Potential cumulative impacts on river flow volume from increased groundwater extraction under the Murray-Darling Basin Plan

ABSTRACT A risk assessment of the reduction of streamflow in the Murray-Darling Basin (MDB) from potential increased groundwater extraction has been conducted. This incorporates the uncertainty of future extraction and connectivity between groundwater and surface water. The predicted impact from forty years of growth in extraction is less than 580 Gl/y, and likely to be in range of 100–400 Gl/y. Over 80% of this impact will result from extraction under limits existing before the Basin Plan, with most impact from extraction outside these limits occurring later. Groundwater units with high risk lie within a range of river valleys and hydrogeological domains, and particularly the Goulburn valley and zones of fresher groundwater discharge. Management rules in the new groundwater management plans are designed to reduce use in high impact zones. Monitoring is required to assess effectiveness of these as use increases and conjunctive water management becomes more common.