On the basis of hydrochemical and biological studies, a trophic gradient has been established between the inshore and the offshore areas of the Dal lake. The inshore areas receive large quantities of raw sewage and agricultural runoff as a result of which high nutrient concentration of water and the presence of dense phytoplankton populations have been registered at these sites.

The Kandy lake, situated in the heart of Sri Lanka's second largest city with a population of nearly 120,000, has been monitored to probe the extent of heavy metal pollution. Although the lake is a source of drinking water to the city, a large number of effluent canals drain into the lake carrying a continuous flow of industrial and domestic waste matter. A total of 66 surface water samples were analyzed for their Fe2+, total Fe, total V, SO 4 2− , Cd2+, and Pb2+ contents.

Two drinking water lakes of Hyderabad - Osman Sagar and Mir Alam, were studied for their chemistry for two years (1977-78). Mir Alam, the older of the two, showed higher silicate content. Dissolved component formed 91-27% of the total silicate content in these lakes.

The mid-canal of Kandy, a 8-km effluent canal that runs through the city, collects massive quantities of domestic, municipal, and agricultural waste products. In this study, 37 samples from canal water and 13 from nearby drinking water wells were analyzed for their total Pb, Cd, V, Fe, and ferrous ion content. The following average values for the canal water were recorded: Pb, 269 μg/liter; Cd, 138 μg/liter; V, 18 μg/liter; total Fe, 4 mg/liter. These values indicate the relative levels of metal input from the effluent sources of the city of Kandy, the second largest city in Sri Lanka.

The important attributes of macrobenthic community structure viz., species composition and number, population density, biomass, and dominance and diversity indices were measured at different depths and discussed in relation to pollution of Lake Naini Tal. The zone below 7 m depth, where anoxic conditions prevailed for most part of the year, showed complete absence of macrobenthos.

For the past five years Hyderabad has been trying to clean the Hussain Sagar Lake, separating the twin cities of Hyderabad and Secunderabad in Andhra Pradesh. The efforts suffered yet another blow on June 20 when the Andhra Pradesh Pollution Control Board (APPCB) denied permission to dredge the mouths of four nalas releasing waste water into the lake and to dispose it of at a nearby quarry.