Physico-chemical investigations in Auranga river estuary (Gujarat)

Abstract

The wastewater streams polluting the Auranga River Estuary were sampled periodically and pollution loads were quantified. The shallow estuary is well mixed with excellent flushing characteristics due to the high sea water influx and strong tidal currents. The flushing time calculated (2.7-4.1 tidal cycles) by applying the fraction of fresh water method was at least three times higher than computed on the basis of the tidal prism method. The load retained in the estuary under continuous flow of pollutants and after a large number of tidal cycles was estimated to be less than 3 times the load introduced per tidal cycle. The suspended load in the estuary varied with the current speed and was mainly due to the dispersion of the bottom sediment into the water column. The inner estuary was freshwater dominated during October while sea water influence prevailed during May. The high dissolved oxygen and low BOD observed throughout the study period indicated good oxidizing conditions