Murray-Darling Basin water issues

Bill McCormick, Science, Technology, Environment and Resources Section

Over the years there has been an over-allocation of water entitlements in many areas of the Murray Darling Basin (MDB). Water resources have not been able to meet the water needed for environmental flows and human requirements. To address the problem the Murray-Darling Basin Ministerial Council introduced a permanent Cap, starting on 1 July 1997. The Cap is a limit imposed on the volume of water which could be diverted from the rivers for other uses such as dams or irrigation.

In 2007 the Commonwealth intervened to address over-allocation and established the Murray-Darling Basin Authority (MDBA). The MDBA was to develop and implement a Basin Plan to include Sustainable Diversion Limits (SDLs). On 1 September 2010 the MDBA announced that it would be publicly releasing the Guide to the Proposed Basin Plan on 8 October 2010. Later it will release the Proposed Basin Plan and the Basin Plan. CSIRO has advised the MDBA about future climate scenarios for use in modeling future water yield from catchments for the Basin Plan. A 2008 amendment to the Commonwealth Water Act 2007 provided a commitment for critical human needs.

The Murray Darling Basin Authority

The MDBA is responsible for planning the integrated management of the water resources of the MDB. The MDBA will prepare the Basin Plan for adoption by the Commonwealth Minister for Water and will implement and enforce the Plan—this will set a new cap on water use in the Basin. The MDBA also advises the Minister on the accreditation of state water resource plans (WRP).

The drought from 2001 through 2009 has severely reduced the water resources of the MDB. The years 2006–07, 2007–08 and 2008–09 had the first, third and seventh lowest inflows to the Murray River on record. The low flows plus continued water use, albeit at reduced levels, resulted in the Lower Lakes dropping to record low levels, exposing acid sulphate soils to the air and increasing salinity levels six-fold. The drought resulted in a decrease in both area of irrigation and volume of water used.

The Basin Plan

The Basin Plan, due to begin in 2011, must contain:

  • long-term average SDLs for the amount of surface water and groundwater that can be taken from Basin water resources
  • requirements that state WRPs must comply with
  • an environmental watering plan for the Basin
  • a water quality and salinity management plan for the Basin and
  • rules about trading of water.

These will operate together to ensure that the social, economic and environmental outcomes of the water resources are not compromised. The Plan will also include an outline of risks to Basin water resources, such as climate change, along with strategies to manage those risks.

The SDLs will be implemented through the water resource plans, which will be developed by the states but accredited by the Commonwealth. However there will be a five-year phase-in period for the SDLs for each WRP.

The Wentworth Group, in a June 2010 paper, argued that the MDB should not have its flow regime reduced below two-thirds of its natural level. To ensure that flow rates stay about this, reductions in SDLs would be required across the Basin. While the SDLs could remain at more than 90 per cent of present diversion levels for most catchments, cuts to diversions in the Murray and Murrumbidgee rivers would have to be 39 per cent and 65 per cent respectively.

Such potentially large reductions in allocations have been of great concern for irrigation and farming groups. Early this year the National Farmers Federation said that, for agriculture, the Basin Plan was a ‘train smash waiting to happen’.

Reduction in water diversions

In the present WRPs, the reduction in water allocations that are necessary to meet the new SDLs will be achieved by the Commonwealth purchasing water entitlements on the water market, and through improving water use efficiency. Two programs aim to achieve this:

  • the $31 billion Restoring the Balance in the Murray-Darling Basin program to purchase entitlements for use as environmental water and
  • the $5.8 billion Sustainable Rural Water Use and Infrastructure program.

The ALP gave a 2010 election commitment that it would buy as much water as necessary from willing sellers to restore the Murray River to health as needed under the Basin Plan.

Mining and water

Farmers in parts of the MDB have raised the issue of the impact of coal mining and coal seam methane extraction on the quantity and quality of the groundwater resources. Section 255A of the Water Act 2007 requires independent studies of the impacts of subsidence mining on the groundwater systems in the Basin before any mining licences are granted. Concerns remain about the impacts of coal seam methane production.

Snowy River flows

The Snowy Mountains Scheme diverted water to the MDB and this reduced the flow of the Snowy River above the Mowamba River to just one per cent of its normal long-term average. In order to reduce the environmental impacts on the Snowy from this diversion, in 2002 NSW, Victoria and the Commonwealth agreed to fund a scheme to return 21 per cent (212 gigalitres) of the Snowy’s original flows by 2012. The recent drought has resulted in a slower release of environmental water than expected. During the 2010 election campaign the ALP announced that it had reached an agreement with the NSW and Victorian Governments. This agreement promised a $13.7 million compensation payment to Snowy Hydro for the 56 gigalitres in water to be released from the Jindabyne Dam into the Snowy River over the next two years.

Library publications and key documents

Murray Darling Basin Authority (MDBA), Issues paper: development of sustainable diversion limits for the Murray-Darling Basin, MDBA, Canberra, 2009, http://www.mdba.gov.au/files/publications/sustainable-diversion-limits-issues-paper-12-11-09.pdf

A Martyn, J Tomaras and B McCormick, Water Amendment Bill 2008, Bills digest, no. 45, 2008–09, Parliamentary Library, Canberra, 2008, http://www.aph.gov.au/library/pubs/bd/2008-09/09bd045.pdf

FHS Chiew, W Cai and IN Smith, Advice on defining climate scenarios for use in the Murray-Darling Basin Plan modelling, CSIRO report prepared for the Murray-Darling Basin Authority, Canberra, 2009, http://www.mdba.gov.au/files/publications/Defining-climate-scenarios-report-from-CSIRO.pdf

Wentworth Group of Concerned Scientists (WGCS) RQ Grafton, I Kowalick, C Miller, T Stubbs, F Verity and K Walker, Sustainable diversions in the Murray-Darling Basin: an analysis of the options for achieving a sustainable diversion limit in the Murray-Darling Basin, Wentworth Group, Sydney, 2010.

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