The requirement commonly placed on hydrogeologists to quantify ‘sustainable’ extraction limits for a groundwater resource implies there is a quantifiable amount of water that can be extracted from a resource without causing unacceptable change in its condition over a given timescale. A central task for hydrogeologists responding to this requirement is to provide the technical information needed by stakeholders and environmental regulators to reach agreement on what are the limits of ‘acceptable change’ to the condition of the resource, whether these be changes in groundwater levels, salinity, discharges to the surface environment, or other groundwater condition indicators.
In the drying and warming climate projected for southern Australia, a change to the condition of some groundwater resources can be expected even in the absence of groundwater extractions. The likely impacts of climate change are therefore an important consideration in the assessment of groundwater extraction limits that aim to maintain the condition of a groundwater resource within agreed limits. The SA Department of Environment, Water and Natural Resources has incorporated projections of climate change and consequent groundwater impacts into the technical assessment of extraction limits for a number of groundwater resources. By incorporating projected regional climate change into predictive model scenarios, we have been able to communicate to stakeholders the relative risks of exceeding agreed resource condition limits under a range of extraction scenarios, with and without the impacts of climate change. By communicating the projected changes with reference to agreed resource condition limits, we have been able to convey an improved understanding firstly of the potential impact of climate change on water availability, but perhaps more importantly, of the need for water users and resource managers to reach collective agreement and compromise on their expectations of the future condition of the resources and environment to which they are accustomed.