The Murray-Darling Basin cap
The Murray-Darling Basin covers a large part of south–eastern Australia, including most of the inland area of NSW. The introduction of the Murray-Darling Basin cap in 1995 was seen as an essential first step in providing for the sustainability of the river systems of the Basin.
The cap is a long term average annual water extraction target which combines with shorter term annual target assessments that take into account annual climatic variations.
The NSW Office of Water monitors extractions and, if growth is occurring, reduces the amount of water that can be taken by licence holders to bring exactions back into line with the cap. The Independent Audit Group of the Murray Darling Basin Authority assesses jurisdictions compliance each year with the cap limits. The 2009/10 assessment report found that NSW diversions were within the Cap for 2009–10 and also remain within the cumulative Cap from 1 July 1997 when assessments began.
This cap on surface water extractions was introduced to prevent further growth in extractions in response to an audit of water use in the Murray-Darling Basin published by the Murray-Darling Basin Ministerial Council in 1995.
This audit found that since the 1950s there has been a continuing increase in the quantity of water diverted from the rivers in the Basin. For example from 1988 to 1994 water consumption across the Basin had increased by 8 per cent – and was continuing to grow. The audit concluded that the high level of use in the Basin was a major factor in river health decline. In a normal year, flows at the end of the Murray were only 20 per cent of their natural level.
Growth in water use in Murray-Darling Basin since 1920
(source: MDBC 1995)