstream - 231224 20 Upstream - 231221 Downstream - 231203 15 Downstream - 231205 Summer max. 10 Winter min.

Water Temperature (°C) Temperature Water 5

0 7778 79 80 81 8283 84 85 86 87 88 89

Figure 17: Temperature data and location of Pykes Creek, Merrimu and Melton Reservoirs Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Adjacent site is plotted in green, upstream sites are plotted in red and purple and downstream sites are plotted in dark blue and light blue (see key).

38 Status of Cold Water Releases from Victorian Dams

Bostock Reservoir Bostock Reservoir has a dam wall 25 m high, a capacity of 7500 ML and a downstream release of just 0.8 to 1.2 ML d-1 into the Moorabool River via a single low level outlet. This dam is considered a maximum priority based on the dam infrastructure but also because of two additional dams upstream. Bolawarrah Reservoir is approximately 5 km upstream and Korweinguboora Reservoir is approximately 10 km upstream. Both of these reservoirs could potentially discharge cold water, which could accumulate in Bostock Reservoir and add to its cold water pollution potential. There are no temperature monitoring stations in close vicinity to the dam. It is therefore recommended that this dam be further assessed and that in the process, the potential cold water releases from the upstream dams also be assessed.

West Barwon Dam West Barwon Dam is 43 m high and has a capacity of 21 898 ML. It has a summer environmental flow release of between 3 and 10 ML d-1 from two possible outlets 9.8 m and 21.8 m below FSL. Monthly water temperature was available for two sites downstream from West Barwon Dam (Figure 18). Site 233214 was approximately 2 km downstream from the dam (unsure of distance downstream from outlet tunnel), while site 233224 is approximately 40 km downstream. The summer maxima below the dam release (233214) appear to be impacted with maxima rarely over 20 oC, however further downstream (233224) the temperatures appear to have recovered (Figure 18). It is difficult to determine if the thermal regime at site 233224 is being influence by the cold water releases from West Barwon Dam due to the lack of monitoring sites and frequency and due to the lack of upstream monitoring sites. Additional monitoring sites a re recommended upstream, within the reservoir and downstream.

Rocklands Reservoir Rocklands Reservoir has a dam wall 17 m high and a capacity of 248 000 ML. It currently discharges summer environmental flows of 10 to 50 ML d-1 into the Glenelg via a single release 13.4 m below FSL.

The recorded monthly temperature information does not indicate a downstream temperature impact (

Figure 19Figure 19). The upstream (238231) is approximately 30 km upstream, while the downstream sites are at the discharge point of the reservoir (238205) and approximately 40 km downstream (238224). While the upstream summer maxima were greater in 1994, the summer maxima at both downstream sites are often 5 to 10 oC higher than the upstream site (Figure 19

Figure 19). This possible lack of downstream impact could be due to low operating dam volumes. Releases from Rocklands Reservoir are made 13.4 m below FSL, however during most summers, the dam surface may be sufficiently low to ensure releases are not made from within the hypolimnion. It is recommended that the next stage of investigations correlate downstream temperatures with the water level within Rocklands Reservoir.

39 Status of Cold Water Releases from Victorian Dams

Current biological knowledge of the Glenelg River below Rocklands Reservoir suggests that cold water pollution could be occurring. Additional monitoring is recommended, particularly in light of possible increases to environmental flow allocations.

233224

West Barwon Dam 233214 Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key

15 Downstream - 233214 Downstream - 233224 10 Summer max. Winter min.

Water Temperature (°C) 5

0 7678 80 82 84 86 88 901 92 94 96 98 Year Figure 18: Temperature data and location of West Barwon Dam and sites within basin 33 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X-

40 Status of Cold Water Releases from Victorian Dams axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in dark blue and light blue (see key).

238224 238231

238205

Modified from DNRE (2000)

Downstream - Upstream comparison 35

25 Key 20 Upstream - 238231 Downstream - 238205 15 Downstream - 238224 Summer max. 10 Winter min.

Water Temperature (°C) 5

0 75 7779 81 83 85 87 89 91 93 95 97

Figure 19: Temperature data and location of Rocklands Reservoir and sites within basin 38 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in dark blue and light blue, while upstream site is plotted in red (see key).

41 Status of Cold Water Releases from Victorian Dams

Investigation of Medium Priority Dams

Lake Buffalo Lake Buffalo Dam is 31 m high and has a volume of 24 000 ML. The outlet pipes are incorporated into the spillway structure at approximately 10 m below FSL. Stratification occurs annually, therefore at, or near FSL the potential to release water from within the hypolimnion is structurally possible. Average daily releases range from 286 to 1827 ML d-1 from the period of 1990 to 2000, however up to 58 % of these discharges can occur as winter releases (W. Francisco, G-MW, pers. comm.). Monthly temperature data indicates that there may have been some cold water releases in 1980 to 1982, however the pattern is irregular (Figure 20). The upstream site (403222) may be too far upstream to be a useful comparison being 6 km upstream, while the downstream site is at the release point. Additional monitoring sites are recommended upstream and further downstream to sample temperature on a more regular basis.

Barkers Creek Reservoir Barkers Creek Reservoir (also known as Harcourt Reservoir) consists of a 13 m high dam wall, with a capacity of 2700 ML and an outlet that is near the bottom of the dam. There are no monitoring sites in the vicinity of this impoundment. Outlet remodelling works are scheduled for the dam, which includes the introduction of a floating arm to reduce the depth of summer releases. The immediate incorporation of a temperature monitoring program will not only provide supporting evidence justify this work, but will also demonstrate the downstream benefits when the work has been completed.

Newlyn Reservoir This reservoir is a deep domestic water supply with a dam wall 12 m high and a capacity of 3300 ML. The outlet pipe for this dam is approximately 8 m below FSL. Newlyn Reservoir flows via Birches Creek into Tullaroop Reservoir (a maximum priority storage in terms of thermal pollution) which is located approximately 35 km downstream. There are no relevant monitoring sites in the vicinity of Newlyn Reservoir. It is recommended that further investigation into this dam be carried out. Future monitoring could be incorporated into the monitoring plan for Tullaroop Reservoir at minimal cost.

42 Status of Cold Water Releases from Victorian Dams

Lake Buffalo

403220

403222 Modified from DNRE (2000)

Downstream - Upstream comparison

25 Key 20 Upstream - 403222 Downstream - 403220 15

Summer max. 10 Winter min.

Water Temperature (°C) 5

0 76 78 80 82 84 86 88 90 Year

Figure 20: Temperature data and location of Lake Buffalo and sites within basin 3 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue, while upstream site is plotted in red (see key).

43 Status of Cold Water Releases from Victorian Dams

Blue Rock Reservoir and Lake Narracan Blue Rock Reservoir is located on the Tanjil River in Gippsland and has a dam wall 75 m high with a capacity of 208 000 ML. The lake is installed with a multi-level offtake, with butterfly valves at 6, 12, 18, 24 and 30 m below full supply level. Between 90 to 150 ML d-1 are released during winter, and between 300 to 400 ML d-1 during summer, with a proportion of releases being made for supply to the hydro-electric plant. No temperature monitoring data is available for this impoundment, however there are anecdotal reports of releases being made from deeper in the water column to prevent cavitation of the power generation turbines. It must be noted that Southern Rural Water strongly disagree with this statement, stating that releases for power generation are only made from the top offtake(s) which are within 5 m of FSL (I. Kitchenn, SRW, pers. comm.). Low level releases may therefore be more common than expected, resulting in downstream cold water releases. Lake Narracan is situated approximately 10 km downstream. Blue Rock Reservoir may be contributing to the cold water accumulation within Lake Narracan. It is therefore recommended that the potential impacts of Blue Rock Reservoir be monitored in conjunction with Lake Narracan. Lake Narracan is dammed by a concrete crest about 6 m high topped by vertical lift gates of 6m depth. The lake capacity is 8000 ML. The lake releases are between 400 to 500 ML d-1 for most of the year, except at times of flooding when water releases can be significantly higher. Most releases are through the penstock bypass, which can accommodate up to 1700 ML d-1 and is about 8 m below FSL. The lake receives water from the Moe River, the Latrobe River and the Tanjil River and regular algal blooms have been reported. There are limited data available from monitoring sites around Lake Narracan (Figure 21). It appears that after 1994, the summer maxima are reduced at approximately 8 km from the dam at the downstream site (238205), compared to the adjacent site on the Morwell River (238231). This information is however inconclusive. Although the releases are from 9 m below FSL, the relatively high releases and the potential for cold water contributions from Blue Rock Reservoir suggest that Lake Narracan be considered as a medium priority, and that monitoring commence as soon as possible.

Moondarra Reservoir This impoundment is a domestic water storage on the Tyers River with a dam wall 39.6 m high and a capacity of 30 311 ML. Outlet butterfly valves are located at approximately 6.4 m, 12.5m, 18.6 m and 25.2 m below FSL. A minimum environmental flow of 30 ML d-1 is released from the dam usually from the highest outlet. Thermal stratification has been previously recorded (B. Wallin, Gippsland Water, pers. comm.). There is a lack of monitoring sites around the reservoir, and therefore further evaluation of Moondarra Reservoir must be undertaken.

44 Status of Cold Water Releases from Victorian Dams

Blue Rock Dam

226005

226408

Lake Narracan

Downstream - Upstream comparison

Key 20 Adjacent stream - 226408

15 Downstream - 226005

10 Summer max. Winter min.

Water Temperature (°C) 5

0 7779 81 83 85 87 89 91 93 95 97 Year

Figure 21: Temperature data and location of Lake Narracan and sites within basin 26 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue, while adjacent site is plotted in green (see key).

45 Status of Cold Water Releases from Victorian Dams

Tarago Reservoir Tarago Reservoir has a dam wall 34 m high, a capacity of 37 574 ML and two outlets at different levels. The mid level outlet is 10 m below FSL and a low level outlet is 18 m below FSL. At present, the reservoir is not in use and all flows are passed downstream via the mid- level outlet. The dam is currently being held at a level between 2 m and 6 m below FSL (R. Yurisich, Melbourne Water, pers. comm.). From the information available, it is difficult to tell whether that Tarago Reservoir is impacting the downstream thermal regime, however, data from monthly water temperature information was inconclusive (Figure 22). Downstream temperatures at site 228219 were not noticeably impacted. There is insufficient information to adequately assess the downstream impact of Tarago Reservoir, therefore more intensive monitoring is required.

Maroondah Reservoir Maroondah Reservoir has a dam wall 41.1 m high, and a capacity of 28 199 ML. The dam is maintained primarily for Melbourne’s domestic water supply, however minimal releases of 1ML d-1 are made from the outlet at 36 m below FSL. No relevant monitoring data was available in this area. Further investigation into the effects of this dam in terms of cold water pollution is needed, particularly if additional environmental releases are required downstream.

