Ecological effects of mine effluents on the South Esk River, north-eastern Tasmania. I. Study area and basic water characteristics

Abstract

The drainage basin of the South Esk River has a temperate climate with moderate rainfall and temperature. Most of the rainfall, which may be unevenly distributed over the catchment, is in winter. although there may be wide fluctuations in successive years. The discharge of the South Esk River reflects the rainfall and is subject to wide short-term fluctuations in winter and the reverse in summer.

The dissolved oxygen concentrations of the river were at, or near, saturation levels. pH was slightly acid and was constant along the river course at any one time, indicating a reasonably well-buffered natural water. pH correlated positively with alkalinity and calcium, magnesium and sodium concentrations, all reaching their highest levels in the summer of 1975-76 after heavy rainfall in 1975. Dissolved carbon dioxide concentrations were generally above saturation levels. The major cation concentrations generally increased down-river. Low levels of phosphate. chloride and nitrate indicate that the South Esk River was free of organic contamination by domestic and agricultural effluents.