River Torrens Water Quality Improvement Trial – Summer 2012/13
https://goyderinstitute.org/water-for-industry/
https://goyderinstitute.org/water-for-industry/
The aim of this study was to investigate whether a controlled upstream release of water could be delivered to the Torrens Lake to effectively dilute the population and control cyanobacteria numbers below a threshold that would force lake closure. The relatively high nutrient loads to the Torrens lake and the shallow morphometry means it is unlikely that physical and chemical conditions can be manipulated sufficiently to prohibit cyanobacterial growth. However, it was postulated that rather than control growth it might be possible to control population size with continual dilution of the population with flow.
For a growth rate of 0.4/day, which is a typical exponential growth rate of cyanobacteria in the Torrens Lake, it was concluded that a diluting flow of at least 10% per day would be required to have noticeable impact on the cyanobacteria population. With a starting cell concentration of 100 cells/mL, a growth rate of 0.4/dayand a diluting flow of 10%, the cell concentration after 20 days would be 74,420 cells/mL, which is below the critical threshold for cell numbers that would force lake closure.
The 2011/12 trial failed to maintain concentrations sufficiently low to avoid lake closure. However, the rainfall was also incredibly low during this period and so the lake population was not reset with elevated rain-event inflows. Sufficient questions remained on the viability of the trial for it to be repeated in the summer of 2012/13.
The results of the trial suggest that if dilution flows are released early enough, the size of the cyanobacterial population can be controlled. However, there is a reliance on rain events to flush the system and dilute the resident cyanobacterial population. Although on average, the flow return interval analysis suggests that rain events occur frequently enough in summer for this strategy to be effective this did not occur in 2011/12 or in 2012/13. In a variable climate like that observed in Adelaide, there may be very long periods between significant rainfall events. This may reduce the confidence in rain events to reset the population. Having even higher flows may dilute the population further and so control cyanobacterial abundance.
Cyanobacteria population showed explosive growth between 24 Dec and 31 Dec 2012. The rate of growth was 1.33 doublings/day, which is a rate four times higher than the long-term average. Flows were released in response to visual observations that cyanobacteria were present but these were unable to significantly reduce the rapid accumulation of biomass. Consequently it can be concluded that the amenity flow released from Hope valley was ineffective at reducing the cyanobacterial abundance during the highest growth period. Furthermore, commencing flows at the first detection of Microcystis aeruginosa would not have prevented lake closure because growth rate was too rapid and population increases could not be offset by dilution. The amenity flow alone was insufficient to prevent lake closure.
There was some concerns that the flow releases are having a detrimental impact on water quality downstream of the Torrens Lake. Sampling for cyanobacteria and Enterococci was initiated at a number of sites downstream and at West Lakes where some of the water was discharged. Cyanobacteria and Enterococci were transported downstream from the lake as a result of the amenity flow releases however, the abundance decreased significantly during river passage resulting in a two log removal (100 times dilution).
In consultation with the Department of Health a revision of the recreational guideline was undertaken. This resulted in an increase in the recreational guideline to a biovolume of 40 mm3/L effectively doubling the tolerable concentrations of cyanobacteria before the lake is closed based on health and exposure risk (biovolume = cell/mL multiplied by voume of cells). This effectively increases the length of time the lake can remain open. Depending on the criteria used to determine the whole lake concentration, the lake could remain open even with a dense bloom. For example if the mean cell concentration in the main lake site (sites 1-6) is used then a mean concentration of 230,000 cells/mL of Microcystis aeruginosa would be permissible and the lake would have remained open all summer. A cautionary note is that at these concentrations dense surface blooms would be present which would be unsightly and may be odorous. It is recommended that the concentration of cyanobacteria at the most upstream site (site 7) be excluded from whole lake determination of mean cell concentration. Cells often accumulate at the upstream site but persist there until they are washed downstream during storm events. The persistent upstream biomass presents a very low risk to lake users and so may unnecessarily bias the value used to determine lake closure.
The amenity flows achieve environmental benefits other than dilution. They serve to maintain water in a river that would have had base flow during summer which has been largely lost by river regulation and catchment development; they provide habitat for native fish; and the water is used to provide water to the Barker Inlet wetlands during long dry summer and there is freshening of water in the entire reach from Hope Valley reservoir to the coast. Amenity flow releases appear to have had a positive effect on native fish communities in the lower Torrens. This translated to increased endemic fish abundance and diversity and a decrease in alien and translocated fish abundance. No immediate negative effects resulting from changes in water quality due to summer flow releases were apparent and, although spawning was stimulated in the alien common carp (Cyprinus carpio), idiosyncrasies in the Torrens morphology meant that these events were of little consequence to fish diversity downstream of the Torrens weir.