Expedition Pass Reservoir This reservoir has been largely decommissioned, but there are still regular releases from a low-level valve for downstream irrigation of an orchard and environmental irrigation of flood plains when the dam is not spilling. Mt. Alexander Shire was unable to supply figures on the height or capacity of the outlet valve, and there are no temperature monitoring sites near the reservoir. However, anecdotal information that released waters are ‘dark in colour’ and have ‘a putrid odour’ suggests that the water is being drawn from lower stratified layers (D. Dumesny, Mt Alexander Shire Council, pers. comm.). This being the case, effects on the quality and temperature of downstream waters are likely. Coliban Water may be able to supply the missing information, as they conducted remodelling of the spillway and intake in 1995. Some form of formal monitoring of this site is recommended to assess the situation further.

46 Status of Cold Water Releases from Victorian Dams

228212 Tarago Reservoir

228206

228219

Downstream - Upstream comparison 25

20 Key Adjacent stream - 228212 15 Upstream - 228206 Downstream - 228219 10 Summer max. Winter min.

5 Water Temperature(°C)

0 76 78 80 82 84 86 88

Figure 22: Temperature data and location of Tarago Reservoir and sites within basin 28 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream site is plotted in blue while the upstream site is plotted in red and the adjacent stream is plotted in green (see key).

47 Status of Cold Water Releases from Victorian Dams

Moorabool Reservoir and Lal Lal Reservoir Moorabool Reservoir is situated on the West Branch of the Moorabool River with a dam wall 13.7 m high and the capacity is 6738 ML. A multi-level outlet tower has release valves at 1 m, 5 m, and 10 m below FSL. Blue-green algal blooms are common during the summer months and may constrain surface releases. It is possible that cold water from Moorabool Reservoir may be affecting release temperatures at Lal Lal Reservoir, which is approximately 15 km downstream. There are no useful monitoring sites upstream or downstream of Moorabool Reservoir. Further investigation is recommended in conjunction with monitoring of Lal Lal Reservoir. Lal Lal Reservoir is situated on the West Branch of the Moorabool River with a dam wall 48 m high and a capacity of 59 549 ML. Regular releases for Bulk Entitlement passing flows and for Geelong domestic demand are made from a multi-level tower with a greatest release depth of 8 m below FSL. Monitoring sites upstream and downstream of Lal Lal Reservoir provided some monthly temperature information (Figure 23). The site upstream (232210) is approximately 4 km upstream, while the two downstream sites (232211, 232204) are approximately 7 km and 20km respectively. Cold water releases do not appear to be impacting downstream summer maxima at the downstream site (232204) in 1994–95 and in 1998, when compared to the upstream site (232210). While this information is inclusive, increased temperature sampling frequency is recommended at these established gauging sites.

48 Status of Cold Water Releases from Victorian Dams

232210 Lal Lal Reservoir

232211

232204

Modified from DNRE (2000)

Downstream - Upstream comparison 30

20 Key Upstream - 232210 15 Downstream - 232211 Downstream - 232204 10 Summer max. Winter min.

Water Temperature (°C) 5

0 7779 81 83 85 87 89 91 93 95 97 99 Year

Figure 23: Temperature data and location of Lal Lal Reservoir and sites within basin 32 Flag symbols denote water quantity and/or quality monitoring stations. Stations marked with a site number are those used in the plot of maximum and minimum temperatures. Map modified from DNRE (2000). Plot shows maximum summer and minimum winter temperatures recorded at each station for the period indicated on the X- axis. Solid lines denote summer maxima, dashed lines denote winter minima. Downstream sites are plotted in dark blue and light blue, while upstream site is plotted in red (see key).

49 Status of Cold Water Releases from Victorian Dams DISCUSSION

The monthly water temperature data available through the Victorian Water Resources Data Warehouse was in most cases the only information available to assess the downstream impact of dams. This information commonly did not provide an adequate interpretation of the true extent of cold water pollution. As a result, the installation of new temperature loggers, often at new sites, was a regular recommendation. Monitoring a number of downstream sites is required to determine the extent of cold water influence. Monitoring upstream sites and sites on adjacent streams is also required to demonstrate the magnitude of impact immediately downstream of the dam. Deficiencies in available data, and the best ways to circumvent these, will be discussed. Of all the maximum (24) and medium (11) priority dams investigated only four have sufficient evidence to indicate unequivocally a downstream impact on the thermal regime. These four included Lake Dartmouth, Lake Hume, Lake Eildon and Lake Eppalock, all of which have been previously identified as cold water polluters. Future monitoring programs need to be standardised and developed in a scientifically rigorous manner to ensure that the downstream impacts of dams can be evaluated. This information will not only determine the magnitude and downstream extent of cold water pollution, but will also provide feedback to ensure better management of released water. Moreover, this information could help guide decisions on future amelioration options. Suggestions will be made for the next stage of monitoring programs.

Location of monitoring sites All dams investigated required additional monitoring sites to more effectively demonstrated and monitor a downstream cold water influence. Even dams such as Dartmouth, Hume and Eildon require additional upstream and downstream sites. A number of comparisons in this report relied on data gathered from monitoring stations some considerable distance upstream from the impoundment being studied (up to 50 km). There are several weaknesses inherent in these types of comparisons. Firstly, sites some distance upstream of the impoundment will almost certainly receive additional inputs prior to entering the reservoir. The thermal characteristics of the river at the monitoring site may therefore be somewhat different to those immediately upstream of the impoundment. Secondly, sites some distance upstream from an impoundment may be located at a considerably higher elevation. Altitude affects thermal characteristics of river waters (Ward 1985), and is likely to result in lower summer and winter peak temperatures at the upstream site than at the site downstream of the dam wall. Thus it becomes more difficult to be confident that a raised winter minimum downstream of an impoundment is due to the effects of the impoundment itself. Conversely, maxima and minima plots of the type in this report may underestimate the effects of the dam on summer maxima if comparison data are taken from a site at higher altitude. As stated in the introduction, a depression of summer temperatures is one of the most ecologically significant effects of cold hypolimnial release dams for native fish populations. Therefore it is of some importance that the degree of any such depression is quantified accurately. The comparison of the release temperatures with the upstream temperatures provides a clear indication of the impact of cold water releases. Therefore, the upstream sites need to be representative of the upstream thermal regime. The downstream sites should be located immediately below the dam releases as well as a number of sites at regular intervals downstream. The spacing of downstream monitoring sites is dependent on the downstream extent of cold water influences and on the occurrence of confluences with other major

50 Status of Cold Water Releases from Victorian Dams streams. Additional monitoring sites may be required in adjacent streams not impacted by cold water releases, to be used as reference streams for comparison. When upstream data of any kind are lacking, off-stream sites have been used to predict upstream or unregulated temperature regimes (Acaba et al. 2000, Growns 1998, this study). However, this type of comparison suffers from two major weaknesses. Firstly, the source waters of the two rivers are necessarily different, and this may affect the temperature of the waters (Ward 1985). Secondly, temperature regimes along rivers are affected by channel form, topography and riparian vegetation (Ward 1985), all of which can differ between adjacent rivers. As a result, the thermal regime of an adjacent river is at best an approximation of a site upstream of a dam even when stream monitoring sites are at similar elevations. A similar argument can be applied to reservoirs that have multiple inflowing streams. If only one tributary is monitored, the assumption is implicit that it is representative of other waters entering the impoundment. The thermal characteristics within an impoundment are dependent on all inputs and therefore each major inflowing tributary should be considered. Perhaps a rule of thumb suggesting that all inflowing rivers contributing ≥ 25% of the outgoing discharge need to be monitored as potential upstream influences.

Temporal resolution of samples The data available through the online warehouse were collected approximately monthly at most sites. This sampling frequency introduces two sources of error into the data to be analysed. Firstly, it is likely that many actual summer maxima and winter minima were missed because they occurred outside the sampling dates. Therefore the average and median maxima and minima presented are conservative estimates. Variation in the yearly maximum temperatures are also likely to be increased due to this erroneous interpretation of the seasonal temperature regime. The assumptions of traditional statistical comparisons would be violated due to errors associated with pseudoreplication (Hulbert 1984). Caution should therefore be used when comparing site summary information as provided in Appendix B. Estimated dates of maximum and minimum temperature will also be affected by the sampling protocol. The median dates presented are constrained in that the data set is restricted to those dates on which sampling actually occurred. For that reason it is difficult to make conclusions as to the effect of any dam on the timing of summer peak temperatures. Secondly, while the data are provided with both a date and time of sampling, the temporal resolution means that it is difficult to assess diel variation within the rivers and how it is affected by the presence of dams. This phenomenon has only been occasionally studied in Australia (Growns 1998, Marchant 1989), but has potential consequences for both fish and macroinvertebrate assemblages. Monthly temperature measurements were often recorded at different times during the day. This would have added extra variability to the data, given that river water temperatures can vary by several degrees over the course of each day. It is therefore also likely that some of the variation in maximum and minimum temperatures plotted is due to the time of day at which the samples were taken, as well as the time of the year. Daily and seasonal variation in water temperatures could be modelled using sine and cosine functions to approximate seasonal and diel variation, as adopted by Acaba et al. (2000) to predict seasonal maxima and minima around three large dams in NSW. Although the report by Acaba et al. (2000) was able to match the modelled data to measure information, the prediction of the number of the most extreme temperatures was not very successful. Therefore it should be noted that some of the year to year variation in maximum and minimum temperatures that we found must be ascribed to the poor temporal resolution of the samples and to the fact that the time of sampling was not constant. There is no substitute for more accurate monitoring data collected with a relevant frequency.

51 Status of Cold Water Releases from Victorian Dams

Improving Temperature Monitoring While the above points serve to undermine confidence in the results presented for dams in Victoria, they highlight the need for better quality monitoring of sites upstream and downstream of dams that are probable causes of thermal pollution. Temperature loggers on all major tributaries upstream of reservoirs (< those contributing ≥ 25 % of the out-flowing discharge) combined with one or more loggers immediately downstream of the impoundment would provide conclusive evidence of thermal pollution. Loggers situated further downstream from the dam would assess the length of river affected. Loggers could be set up to take multiple readings each day, eliminating some of the temporal resolution effects outlined above and allowing an exploration of the effects of the impoundment on diel temperature variation. Temperature monitoring over a number of seasons may be required to confidently assess the full impact of cold water releases. Australian rivers are characterised by extremely high variability in annual flows (McMahon and Finlayson 1995), and so reservoir levels are also extremely variable. This can affect the level of disturbance to the downstream thermal regime. Miniature self-contained temperature loggers (Stowaway ® TidbiT®) retail for around $200 and will collect 5 years worth of hourly data. Such costs seem justified if they prevent spending on unnecessary outlet works, and if they properly assess the threats to native riverine assemblages. Continuous monitoring would enable an assessment of temperature changes associated with sudden dam releases on a real-time basis and therefore provide valuable feedback to dam management attempting to minimise downstream impacts. Alternatively, such information may also obviate the need for expensive re-modelling of the outlet works ($5 to 30 M per dam; Sherman 2000) by indicating minimal downstream impacts. For some sites, another few seasons of monitoring could only serve to better elucidate a problem that is apparent from the existing data and previous studies. In Victoria, such sites include Dartmouth Dam, Lake Eildon, Lake Hume and Lake Eppalock. For cases such as these, remediation works should not be delayed while more data is collected.

