Water Quality Research Australia Membership at December 2008 Industry Members • Australian Water Association Ltd • Degrémont Pty Ltd • Barwon Region Water Corporation “Barwon Water” • Central Highlands Water • City West Water Ltd • Coliban Region Water Corporation • Department of Human Services (Vic) • Goulburn Valley Regional Water Corporation A Practical Guide “Goulburn Valley Water” • Grampians Wimmera Mallee Water Corporation • Hunter Water Corporation to Reservoir Water Quality Research Australia Limited • Melbourne Water Corporation GPO BOX 1751, Adelaide SA 5001 • Power & Water Corporation • South East Water Limited For more information about WQRA visit the website Management • Sydney Catchment Authority www.wqra.com.au • Sydney Water Corporation • United Water International Pty Ltd • Wannon Region Water Corporation • Water Corporation of WA • Yarra Valley Water Ltd Research Report 67 • South Australian Water Corporation • Central Gippsland Regional Water Corporation Research Members • Australian Water Quality Centre • Centre for Appropriate Technology • Curtin University of Technology • Flinders University • Griffith University • Monash University • RMIT University • University of Adelaide • University of NSW • The University of Queensland • University of South Australia • University of Technology, Sydney • University of Wollongong, Faculty of Engineering, The Cooperative Research Centre (CRC) for Water Quality and • Victoria University Treatment operated for 13 years as Australia’s national drinking water research centre. It was established and supported under the General Members Australian Government’s Cooperative Research Centres Program. • Cradle Coast Water • Department of Water (WA) The CRC for Water Quality and Treatment officially ended in October 2008, and has been succeeded by Water Quality • Esk Water Authority Research Australia Limited (WQRA), a company funded by the • Lower Murray Urban and Rural Water Corporation Australian water industry. WQRA will undertake collaborative “LMW” research of national application on drinking water quality, recycled Research Report • NSW Water Solutions, Commerce water and relevant areas of wastewater management. • NSW Department of Health • Orica Australia Pty Ltd The research in this document was conducted during the term of the CRC for Water Quality and Treatment and the final report completed under the auspices of WQRA. 67 A Practical Guide to Reservoir Management Contributing Authors, Justin Brookes1, Mike Burch2, Matthew Hipsey3, Leon Linden1, Jason Antenucci3, Dennis Steffensen2, Peter Hobson2, Olivia Thorne4, David Lewis1, Stephanie Rinck-Pfeiffer5, Uwe Kaeding5, Paul Ramussen5 1 The University of Adelaide 2 The Australian Water Quality Centre 3 The Centre for Water Research, UWA 4 The University of Cambridge 5 United Water International Research Report No 67 A PRACTICAL GUIDE TO RESERVOIR MANAGEMENT DISCLAIMER The Cooperative Research Centre for Water Quality and Treatment officially ended October 2008, and has been succeeded by Water Quality Research Australia Limited (WQRA), a company funded by the Australian water industry. WQRA and individual contributors are not responsible for the outcomes of any actions taken on the basis of information in this research report, nor for any errors and omissions. WQRA and individual contributors disclaim all and any liability to any person in respect of anything, and the consequences of anything, done or omitted to be done by a person in reliance upon the whole or any part of this research report. This research report does not purport to be a comprehensive statement and analysis of its subject matter, and if further expert advice is required the services of a competent professional should be sought. © Water Quality Research Australia Limited 2008 Location: WQRA Head Office Level 3, 250 Victoria Square, Adelaide SA 5000 Postal Address: GPO BOX 1751, Adelaide SA 5001 For more information about WQRA visit the website www.wqra.com.au A Practical Guide to Reservoir Management Research Report 67 ISBN 18766 16938 2 CRC FOR WATER QUALITY AND TREATMENT – RESEARCH REPORT 67 FOREWORD Research Report Title: A Practical Guide to Reservoir Management Contributing authors: Justin Brookes1, Mike Burch2, Matthew Hipsey3, Leon Linden1, Jason Antenucci3, Dennis Steffensen2, Peter Hobson2, Olivia Thorne4, David Lewis1, Stephanie Rinck-Pfeiffer5, Uwe Kaeding5, Paul Ramussen5 Project Leader: Justin Brookes Research Nodes: 1The University of Adelaide 2The Australian Water Quality Centre 3The Centre for Water Research, UWA 4The University of Cambridge 5United Water International CRC for Water Quality and Treatment Project No. 2.2.2.3 – Integrated models and guidance manuals for reservoir management 3 A PRACTICAL GUIDE TO RESERVOIR