Double Accounting of Surface Water and Groundwater Resources
Abstract
The interconnection between groundwater and surface water is a poorly understood process in Australia. Consequently we have developed separate management systems which treat groundwater and surface water as separate resources. The often significant time lag between groundwater use in a catchment and reduced stream flow acts to cause water managers and the community in general to ignore this problem.
Time lags for bores located tens of kilometres from streams may commonly be several decades and experience from USA indicates that these effects slowly emerge. The separate development of groundwater and surface water has resulted in double accounting of the one parcel of water, once as groundwater and then a second time as surface water baseflow. The extent of the double accounting across Australia is unknown. Estimates for the Murray Darling Basin suggests a double accounting problem in the order of 500 GL/year over the next few decades or so.
A fundamental cultural change in water management is required to address this issue. Catchment scale total water balances are required to initially define the problem. The impact on water resource management plans throughout Australia will be profound.
Authors
Dr Richard Evans