Research and monitoring protocol Future research and monitoring strategies need to consider the physical and the biological implications of cold water releases, and more importantly detect an interaction between the two. Mitigation works are very expensive, therefore it is essential that monitoring programs are scientifically rigorous and logistically feasible. A multi-disciplinary approach is required to grasp the full biological consequences of cold water pollution and restorative changes associated with increased release temperatures. It is also important that the application of these monitoring strategies is undertaken on a site by site, or location by location basis, to take into account local conditions and issues.

Water temperature monitoring There is a lack of physical water temperature information upstream and downstream from dams suspected of releasing cold water. It is important to note that the equipment to collect this information is relatively inexpensive to install ($11 200 to $24 900) and maintain ($ 25 210 p/a )The ranges in price are a function of the number of temperature loggers required and are based on having 4 to 8 loggers within the dam, 1 to 6 upstream sites and 3 to 6 downstream sites (each with two loggers per site). The range of total costs is dependent on the number of upstream tributaries and the magnitude of dam release. Because the temperature data loggers are relatively inexpensive, the cost of the installation of a number of loggers both upstream and downstream is financially feasible. This information should enable an assessment of the direct relationship between dam releases and immediate downstream water temperatures, as well as the extent of the cold water impacts. The installation of upstream (and/or adjacent

52 Status of Cold Water Releases from Victorian Dams stream) temperature loggers will enable the comparison of the cold water releases to natural (unaffected) conditions. Two data loggers will be installed at different heights in the water column in as a semi-permanent fixture at each monitoring site to account for temperature variations. An absolute bare minimum would involve one logger upstream. One logger at the release depth in the impoundment and one logger downstream at an approximate installation cost of $3500 and an annual maintenance cost of $13 000. The maintenance of the temperature loggers and the collection of additional water temperature profile information at each site should be conducted at least every four months. Each maintenance trip will involve retrieving, down-loading and reinstalling temperature loggers. Also temperature profiles will be conducted horizontally and vertically across the river profile at each site, as well as vertically within the dam.

Biological Monitoring It is necessary to characterise and describe the impact of cold water releases currently occurring prior to investigating the changes associated with amelioration works. The assemblage composition of freshwater fish downstream of dams is often a good reflection of the biological impact of cold water releases. For example, the occurrence of healthy Brown trout populations downstream of dams can be directly attributed to cold water releases and related to the length of stream impacted. Alternatively, the occurrence of a range of size classes of native fish species such as Murray cod is indicative of a relatively unaffected thermal regime. Fish are an ideal biological indicator for such an investigation due to their mobility and the relative ease of sampling. A healthy downstream fish population may indicate that minimal release strategy changes may be required. The other advantage in collecting this information is that the biological response to future amelioration efforts can be assessed. There would appear to be little sense in conducting such expensive operations on dam release structures for biological reasons if the biological responses are not being monitored. Fish populations should be sampled at least three times a year, and twice during the normal spawning periods to determine the reproductive condition of captured fish. A number of replicate samples are required at each site to account for measurement error and confounding issues such as habitat preferences and flow variation. The fish surveys should establish the occurrence and condition of fish communities, however, larval sampling will determine if successful spawning occurred. An evaluation of the successful cohorts within the population will provide evidence of successful spawning in previous seasons. Successful spawning of fish is one of the best criteria to biologically assess the viability of fish populations. Larval collection nets should be sampled every fortnight over a period from mid October to mid December at regular distances downstream from the dam. The composition of macroinvertebrates can provide a rapid interpretation of the physical environment at that particular site. The advantages of monitoring macroinvertebrates are related to their limited mobility, but also their relatively high abundance and species variability. The comparatively shorter life cycles of macroinvertebrates ensures that more immediate impacts can be assessed rather than remnant impacts from previous months. The composition downstream from dams has been observed to be less diverse and to be dominated by more temperature tolerant species. There have been few studies in Australia that specifically investigated the impact of cold water dam releases on macroinvertebrate populations. Those that have considered cold water releases as a potential issue have not had the sampling design to adequately determine a direct cause and effect. The patterns of macroinvertebrates

53 Status of Cold Water Releases from Victorian Dams immediately downstream from a dam are likely to be strongly influenced by the lack of recruitment due to downstream drift. The project design should therefore incorporate this potentially complicating influence and consider it as a covariate in the data analysis. The composition of freshwater macrophytes can also provide some evidence of the physical environment at that particular site. Macrophytes are unable to move and therefore are directly influenced by their surroundings, and unlike other plants, are able to utilise the elements in the water through the leaves. The composition downstream from dams has been observed to be less diverse and dominated by more temperature tolerant species. There have been few studies in Australia that specifically studied the impact of cold water dam releases on macrophyte populations. Other potential influences below dams include increased flow reliability, reduced scouring flows and reduced turbidity. The sample design should sample upstream and downstream and is required to be sufficiently robust and needs to incorporate additional habitat measurements to compensate for these other potential influences.

Assessment Criteria Before large scale monitoring programs are established it is important to consider how this information will be used to assess the impacts and subsequent improvements if and when mitigation works are introduced. There are a number of physical influences such as ambient air temperature and riparian cover that also influence stream temperatures. Additionally, the relationship between dam discharges and temperature are closely linked. These influences must be considered in the design of the monitoring programs and the analysis of the water temperature information. Moreover, the dam releases need to be correlated with stream temperatures to provide feedback to water release management. The influence of dam releases may also be significant if stratification does not occur. The minimum seasonal temperature may be increased and the seasonal phase shift may still occur downstream due to the insulation properties of a large body of water (Ward 1985). Stratification within the dam will result in greater downstream changes in the thermal regime than releases from a dam that is not stratified. The distinction between these two scenarios also needs to be explored and described for each maximum and medium priority dam. The utilisation of the ANZECC & ARMCANZ (2000) guidelines (temperatures outside the 20th and 80th percentiles of natural temperatures) is not immediately applicable to most cold water pollution sites. Firstly, identification of the natural thermal regime is a contentious issue and not always possible. This is, however, an important issue to consider and is best assessed on a catchment basis to reduce the amount of variability when comparing the thermal regimes of different streams or sites within the same stream. Previous techniques have used ambient air temperatures and the application of mathematical functions that replicate these patterns, however, the best approach is to have carefully selected and representative sampling locations and a sufficient sampling frequency. Secondly, the application of these criteria ignores the numerous impacts that cold water releases can have on the downstream thermal regime. As mentioned earlier these physical impacts of hypolimnial releases include reduced diel and seasonal temperature variation, increased temperature minima, decreased temperature maxima and perhaps more biologically important, rapid drops in temperature. The assessment process needs to be an interactive management and monitoring strategy. As more information is collected, a greater understanding of the impacts will be developed, which should ultimately improve water release management strategies and help refine monitoring programs. The criteria used to define the acceptable releases also need to be flexible enough to be applicable to all situations. The specific issue within each catchment needs to be considered in the overall management and monitoring approach.

54 Status of Cold Water Releases from Victorian Dams

Management of cold water pollution There are a number of strategies that have been proposed for the management of cold water pollution. These are summarised by Sherman (2000). The strategies can be divided into two main types. Firstly, there are those that seek to break down thermal stratification within the impoundment, thereby resulting in constant water temperatures at all depths. Air bubbles pumped from diffusing bars at the bottom of reservoirs have been used to this end, but are expensive to run, and are probably impractically expensive for deep reservoirs (King 1981; Brown 1986). Other strategies include the use of impellers to mix waters (Lugg 1999). These may be coupled with columns or piping to ensure that surface and bottom waters are mixed (Sherman 2000). Secondly, there are those strategies that seek to release only water from the epilimnion. These include the use of multi-level offtake towers and variable level intake structures or the installation of siphons over dam walls (Lugg 1999). Another strategy that achieves this end is the placement of semi-rigid ‘curtains’ around the outlet towers that extend from the bed to near the surface. When water is released from between the dam wall and the curtain, it is replaced by surface water from the impoundment (Sherman 2000). A third type of strategy that has been hypothesised is to heat released water either artificially or by solar power (Lugg 1999). The costs involved with artificial heating and the inability to use solar heating at night make these options unfeasible.

Operational constraints Any procedure that results in the release of epilimnetic water rather than hypolimnetic water would not only lead to an improvement in the temperature regime, but would also improve downstream dissolved oxygen levels and reduce the concentration of nutrients and some toxicants. There are, however, some constraints to surface water releases. Some dams are prone to algal blooms in the surface waters during warmer months. During these periods, releases from the epilimnion may be hazardous. Destratification techniques under this condition can not only increase the release temperature, but can also increase mixing in the vicinity of the release tower to prevent algal accumulation and subsequent releases. Conversely, the wisdom of destratifying very large water bodies has been questioned as it would only result in the mixing of a small volume of warm surface water with a large volume of hypolimnial water, resulting in minimal changes to the temperature (Mackay and Shafron 1998). Moreover, in some impoundments destratification processes may result in the mixing of bottom sediments, thereby increasing turbidity and the overall quality of the surface water. Other operational constraints include delays in the time to change over to new outlet points and the associated logistical problems with this procedure. There are also potential cavitation problems for the turbines used for power generation at hydroelectric dams. Additionally, there may be an associated problem due to an increase in the retention time of the water in the bottom of the dam, which may not be desirable in cases where sediment and certain compounds are able to accumulate (Rish et al. 2000). Downstream water demand is also a major consideration. In general, irrigation reservoirs are fullest around December and lowest around May, particularly where the dam is not designed as a carry over storage (Ian Kitchenn, Southern Rural Water, pers. comm.). Usage patterns of these storages will need to be considered as operational constraints, and built in to any management plans. Release strategies should be negotiated to ensure that the volume of supply is not compromised, but where the downstream extent of cold water impact is also minimised. It is important to note that these solutions will be possible only on a catchment scale and may not be immediately transferable to other systems.

