Lakes and tanks in the metropolitan area of Greater Bangalore and the district of Bangalore Urban are reservoirs of varying sizes constructed over a number of centuries by various empires and dynasties for rainwater harvesting. Historically, these reservoirs were primarily either irrigation tanks or for the water supply, with secondary uses such as bathing and washing. The need for creating and sustaining these man-made dammed freshwater reservoirs was created by the absence of a major river nearby coupled with a growing settlement. As Bangalore grew from a small settlement into a city, both of the primary historical uses of the tanks changed. Agricultural land witnessed urbanization and alternate sources of water were provisioned, such as through borewells, piped reservoir water and later river water from further away.
The topography of the three main gentle natural valley systems allowed for the creation of interconnected tanks and wetlands where water flows downstream through a series of channels or drains. These tank cascades or chains have seen accelerated change and fragmentation caused by urbanisation in the past four decades. Some lakes have been redefined as recreational spaces. Some have been built upon. Other lakes have reduced in size and are in various stages of deterioration. While associated pollution is rampant such as the case of Bellandur Lake which is used as a sewage tank, numerous public and private efforts have been undertaken to address sewage treatment, prevention of dumping and encroachment.
Terminology Lakes are called keregalu (ಗಳು) in Kannada language, and are traditionally referred to as tanks. Researcher Rohan D'Souza has suggested that the concept of 'kere' and 'lake' differ; for example the former also refers to the wetland and bund while the latter focuses more on a body of water surrounded by land. When the forest department started to have a larger role in the administration of these waterbodies in the 1980s the word 'lake' started to be used as compared to 'kere' or 'tank'. In accordance with this terminology, communication and practices related to these waterbodies were impacted. Anthropologist Smriti Srinivas writes that tank is also a simplification that incorporates both natural and manmade waterbodies into its context since identification of bodies of water in the region that were historically natural is a task. A 1986 report classifies some tanks as 'disused' tanks.
There is no specific definition for what a lake is in India. Urban lakes also have no specific definition. In Bangalore, smaller waterbodies 1-3 acre in size are called gokattes and waterbodies less than 1 acre are called kuntes. The words kere and katte go back to usage by the Hoysala's. Kaluves can be translated as canals, while in the context of Bangalore rajakaluves refer to bigger or large canals, channels or drains, specifically storm water drains, that connect the lake cascades. Kalyanis refer to square tanks used for immersion (see temple tanks). Other bodies of water include a well, 'bhavi', and pond for domestic use, 'kola'.
History Rainwater has been stored in reservoirs or irrigation tanks in the Indian subcontinent for many centuries. In Bangalore and the surrounding regions of Mysore these tanks numbered in the thousands and varied in size according to the rains. They were made primarily for the purposes of irrigation and drinking water, and secondary uses such as fishing, washing and other domestic needs. Inscriptions provide some insight into their history. The history and creation of the reservoirs is linked to different empires, dynasties and periods of the British Raj. The Ganga and Chola dynasty, the Hoysala Empire, the Vijayanagara Empire, Hyder Ali and Tipu Sultan and the Wadiyar dynasty are all associated tanks in Bangalore, including their creation, maintenance and use. These tanks or lakes along with open water wells constituted the water supply infrastructure. Socio-economic factors, population distribution, caste, and wealth affected interaction with water bodies. The neerganti were organised labour traditionally associated with regulating irrigation water. Voddas were the tank builders. The traditional well diggers are the Manu Waddar. The Vanniyakula Kshtriya or Thigala were horticulturists associated with lakes such as Sampangi. They brought the Karaga celebration to Bangalore. The roles of these communities have been diluted over time. Cultural and religious associations abound. Urbanisation has had diverse but mixed influence on these communities. It is often the case that when the history of these tanks is discussed it is idealized.
The dependence on tanks and other sources of water such as wells reduced with the implementation of schemes that brought water from Hesaraghatta Lake in 1894, T G Halli Reservoir in 1933, and Cauvery River from the 1970s. Borewells also reduced dependence on reservoirs. The Dharmambudhi Tank is used as an example to portray historical change, and change of a commons in Bangalore over the centuries. The tank goes back to at least the 16th century; some historical references point to a much earlier reservoir at the same location. The lake would be used until the end of the 19th century after which is saw unchecked decay as a waterbody. However its lakebed was located in prime area and continued to be used for various events, festivals, and gatherings. Part of the lakebed was still wetland and had wells. In the 1960s a portion of the lakebed was set aside for the construction of a bus stand. Of the many channels and lakes that were connected to Dharmabudhi in the past such as the former Sampangi Lake, Kempambudhi Lake and Sankey Tank remain.
