NAINITAL town's Naini lake is shrinking and its water becoming increasingly murky. The quality of water in the lake, which is the sole source of drinking water for the people of the town, has deteriorated alarmingly. The discharge of sewage into the lake and inappropriate construction activity in the lake's catchment area are the villains of the piece. The lake is fed by rainfall (2,220 mm-2,500 mm annually), and rainfed springs.

Monsoon overflow from the lake passes through the Balia nullah, which empties into the Balia ravine. It is central to Nainital's existence. "The Balia nullah controls the stability of the entire lower portion of the town between the outfall of the lake and the Brewery