Murray-Darling Basin Groundwater — a Resource for Thefuture Groundwater Bro-R 4/6/01 11:09 AM Page 3 Foreword
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Groundwater bro-r 4/6/01 11:09 AM Page 1 MURRAY-DARLINGMURRAY-DARLING BASINBASIN GroundwaterGroundwater aa Resource Resource for for theFuture theFuture Groundwater is a major natural resource in the Murray-Darling Basin. Its current and future management will have a fundamental impact on the economic viability of many of the Basin’s regional communities. In some parts of the Basin, groundwater is an underutilised resource: in others, it is being used unsustainably. Groundwater bro-r 4/6/01 11:09 AM Page 2 The priorities for groundwater management vary across the Murray-Darling Basin. In the south, the major issues are rising groundwater levels and land and water salinisation. In the north, the issues are unsustainable demand and declining groundwater levels. Fundamental in all areas is the need to manage groundwater and surface water as two parts of one hydrological system. Table of Contents Introduction 5 The hydrogeology of the MDB 8 Major groundwater issues in the MDB 15 The changing picture 26 A resource for the future 27 Glossary 28 References and additional reading 30 Further information 31 Published by the Murray-Darling Basin Commission, GPO Box 409, Canberra, ACT 2601. ISBN 1 875209 61 1 Cover illustrations The Condamine Valley in south-east Queensland illustrates the productive use of groundwater, in conjunction with surface water sources, for the irrigation of crops such as cotton and oilseeds. The Chowilla wetland in the Riverland district of South Australia.The destructive results of rising groundwater levels are seen in the dead trees and the salt encrusted surface where little or no vegetation can survive. The wetland values have been significantly degraded. 2 Murray-Darling Basin Groundwater — a Resource for theFuture Groundwater bro-r 4/6/01 11:09 AM Page 3 Foreword Within the Murray-Darling Basin status of Groundwater 1992 and the 1997 Salt Trends report which analysed groundwater is a major resource. long-term water salinity trends for the However, its value to date has been region. Together these valuable management and educational tools will substantially underestimated. In support the work being done to prepare addition, environmental the draft salinity management strategy due to be completed in the year 2000. mismanagement in the Basin over the The groundwater booklet has been prepared by Dr Peter Crabb under the past one hundred and fifty years has auspices of the Murray-Darling Basin moved groundwater systems into a Commission’s Groundwater Reference Group. It is based on material collected period of instability. Without adequate from two sources; a community education program, The Sleeping Giant, management the groundwater is also which was developed to help explain at risk of contamination. Rising dryland salinity processes in the southern part of the Basin and a paper presented groundwater is mobilising salt in many to the International Groundwater Conference held in Melbourne in areas. Elsewhere, where the resource is February 1998, Salinity in the Murray- being overused, rapid falls are being Darling Basin: a Critical Challenge for the 21st Century. experienced. It will take many decades This booklet has been designed to be useful to water managers, policy makers, to adjust to a new equilibrium. students and those members of the public with an interest in the groundwater o deal with this situation it is vital systems of the Murray-Darling Basin. that we become more skilled and Although salinity issues are discussed Tknowledgeable in the way in which they are not the primary focus of the we protect and manage groundwater. publication. A listing of relevant Research to improve policy and publications and details of relevant planning, a better understanding of what websites have been included to assist is required to manage and allocate readers wanting more information. groundwater sustainably, and The groundwater booklet will educational campaigns to explain key issues, are all required. promote understanding of a vital natural This booklet is one of a range of resource in the Murray-Darling Basin products that are being produced by the and I commend it to you. Commission in order to increase the knowledge of groundwater issues in the Murray-Darling Basin. Related products include the Basin series of groundwater maps which describe the situation in 1988 (and thus provide base line data for researchers and managers wanting to Professor John Lovering determine rates of change since that time), President a technical report titled Murray-Darling Basin Murray-Darling Basin Commission Murray-Darling Basin Groundwater — a Resource for theFuture 3 Groundwater bro-r 4/6/01 11:09 AM Page 4 DRYLAND & URBAN SALINITY IN THE MURRAY-DARLING BASIN Dryland salinity Figure 1: Areas of dryland salinity and urban locations with salinity problems identified in 1996 Source: Crabb 1997, 