55 Status of Cold Water Releases from Victorian Dams

Recommendations It is recommended that monitoring commence as soon as possible for those dams identified as maximum priority, and amelioration options should be considered at the earliest opportunity. Dams ranked as medium priority for future research should also monitored and additional information should be sourced to assess the downstream effects. Those dams listed as minimum priority should be considered for future monitoring program, particularly those releasing significant downstream Spring - Summer flows. It is also recommended that one or two case study dams be undertaken in Victoria to demonstrate the benefits of the amelioration of cold water discharges. It will be important to demonstrate with these case studies the downstream improvement in the temperature regime and the improvement in biological diversity and viability. We should not continue to investigate the impacts, but instead do something to improve the situation. During the course of this project, a number of necessary tasks became apparent. Many of these were beyond the scope of this study, but appear to represent the next set of logical tasks (Figure 24). There is strong evidence that many of the dams in Victoria have infrastructure capable of releasing cold water. The following steps should be undertaken as the next investigative phase: ¾ Undertake a preliminary continuous water temperature monitoring program upstream, within the impoundment and downstream for all maximum and medium research priority dams ¾ Review the operation procedures, release strategies and operation constraints of all dams listed as maximum and medium research priority ¾ Undertake preliminary hydrodynamic assessment of maximum and medium priority dams to determine if stratification is likely. This includes modelling of within dam stratification as well as downstream heat flux calculations ¾ Determine the value of additional monitoring information including all physical and biological datasets for each maximum and medium priority dams ¾ Determine the biological significance of downstream populations of fish, macroinvertebrates and macrophytes (Figure 24)

56 Status of Cold Water Releases from Victorian Dams

11 MEDIUM PRIORITY DAMS + 24 MAXIMUM PRIORITY DAMS

ESSENTIAL MONITORING PROGRAM ADDITIONAL ASSESSMENTS

Stratification and cold Cold water releases water releases? likely to be an issue? NO NO

YES

Review monitoring program Encourage greater monitoring and operation procedures (see following recommendations)

FURTHER MONITORING AND ASSESSMENT

G Instigate large scale temperature monitoring program G Undertaken risk assessment of dam releases G Instigate mitigation investigations and works

Figure 24: Research steps required to determine the extent and impact of cold water pollution in Victoria Once these tasks have been completed, it will be necessary to interrogate the water temperature monitoring data using an approved evaluation technique to determine if stratification is occurring within each impoundment and if cold water releases are being made. If so, a large scale monitoring program will be required to determine the extent of the cold water pollution. Where additional information and assessments (as tasks above) suggest that stratification and cold water releases are unlikely and preliminary water temperature monitoring confirm that there is no downstream impact, these dams could be removed from the maximum and medium research priority lists. Conversely, where additional information indicates stratification and cold water releases are possible, and may be impacting of the downstream environment and biota additional monitoring and assessment is recommended. The additional monitoring involves more intensive water temperature monitoring programs (as mentioned above) as well as a risk assessment of the cold water releases on the downstream environment and aquatic biota. Additionally, a number of steps that be required to formalise and encourage the investigation and implementation of appropriate mitigation works. These tasks are summarised below: • Develop and gain consensus on a monitoring strategy and assessment criteria to be adopted for all maximum and medium priority dams (national coordination may be required (IRN 2001))

57 Status of Cold Water Releases from Victorian Dams

• Encourage additional monitoring effort for all priority dams, including the installation of continuous water temperature loggers at least at one site upstream, and three sites downstream • Encourage a greater monitoring program within dams, including depth profiles and stratification measurements for all maximum and medium priority dams • Investigate the relationship between releases and the extent of cold water pollution for all maximum and medium priority dams • Attempt to minimise current impacts by alterations to release management without compromising water supply to other downstream users • Develop a decision tree to help define the best mitigation options for dams releasing cold water • Develop an agreed approach to prioritise mitigation works on dams in relation to the social, economic and environmental risks and consequences • Encourage a greater community understanding and ownership of the biological consequences of cold water pollution

58 Status of Cold Water Releases from Victorian Dams

CONCLUSION

An investigation of the dam wall size, capacity and release structures and patterns was undertaken to determine the number of Victorian dams that have the potential to contribute to thermal pollution. This report has improved the knowledge base of the extent of cold water pollution in Victoria. By undertaking a scoping study across the state and attempting to determine the extent of the cold water releases, it has achieved two major recommendations from the Thermal Pollution workshop (IRN 2001). The ability of this study to assess the effects of dams on downstream thermal regimes was constrained by the amount and type of temperature data available around ‘candidate’ dams. The number and positioning of monitoring sites, as well as the temporal resolution of available data led to results that were quite variable, and could on occasions be non-representative of thermal conditions above and below dams. The 24 maximum and 11 research priority dams identified was higher than expected. Based on the infrastructure and the release strategies of each of these dams, it is likely that cold water releases are occurring. However, the downstream extent and biological impact for most of these dams is It is important the research steps required to determine the magnitude and extent of cold water pollution outlined in this report are undertaken as soon as possible and not left for another ten years. There is sufficient evidence to demonstrate that aquatic biota are impacted by cold water releases. Mitigation works and alternative release strategies need to be undertaken as soon as cold water releases have been confirmed. Funding for these mitigation works are likely to be limited, however, the directions for future research as provided in this report should help prioritise the more immediate dams requiring amelioration.

59 Status of Cold Water Releases from Victorian Dams

ACKNOWLEDGEMENTS

The authors wish to thank the following people for help and assistance in findings, preparing and completing this report: • The steering committee from the project convened by Paul Bennett and including Pat Feehan (Goulburn-Murray Water), Graham Hawke (Southern Rural Water), John Martin (Wimmera-Mallee Water), and John Woodland (Melbourne Water) • The Catchment and Water Division at the Department of Natural Resources and Environment for providing the funding to undertake this study • The representatives from each of the water authorities that provided information for our survey, with reviews and draft comments, especially those referred to as personal contacts • Dr Angus Webb's managers at the Water Studies Centre at Monash University for permitting extra time and effort required to finish this report and present the findings at the IRN 2000 Workshop • Siraj Perera and Graham Quarrell (Department of Natural Resources and Environment) for initially supplying the data from the Victorian Dams Database • Pam Clunie for reviewing the final draft • People for providing on-hand support including Paul Bennett, Paulo Lay and Tim O'Brien

60 Status of Cold Water Releases from Victorian Dams

REFERENCES

Acaba, Z., Jones, H., Preece, R., Rish, S., Ross, D. and Daly, H. (2000). The Effects of Large Reservoirs on Water Temperature in Three NSW Rivers Based on the Analysis of Historical Data. Sydney, Centre for Natural Resources, NSW Department of Land and Water Conservation: 52 pp.

Alabaster, J. S. and Lloyd, R. (1980). Water Temperature. Water Quality Criteria of Freshwater Fish. London-Boston, Butterworths: pp. 47-84.

Almodóvar, A. and Nicola, G. G. (1999). Effects of a Small Hydropower Station Upon Brown trout, Salmo tutta L., in the River Hoz Seca (Tagus Basin, Spain) One Year After Regulation. Regulated Rivers: Research and Management 15: 477-484.

ANZECC & ARMCANZ (Australian and New Zealand Environment and Conservation Council), Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (2000). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Volume 1. The Guidelines. (Table 3.3.1).

Armour, C. L. (1991). Guidance for Evaluating and Recommending Temperature Regimes to Protect Fish. Washington, U.S Fish and Wildlife Service National Ecology Research Centre. pp. 1 –13.

Baxter, R. M. (1977). Environmental Effects of Dams and Impoundments. Annual Review of Ecology and Systems 8: 255-283.

Bayly, I. A. E. and Williams, W. D. (1973). Inland Water and their Ecology. Longman, Hawthorn. 314 pp.

Blyth, J. D. (1980). Environmental Impact of Reservoir Construction: the Dartmouth Dam Invertebrate Survey: A Case History. In: An Ecological Basis for Water Resource Management. W. D. Williams (ed). Canberra, National University Press: pp.181-191.

Blyth, J. D., Doeg, T. J. and St Clair, R. M. (1984). Response of the Macroinvertebrate Fauna of the Mitta Mitta River, Victoria, to Construction and Operation of Dartmouth Dam. 1. Construction and Initial filling period. Occasional Papers from the Museum of Victoria 1: 83-100.

Boon, P. J. (1988). The impact of river regulation on invertebrate communities in the U.K. Regulated Rivers: Research and Management 2: 389-409.

Boles, G. L. (1981). Macroinvertebrates Colonisation of Replacement Substrate Below a Hypolimnial Reservoir. Hydrobiologia 78: 133-146.

Brizga, S.O and Finlayson, B.L. (1992). The Snowy River Sediment Study: Investigation into the Distribution, Transport and Sources of Sand in the Snowy River between Lake Jindabyne and Jarrahmond. Unpublished report prepared for the Department of Water Resources, Victoria. University of Melbourne, Melbourne, Victoria.

Brown, I.R. (1986). Review of the Application of Aeration/ Destratification Techniques in Australian Surface Water Storages, Engineering and Technical Services Division, Department of Local Government, Queensland.

Cadwallader, P. L. and Gooley, G. J. (1985). Propagation and Rearing of Murray cod Maccullochella peeli at the Warmwater Fisheries Station Pilot Project Lake Charlegrark. Fisheries and Wildlife Service, Department of Conservation, Forests and Lands, Victoria.

Céréghino, R. and Lavandier, P. (1998). Influence of Hypolimnetic Hydropeaking on the Distribution and Population Dynamics of Ephemeroptera in a Mountain Stream. Freshwater Biology 40: 385-399.

61 Status of Cold Water Releases from Victorian Dams

Chessman, B. C. and Robinson, D. P. (1986). Management of Environmental Releases during Reservoir Filling: Lessons from a study of Macroinvertebrate Fauna in the Tanjil River, Victoria, in 1986, National Environmental Information in Engineering, Melbourne, Institution of Engineers Australia National Conference Publication No. 86/2, Institution of Engineers Australia, Canberra, ACT pp. 70-74.

Clarkson, R. W. and Childs, M. R. (2000). Temperature Effects of Hypolimnial-Release Dams on Early Life Stages of Colorado River Basin Big-River Fishes. Copeia 2000 (2): 402- 412.

Cech, J. J. Jr., Mitchell, S. J., Castleberry, D. T. and McEnroe, M. (1990). Distribution of California stream fishes: influence of environmental temperature and hypoxia. Environmental Biology of Fishes 29: 95-105.

Coleman, D. (1978). Downstream Effects of the Gordon Dam, Hydro-Electric Commission, Hobart, Tasmania.

Comargo, J. A. and Voelz, N. J. (1998). Biotic and Abiotic Changes Along the Recovery Gradient of Two Impounded Rivers with Different Impoundment Uses. Environmental Monitoring and Assessment 50: 143-158.

Coutant, C. C. (1987). Thermal Preference: When Does an Asset Become a Liability? Environmental Biology of Fishes 18(3): 161-172.

Coon, T.G. (1987). Responses of Benthic Riffle Fishes to Variation in Stream Discharge and Temperature. In: Community and Evolutionary Ecology of North American Stream Fishes. W.J. Matthews and D.C. Heins (Ed.s), University of Oklahoma Press, Norman. pp. 77-85.

Crawshaw, L. I. (1979). Responses to Rapid Temperature Change in Vertebrate Ectotherms. American Zoologist 19: 225-237.

Crisp, D.T. (1987). Thermal 'Resetting' of Streams by Reservoir Releases with Special Reference to Effects on salmonid fishes. In: Regulated Streams: Advances in Ecology, J.F. Craig and J.B. Kemper (eds) Plenum Press, New York, pp. 163-182.

