Lakes in Bengaluru
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.
[3] 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.
[18] In Bangalore and the surrounding regions of Mysore these tanks numbered in the thousands and varied in size according to the rains.
[18] They were made primarily for the purposes of irrigation and drinking water, and secondary uses such as fishing, washing and other domestic needs.
[23] Socio-economic factors, population distribution, caste, and wealth affected interaction with water bodies.
[55] Government administration of the lakes in the city mainly fall under a few urban local and state regulatory bodies.
[56][57] Outside the city management is under the village and district Panchayats, and the Minor Irrigations department depending on the size of the lake.
[58][59] There are numerous measures undertaken, debated and contested by stakeholders in relation to the rejuvenation (restoration, revival, rehabilitation, conservation) of lakes.
[62] The Koliwad committee, set up by the Karnataka legislature in 2014,[63][64] reported thousands of acres of encroachment of lake land.
[65] 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.
These naturally undulating terrain of hills and valleys lends itself to the development of tanks that can capture and store rainwater.
[63] A 2018 study by an autonomous institute under the Karnataka government counted 1521 water bodies in the Bangalore Metropolitan Area, out of which 837 were disused.
[116] Measures to minimize pollution during the festival include use of earthen idols and smaller disconnected artificial tanks.
[117] This is followed by a constructed wetland spread over about 11 acres consisting of shallow followed by deeper settling basins with a variety of aquatic plants.
[121][122] While there are similarities between cities in the causes of the floods, Bangalore has some unique exacerbating features with regard to its lake ecosystem.
The revised list of 1994 also contains recorded sightings such as that of little grebe at Ulsoor tank in 1930 and data from the waterfowl census conducted since 1987.
Out of 97 tanks that were observed in a radius of 30 km, unregulated mudlifting and brickmaking were practiced in a large number of the lakes.
The ninth and tenth edition of the census of wetland and water birds in 1995 and 1996 conducted by the Birdwatchers' Field Club in coordination with the state forest department found 29 lakes which had twenty or more species such as Hebbal, Hosakote and Kalkere.
[125] A study using eBird data from 2014 to 2019 from 44 lakes in the city had a sample size that included a total of 263 species.
[136] Fishes bred for food include carps such as catla, labeo, mrigal, and other types such as tilapia, catfish.
[136] Imagery from the Indian Remote Sensing Programme for the years 1988-2001 were used to assess growth of water hyacinth in six lakes in Bangalore.
[108] In the mid-1980s Neochetina eichhorniae, used in the biocontrol of water hyacinth, was released on an experimental basis in a specific area of Bellandur Lake.
The insect had also been recorded in the coming months in downstream Varthur Lake signifying a capability to migrate.
[140] Common emergent aquatic plants include alligator weed, pink morning glory and cattail.
[141] Common submerged aquatic plants include those from the genus Aponogeton, Potamogeton and the highly invasive Hydrilla, Elodea.
[144] Algal diversity observed included 124 species belonging to 58 genera of the four classes Chlorophyceae, Cyanophyceae, Bacillariophyceae and Euglenophyceae.
This comes into question during efforts to enhance the biodiversity and aesthetics of the lakes through the creation of artificial islands and tree parks, and opposition to "soup bowl" structured restoration.
[155][156] Naturalist Zafar Futehally suggests a balance by restricting soup bowl structure to select lakes, and allowing the others to develop with more concern for aquatic birds and recreation.
[156] In 2023 The New York Times reported about conservationist Anand Malligavad who has restored 35 lakes in Bengaluru, with the help ancient Chola methods of water management, which don't need maintenance.
