Urban nutrient inputs and phytoplankton biomass in a small impoundment on the River Murray, Australia

Murray-Darling Freshwater Research Centre

MDFRC item.

Lake Mulwala is a small (116.5 x 106m3) impoundment on the River Murray, Australia, used for water supply and recreation. Earlier studies (Walker & Hillman 1982) showed that phosphorus was the nutrient in shortest supply in the lake. Statistical analysis indicated that phytoplankton biomass was usually inversely related to levels of abiogenic turbidity. During periods of low turbidity algal biomass correlated with total-phosphorus concentrations and showed some inverse relationship with water replacement time. The relationship between water chemistry in the lake and that of the major influent streams is also analysed. Finally, changes in nutrient inputs from an urban catchment over a 10-year period are analysed and related to changes in inputs to Lake Mulwala some 160 km downstream.