Pulicat Lake - Hydrology

Hydrology

Three major rivers which feed the lagoon are the Arani River at the southern tip, the Kalangi River from the northwest and the Swarnamukhi River at the northern end, in addition to some smaller streams. The Buckingham Canal, a navigation channel, is part of the lagoon on its western side. The lagoon's water exchange with the Bay of Bengal is through an inlet channel at the north end of Sriharikota and out flow channel of about 200 metres (660 ft) width at its southern end, both of which carry flows only during the rainy season.

The water quality of the lake varies widely during various seasons – summer, pre–monsoon, monsoon and post–monsoon – as the depth and width of the lake mouth varies causing a dynamic situation of mixing and circulation of waters. The resultant salinity variation and DO (dissolved oxygen) affects the primary production, plankton, biodiversity and fisheries in this lake.

Salinity values vary from zero during the monsoon to about 52 ppm (hyper saline) during post and pre–monsoon seasons. Adjustment to this wide variation is difficult for sessile and sedentary species in the lake. However, euryhaline species still dwell in the lake.

The benthic or the bottom habitat of this lagoon is classified into three zones. The southern zone, the first zone, is dominated by sand with some admixture of mud. The second zone at the northern region is wholly muddy. The third zone with sand and mud in equal parts is overgrown with patches of weeds and is reported to be rich in benthic biodiversity.

Toxicity levels of heavy metals such as magnesium, lead, zinc, nickel, cadmium, aluminum and copper and chemicals such as ammonia, sulphate and fluoride in the lake are well within permissible limits.