Rivers, lakes and wells are important sources of water in a region.

Water is an essential component of an eco-system. It sustains life on earth. A community depends on water for its domestic, agriculture and industrial needs. Availability of water has been a factor in the development of various civilisations near lakes and rivers. At a particular stage in development, tanks and wells are introduced to harvest rain and ground water. Wells and tanks are the sources of water in most places even today. Tanks harvest rainwater and store it, while wells tap water stored underground.

The total water spread in India is about 4.5 million hectares. Inland aquaculture resources cover about 3 million hectares. These include about 0.72 million hectares of natural lakes and 2.0 million hectares of constructed reservoirs. The state of Karnataka has about 2000 perennial and about 30,000 seasonal tanks with a total water spread area of 3,000,000 hectares. The average annual fish yield from these tanks is estimated to be about 350 kg fish per hectare per year.

In June 1995, there was a large-scale episodal mortality among the freshwater fishes of certain lakes of Bangalore city in Karnataka state, India.. We conducted an intensive study of the Sankey Lake, which is situated in Sadashiva Nagar of Bangalore city, where fish mortality occurred on quite a large scale during June-July 1995. This episode follows immediately after fish deaths in Lalbag Lake, which is located about 12 kilometers away.