159 4 Murray-Darling Basin Groundwater — a Resource for theFuture Groundwater bro-r 4/6/01 11:09 AM Page 5 Introduction he Murray-Darling Basin (MDB) covers an area of water supplies, reservoirs and other control structures 1.06 million square kilometres in inland south- have been built on almost all of the Basin’s rivers. As a eastern Australia. It has been described as result, the Murray-Darling – and especially the Murray - TAustralia’s most important natural resource. is a highly regulated river system. Though only 14 per cent of Australia’s total area, the The surface resources constitute the main source of annual gross farm gate value of the Basin’s agricultural water within the Basin, but they are only part of the much production is over $9 billion, some 41 per cent of the larger hydrological system that also includes groundwater national total. This includes approximately 75 per cent of (see Box page 12). Within this total system, water moves Australia’s total irrigation agriculture. The annual value back and forth between surface and groundwater of the Basin’s manufacturing industry is more than $10 sub-systems and their dependent eco-systems, affecting billion (over 70 per cent of it dependent in some way on both the volume available for use and its quality. Further, it agriculture), mining $1.6 billion, and tourism over $3.4 is increasingly evident that many of the MDB’s resource billion. Beyond the Basin, there is Adelaide (with a and environmental degradation problems are linked to its manufacturing sector generating more than $12 billion groundwater and the movement of water and its entrained per year), much of rural South Australia, and the ‘Iron salt between the surface and sub-surface systems. Triangle’ at the head of Spencer Gulf (where Land and water management practices of the past 150 manufacturing is worth over $1 billion a year). All of years, such as the clearing of native vegetation, the switch these activities – and a population of close to two million from pasture to cropping and the development of within the Basin and over one million beyond the Basin irrigation systems, have had a serious destabilising effect in South Australia – are dependent on the Murray- on the groundwater systems of the Murray-Darling Basin. Darling Basin’s water resources. The changes have contributed to significant degradation However, water is in limited supply in the MDB. problems, including salinisation of irrigated and dryland Diversions for agriculture, industry and domestic areas, increasing stream salinity levels, waterlogging, soil consumption have reduced the median annual flow out erosion, and increased toxic algal blooms. The growing of the Murray Mouth by 80 per cent. The main demands for water from the Basin’s rivers have resulted consumer is irrigation which uses 95 per cent of all water in greatly reduced flows and changes to the seasonal flow diverted from the Basin’s streams and rivers. Just three patterns. These have degraded many riverine rivers, the Upper Murray, Murrumbidgee and Goulburn, environments. For the groundwater resources of the account for over 45 per cent of the Basin’s total runoff. southern parts of the MDB, the current land management Overall, some 86 per cent of the Basin contributes practices have produced changes that are akin to those virtually no runoff to the river systems, except during which occurred during earlier periods of climate change. floods. In order to make maximum use of the limited The consequences of poor management are evident The Hume Dam forms one of the major reservoirs on the River Murray. The stored water comes from surface runoff and groundwater flow into the catchment’s streams. Murray-Darling Basin Groundwater — a Resource for theFuture 5 Groundwater bro-r 4/6/01 11:10 AM Page 6 The Murray Bridge-Onkaparinga Pipeline, one of a number that take water from the Murray to Adelaide and other parts of South Australia. Groundwater flows have a significant impact on the quality of water supplies, in South Australia, and in many other parts of the MDB. throughout the Basin. In addition, there is substantial Such serious resource degradation problems, especially risk of contamination of the groundwater if adequate the salinity problems in the Murray Valley, gave rise in protection, planning and management is not 1987 to the Murray-Darling Basin Initiative, which implemented. The National Guidelines for the Protection of brings together the Commonwealth and State and Groundwater provide useful guidance in this regard. Territory governments involved in the management of In the northern parts, the high variability of surface flow the Basin’s resources. Improving the management of the has caused a greater demand for groundwater than is the Basin’s resources, and especially its water, is the focus of case further south. As a result, in many areas groundwater the Initiative’s activities. Groundwater is an increasingly levels and water pressure are falling. In contrast, under important part of this focus.