The proposed ‘environmentally sustainable level of take’ for surface water of the Murray–Darling Basin: Method and outcomes November 2011 Published by the Murray–Darling Basin Authority © Copyright Commonwealth of Australia (Murray–Darling Basin Authority) 2011 MDBA publication no: 226/11 ISBN (print): 978-1-921914-88-1 ISBN (online): 978-1-921914-87-4 This report may be cited as: Murray‐Darling Basin Authority 2011, The proposed “environmentally sustainable level of take” for surface water of the Murray‐Darling Basin: Methods and outcomes, MDBA publication no: 226/11, Murray‐Darling Basin Authority, Canberra. © Copyright Commonwealth of Australia 2011. This work is copyright. With the exception of the photographs, any logo or emblem, and any trademarks, the work may be stored, retrieved and reproduced in whole or in part, provided that it is not sold or used for commercial benefit. Any reproduction of information from this work must acknowledge the Murray–Darling Basin Authority, the Commonwealth of Australia or the relevant third party, as appropriate, as the owner of copyright in any selected material or information. Apart from any use permitted under the Copyright Act 1968 (Cth) or above, no part of this work may be reproduced by any process without prior written permission from the Commonwealth. Requests and inquiries concerning reproduction and rights should be addressed to the Commonwealth Copyright Administration, Attorney General’s Department, National Circuit, Barton ACT 2600 or posted at http://www.ag.gov.au/cca. Disclaimer This document has been prepared by the Murray‐Darling Basin Authority for general use and to assist public knowledge and discussion regarding the integrated and sustainable management of the Basin’s natural water resources. The opinions, comments and analysis (including those of third parties) expressed in this document are for information purposes only. This document does not indicate the Murray‐Darling Basin Authority’s commitment to undertake or implement a particular course of action, and should not be relied upon in relation to any particular action or decision taken. Users should note that developments in Commonwealth policy, input from consultation and other circumstances may result in changes to the approaches set out in this document. Page i Foreword The Water Act 2007 established the Murray‐Darling Basin Authority (MDBA) and has tasked it with the preparation of a Basin Plan to provide for the integrated management of the Basin’s water resources. Central to the Basin Plan is the need to determine the Environmentally Sustainable Level of Take (ESLT). This report describes the method used by the Authority to determine the ESLT for surface water resources and describes the environmental objectives, ecological targets and environmental outcomes that can be achieved under the proposed ESLT. This report consists of: An executive summary providing an overview of the report; A description of the background and methods used to determine the ESLT and hence the Sustainable Diversion Limits (SDLs) (Sections 1‐8); An assessment of the environmental flow outcomes that may be achieved (Section 9); An assessment of the uncertainties and limitations in the method (Section 10); and A discussion of the adaptive management processes proposed from here to 2019 (Section 11). This is just one of the supporting documents associated with the proposed Basin Plan. Other documents provide further detail in key areas including: The report focusing on the process used to determine the ESLT and SDL for groundwater is The Groundwater SDL methodology for the Murray‐Darling Basin Plan (CSIRO and SKM 2010); A more detailed socio‐economic assessment can be found in the report titled Social and economic analyses and the draft Murray–Darling Basin Plan; A detailed description of the Environmental Watering Plan, which will guide actual decisions on environmental flow events, can be found at the MDBA website titled “Environmental Watering Plan: What’s in it and how it works”; a detailed modelling report (in preparation); environmental water requirement descriptions for indicator sites (in preparation); and a review of the science underpinning the ESLT (to be released during the 20 week consultation period). Page ii Executive summary The Murray‐Darling Basin Authority (MDBA) has a vision of a healthy working Basin that has vibrant communities, productive and resilient industries, and healthy and diverse ecosystems. One of the key actions to achieving a healthy working Basin is the need to ensure that there is balance between the water needs of communities, industries and the environment, while at the same time protecting and restoring the ecological and other values of water‐dependent ecosystems so they remain healthy. The Basin Plan aims to do this through the establishment of Long‐Term Average Sustainable Diversion Limits (SDLs), which come into effect in 2019, along with a range of other measures that will improve the management of water in the Basin. The SDLs are limits on the volumes of water that can be taken for human uses (including domestic, urban and agricultural use) and are set at both a catchment and Basin scale. The Water Act requires that these new limits are determined on the basis of an assessment of the Environmentally Sustainable Level of Take, or ESLT. This report provides a summary of the method used by MDBA to determine the ESLT for surface water resources and describes the environmental objectives, ecological targets and environmental outcomes that can be achieved under the proposed ESLT. The need for change For more than a hundred years, the infrastructure and management of the Murray‐Darling Basin has been developed to secure social and economic outcomes. Many rivers have been modified and become highly managed systems to supply drinking water to towns and cities, support agriculture, mitigate floods and droughts, and allow for irrigation. This development has supported one of the most productive food and fibre regions in Australia. However, there have been substantial environmental impacts that now undermine the very agricultural and community values that the Basin supports. These environmental impacts have long been recognised and the recent drought exposed the limits and weakness of how water is currently managed in the Basin. The Murray Mouth was only kept open by constant dredging. Wetlands and floodplains across the Basin from Queensland to South Australia all experienced widespread environmental degradation. Some irrigators received no water in some years, while towns and cities experienced harsh water restrictions. History of water reform The history of water reform in the Murray‐Darling Basin, in response to declining environmental health, is long and ongoing. The first steps are perhaps hard to single out, but it is clear that the decline in environmental condition contributed to the establishment of the Murray‐Darling Basin Initiative and Murray‐Darling Basin Commission in the 1980s. In 1994, the Council of Australian Governments adopted a strategic water reform framework. The main objectives were to establish an efficient and sustainable water industry, and to stop widespread natural resource degradation partly caused by consumptive water use. The Council of Page iii Australian Governments reinforced and extended these strategic water reforms in 2004 through the Intergovernmental Agreement on a National Water Initiative. As the reforms have been implemented, a growing body of evidence has accumulated indicating that the water resources of the Basin are being overextended, while the ecological health of the Basin is under increasing stress and is degrading. This includes the decline of wetlands with associated loss of vegetation and collapse of waterbird breeding. Initial steps to limit extractions were taken in 1995 with the Commonwealth and Basin states agreeing to cap surface‐water extractions in the Basin generally at 1993–94 levels of use (the Cap). In 2002, in response to evidence showing the declining health of the River Murray system, governments established The Living Murray initiative. Supported by scientific assessment of environmental water requirements, the governments agreed to recover an average of 500 GL per year as a ‘first step’ towards securing the long‐term ecological health of six icon sites, and agreed to concurrently invest in infrastructure to make the best use of the water available to the environment and achieve other ecological outcomes, including fish passage. In response to extreme drought, exacerbated environmental stress across the Basin, and growing evidence that further action was needed to address environmental decline, the Australian Parliament passed the Water Act 2007 (Cwlth). The Water Act established the MDBA with the powers necessary to develop and implement new Basin‐wide water planning and management arrangements, including legally enforceable limits on the amount of water that can be taken for consumptive use. Requirements of the Water Act A key component of the Basin Plan is to provide for the establishment and enforcement of environmentally sustainable limits on the quantities of surface water and groundwater that can be taken from Basin water resources. The Act provides objects, context, definitions and other directions to guide the determination of these limits. Whilst the Water Act provides overarching objects and requirements, it does not prescribe specific environmental targets or outcomes (such as a level of protection or