On balance the amenity flows are insufficient on their own to provide relief against high cyanobacterial growth, however, if coupled with algicidal technology such as hydrogen peroxide they may attain the upstream and downstream benefits and cyanobacterial control in-lake. A larger flow volume released from Hope Valley would have greater dilution effects and so slow the increase in population expansion in the lake. In the absence of rain events to reset the cyanobacterial populations in the lake, large water releases from upstream reservoirs could fulfil a similar role.
This project was an experimental trial but was also a high-profile strategy to improve water quality in the River Torrens. The results were used immediately for setting flow targets maintain cyanobacterial populations below concentrations that would force lake closure. The trial 2011/12 had unanswered questions and so was repeated to determine whether this is an appropriate long-term strategy for controlling cyanobacteria in the River Torrens.
Chris Wright holds significant experience in public sector senior leadership, having led policy, scientific and operational business units over the last twelve years in both State and Commonwealth government agencies. Chris has excellent experiences in leading policy and strategy formulation. He is skilled in building and maintaining networks across the public and private sectors to facilitate business delivery; leading and negotiating with others to achieve outcomes; and in bridging the science-policy gap, drawing on earlier roles in geospatial information systems (GIS) consulting. Chris’s formal qualifications include a Bachelor of Social Science, a Masters of Spatial Information Science and graduation from the AICD Company Directors course in 2019.
Dr Ilka Wallis is a hydrogeologist with areas of expertise in quantitative hydrogeology and geochemistry. Ilka focuses on the development of reactive geochemical transport models which integrate fundamental processes that are normally studied in isolation (hydrogeological, mineralogical, geochemical and biochemical).
Ilka is also an Adjunct Professor, Department of Civil Engineering, University of Manitoba, Canada since 2017.
Peter Goonan is the Principal Aquatic Biologist in the Environmental Science Branch of the EPA. He has over 30 years’ experience monitoring the condition of aquatic ecosystems in SA and assessing the environmental effects caused by discharges, deposits and contaminants entering inland and coastal waters. He specialises in aquatic invertebrate identification and their responses to contaminants and water quality stressors. He also provides expert professional advice relating to water quality risks, regulation, policy, and strategic directions, and represents the EPA as an expert witness in court.
Dr Paul Monis is a technical expert within SA Water’s Business Services group, which provides scientific expertise to support the delivery of water and wastewater services to SA Water’s customers. He has specialist expertise in the areas of biotechnology and microbiology, with almost 20 years’ experience applying DNA-based and other technologies to address water quality challenges posed by microorganisms, especially enteric pathogens. Dr Monis also holds title of Adjunct Associate Professor at Flinders University, the University of Adelaide and UniSA.
Jennie’s role in the Department for Environment and Water (DEW) allows her to foster and strengthen opportunities for researchers to better connect with government to enable evidence-based decision making. Jennie has extensive experience working in both universities and government, allowing her to bridge the divide between the two sectors. She is focused on connecting natural resource researchers with natural resource decision makers, and facilitating fit for purpose partnerships.
Dr Tanya Doody is a Principal Research Scientist working on high impact spatial eco-hydrological projects within CSIRO’s Land and Water Business Unit. Dr Doody leads the Managing Water Ecosystems Group, based in Adelaide, Albury and Canberra and has significant experience in quantifying the water requirements of vegetation and at times, their impact on water resources. This involves ecophysiological field-based research to underpin remote sensing tools to scale regionally to improve our understanding of the effect of flood regimes on the health of water-dependent ecosystems on the Murray-Darling Basin floodplains. Additional research includes investigating the ecological response of vegetation to water availability and environmental water to inform integrated basin water planning and management.
Professor Lin Crase is Professor of Economics and Dean of Programs (Accounting & Finance) at UniSA. He joined UniSA in February 2016 as Head of School of Commerce. Prior to commencing at UniSA, Lin was Professor and Director of the Centre for Water Policy and Management at La Trobe University.
Lin’s research has focused on applied economics in the context of water. He has analysed water markets and the property rights that attend them, water pricing and numerous applications of water policy. Whilst his expertise includes the Murray-Darling Basin in Australia, he has also worked on projects in south Asia, Japan and Europe. Lin has published over 100 journal articles, numerous book chapters, four books and a range of other papers and opinion pieces.
Justin has broad research interests in limnology and water treatment with a primary focus on coupling between hydrodynamics, biology and water quality contaminants such as cyanobacteria and pathogens. He is a founding member of the management committee of the IWA Specialist Group on Lake and Reservoir Management and member of the Steering Committee for the Global Lakes Ecological Observatory Network.
Justin has a PhD and a Bachelor of Science degree with Honours from the University of Adelaide.
