Estuaries along the coast of India

An estuary is a channel that has the sea at one end and a river at the other; in an estuary, seawater is appreciably diluted. The complete salinity range from 0-35 ppt is seen from the head (river end) to the mouth (sea end) of an estuary. About 100 such channels of varying sizes and shapes occur along the coast of India. Each estuary receives its freshwater from drainage channels of a river basin. The major river basins of India are shown in Fig. 28 together with some of the major riverine/estuarine channels. The banks of estuarine channels form a favoured location for human settlements, which use the estuaries for fishing and commerce, but nowadays also for dumping civic and industrial waste. Estuaries are usually biologically highly productive zones. They also act as a filter for some dissolved constituents in river water; these precipitate in the zone where river water meets seawater. More important is the trapping of suspended mud and sand carried by rivers which leads to delta formations around estuaries. Major estuaries occur in the Bay of Bengal. Many estuaries are locations of some of the major seaports. Most of the India’s major estuaries occur on the east coast. In contrast, the estuaries on the west coast are smaller. Two typical examples of estuaries on the west coast are the Mandovi and Zuari estuaries located to the north and south of the main campus of the National Institute of Oceanography at Dona Paula, Goa.