Topography and Hydrology
The topographic setting of the city has radial slopes towards east and west with a smooth ridge running north to south; rainfall over the ridge area gets divided and flows east or west into the three gentle slopes and valleys of Koramangala–Challagatta, Hebbal and Vrishabavathi. Doddabettahalli 1,062 m (3,484.3 ft) is the highest point on this ridge. These naturally undulating terrain of hills and valleys, lends itself perfectly to the development of lakes that can capture and store rainwater. Small streams are formed by each valley starting with the ridge at the top. A series of shallow tanks varying in size are developed. The gentle topography has also good potential of ground water development.
Water resources are important for urban areas as they provide for a wide range of uses. Bangalore, with annual rainfall of 900 mm (3.0 ft) with three different rainy seasons covering nine months of the year. June to October is the rainy season accounting for 64% of the total annual rainfall in the S-W monsoon period and 324 mm (1.1 ft)during the N–E monsoons (November – December.). It has a salubrious climate with an annual mean temperature of 24 °C (75.2 °F) with extremes ranging from 37 °C (98.6 °F) to 15 °C (59.0 °F) . The streams between ridges and valleys have been dammed at suitable locations creating a cascade of reservoirs in each of the three valley systems. Each lake stores rain water from its catchments with excess flows spilling downstream into the next lake in the cascade. The storm water runs off through drains only. These drains often carry sewage in it, which results in the lakes getting polluted. Many lakes have reportedly springs at the bottom of the lakes, some of which are stated to be choked due to silt, which also feed the lakes.
The dependence on lakes, tanks, ponds, wells and other sources, in the past for supply of raw water to the city was de–linked with treated supplies arranged from river based schemes such as the "Chamarajendra Water Works" (Hesaraghatta Lake) built in 1894 and the "Chamarajasagar Reservoir" at T G Halli across the Arkavathy River in 1933 and subsequent sourcing from the Cauvery River schemes.
Read more about this topic: Lakes Of Bangalore
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