Environmental studies of the Ambika and associated river estuaries

Abstract

The tide dominated coastal plain Ambika, Kaveri and Kareira estuarine system has been investigated to evaluate the influence of industrial and domestic wastewater discharges on the water quality. The wastewater streams were gauged and the pollution loads quantified. High sea water influx, strong currents and small low tide volume rendered the estuaries well mixed with excellent flushing characteristics. The fraction of freshwater method gave a flushing time of 2.5 and 5.8 tidal cycles in October and May, respectively. Although a tidal range of 1.2 m (spring) was observed 20 km inland, there was no intrusion of saline water except in May. The estuarine zone is characterized by high and variable suspended load. Nutrients, pH and trace metal concentrations in water were the natural background levels. The high BOD (24600 kg day -1) and the riverine flow influenced the distribution of dissolved oxygen in the Ambika estuary to a considerable extent. About 10 km stretch of the estuary had DO below 3 mg 1-1 when the reiverine flow was weak