Rainwater Harvesting Scenario in Bangalore
Bangalore: With a population of 5,686,000, Bangalore is India's fifth largest city. As per the estimates of the Bangalore Water Supply and Sewerage Board (BWSSB), the total demand of water is 840 million litres per day (MLD) (assuming a population of 6 million and a supply rate of 140 litres per capita per day [lpcd]). (The demand works out to be 1200 MLD, at the standard rate of 200 lpcd set by the Bureau of Indian Standards [BIS] for water supply in urban areas). Corresponding demand supply gaps are 135 and 495 MLD.

SOURCES OF WATER:
Surface water:

Source	Design capacity (MLD)	Present withdrawl (MLD)3
1.Arkavathy river a) Hesarghatta b) T.G.Hally	36 148	6.0 36.0
2.Cauvery river a) Stage-I b) Stage-II c) Stage-III	135 135 270	135 135 270
	724	582

Source:
1. http://www.bwssb.org/my_html/nodal_info.html
2. A conceptual frame for rainwater harvesting in Bangalore, STEM, 2001
3. Vishwanath. S, 2000, Personal Communication

To meet the demand supply gap, the government has already proposed to extract 770.0 MLD of water from the Cauvery river under Cauvery stage IV project (Phase I and Phase II). The production cost of this water per kilolitre is expected to be Rs. 45.70. (On completion of these phases total extraction from the Cauvery for Bangalore alone would be 1310 MLD i.e. 478 billion litres in a year or 16.78 thousand million cubic feet [TMC])

Ground water extraction: According to a study conducted by the Centre for Symbiosis of Technology, Environment and Management (STEM), a Bangalore-based research group, the demand supply gap is met by groundwater exploitation. It is estimated that 40 per cent of the population of Bangalore is dependent on groundwater.

source: http://www.rainwaterharvesting.org/Crisis/Urbanwater-scenario.htm