Doeg, T. J. (1984). Response of the Macroinvertebrate Fauna of the Mitta Mitta River, Victoria, to the Construction and Operation of Dartmouth Dam. 2. Irrigation Release. Occasional papers from the Museum of Victoria 1: 101-108.

DNRE (2000). Victorian Water Resources Data Warehouse, Department of Natural Resources and Environment. 2000. URL http://www.vicwaterdata.net

Elliot, J. M. (1981). Some aspects of Thermal Stress on Freshwater Teleosts. In: Stress in Fish. A. D. Pickering. London and New York, Academic Press: pp. 209-245.

Ellis, M. M. (1941). Freshwater Impoundments. Transactions of the American Fisheries Society. 71: 80- 93, Cited In: Baxter, R. M. (1977). Environmental Effects of Dams and Impoundments. Annual Reviews of Ecology and Systems 8: 255-283.

Fearnside, P. M. (1989). Brazil's Balbina Dam: Environment Versus the Legacy of the Pharoahs in Amazonia. Environmental Management 13: 401-423.

Finlayson, B. L., Gippel, C. J., and Brizga, S.O. (1994). Effect of Reservoirs on Downstream Aquatic Habitat. Water 21: 15-20.

Gippel, C. J., Marchant, R., Stewardson, M. J., Brizga, S. O., Campbell, I.C., Woodfull, I., Finlayson, B. C. and McMahon, T.A. (1992). A Review of Environmental Water Requirements of the Thomson River from Thomson Dam to Cowwarr Weir. Melbourne, Unimelb Limited: 89 pp.

62 Status of Cold Water Releases from Victorian Dams

Gippel, C. J. and Finlayson, B. L. (1993). Downstream Environmental Impacts of Regulation of the Goulburn River, Victoria, Hydrology and Water Resources Symposium, Newcastle, The Institution of Engineers Australia 93/14: 33-38. Goodling, J. S. and Arnold, T. G. (1972). Deep Reservoir Thermal Stratification Model. Water Resources Bulletin of the American Water Resources Association 8 (4): 745-749. Growns, J. (1998). The Campaspe River Project. Water 25(3): 13-14.

Harleman, D. R. F. (1982) Hydrothermal Analysis of Lakes and Reservoirs. Journal of the Hydraulic Division, Proceedings of the American Society of Civil Engineering 108: 302-325.

Harris, J. H. (1997). Environmental Rehabilitation and Carp Control. In: Controlling Carp: Exploring the options for Australia. Proceedings of a workshop 22-24 October 1996. Tilzey R. and Roberts J. (eds) Albury, CSIRO Land and Water, Griffith NSW. 129 pp.

Hokanson, K. E. F., Kleiner, C. F. and Thorslund, T. W. (1977). Effects of Constant Temperatures and Diel Temperature Fluctuations on Specific Growth and Mortality Rates and Yield of Juvenile Rainbow trout, Salmo gairdneri. Journal of Fisheries Research Board of Canada 34: 639-648.

Hutchison, V. H. and Maness, J. D. (1979). The Role of Behaviour in Temperature Acclimation and Tolerance in Ectotherms. American Zoologist 19: 367-384.

Humphries, P. and Lake, P. S. (2000). Fish larvae and the management of regulated rivers. Regulated Rivers: Research and Management 16: 421-432.

Hurlbert S.H. (1984). Pseudoreplication and the Design of Ecological Field Experiments. Ecological Monographs 54(2):187-211.

Hynes, H.B.N (1970). The Ecology of Running Waters. University Toronto Press, Toronto.

IRN (Inland Rivers Network) (2001). Inland Rivers Network News, June 2001. Greg Williams (ed). 6 (2), 27 pp.

Jaske, J.T. and Goebel, J.B (1967). Effects of Dam Construction on Temperature of Columbia River. Journal of the American Water Works Association 59: 935-942.

King, D. L. (1981). Discussion-Section 15, Destratification of Lakes and Reservoirs to Improve Water Quality, F.L. Burns and I.J. Powling (eds). Australian Water Resources Council Conference Series. No.2: 699 pp.

Koehn, J. D. and O' Connor, W. G. (1990). Biological Information for Management of Native Freshwater Fish in Victoria. Freshwater Fish Management Branch, Arthur Rylah Institute for Environmental Research, Department of Conservation and Environment, Melbourne.

Koehn, J. D., Doeg, T. J., Harrington, D. J. and Milledge, G. A. (1995). The Effects of Dartmouth Dam on the Aquatic Fauna of the Mitta Mitta River. Melbourne, Department of Conservation and Natural Resources.

Konstantinov, A. S., Zdanovich, V. V., and Tikhhomirov, D. G. (1989). The Effect of Temperature Fluctuations on Metabolic Rate and Energetics of Juvenile Fish. Voprosy Ikhtiologii 29: 1019-1027.

Krenkel, P. A., Lee, G. F. and Jones, R. A. (1979). Effects of TVA Impoundments on Downstream Water Quality and Biota. In: The Ecology of Regulated Streams. Ward J.V and Stanford J.A. (eds). Plennum, New York. pp. 289-306.

Lake, J. S. (1967). Rearing Experiments with Five Species of Australian Freshwater Fish. Australian Journal of Marine and Freshwater Research 18: 155-173.

63 Status of Cold Water Releases from Victorian Dams

Langdon, J.S., Gudkovs, N., Humphrey, J.D. and Saxon, E.C. (1985). Deaths in Australian Freshwater Fishes Associated with Chilodonella hexasticha Infection. Australian Veterinary Journal 62: 409-413 In: Pusey, B. J., Arthington, A. H. and Kennard, M. J. (1998). Environmental Flow Management in the Australian Landscape. Nathan, Centre for Catchment and Instream Research, Faculty of Environmental Sciences, Griffith University. 321 pp.

Llewellyn, L. C. (1971). Breeding Studies on the Freshwater Forage Fish of the Murray-Darling River System. The Fisherman. June, pp. 1-12.

Llewellyn, L. C. (1973). Spawning, Development and Temperature tolerance of the Spangled perch, Madigania unicolor (Gunther), from the Inland Waters of Australia. Australian Journal of Marine and Freshwater Research 73: 73-94.

Lugg, A. (1999). Eternal Winter in Our Rivers: Addressing the Issue of Cold Water Pollution. NSW Fisheries.

Mackay, N. J. and Shafron, M. (1998). Water quality. Proceedings of the workshop on native fish management. Murray-Darling Basin Commission. Canberra, 16-17 June. pp. 137 –148.

Marchant, R., Graesser, A., Metzeling, L., Mitchell, P., Norris, R. and Suter, P. (1984). Life Histories of some Benthic Invertebrates from the Latrobe River, Victoria. Australian Journal of Marine and Freshwater Research 35: 793-806.

Marchant, R. (1989). Changes in the Benthic Invertebrate Communities of the Thomson River, southeastern Australia, after Dam Construction. Regulated Rivers: Research and Management 4: 71- 89.

Martinez, P. J., Chart, T. E., Trammell, M. A., Wullschleger, J. G. and Bergersen, E. P. (1994). Fish Species Composition Before and After Construction of a Main Stem Reservoir on the White River, Colorado. Environmental Biology of Fishes 40: 227-239.

Matthews, W. J. (1998). Patterns in Freshwater Fish Ecology. Chapman and Hall, New York. 756 pp.

McMahon, T. A. and Finlayson, B. L. (1995). Reservoir System Management and Environmental Flows. Lakes and Reservoirs: Research and Management 1: 65-76.

Milton, D. A. and Arthington, A. H. (1983). Reproduction and Growth of Craterocephalus marjoriae and C. stercusmuscarum (Pisces: Atherinidae) in south-eastern Queensland, Australia. Freshwater Biology 13: 589-597.

Milton, D. A. and. Arthington, A. H. (1984). Reproductive Strategy and Growth of the Crimson-spotted rainbowfish, Melanotoenia splendida fluviatilis (Castelnau) (Pisces: Melanotaeniidae) in south-eastern Queensland. Australian Journal of Marine and Freshwater Research. 35: 75-83.

Milton, D. A. and Arthington, A. H. (1985). Reproductive Strategy and Growth of the Australian smelt Retropinna semoni (Weber) (Pisces: Retropinnidae), and the Olive perchlet, Ambassis nigripinnis (DeVis) (Pisces: Ambassidae) in Brisbane, south-eastern Queensland. Australian Journal of Marine Freshwater Research 36 (3): 329-347.

Mitchell, P. (1999). Mitta Mitta River, Biological Monitoring Program (1987-1996). A Report Prepared for Goulburn-Murray Water. Australian Technologies. 75 pp.

Moyle, P. B. (1976). Inland Fishes of California. University of California Press, Berkeley. 405 pp.

Pozo, J., Orive, E., Fraile, H. and Basaguren, A. (1997). Effects of the Cernadilla-Valparaiso Reservoir System on the River Tera. Regulated Rivers: Research and Management 13: 57-73.

64 Status of Cold Water Releases from Victorian Dams

Precht H., Christopherson J., Hensel, H. and Larcher, W. (1973). Temperature and Life. Springer- Verlag, New York.

Pusey, B. J., Bird, J., Kennard, J. M. and Arthington, A.H. (1997). Distribution of the Lake Eacham Rainbowfish in the Wet Tropics region, north Queensland. Australian Journal of Marine and Freshwater Research 45: 1319 – 1328.

Pusey, B. J., Arthington, A. H. and Kennard, M. J. (1998). Environmental Flow Management in the Australian Landscape. Nathan, Centre for Catchment and Instream Research, Faculty of Environmental Sciences, Griffith University. 321 pp.

Rish, S., Preece, R. and Dudgeon, S. (2000). Status of Temperature Management Capabilities at Water Storages Operated by Department of Land and Water Conservation, Internal Report, Centre for Natural Resources, Department of Land and Water Conservation, NSW. 30 pp.

Rosenberg, D. M, Bodaly, R. A, Hecky, R. E, and Newbury, R.W (1997). The Environmental Assessments of Hydroelectric Impoundments and Diversions in Canada. P 71-104 In: Healy M.C and Wallace R.R (eds). Canadian Aquatic Resources. Canadian Bulletin of Fisheries and Aquatic Science. 215.

Rowland, S. J. (1983). Spawning of the Australian Freshwater Fish Murray cod, Maccullochella peeli (Mitchell), in Earthen Ponds. Journal of Fish Biology 23: 525-534.

Saddlier, S. R. and Doeg, T. J. (1997). The Fish and Aquatic Macroinvertebrate Fauna of the Yarra River: The impacts of 4 years of an Environmental Water Release from the Upper Yarra Reservoir. A Consultants Report. Marine and Freshwater Resources Institute, Department of Natural Resources and Environment. Victoria. 43 pp.

