a catchment area of 18.96 km2 to create the Vihar Lake. The Powai-Kanheri hill ranges form the catchment area, which drains the rain water into the lake. For this purpose, three earthen embankment dams with a masonry spillway section were constructed to create a reservoir of 9200 million gallons capacity at the full reservoir level of 80.42 metres. The lake has a maximum water depth of 34 m and a minimum of 12 m. The lakes water spread area is 7 km2. The dam height was raised in 1872 resulting in increase of water supply from 32 million gallons (catering to a population of 0.7 million) to 36 million gallons. Flora and fauna The lake and its catchment are protected by the Brihanmumbai Municipal Corporation and Sanjay Gandhi National Park Authority. The catchment areas of Vihar lake has high hills rising on all sides. The seclusion, protection, and security provided under the Sanjay Gandhi National Park has ensured well wooded hill slopes and abundant natural regeneration. Higher percentage of khair species has been noted in the catchment area of the lake. As the lake is situated inside the Sanjay Gandhi National Park, the flora and fauna reported for the park would be relevant to the lake. However, fresh water crocodiles Mugger or Marsh crocodiles (Crocodilus palustris) are known to inhabit the lake in sustainable numbers. As it is difficult to sight them in the lake, the park has set up a Crocodile Park’ to view the reptiles of different sizes. Limnology Limnological studies carried out by the Central Public Health Engineering Research Institute, Nagpur, India, in 1964, indicated an unstable thermal stratification in the lake waters. The dissolved oxygen (DO) values were found to increase in some months and carbon dioxide was found to be less at the surface than at the bottom. In cooler season, the surface water was found to be less alkaline, which could be attributed to the photosynthesis activity of the algae. The pH stratification was found to be unstable. Interrelation was attributed to fluctuations in the chlorophyll, pH and DO values and nitrates were generally absent on the surface and no sulphates were detected. An odd event In the year 2006, finding sweet water at the Mahim Creek (a semi enclosed area), where fresh water and sea water meet, created a lot of excitement among the public. The health department of BMC who analysed the