Effectiveness of cold water pollution mitigation at Burrendong Dam using an innovative thermal curtain

Gray, Rachel Leigh

Effectiveness of cold water pollution mitigation at Burrendong Dam using an innovative thermal curtain

Gray, Rachel Leigh

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Publication Type:: Thesis
Issue Date:: 2016

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Field	Value	Language
dc.contributor.author	Gray, Rachel Leigh
dc.date.accessioned	2016-06-27T00:38:40Z
dc.date.available	2016-06-27T00:38:40Z
dc.date.issued	2016
dc.identifier.uri	http://hdl.handle.net/10453/44199
dc.description	University of Technology Sydney. Faculty of Science.	en_AU
dc.description.abstract	Many dams in Australia are known to create thermal pollution in rivers, often for hundreds of kilometres downstream of the dam wall. Low-level releases from a reservoir during periods of thermal stratification disrupt the downstream thermal regime by supressing the water temperature and reducing the diel variation. Low-level releases have also been linked to elevated nutrient concentrations and altered phytoplankton density and community structure downstream from the dam. To reduce the problem, Burrendong Dam has been fitted with an innovative thermal curtain that directs warmer surface water to the low-level off-take. This study set out to quantify the magnitude and extent of cold water pollution along the Macquarie River downstream of Burrendong Dam before and after the curtain was implemented. It also aimed to quantify the effect of the dam on nutrient concentrations and phytoplankton density (indicated by chlorophyll a concentrations) and community structure before and after thermal curtain operation. This was achieved through analysis of time-series data from temperature loggers installed within the impoundment, upstream and downstream in the Macquarie River, prior to the installation of the thermal curtain. Water samples for analysis of nutrients, phytoplankton concentrations (chlorophyll a) and community structure were collected within the reservoir and upstream and downstream of the dam. CWP was shown to be a long-term problem in downstream river reaches, caused by the release of hypolimnial waters from the dam. Epilimnial releases with use of the curtain improved the thermal regime (mean daily and mean monthly temperature, and diel temperature range) below the dam so that it more closely resembled the upstream thermal regime with an improvement of approximately 2°C. Fluctuations in nutrients occurred in the hypolimnion of Burrendong Dam during thermal stratification, probably due to the development of an oxycline and subsequently low oxygen concentrations in the hypolimnion. Nutrient concentrations increased at the outlet as a result of hypolimnial releases, with the concentrations breaching the trigger values outlined by ANZECC which indicate ecological disturbance. This study found a substantial increase in the cell count of cyanobacteria at the dam outlet, which may lead to water quality issues in the Macquarie River downstream of the dam. The results of this study will be useful to assist in the management routine of the thermal curtain at Burrendong Dam, to maximise the efficiency of CWP mitigation, whilst not compromising the downstream ecological health in terms of nutrient and cyanobacteria concentrations.	en_AU
dc.format	Thesis (MSc)
dc.language.iso	en_AU	en_AU
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/44199/2/02whole.pdf
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	au.edu.uts.lib/ppc
dc.rights	info:eu-repo/semantics/openAccess
dc.title	Effectiveness of cold water pollution mitigation at Burrendong Dam using an innovative thermal curtain	en_AU
dc.type	Thesis	en_AU
utslib.copyright.status	open_access

Abstract:

Many dams in Australia are known to create thermal pollution in rivers, often for hundreds of kilometres downstream of the dam wall. Low-level releases from a reservoir during periods of thermal stratification disrupt the downstream thermal regime by supressing the water temperature and reducing the diel variation. Low-level releases have also been linked to elevated nutrient concentrations and altered phytoplankton density and community structure downstream from the dam. To reduce the problem, Burrendong Dam has been fitted with an innovative thermal curtain that directs warmer surface water to the low-level off-take. This study set out to quantify the magnitude and extent of cold water pollution along the Macquarie River downstream of Burrendong Dam before and after the curtain was implemented. It also aimed to quantify the effect of the dam on nutrient concentrations and phytoplankton density (indicated by chlorophyll a concentrations) and community structure before and after thermal curtain operation. This was achieved through analysis of time-series data from temperature loggers installed within the impoundment, upstream and downstream in the Macquarie River, prior to the installation of the thermal curtain. Water samples for analysis of nutrients, phytoplankton concentrations (chlorophyll a) and community structure were collected within the reservoir and upstream and downstream of the dam. CWP was shown to be a long-term problem in downstream river reaches, caused by the release of hypolimnial waters from the dam. Epilimnial releases with use of the curtain improved the thermal regime (mean daily and mean monthly temperature, and diel temperature range) below the dam so that it more closely resembled the upstream thermal regime with an improvement of approximately 2°C. Fluctuations in nutrients occurred in the hypolimnion of Burrendong Dam during thermal stratification, probably due to the development of an oxycline and subsequently low oxygen concentrations in the hypolimnion. Nutrient concentrations increased at the outlet as a result of hypolimnial releases, with the concentrations breaching the trigger values outlined by ANZECC which indicate ecological disturbance. This study found a substantial increase in the cell count of cyanobacteria at the dam outlet, which may lead to water quality issues in the Macquarie River downstream of the dam. The results of this study will be useful to assist in the management routine of the thermal curtain at Burrendong Dam, to maximise the efficiency of CWP mitigation, whilst not compromising the downstream ecological health in terms of nutrient and cyanobacteria concentrations.

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