Saltveit, S. J., Bremnes, T., and Brittan, J.E. (1994). Effect of a Changed Temperature Regime on the Benthos of a Norwegian Regulated River. Regulated Rivers: Research and Management 9: 93-102.

Sherman, B. S. (2000). Mitigating Cold Water Pollution Below Dams. ANCOLD 2000 Conference on Dams.

Sweeney, B. W. and Vannote, R. L. (1978). Size Variation and the Distribution of Hemimetabolous Aquatic Insects: Two Thermal Equilibrium Hypotheses, Science 200: 444-446.

Tanck, M. W. T., Booms, G. H. R., Eding, E. H., Bonga, S. E. W. and Komen, J. (2000). Cold Shocks: A Stressor for Common Carp. Journal of Fish Biology 57: 881-894.

Thoms, M., Suter, P., Roberts, J., Koehn, J., Jones, G., Hillman, T. and Close, G. (1998). River Murray- Dartmouth to Wellington and the Lower Darling River. Report of the River Murray Scientific Panel on Environmental Flows. Murray-Darling Basin Commission. Canberra.

Vannote, R. I. and Sweeney, B. W. (1980). Geographic Analysis of Thermal Equilibria: A Conceptual Model for Evaluating the Effect of Natural and Modified Thermal Regimes on Aquatic Insect Communities. The American Naturalist 115(5): 667-695.

Vannote, R. L., Minshall, G. W., Cummins, K.W., Sedell, J.R, and Cushing, C.E. (1980). The River Continuum Theory. Canadian Journal of Fisheries and Aquatic Science 37(1): 130-137.

Walker, K. F. (1979). Regulated Streams in Australia: The Murray-Darling River System. In: The Ecology of Regulated Streams. Ward, J. V. and Stanford, J. A (eds), Plenum Press. New York. Pp 143- 163.

Walker, K. F. (1980). The Downstream Influence of Lake Hume on the River Murray. In: An Ecological Basis for Water Resource Management. Canberra. Williams, W. D. (ed) Australian National University Press: pp.182-191.

65 Status of Cold Water Releases from Victorian Dams

Walker K. F. (1985). A Review of the Ecological Effects of River Regulation in Australia. Hydrobiologia 125: 111-129.

Ward, J. V. (1976a). Comparative Limnology of Differentially Regulated Sections of a Colorado Mountain River. Archiv fur Hydrobiologie 78: 319-342.

Ward, J. V (1976b). Effects of Thermal Constancy and Seasonal Temperature Displacement on Community Structure on Stream Macroinvertebrates. Thermal Ecology, II. Esch, G. W. and McFarlane, R.W. (eds), ERDA Symp. Ser. (CONF.-750425): pp. 302-307.

Ward, J. V. and Stanford, J. A. (1979). Ecological Factors Controlling Stream Zoobenthos with Emphasis on Thermal Modification of Regulated Streams. In: First International Symposium on Regulated Streams. Ward, J. V. and Stanford, J. A (eds), Eyrie, Pennsylvania, Plenum Press. pp. 35 – 55.

Ward, J. V. and J. A. Stanford (1982). Thermal Responses in the Evolutionary Ecology of Aquatic Insects. Annual Review of Entomology 27: 97-117.

Ward, J. V. (1985). Thermal Characteristics of Running Water. Hydrobiologia 125: 31-46.

Whittington, J. and Hillman, T. (1999). Sustainable Rivers: the Cap and Environmental Flows, 14-page colour brochure, Cooperative Research Centre for Freshwater Ecology and Murray-Darling Freshwater Centre, Albury, NSW.

Wieser, W. (1973). Temperature Relations of Ectotherms: A Speculative Review. In: Effects of Temperature on Ectothermic Organisms. Wieser, W. (ed) pp. 1-24.

66 Status of Cold Water Releases from Victorian Dams

Personal contacts Doug Connors (Manager Operations) Southern Hydro Kiewa Valley Hwy, Mount Beauty, 3699 Phone (03) 5754 3222 e-mail: [email protected]

Bruce Duncan (Headworks Manager) Coliban Water 2 Alder Street, Golden Square, 3555 Phone (03) 54341222

Darren Dumesny (Newstead Customer Service Centre) Mount Alexander Shire Council Technical Services, Planning, Building and Health Lyons Street, Castlemaine, 3450 Phone (03) 5471 1750

Wayne Francisco (Headworks Business Planner) Goulburn-Murray Water 40 Casey Street, Tatura, 3616 Phone (03) 5833 5719 e-mail: [email protected]

Geoff Harris (Dam Operations Manager) Southern Rural Water 88 Johnston Street, Maffra, 3860 Phone (03) 5139 3131

Ian Kitchenn (Manager - Headworks Assets) Southern Rural Water 88 Johnston Street, Maffra, 3860 Phone (03) 5139 3131

Peter Liepkalins (Dam Operations Manager) Goulburn-Murray Water Dartmouth Dam, Victoria, 3701 Phone (02) 6072 4411 e-mail: [email protected]

Simon Nicol (Freshwater Ecology) Arthur Rylah Institute, Department of Natural Resources and Environment 123 Brown Street, Heidelberg, 3084 Phone (03) 9450 8641 e-mail: [email protected]

Siraj Perera (Senior Policy Analyst- Catchment and Water Division) Department of Natural Resources and Environment 240-250 Victoria Pde, East Melbourne, 3002 Phone (03) 9412 4062 e-mail: [email protected]

Bruce Wallin Gippsland Water Hazelwood Road, Tralagon, 3844 Phone (03) 5177 4600

Rob Yurisich (Water Resources Engineer) Melbourne Water Planning Division, 68 Ricketts Rd., Mt. Waverley, 3000 Phone: (03) 9565 1913

67 Status of Cold Water Releases from Victorian Dams

Appendix A: Dams greater than 5 m and associated temperature research priority level

Dam Ref. No. Name Height Capacity Priority Reason / Comment

Barwon Water 61 Bostock Reservoir 25 7500 Max 0.8 - 1.2 ML/day BE release required from low level valve only 0.1 - 0.6 ML/day BE release required to East Branch of Moorabool River 64 Korweinguboora Reservoir 12 2091 Min (15km to Bostock) 74 Upper Stoney Creek No. 1 26.2 3443 Min No passing environmental flow required, but capable of releases throught new outlet tower 77 West Barwon Reservoir 43 21898 Max 3 - 10 ML/d environmental flows. Releases 9.8m and 21.8m below FSL No passing environmental flow required, but capable of releases from multi-level offtake 55 West Gellibrand Dam 21.34 2000 Min (Large Volume)

Central Highlands Water 12 Gong Gong Reservoir 23.8 1905 Min Releases via pipeline to Lake Wendouree ONLY 250 Lal Lal Reservoir 48 59549 Med Releases from multilevel tower at greatest depth of release ~8 m Inoperative multi-level tower with three valves constantly open at 1, 5.2, 9.4 m 16 Moorabool Reservoir 13.7 6737 Med below FSL

Coliban Water 33 Barkers Creek Reservoir 13 2700 Med Outlet remodelling scheduled including floating arm to reduce depth of summer releases Last of three storages. Environmental releases from multi-level offtake to Coliban 42 Malmsbury Reservoir 24 18000 Max River via channel

East Gippsland Water 240 Nicholson Dam 10.5 640 Min Three outlets at 4m, 7.5m and 9.5m below FSL - operated to minimise effects

Gippsland Water 79 Buckleys Hill 7 250 None Offstream to power station 80 Clarkes Road 10.5 120 None Offstream - used by Loy Yang 81 Erica 7 60 None OffstreamTown Supply 83 Hazelwood No. 5 8.3 840 None Offstream - power station 84 Main Storage Dam - Pine Gully 17 448 None Offstream- used by Australian Paper 85 Moondarra Reservoir 39.6 30311 Med Butterfly valve - Releases from multi-level offtake at greatest depth of 6.5 m

Glenelg Region Water Authority 88 Cruckoor Reservoir 9.5 990 None No comment provided 89 Dunkeld - Basin No 2 5.3 36 None No comment provided 90 Dunkeld - Storage No. 3 13 112 None No comment provided 91 Dunkeld Basin No. 1 7 36 None No comment provided 94 Hartwichs Reservoir 8 380 None No comment provided 95 Hayes Reservoir 8 1200 None No comment provided 96 Konong Wootong 8.5 1900 None No comment provided 98 Mt. Rouse 7.9 90 None No comment provided 99 Old Reservoir 5.5 125 None Domestic supply to pipeline 100 Service Basin No. 1 5 65 None No comment provided 101 Service Basin No. 2 5 65 None No comment provided

Goulburn-Murray Water FSL at 264.4m, outlet pipes incorporated in spillway structure at 255, spillway at 195 Buffalo 30 24000 Med 256.3m (max 9.4m below FSL) FSL: 208.46, top release from 189.4m (19.1 mm below FSL)Annual stratification, 186 Cairn Curran Reservoir 44 148800 Max Annual algal blooms 102 Campaspe Weir 12.8 2700 None Regulating pondage, surface spill gates FSL: 288.9, top release from 240m (48.9m below FSL)Annual stratification, algal 197 Eildon 79.2 3390000 Max blooms 2 in five years 188 Eildon Pondage Weir 12 5100 Min Sluice Gate at 217.6 AHD FSL: 193.91, top release from 190.3m (3m below FSL), lowest at 163.4m (30.5m 189 Eppalock Reservoir 45 312000 Max below FSL) Annual stratification 191 Goulburn Weir 15 35400 None Regulating pondage, surface spill gates 192 Hepburns Lagoon 6 3000 Min Unknown FSL: 160.20, pipe release at 150.4m (9.8m below FSL) Annual stratification, 193 Laanecoorie Reservoir 22 8000 Max occasional algal blooms 205 Mildura Weir 6.7 36200 None Regulating pondage, surface spill gates 200 Mokoan 13.7 365000 None FSL: 166.93, top release from 159m (7.9m below FSL) annual algal blooms 104 National Offtake 7.3 36800 None Regulating pondage, surface spill gates 206 Newlyn Reservoir 12 3300 Med FSL: 532.09, top release from 524.8m (7.3m below FSL) Annual stratification FSL: 264.5, top release from 248.4m (16.1m below FSL) Annual stratification, 207 Nillahcootie Reservoir 34.3 40000 Max algal blooms 2 in 5 years FSL: 86.05, top release from 80m (6m below FSL) infrequent stratification, Torrumbarry Weir 10.5 36,000 Min potential algal blooms FSL: 222.8, top release from 210.1m (12.7m below FSL) Annual stratification, agal 215 Tullaroop Reservoir 42 74000 Max blooms 4 years in 5 216 Waranga Basin 12.2 411000 None Regulating pondage, surface spill gates 280 Warrigal Creek 6.4 0 None FSL: 408.12, top release from 389.7m (bellmouth 18.4m below FSL) Annual 201 William Hovell 37.3 13500 Max stratification, algal blooms 1 in 5 years

68 Status of Cold Water Releases from Victorian Dams

Appendix A: (Cont.)

