Water Quality History of Murrumbidgee River Floodplain Wetlands

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The condition of floodplain wetlands is a function of internal and external forces and functions. Wetlands vary longitudinally down a floodplain following principals enshrined in the River Continuum Concept whereby the nature and concentration of solutes and sediments change with distance from source. This observation pertains directly to the main river channels but influences the wetland mostly in times of flood as,during low flow,connection between the river and the wetland may be severed.

This exchange between river and wetland (described in Hillman,1986) varies transversely across the floodplain with wetlands proximal to the main channel having longer and more frequent connection than wetlands at the floodplain margin. In the Murray Darling Basin the condition ofthe main channel has been impacted by human settlement and development that has increased the flux of nutrients, sediment and salts and regulatedflow and extracted water. As a result the water of the main lowland rivers of the Murray Darling Basin is more saline, nutrient rich and turbid. The flows of the rivers have become lower, less variable and of lower amplitude withnaturalwinter/spring peak flows skewed towards spring/summer to accommodate the irrigation industry (Jones et al., 2002; Norris et al., 2002). As a result of these changesthe quality ofthe water entering floodplain wetlands has declined. In response to this degradation of wetland condition there has been deliberate action to rehabilitate and restore wetlands across Australia.