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Source: Murray Darling Basin Authority

Water accounting in the Murray–Darling Basin occurs at various scales—each accounting system has a different purpose. The Murray–Darling Basin Authority (MDBA) accounts for Basin-wide water use (or take) over the long-term and monitors trends to ensure Basin state governments remain within their water use limits.

Prior to the Basin Plan, accounting and compliance of long-term water use was under the Murray–Darling Basin Cap on diversions which commenced in 1997. Since the Basin Plan came into effect in 2012, there has been a process in place to transition from the Cap to the new sustainable diversion limits, which began on 1 July 2019.

The seven-year transition period showed a trend that use was less than the Cap on diversions in a number of valleys, as surface water accounting ‘credits’ were accumulating. The same trend was also apparent in the trial sustainable diversion limit accounts.

This trend has raised questions about whether use will also be less than the sustainable diversion limits, when formal compliance reporting commences.

In 2020, the MDBA undertook analysis to better understand trends in water use in four key catchments in the southern Basin; the Murrumbidgee, NSW and Vic Murray and the Goulburn. The summary document Analysing trends in water use in the southern Basin and full report Trends in water use relative to the sustainable diversion limit in the southern Murray-Darling Basin can be accessed below.