Dam Ref. No. Name Height Capacity Priority Reason / Comment

Goulburn Valley Water 129 55 ML Storage 7 55 None Off river storage 164 Andersons Road No. 3 8.5 66 None Off river storage 166 Aub Cuzens 9 100 None Off river storage 167 Broadford No. 2 11 32 None Out of service 168 Broadford No. 3 12 100 None Off river and discharges to pipe 165 Hollow Back 7.8 117 None Off river storage 112 New Honeysuckle 10.7 122 None Spillway to be decommissioned 130 No. 3 Storage 7 40 None Off river storage 277 Polly McQuinn Weir 13 136 None Dam silted to depth of ~ 1 m 131 Ritchie Reservoir 7.6 180 None Off river storage 169 Sunday Creek Reservoir 30 1700 Min Releases from multi-level offtake at greatest depth of 6 m 171 Wallan Service Basin 13.8 87 None Off river storage

56 Waterhouse Dam 17 250 None Spillway

Grampians Region Water Authority 254 Birchip No. 5 5 229 None Off river storage 255 Dimboola 6 400 None Off river storage 235 Halls Gap Reservoir 7.5 66 None Off river storage 2 Langhi Ghiran Reservoir 10 68 None No environmental releases, spillway flows only 109 Marnoo 6 72 None Off river storage 110 Minyip 1,2 7 70 None Off river storage 111 Minyip 3 5 230 None Off river storage 3 Mt Cole Reservoir 27.5 810 None No environmental releases, spillway flows only 260 Natimuk 2 5.8 110 None Off river storage 4 Olivers Gully Reservoir 10.7 340 None Off river storage 262 Ouyen No. 3 5.5 146 None Off river storage 236 Panrock Creek Reservoir 8 77 Min Low use but may discharge to small stream 265 Rainbow No. 5 5.5 121 None Off river storage 267 Rupanyup 4 5 74 None Off river storage 234 Service Basin No. 6 7.6 119 None Off river storage

Hepburn Shire 311 Daylesford Lake 14 800 None Release structures currently under review. Currently only capable of spilling

Melbourne Water 135 Beaconsfield Reservoir 24 912 None Off river storage 136 Bittern Reservoir 7.6 566.5 None Off river storage Releases made from outlet at 1/3 FSL to pipeline. Joins Cardinia Creek several kms 137 Cardinia Reservoir 86 286911 Max downstream 138 Devilbend Reservoir 19.8 14600 None Off river storage 139 Dromana 10 79 None Off river storage 140 Frankston Reservoir 19 680 None Off river storage 141 Gembrook 11.6 55 None Off river storage (Yarra Valley Water) 142 Greenvale Reservoir 52 27501 None Off river storage 143 Johns Hill 26.2 375 None Off river storage (Yarra Valley Water) 144 Maroondah Reservoir 41.1 28199 Med 1 ml/d from low level, which may be entire flow during dry periods. 145 Merricks Basin 5.5 55 None Off river storage (South East Water) 146 Mornington 7 218 None Off river storage 147 Mt. Eliza 5.5 60 None Off river storage (South East Water)

148 O'Shannassy Reservoir 34 3123 Max 3 ml/d supplemented by spills. During summer, low level release may be entire flow 149 Packenham No. 2 7 101 None Off river storage 150 Rosedale Grove 5.5 52 None Off river storage (South East Water) 151 Rosedale Grove No. 2 7 115 None Off river storage (South East Water) 152 Running Creek Reservoir 18 255 None Almost all inflow downstream via a low-level scour

153 Silvan Reservoir 40 40581 Max 2 ml/d from offtake approximately 2/3 of the way from the bottom of the reservoir 154 Sugarloaf Reservoir 89 99222 None Off river storage

155 Tarago Reservoir 34 37574 Med Most inflow released downstream from fixed level port 4-9 m below surface level 156 Thomson Reservoir 166 1123089 Min Releases drawn from 6 m below surface using variable level offtake 281 Thomson Saddle Dam 30 1123089 None Releases drawn from 6 m below surface using variable level offtake 157 Toorourrong Reservoir 7 300 None 0.2 ml/d environmental flow released. Not described as low level release 158 Tyabb Storage 8 318 None Off river storage 159 Upper Yarra Reservoir 89 204985 Max 10 ml/d from outlet 15 m below FSL 160 Westernport No. 1 Basin 5.5 68 None Off river storage (South East Water) 161 Whitelaws Weir 10 None Spillway 162 Yan Yean Reservoir 9.6 33085 None Off river storage

Mount Alexander Shire 36 Expedition Pass Reservoir 18 300 Med Poor quality water released from low-level valve periodically

Murray-Darling Basin Commission 283 Hume Weir 48.2 3038000 Max Releases made at 34.3 m below FSL mostly through power station (20,000 ML/d)

69 Status of Cold Water Releases from Victorian Dams

Appendix A: (Cont.)

Dam Ref. No. Name Height Capacity Priority Reason / Comment

North East Water 239 Dartmouth Water Storage 10 87 None Spillway 26 Kerferd 11 900 None Spillway

27 Loombah Weir 13.5 677 Max Last of two storages. Environmental flow releases to Ryans Creek via multi-level offtake 28 McCall - Say 22.8 1133 None All releases directly to Loombah Weir 181 Nill Gully 12.5 410 None Off river storage 247 Springhurst 11.79 40 None Spillway

Northern Grampians Shire 310 Teddington No 2 10 810 None Nearly all water piped to town

South Gippsland Water 222 Battery Creek Storage 14 96 None No discharge 121 Bellview Creek Reservoir 14 454 None Top or mid-level discharge 224 Foster Service Basin 6 27 None No discharge 125 Hyland Reservoir (No 3) 17 800 None Discharges to Hyland no. 2 269 Inverloch Storage Basin 6 227 None No discharge 270 Lance Creek Reservoir 14.2 4600 None Artificially destratified 122 Little Bass Reservoir 9.8 250 None Artificially destratified 123 Ness Gully Creek 11.3 105 None Floating arm offtake 124 No. 2 Basin (Reservoir no. 1) 11 205 None Artificially destratified 127 Reservoir No. 2 5 182 None discharges to Reservoir no. 1 226 Toora/Port Franklin Service Basin 6 30 None No discharge 128 Western Reservoir (No 4.) 17 1137 None Discharges to Hyland

South West Water 228 Cobden 6 51 None Offstream to pipeline 229 Donalds Hill 5.41 207 None Offstream to pipeline 230 Mt. Ewen 6 625 None Offstream to pipeline 232 Tank Hill 18.89 774 None Offstream to pipeline 233 Warrnambool Storage Basin 5 320 None Offstream to pipeline

Southern Grampians Shire 97 Hamilton (Lake) 6.1 600 None Scour valve used occasionally to empty lake. Takes ~8 weeks

Southern Hydro

295 Mt Beauty Regulator 20 900 Max Final discharge point for Southern Hydro system generating flows and environmental flows

Southern Rural Water Butterfly valve - 5 offtakes at 6 m intervals. Top one 6 m below FSL. Seasonal releases 300- 185 Blue Rock Reservoir 75 208000 Med 400 ML/d to Tanjil 190 Glenmaggie Reservoir 37 190400 Max 2 subsurface offtakes (3m below FSL), lower offtakes - top one 16 m below FSL 308 Lake Narracan 16.5 8000 Med Single lift gate 6 m below FSL. Average flows 400-500 ML/d to Latrobe R. Single intake at base of reservoir 15 m below FSL. Discharges to Werribee R. at peaks 270 203 Melton Reservoir 35 17150 Max ML/d with median 100 ML/d Merrimu Reservoir 34 35000 Max Multi-level outlet, with offtakes at 6 m intervals over the height of the dam. Single intake at base of reservoir 20 m below FSL. 2 km to junction with Werribee River. 209 Pykes Creek Reservoir 39 24500 Max Maximum seasonal flows 100-130 ML/d Mutlilevel offtake (4m, 8m, 12m below FSL with additional lower offtakes) Small releases to 211 Rosslynne Reservoir 36 24500 Min Jacksons Creek

Wimmera-Mallee Water FSL at 276.5, bottom release at 240.2 (36.3M below FSL). Discharges 100-250 ML/d 194 Bellfield 36 78500 Max during dry years to Fyans creek FSL at 195.5m, single release at 182.1m (13.4m below FSL). Summer 210 Rocklands Reservoir 17 248000 Max environmental flows 10-50 ML/d into Glenelg River FSL at 441.7m, number of releases at 437.4m (4.3 m below FLS). Continuous 217 Wartook Reservoir 8.2 29400 Min dicharge of 5 - 35 ML/d to McKenzie River

Red cells associated with maximum research priority dams Orange cell associated with medium priority research dams Yellow cells associated with minimum research priority dams

70 Status of Cold Water Releases from Victorian Dams

Appendix B: Summary Statistic for all sites presented in report

Dam Site Number Maximum Temperature Minimum Temperature Temperature Variation No. of days over No. of Period of data avg sd median avg sd median avg sd median 18+ 20+ Readings

Maximum Priority Dams

Dartmouth 401203 (u/s) 21.2 2.0 21.0 3.9 1.1 4.0 17.2 2.3 17.0 47 31 224 (1/11/80 - 30/4/99) 401211 (d/s) 17.7 3.6 17.0 8.4 0.8 8.0 9.2 3.9 9.0 32 18 227 (1/11/80 - 30/4/99) 401204 (d/s) 22.6 3.0 23.0 7.0 0.9 7.0 15.6 3.2 15.3 260 159 1211 (1/11/80 - 30/4/99)

Hume Dam Jingellic (u/s) 26.0 1.7 26.0 6.6 1.0 6.5 19.4 1.9 19.5 250 174 710 (1/1/85 - 30/12/99) Heywoods (d/s) 22.4 1.1 22.9 8.5 1.2 8.5 13.7 0.9 13.7 206 141 632 (1/1/85 - 30/12/99) Hume 26.3 1.1 26.3 9.0 1.0 9.1 17.2 1.8 17.3 299 245 632 (1/1/85 - 30/12/99) Yarrawonga (d/s) 25.1 1.9 26.0 8.0 2.3 8.0 17.0 1.5 17.0 240 181 559 (1/1/85 - 30/12/99)

Mt. Beauty Pondage 402223 (a/s) 17.1 1.8 17.5 4.5 1.3 4.0 12.4 2.4 13.0 6 2 94 (1/5/91 - 30/4/99) 402206 (a/s) 20.0 2.4 20.0 6.9 1.4 7.0 13.1 2.6 13.0 24 16 68 (1/11/75 - 30/4/88) 402203 (d/s) 21.3 2.4 21.0 4.8 0.9 5.0 16.6 2.3 16.5 37 27 177 (1/11/75 - 30/4/88) 402203 (d/s) 20.1 2.2 19.5 5.9 1.0 6.0 13.9 2.3 14.0 15 7 94 (1/5/91 - 30/4/99)