Daniel Flaherty is the Accountant for the Goyder Institute for Water Research.
Daniel has extensive experience in higher education having worked in senior financial management roles at the University of South Australia, Flinders University and the University of Adelaide over the past 26 years. Daniel has also been a Board Director on a number of university related entities. Prior to that, Daniel has worked in a range of agencies in the Commonwealth and State Governments.
Daniel is a Fellow of CPA Australia and has a Bachelor of Economics from the University of Adelaide.
Alec Rolston joined the Institute in 2021 as Research Program Manager of the Goyder Institute’s research projects in the Healthy Coorong, Healthy Basin program. He has extensive experience in integrated water resource management, integrated catchment management, drinking water source protection and wetland ecology, conservation and management across Europe and Australia.
Alec holds a PhD from the National University of Ireland Maynooth and has worked with An Fóram Uisce|The Water Forum and the Dundalk Institute of Technology in Ireland as well as the MANTEL Innovative Training Network across Europe.
Alec spent his early career in Adelaide working with Flinders University through the Coorong, Lower Lakes and Murray Mouth (CLLAMM) Ecology Research Cluster and within the Department for Environment and Water.
Daniel Pierce has managed research projects at the Goyder Institute for Water Research since November 2017 under both the second and third terms of the Institute.
Daniel brings experience in project management and knowledge transfer and application from 4 years working as a Senior Hydrogeologist in the Department for Environment and Water (DEW) in South Australia and from 13 years of private sector work in environmental management, science and engineering in Australia and the South Pacific. His work with DEW has included providing technical advice to the development and revision of Water Allocation Plans around South Australia in collaboration with researchers and policy makers, and managing a team of groundwater modellers and hydrogeologists involved in an assortment of water resource management issues.
Daniel has a Bachelor of Engineering (Hons, Environmental) and a Bachelor of Science (Geography) from the University of Western Australia.
Professor Lombi’s main contributions to environmental research cover various aspects of contaminant risk assessment, biogeochemistry, ecotoxicology and waste management. Furthermore, the methodological development he has pursued in his research has provided the basis for collaborative efforts in a variety of research areas ranging from soil fertility and plant physiology to human health issues related to contaminant uptake via occupational exposure and diet. In the last few years he has been increasingly focusing on the transformation and toxicity of manufactured nanomaterials in the environment.
Dr Carmel Pollino is a Research Director for Land and Water at CSIRO. She has 20 years of experience working on water issues in Australia and throughout Asia. Carmel has degrees in science and environmental law and works across the science and policy interface. Significant areas of research in Environmental Flows, Hydrology, Ecology and Integrated River Basin Planning. Carmel is the lead and also a contributor to global working groups on water and has published widely in this domain.
Professor Bronwyn Gillanders is interim Head of School of Biological Sciences at the University of Adelaide. Prof Gillanders completed her BSc at the University of Canterbury, MSc at the University of Otago and her PhD at the University of Sydney. She has a research background in environmental science focused predominantly on freshwater and marine ecology.
Her research interests include integrated marine management; coastal carbon opportunities; multiple use activities and cumulative impact assessment; biology, ecology and fisheries of cephalopods; stocking and provenance of fish; plastics in the marine environment including in seafood; use of fish bones (and other calcified structures) for assessing ecological and environmental change. She has trained and mentored ~70 Honours and Higher Degree Research students and shaped the future of 1000s of students through her undergraduate teaching. She is passionate about encouraging capable women to enter and remain in science careers.
Dan Jordan is the Director, Water Security, Policy and Planning, Department for Environment and Water (DEW). Dan is also the Basin Officials Committee Alternate Member for South Australia.
Professor Okke Batelaan is a graduate of the Free University of Amsterdam, Netherlands (MSc – Hydrogeology) and of the Free University Brussels, Belgium (PhD – Engineering). He worked for more than 20 years at the Free University Brussels and also led the hydrogeology group at the KU Leuven, Belgium since 2006. He was chairman of the Interuniversity Programme in Water Resources Engineering.
Since 2012 Okke Batelaan is Strategic Professor in Hydrogeology and currently Dean of the School of the Environment, Flinders University. Okke has broad experience in teaching groundwater hydrology, groundwater modelling, GIS and remote sensing for hydrological applications. He was supervisor of more than 140 MSc and 25 PhD students. He has extensive research experience and a publication record in shallow groundwater hydrology and modeling, recharge-discharge estimation and modeling, urban hydrology and distributed modelling, ecohydrology and impacts of land use and climate change on groundwater systems. He coordinated and participated in a large number of projects in Europe, Africa, South America, Asia and Australia. He is editor-in-chief of Journal of Hydrology: Regional Studies and of MDPI-Hydrology.
