Issue Paper 4
National Groundwater Committee
Department of the Environment and Heritage, 2004
About the issue paper
The sustainable yield approach to groundwater management defines the bulk volume of water that can be sustainably extracted on an annual basis from a defined groundwater management unit (GMU) or zone over a specified time period. However, as hydrogeological conditions are seldom uniform within a GMU, climate is not constant, and bores are not evenly distributed across the aquifer, there may be local problem areas requiring additional management. These local problem areas occur where groundwater levels continue to decline even when overall extraction for the GMU is within the sustainable yield. Such areas are generally caused by a high density of pumping bores and/or variable hydrological/climatic conditions.
As groundwater development intensifies across Australia, many GMUs are becoming allocated up to their estimated sustainable yield. Once fully developed, there is heightened potential for these systems to have local areas with unsustainable levels of extraction and resultant unacceptable impacts. Local impacts and consequences of unsustainable levels of extraction can include:
- lost ability to access the resource when water levels fall below pumping bores, particularly shallower stock and domestic bores and wells;
- increased pumping costs;
- deterioration of water quality;
- release of acid drainage from acid sulphate soils;
- saline water intrusion or upcoming;
- inability of the aquifer to fully recover between pumping seasons;
- reduction in water for groundwater dependent ecosystems such as wetlands or rivers;
- interference with springs;
- in extreme cases, land subsidence.
The increasing potential for unacceptable local impacts has led to a recent recognition that micro-management of groundwater resources is needed in addition to broad-scale management to sustainable yield. Micro-management refers to finer control of the spatial distribution and timing of groundwater extraction at a local or even individual farm scale.