Lake William Hovell 403244 (a/s) 16.7 2.0 16.0 6.3 1.3 6.0 10.1 2.3 10.5 6 2 120 (1/12/86 - 30/4/99) 403228 (d/s) 20.9 2.2 20.0 6.9 1.1 7.0 13.9 2.7 13.5 21 11 88 (1/11/91 - 30/4/99) 403240 (d/s) 21.6 21.6 9.0 2.1 9.0 11.1 11.1 2 1 8 (1/6/79 - 30/8/82) 403223 (d/s) 24.9 1.8 25.5 7.7 0.8 7.8 17.1 2.3 17.8 50 38 112 (1/11/91 - 30/4/99)

Lake Nillahcootie and 404208 (a/s) 23.3 1.5 24.0 7.3 2.3 7.5 15.9 2.7 16.0 44 31 132 (1/11/76 - 30/4/88) Loombah Weir 404206 (d/s) 21.7 1.5 22.0 7.6 1.5 8.0 14.2 2.1 14.0 94 56 260 (1/11/76 - 30/4/99) 404216 (d/s) 24.7 1.8 24.0 8.6 1.8 8.0 16.3 1.9 16.0 114 94 236 (1/11/79 - 30/4/99) 404207 (d/s) 24.7 2.8 25.0 7.8 1.3 8.0 16.8 2.9 17.0 115 84 280 (1/11/76 - 30/4/99)

Lake Eildon 405227(u/s) 20.2 2.5 20.0 6.6 1.7 7.0 13.6 3.7 12.5 30 15 179 (1/11/76 - 30/10/90) 405214 (u/s) 22.9 2.4 24.0 6.0 1.5 6.0 17.0 2.7 17.0 74 52 265 (1/11/76 - 30/4/99) 405219 (u/s) 21.5 2.5 21.0 6.1 1.7 7.0 15.6 3.3 16.0 43 22 229 (1/11/76 - 30/4/99) 405218 (u/s) 22.7 2.5 22.5 5.5 1.3 6.0 17.2 3.1 17.0 38 20 135 (1/11/76 - 30/4/88) 405203 (d/s) 14.7 2.0 15.0 9.4 0.7 9.5 5.2 2.2 5.0 3 0 268 (1/11/76 - 30/4/99) 405203 (d/s) 15.0 1.9 15.0 9.3 0.7 9.0 5.5 2.2 5.0 3 0 231 (1/11/76 - 30/4/99) 405203 (d/s) 14.9 1.6 15.0 9.3 0.7 9.0 5.6 2.0 5.5 2 0 166 (1/11/76 - 30/10/90) 405203 (d/s) 15.3 1.4 15.0 9.2 0.8 9.0 6.3 1.7 6.0 2 0 136 (1/11/76 - 30/4/88) 405202 (d/s) 18.3 1.4 18.0 5.9 6.3 7.5 12.9 5.9 10.5 24 3 173 (1/11/76 - 30/10/90)

Malmsbury Reservoir 406213 (a/s) 24.6 2.2 24.0 6.7 1.0 7.0 17.9 2.4 18.0 120 87 295 (1/11/76 - 30/4/99) 406215 (d/s) 24.1 3.0 24.0 6.3 1.3 6.0 17.7 3.5 18.0 103 67 292 (1/11/76 - 30/4/99)

Lake Eppalock 406215 (u/s) 24.1 3.0 24.0 6.3 1.3 6.0 17.7 3.5 18.0 103 67 293 (1/11/76 - 30/4/99) 406213 (u/s) 24.6 2.2 24.0 6.7 1.0 7.0 17.9 2.4 18.0 120 87 296 (1/11/76 - 30/4/99) 406207 (d/s) 18.5 1.6 18.0 8.0 1.0 8.0 10.5 1.7 10.5 40 6 265 (1/11/76 - 30/4/99) 406202 (d/s) 25.5 1.9 26.0 8.2 0.9 8.0 17.2 1.9 17.5 477 356 1107 (1/11/76 - 30/4/99)

Cairn Curran, Tullaroop 407215 (u/s) 23.0 2.0 22.8 7.0 0.8 7.0 15.9 2.0 15.8 109 72 298 (1/11/76 - 30/4/2000) and Laanecoorie 407221 (u/s) 22.8 2.2 23.0 6.9 0.7 6.9 16.0 2.2 15.8 94 60 277 (1/11/76 - 30/4/2000) 407220 (u/s) 21.3 1.9 21.5 8.1 1.1 8.3 13.1 2.0 12.8 74 42 234 (1/01/91 - 30/4/99) 407222 (u/s) 22.6 1.6 22.0 6.5 0.9 6.0 16.0 1.4 16.0 47 28 137 (1/11/76 - 30/4/2000) 407210 (d/s) 21.8 1.7 21.5 8.6 0.7 8.5 13.3 1.9 13.0 63 41 144 (1/11/77 - 30/4/99) 407203 (d/s) 23.7 1.2 24.0 8.5 0.9 8.7 15.2 1.7 15.5 127 90 265 (1/11/76 - 30/4/2000) 407229 (d/s) 24.2 1.4 24.0 9.0 0.9 9.0 15.1 1.2 15.0 48 34 102 (1/11/76 - 30/4/2000)

Lake Bellfield 415217 (u/s) 17.3 2.1 17.0 7.8 0.9 8.0 9.6 2.5 9.0 6 3 154 (1/11/75 - 30/4/90) 415214 (d/s) 20.6 2.0 21.0 9.1 1.1 9.0 11.6 2.0 11.0 37 22 171 (1/11/75 - 30/4/90)

Glenmaggie Reservoir 225230 (a/s) 22.7 3.6 22.0 6.5 1.2 6.5 16.5 3.8 17.0 50 33 138 (1/11/76 - 30/4/87) 225209 (u/s) 24.0 2.8 23.0 6.5 1.1 6.0 17.4 3.2 16.5 101 71 295 (1/11/76 - 30/4/99) 225204 (d/s) 22.6 1.7 22.0 9.2 0.8 9.0 13.6 1.8 13.5 68 47 148 (1/11/76 - 30/4/87) 225204 (d/s) 22.2 1.5 22.0 9.0 0.8 9.0 13.2 1.7 13.0 123 85 293 (1/11/76 - 30/4/99)

Cardinia 228217 (a/s) 21.3 1.3 22.0 7.9 1.6 7.5 13.4 2.3 13.0 49 27 155 (1/11/76 - 30/4/90) 228228 (d/s) 22.6 2.2 22.0 7.8 1.9 8.0 15.1 2.7 15.5 51 33 153 (1/11/76 - 30/4/90)

Upper Yarra Valley 229108 (d/s) 19.2 1.5 19.0 7.0 1.3 7.0 12.3 0.9 12.0 17 4 78 (1/11/76 - 30/4/93) 229212 (d/s) 18.3 2.1 18.0 7.3 1.3 7.0 11.0 2.5 11.0 26 6 256 (1/11/76 - 30/4/99) 229653 (d/s) 19.8 2.6 20.5 8.8 1.0 8.5 11.0 3.5 12.0 7 4 29 (1/11/91 - 30/11/93)

Pykes Creek Reservoir 231225 (a/s) 18.9 2.5 18.0 6.3 1.4 6.0 12.1 2.3 12.5 18 6 141 (1/5/77 - 30/4/90) 231203 (d/s) 18.2 1.2 18.0 7.1 1.2 7.0 11.3 1.4 11.5 23 3 151 (1/5/77 - 30/4/90)

71 Status of Cold Water Releases from Victorian Dams

Appendix B: Cont.

Dam Site Number Maximum Temperature Minimum Temperature Temperature Variation No. of days over No. of Period of data avg sd median avg sd median avg sd median 18+ 20+ Readings Merrimu Reservoir 231224 (u/s) 25.1 2.1 25.3 8.3 1.0 8 16.2 2.4 16.6 34 21 14 (12/10/77 - 20/2/84)

Melton Reservoir 231211 (u/s) 22.5 2.1 22.5 7.7 1.5 8.0 15.0 1.7 14.0 16 11 39 (1/11/86 - 30/4/90) 231205 (d/s) 20.5 1.0 20.0 9.0 1.0 9.0 11.7 1.5 12.0 15 8 42 (1/11/86 - 30/4/90)

West Barwon Dam 233214 (d/s) 17.6 1.7 18.0 7.7 1.3 8.0 9.9 2.2 10.0 16 3 251 (1/11/77 - 30/4/99) 233224 (d/s) 22.4 2.3 22.0 8.5 1.9 8.0 14.2 2.8 14.0 70 41 224 (1/11/77 - 30/4/99)

Rocklands Reservoir 238231 (u/s) 19.0 3.5 18.0 7.0 1.6 7.0 12.2 3.6 12.0 29 12 267 (1/9/75 - 30/6/99) 238205 (d/s) 23.7 1.7 24.0 8.8 0.9 8.5 14.8 2.3 15.0 42 29 144 (1/4/91 - 30/4/99) 238224 (d/s) 23.4 1.8 23.5 8.9 1.8 9.0 14.7 2.1 14.5 114 80 267 (1/9/75 - 30/6/99)

Medium Priority Dams

Lake Buffalo 403222 (u/s) 20.9 2.3 20.5 5.9 1.5 6.1 15.0 3.0 14.3 37 23 163 (1/11/76 - 30/4/90) 403220 (d/s) 22.2 1.4 22.0 7.6 0.8 8.0 14.8 1.5 14.0 54 35 137 (1/11/76 - 30/4/90)

Narracan 226408 (a/s) 22.1 2.2 22.0 9.3 1.0 10.0 13.1 3.0 14.0 25 11 96 (1/5/91 - 30/4/99) 226005 (d/s) 23.0 2.1 22.0 10.2 1.7 10.0 12.8 1.5 13.0 118 80 254 (1/11/77 - 30/4/99)

Tarago 228212 (a/s) 17.3 2.0 18.0 6.2 2.5 6.0 11.4 2.5 12.0 12 2 149 (1/11/76 - 30/4/90) 228206 (u/s) 17.4 1.5 17.5 7.0 1.5 7.2 10.7 2.0 9.9 9 2 153 (1/11/76 - 30/4/90) 228219 (d/s) 18.4 1.8 18.8 7.7 2.4 8.0 10.9 2.5 10.5 21 11 151 (1/11/76 - 30/4/90)

Lal Lal Reservoir 232110 (u/s) 20.0 3.3 20.0 5.6 1.4 6.0 14.1 3.0 14.0 45 17 251 (1/11/76 - 30/4/99) 232211 (d/s) 19.4 2.1 19.0 6.3 1.5 6.0 13.1 2.1 13.0 29 10 153 (1/11/76 - 30/4/90) 232204 (d/s) 19.6 2.0 19.0 6.5 1.5 6.7 13.1 1.8 12.5 57 20 287 (1/11/76 - 30/4/2001)

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