The Bangalore district supports about 461 tanks serving the irrigation needs to various capacities (Bangalore Gazetteer, 1981). Most of these tanks are seasonal and carry water for six months during a year. (Bangalore: North - 98 tanks, South - 166 tanks , Anekal - 197 tanks).

Bangalore North supports about 98 tanks irrigating about 2,102 ha of land. These are mostly seasonal and carry water for about six months in a year. The biggest tank in the Taluk is Hesaraghatta with a catchment area of 490 sq.kms. The total surface water potential created in the taluk is about 2,330 ha.

Bangalore South taluk has about 166 tanks irrigating about 4,450 ha of land. The major tanks include those of Bellandur and Varthur with a catchment area of 3.5 and 1.8 sq.km respectively. The taluk includes parts of Chamarajaendra reservoir and Hoskote tanks with the total surface water potential created is about 5,610 ha.

The total surface water potential created by these tanks is about 12,541 hectares accounting to about 54 percent of the total water resources of the district.

Drainage

The drainage pattern of the Bangalore North taluk is governed by the Granitic ridge running NNE to SSE almost to the middle of the taluk. The drainage towards the east is made up of a network of nalas, generally flowing from west to east with storage tanks along the nalas, ultimately feeding the South Pinakini River on the western half, the nalas generally flow from east to west, ultimately draining into the Arkavati River.

The Bangalore South taluk drains to the east into the South Pinakini basin and to the west into the Arkavati basin. The Vrishabhavati is the only minor river which flows in the taluk and ultimately joins the river Arkavati. The Eastern portion of the taluk is marked by a series of tanks varying in size from small ponds to considerably large tanks.

Rivers

Bangalore has no major rivers flowing in the district. The Arkavati River flows in the district for a small distance in Bangalore North taluk and the Dakshina Pinakini touches the borders of the district to the North-East of the Anekal Taluk.

The Vrishabhavati, a tributary of Arkavathi that takes its birth in the Bangalore City at Basavanagudi, flows in the district before joining the Arkavati near Muduvadidurga and the Suvarnamukhi from Anekal Taluk joins the tributary before joining the Arkavati.

Ground water

Ground water in the district occurs under water table conditions in the weathered mantle of the granitic gneisses & in the joints, crevices and cracks of the basement rock. Ground water is developed largely by means of open wells. Open wells as well as bore wells can both yield between 70 to 90 meters of water per day.

Climate

Bangalore is considered to be climatically a well-favored district. The climate of the district is classed as the seasonally dry tropical savanna climate with four seasons. The dry season with clear bright weather is from December to February with summer from March to May, followed by the southwest monsoon season from June to September. October and November constitute the post-monsoon or retreating monsoon season. The main features of the climate of Bangalore are the agreeable range of temperatures, from the highest maximum of 33^o C in April to the lowest minimum of 14oC in January. The two rainy seasons, June to September and October to November, come one after the other but with opposite wind regimes, corresponding to the southwest and northeast monsoons.

The climate of the district is Dry tropical savanna with four seasons.

Dry	Characterised with bright weather from Dec to Feb
Summer	Characterised by high temperatures, from March - May
Monsoon	South-West monsoon, Jun - Sept
Post-monsoon	Oct - Nov

Temperature

Bangalore records high temperatures during April with daily mean temperatures of 33.4 ( C^o and mean daily minimum in the month of December) at 25.7 ( C^o, as the coolest month>.

Relative Humidity

The mean monthly relative humidity is the lowest during the month of March at 44% and records highest between the months of June and October at 80 to 85%.

Rainfall

The mean annual rainfall is 859.6 mm, with three different rainy periods covering eight months of the year. June to September being rainy season receives 54% of the total annual rainfall in the S-W monsoon period and 241-mm during the N-E monsoons (Oct. - Nov.)

Wind

The surface winds in Bangalore have seasonal character with the Easterly components predominating during one period followed by the Westerly in the other. The high wind speed averages 17 kmph during the westerly winds in the month of July and a minimum of 8-9 kmph during the months of April and October.

The Bangalore supported about 29 waterbodies in 1870 spread over the district serving the drinking water needs, acting as recharging zones of the water table. The prominent among them are the Ulsoor, Sankey, Millers, Sampamgi, Kampamudhi, Dharmamudhi, etc.

With increasing population and unplanned urbanisation have resulted in not only loss in number of water bodies, due to encroachments, etc., and also contributed to the declined water quality owing to sewage. The prominent tanks that have been breached due to unplanned urbanisation include Millers tank, Shulay tank, Akkithimanalli tank, Domlur tank, Sampangi tank, and Dharmamudhi tank. Our recent study shows that about 60% of the existing tanks are fed by discharge of sewage from the neighboring areas.