Assessment of the impact of developmental activities on estuarine environments of Mandovi and Zuari rivers of Goa along the west coast of India

Abstract

This paper discusses physico-chemical and biological data for EIA as regards construction of two jetties in the estuarine environments of Mandovi and Zuari rivers of Goa (India). Multivariate statistical techniques (Factor analysis) applied to physico-chemical data in water and sediments separately over different tidal periods, indicated a total of 6 factors each explaining 91% of the total variance during high tide and 84% of the total variance during low tide in Mandovi. Similarly, in Zuari, altogether 4 factors explained 78% of the total variance during low tide and 6 factors explained 83% of the total variance during high tide. In sediments, a total of 2 factors explained 73% of the total variance in Mandovi and 3 factors explained 95% of the total variance in Zuari river irrespective of tides. Observed increases in ammonia, PHc, Hg, etc in these rivers suggested contamination from domestic waste /organic matter, boat traffic and ship building activities. Though, jetty construction would disturb bed sediments and increase trace metals, micronutrients and organic load, increasing oxygen demand of riverine water, the resultant spring tide currents in NESW direction with a maximum speed of 1.08 ms-1 in Mandovi and in E-W direction Zuari with a maximum speed of 0.97 ms-1, as observed from MIKE 21 HD model, in construction area of these estuaries would flush the contaminants out to the sea minimizing the impact due to construction