MANAGEMENT EXECUTIVE SUMMARY This report summarises a range of studies and consolidated practical knowledge related to reservoir management in the Australian context, which also have wider international application. The guide provides an overview of processes that impact upon drinking water quality in reservoirs and also a range of selected procedures and tools for reservoir management. This is supported by a series of case study investigations that were largely carried out within the Source Water Program of the CRC for Water Quality & Treatment. The first section of this guide deals with reservoir monitoring and modeling with discussion about the application of hydrodynamic models in reservoir management. It is followed by sections on catchment- derived contaminants, including description and case studies of the use of a simple model to assess contaminant transport, such as pathogens in reservoir inflows. The guide outlines the importance of natural organic matter dynamics and transformations in reservoirs. Subsequent sections address reservoir-derived contaminants such as cyanobacteria and iron and manganese and provide a case study of the use and importance of variable depth reservoir offtakes to optimise withdrawal of the best quality water. The guide includes discussion of managing the impacts of wildfire on water quality and has an overview of the emerging area of climate change and reservoir management. Reservoir management should be considered in the context of the Framework for Management of Drinking Water Quality contained in Chapter 2 of the Australian Drinking Water Guidelines (ADWG), (http://www.nhmrc.gov.au/publications/synopses/_files/adwg_11_06_chapter_2.pdf). This Framework offers effective means of assuring drinking water quality and the protection of public health through adoption of a preventive management approach that encompasses all steps in water production from catchment to consumer. When using the Framework there are a number of elements that need to be considered in relation to reservoir management including: assessment of the role and importance of the reservoir in the context of the overall supply system; identification of preventive measures available for water quality management in the reservoir; and the identification of operational and process controls available. It is important to note that reservoirs can form one of the important barriers to contamination in this preventive strategy from ‘catchment to tap’, however they can also be a source of water quality deterioration. The first step in the development of a reservoir management plan using this key element approach should be to consider the potential hazards from catchment activities and the circumstances under which these will develop as risks to water quality. This risk assessment not only informs the reservoir management plan but may also reveal opportunities for managing contaminants at the source. The most common contaminants of concern generated from catchments are pathogens, particulates and natural organic matter but in some cases industrial and agricultural chemicals may also be important. High rainfall and associated inflows represent the major risk period to deliver these contaminants. During storage of water in the reservoir a number of beneficial water quality changes can occur. Reduced water movement increases the rate of sedimentation of particulates. This reduces turbidity and may also result in the sequestering of the contaminants associated with the particles. Many of the pathogens of concern are attenuated by environmental conditions with temperature and UV being the most critical factors. They may also be consumed by grazers. Chemical contaminants may be subject to beneficial transformations that can de-toxify them. Understanding these mechanisms is critical to the understanding of the effectiveness of reservoirs as barriers to contamination. Of particular importance is a good knowledge of the hydrodynamic processes that control water movement in the reservoir as this will determine the length of time the water is retained and the environmental conditions that it will be subjected to. Issues such as the thermal stratification and the short-circuiting of inflows can have significant impacts. Reservoirs may also be sources of contamination. Contaminants sequestered in the sediments can be resuspended during periods of high flow and bound contaminants may be released if the water chemistry changes. Contaminants that are important in this regard include iron, manganese and nutrients that can be released from sediments under anoxic conditions. Biological growths in the reservoir may also impair water quality and of particular concern is the growth of cyanobacteria which can produce toxins and off-flavours. 4 CRC