Impact of water quality changes on harbour environment due to port activities along the west coast of India

Abstract

Physico-chemical and biological studies were carried out in 3 major harbours (Kandla, Mormugao and Mangalore) along the west coast of India over different periods from 2002 to 2007. R-mode factor analyses, water quality index (WQI) and hydrodynamic modeling were used to understand the dominant parameters influencing water quality, trace the sources of contaminants, their impact on harbour environments and their fate. Factor analyses showed the dominance of anthropogenic nutrients, petroleum hydrocarbons and phenols, while the dominance of suspended solids, turbidity and salinity from natural effects in Kandla harbour. Despite large availability of nutrients, a significant decrease in chlorophyll a and primary productivity during monsoon suggested detrimental effects of the dominant contaminants. Mormugao harbour showed year round dominance of microbes, anthropogenic nitrogen compounds, petroleum hydrocarbons and heavy metals from sewage, boat traffic and port activities, with significant negative effect on chlorophyll a during post-monsoon. New Mangalore harbour showed the dominance of anthropogenic nitrite, ammonia, petroleum hydrocarbons, cadmium and mercury from sewage, industrial discharges and port activities. Overall Index of Pollution (OIP values) of harbour waters, evaluated from WQI of each water quality parameter showed increases (OIP greater than 4) in Kandla harbour suggesting polluted water during all seasons. Mormugao harbour showed acceptable to slightly polluted water (OIP: 2.51-2.75) mostly during post-monsoon, while New Mangalore harbour showed acceptable water quality (OIP: 1- 2). Hydrodynamics indicated that strong ebb currents (0.09-2 m/s) in Kandla harbour transport anthropogenic contaminants to the inner Gulf of Kutch; while in Mormugao harbour, the coastal water enters the estuarine mouth from north and flows out towards south and transports the contaminants to the coastal water, augmented by E-W flowing tidal currents. In New Mangalore harbour, the strong seasonal currents and seasonal winds keep the water well mixed and aerated and help in driving the contaminants away from the shore