As part of the development of a strategy to address the risks, the Commission is continuing to fund research to inform decisions by the Murray-Darling Basin Ministerial Council (the Council), Commission and partner governments. The reports below summarise the individual and cumulative impacts of the risks upon the shared water resources of the Murray-Darling Basin (as understood at the time of drafting). Reports relating to specific risks are listed later under the individual risks headings.
Review of selected factors that may change future flow patterns in the River Murray System , Murray-Darling Basin Commission (Earth Tech Engineering Pty Ltd, August 2003)
The shared water resources of the Murray-Darling Basin and (CSIRO, 2006) outlines the hydrology and key resource management strategies of the Basin.
The identified risks include:
Climate change is estimated to cause the largest and most likely reduction in flow, accounting for almost half of the estimated reduction in water volumes. A number of studies claim that the future climate of the Basin will be characterised by higher temperatures and reduced rainfall, resulting in reduced inflows to reservoirs and increased evaporation.
For more information on current research visit South East Australian Climate Initiative (SEACI)
Groundwater stores are being depleted in certain parts of the Basin due to growth in agricultural development resulting in increased groundwater extraction. A depletion of the groundwater resources is likely to impact on surface water flows depending on the level of connectedness between aquifers and the river system.
Summary of Estimated Impact of Groundwater Use on Streamflow in the Murray-Darling Basin (the Overview report) (Resource & Environmental Management, December 2004)
Evaluation of the Connectivity Between Surface Water and Groundwater in the Murray-Darling Basin (Resource & Environmental Management, July 2006).
Information for Groundwater Management in the Murray-Darling Basin
Copies of this report are available by request only via phoning the Information Officer on 02 6279 0434.
There is strong evidence to suggest the number and size of farm dams have increased significantly in the last ten years. Farm dams capture surface flows resulting in reduced flow to streams. The estimated impact of farm dams on water volume is second only to climate change; however the future impact will depend on the potential for future agricultural development and the effectiveness of legislation or policies to restrict further establishment of farm dams.
It is recognised that farm dams often provide economic, social and environmental benefits.
Previous studies (Agrecon 2005) have shown that farm dam numbers have increased in number and size over time, with the largest increases following major droughts. These studies have been very localised in nature and as such the results have high levels of uncertainty when extrapolated to other parts of the MDB.
To provide more accurate information on the development of artificial water bodies within the MDB a new project was developed specifically to look at changes in the number, location and size of dams from 1994 to 2005 using historic and recent satellite imagery.
In the short term, bushfire events can significantly affect water quality and reduce surface and groundwater levels in the longer term as vegetation regenerates. It is expected that climate change will lead to more frequent and intense bushfire events.
Following the 2003 bushfires, which burnt over a million hectares of forest and grazing land, a major study was commissioned to assess the likely impacts of the fires on water quality and quantity.
Increased areas of plantation forestry may reduce the mean annual water yield in a catchment, due to trees requiring more water than other vegetation types.
It is recognised that plantations have social, economic and environmental benefits. Strategically placed plantation forests may reduce groundwater recharge and address salinity.
It is estimated that improvements in the water use efficiencies in irrigation may result in reduced flows back to the stream. It is possible that this may result in increased salinity levels in rivers as salt is concentrated in the reduced return volume of water flowing back to the stream. There may also be water quality benefits as the return flow from irrigation may carry large amounts of pollutants.