Water Availability in the Wimmera a Report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project
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Water Availability in the Wimmera A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project October 2007 Murray-Darling Basin Sustainable Yields Project acknowledgments The Murray-Darling Basin Sustainable Yields Project is being undertaken by CSIRO under the Australian Government's Raising National Water Standards Program, administered by the National Water Commission. Important aspects of the work were undertaken by Sinclair Knight Merz; Resource & Environmental Management Pty Ltd; Department of Water and Energy (New South Wales); Department of Natural Resources and Water (Queensland); Murray-Darling Basin Commission; Department of Water, Land and Biodiversity Conservation (South Australia); Bureau of Rural Sciences; Salient Solutions Australia Pty Ltd; eWater Cooperative Research Centre; University of Melbourne; Webb, McKeown and Associates Pty Ltd; and several individual sub-contractors. Murray-Darling Basin Sustainable Yields Project disclaimers Derived from or contains data and/or software provided by the Organisations. The Organisations give no warranty in relation to the data and/or software they provided (including accuracy, reliability, completeness, currency or suitability) and accept no liability (including without limitation, liability in negligence) for any loss, damage or costs (including consequential damage) relating to any use or reliance on that data or software including any material derived from that data and software. Data must not be used for direct marketing or be used in breach of the privacy laws. Organisations include: Department of Water, Land and Biodiversity Conservation (South Australia), Department of Sustainability and Environment (Victoria), Department of Water and Energy (New South Wales), Department of Natural Resources and Water (Queensland), Murray-Darling Basin Commission. CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it. Data is assumed to be correct as received from the Organisations. Citation CSIRO (2007). Water availability in the Wimmera. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. 108 pp Publication Details Published by CSIRO © 2007 all rights reserved. This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from CSIRO. ISSN 1835-095X Cover Photo: Channel, Grampians region courtesy of the Wimmera CMA, Victoria Director’s Foreword Following the November 2006 Summit on the Southern Murray-Darling Basin, the Prime Minister and Murray-Darling Basin state Premiers commissioned CSIRO to report on sustainable yields of surface and groundwater systems within the Murray-Darling Basin. This report from the CSIRO Murray-Darling Basin Sustainable Yields Project details the assessments for one of 18 regions that encompass the Basin. The CSIRO Murray-Darling Basin Sustainable Yields Project is providing critical information on current and likely future water availability. This information will help governments, industry and communities consider the environmental, social and economic aspects of the sustainable use and management of the precious water assets of the Murray-Darling Basin. The project is the first rigorous attempt worldwide to estimate the impacts of catchment development, changing groundwater extraction, climate variability and anticipated climate change, on water resources at a basin-scale, explicitly considering the connectivity of surface and groundwater systems. To do this, we are undertaking the most comprehensive hydrologic modelling ever attempted for the entire Basin, using rainfall-runoff models, groundwater recharge models, river system models and groundwater models, and considering all upstream-downstream and surface- subsurface connections. We are complementing this work with detailed surface water accounting across the Basin – never before has surface water accounting been done in such detail in Australia, over such a large area, and integrating so many different data sources. To deliver on the project CSIRO is drawing on the scientific leadership and technical expertise of national and state government agencies in Queensland, New South Wales, Victoria, the Australian Capital Territory and South Australia, as well as the Murray-Darling Basin Commission and Australia’s leading industry consultants. The project is dependent on the cooperative participation of over 15 government and private sector organisations contributing over 100 individuals. The project has established a comprehensive but efficient process of internal and external quality assurance on all the work performed and all the results delivered, including advice from senior academic, industry and government experts. The project is led by the Water for a Healthy Country Flagship, a CSIRO-led research initiative which was set up to deliver the science required for sustainable management of water resources in Australia. The Flagship goal is to achieve a tenfold increase in the social, economic and environmental benefits from water by 2025. By building the capacity and capability required to deliver on this ambitious goal, the Flagship is ideally positioned to accept the challenge presented by this complex integrative project. CSIRO has given the Murray-Darling Basin Sustainable Yields Project its highest priority. It is in that context that I am very pleased and proud to commend this report to the Australian Government. Dr Tom Hatton Director, Water for a Healthy Country National Research Flagships CSIRO Executive Summary Background The CSIRO Murray-Darling Basin Sustainable Yields Project is providing governments with a robust, Basin-wide estimate of water availability on an individual catchment and aquifer basis, taking into account climate change and other risks. This report describes the assessment undertaken for the Wimmera region. While key aspects of the assessment and modelling methods used in the project are contained in this report, fuller methodological descriptions will be provided in a series of project technical reports. The Wimmera region is in western Victoria and represents 3 percent of the total area of the Murray-Darling Basin (MDB). Executive Summar The region is based around the terminal Wimmera River, Avon River and Yarriambiack Creek. The population is around 50,000 (or 2.5 percent of the MDB total), concentrated in the major centres of Horsham, Stawell and Ouyen. The dominant land use is broadacre cropping of cereals, pulses and oilseeds in the central and northern areas, and dryland livestock grazing in the south. There are currently 6000 ha of irrigated cropping with the major enterprises being vines, pastures and orchards. The area of commercial plantation forestry in the region is small and farm dams are predominantly used for stock and domestic purposes. Native vegetation covers over 16 percent of the region. The region includes the nationally significant wetlands Lake Hindmarsh and Lake Albacutya. y The region uses 1 percent of the surface water diverted for irrigation and urban use in the MDB and uses less than 0.1 percent of the MDB groundwater resource. There are major water storages at the foothills of the Grampians Ranges. Surface water diversions are primarily for stock and domestic use, but also for urban supply and limited irrigation. There are three groundwater management units (GMUs) in the western part of the region. Groundwater extraction is also primarily for stock and domestic use, as well as some urban supply and limited irrigation. Key Messages The key messages relating to climate, surface water resources, groundwater and the environment are presented below for scenarios of current and possible future conditions. The scenarios assessed are defined in Chapter 1. Historical climate and current development (Scenario A) The average annual rainfall for the entire Wimmera region is 403 mm and modelled average annual runoff is 16 mm. Rainfall is generally higher in the winter half of the year and most of the runoff occurs in winter and early spring. The region generates about 1.7 percent of the total runoff in the MDB. Average annual groundwater recharge, based on throughflow to confined aquifers, is around 12 GL/year. The surface water assessments of this project only consider implementation of Stage 1 of the Wimmera-Mallee Pipeline Project. For these conditions average annual surface water availability is 206 GL/year and current water use represents 20 percent of this available water. However, on average, 59 percent of the available water is diverted for use, as losses in the distribution system are high. The maximum allocation for all users (including the environment) under the Wimmera and Glenelg River surface water Bulk Entitlements is 206 GL/year.