Sampangi lake supported both the Pete and cantonment. It provided irrigation for millet and paddy cultivation. Construction in the area included a park in 1879, a hospital in 1886 and a school in 1898. Around 1895 the lake stopped being used officially as a water source and inflow channels severed. There were contesting claims as to how the lake and lakebed should be used. By 1935 all that remained was a small square tank. On the lakebed several constructions followed. An eponymously named stadium was constructed on a portion of Sampangi lake in 1946, now known as the Sree Kanteerava Stadium. This was followed by an increase in surrounding built up area. In 1995, another portion of the former wetland was used to build the Kanteerava Indoor Stadium.
Lakes or tanks, including dry ones, have been converted to commercial areas, industries, government buildings, bus stands, sports facilities, playgrounds and residential colonies, a few tanks were breached under a malaria eradication programme. When Bangalore Golf Course was formed in 1876, it was located in the center of the city, and then land was relatively easily obtained. In 1973 the Karnataka Golf Association was formed and the members started looking for a location to set up a golf course. Among the several locations Challaghatta lake or tank was suggested, then located on the outskirts of the city. At the time there were ample lakes in the city and not much fuss was made related to the lake itself. After a number of administrative processes involving multiple departments of the local administration and multiple Chief Ministers, and conversion of the area into a golf course designed by an Australian architectural firm, the first 9 holes were inaugurated in 1986. Multiple national and international golf tournaments have been held at the course.
In 1986 the Lakshman Rau committee (under a retired administrative officer; see N. Madhava Rao) came out with a report highlighting the failure to maintain various tanks and made comments covering lake boundaries, water quality, the construction of tree parks in areas breached, to monitoring and conducting further study for new tanks. via indiawaterportal.org The committee identified 127 lakes and transferred 90 to the forest department. Since the 1980s custody of the lakes in the city has seen numerous changes. The former Lake Development Authority experimented with public–private participation which included leasing out of four lakes. Government administration of the lakes in the city mainly fall under a few urban local and state regulatory bodies. Outside the city management is under the village and district Panchayats, and the Minor Irrigations department depending on the size of the lake. Others forms of participation in the form of corporate social responsibility, general public involvement, including coordination with government efforts, and formation of lake groups, has resulted in some lakes seeing successful attempts at conservation and rejuvenation. There are numerous measures undertaken, debated and contested by stakeholders in relation to the rejuvenation (restoration, revival, rehabilitation, conservation) of lakes. Failure of these processes has been observed. Urbanization has impacted the lakes in various ways, some lakes have completely disappeared, others have been reduced to pools, some have been encroached upon, some are in various stages of deterioration, some have dried up, and some have been leased. The Koliwad committee, set up by the Karnataka legislature in 2014, reported thousands of acres of encroachment of lake land.
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. The average elevation is roughly . These naturally undulating terrain of hills and valleys lends itself to the development of tanks 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 by the construction of bunds. A tank generally consists of a shallow inflow area and a relatively deeper outflow area where the bund is. The tank can further be zoned into a flooded area and a waterlogged zone. Monsoons recharge the tanks and the outflow can be regulated for irrigation of monsoon crops during the last six months of the year. Most tanks are dry a couple of months before the onset of the new monsoon. A second crop can be considered on the basis of water levels. Other seasonal changes affect the water level. Urban sewage inflow allows some lakes to retain their water spread for a longer period. Initially serving as a water source, these tanks over time also developed features of closed water lentic ecosystem habitats. The catchments on the east and west of the ridge belong to the Ponnaiyar River and Arkavathi River respectively. Both these rivers flow into the Kaveri.
The tank-canal linkages or rajakaluves (large canals or stormwater canals) were redefined by the colonial administration once they became the location for the sewerage network. Rajakaluves now refer to both the inter-lake linkages and the sewerage, and are translated as stormwater drains. In the 21st century there are 842 km in the drain network. Urbanisation has impacted these. Ensuring adequate water flow and no blockages is undertaken by the local administration. Encroachment of storm drains and catchment areas can cause both drying up and flooding of lakes. These drains often carry sewage in it, which results in the lakes getting polluted.
Bangalore has a mean annual rainfall of with June to September seeing the majority of rainfall. 2022 was the wettest year with over 1700mm of rainfall. The city sees around 60 rainy days a year. The minimum rainfall is 587.8 mm/year. An estimate of the rain water potential is 45000 million litres. The annual mean temperature is with extremes ranging from to . The highest and lowest temperature ever recorded in Bangalore has been 38.9 °C and 7.8 °C. in 1931 and 1884 respectively.
Quantity