Saturday, May 26, 2007

Groundwater & Australia’s rivers

I posted a week ago on the controversy surrounding the possible double counting on water supplies by ignoring the role groundwater plays in generating stream flow. I have just come across a report by hydrologist, Dr Richard Evans, which sets out the issues accurately in clear, non-technical language with easy-to-follow diagrams. He sets out what we know, what we need to know and why integrated management of stream water and groundwater is essential. The report is here. Land and Water Australia’s research portfolio on groundwater and groundwater recharge (which includes this report) is here.

A troubling issue is that extensive use of groundwater of the type forced by the recent drought can make it very difficult for stream flow to regenerate – stream flow might in the main be diverted into groundwater supplies. Moreover these types of effects can often only be observed with a lag. The figures I cited in the previous post seem to just be approximations or guesses but they do suggest the severity of what seems to be a critically serious situation.

This Summary of Dr Evan’s report on interactions between groundwater and stream flow should be read by anyone seeking to appreciate the extent of Australia’s current water supply crisis. It is a crisis and a thoroughgoing change in our attitude to agricultural water uses is called for in Australia. From the Summary:

Groundwater and surface water resources are often closely linked. This has particular implications for Australia and how we manage our water. As a result of this connectivity it is possible to allocate the same resource twice, to surface water users and to groundwater users. This double allocation of the same water has reduced the flow in our rivers and streams.

There has never been a nationwide review of surface water and groundwater interaction in Australia and consequently the extent of double allocation is unknown. There is also no national approach to managing our groundwater, nor an agreed method for assessing its links to surface water.

The lack of understanding of the links between groundwater and surface water has contributed to the nation’s present water shortage. This has been exacerbated by dry conditions over the last decade and by rising demands for water.

It is suggested that tackling the impacts of surface water and groundwater interaction requires a national approach on three fronts - technical, managerial and educational.

Several approaches are proposed for assessing and managing our groundwater resources, and recommendations made for their adoption.

It is also argued that remedying the over-allocation of surface water and groundwater should be borne equitably by all users, with cuts and restrictions applied generally rather than to groundwater users alone.

1 comment:

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