Variation of physico-chemical characteristics with tide in Visakhapatnam Harbour waters, east coast of India

Abstract

Variations in physico-chemical parameters (DO, BOD, NO₂, SiO₄, PO₄ suspended solids, salinity and currents) observed in the waters of main channel of Visakhapatnam Harbour over a tidal cycle in different seasons from February 1982 to January 1983 are presented. In general, tidal variations in these parameters in surface waters show increasing trend during flood tide and decreasing trend during ebb tide. However, the nutrient concentrations at st C (entrance channel) show the reverse trend. The wide fluctuations in physico-chemical parameters at st A (northwestern arm) may be attributed to the closeness of the station of the discharge point of industrial pollutants. No significant variation is found during a tidal cycle in bottom water. Variations in wind during different seasons influence the current speeds in addition to tide in the Visakhapatnam Harbour. The net cross sectional discharges through the mouth of harbour into the sea during premonsoon, monsoon and postmonsoon seasons are 26.51, 47.30 and 19.64 m³ S^-1 respectively.