Tank cascades at risk - Bengaluru

South-east Bengaluru's terminal kere chain: HSR Layout's Agara feeds storm drains toward Bellandur (317 ha, terminal lake of the K&C valley receiving sewage from ~40% of Bangalore), which discharges through a downstream weir into Varthur (155 ha), which in turn drains east toward the Dakshina Pinakini basin. The chain became national news on 16 Feb 2017 when surfactant foam ignited at the Bellandur weir on Sarjapur Road. The NGT subsequently constituted a Bellandur-Varthur monitoring committee under retired Justice Santosh Hegde and ordered a 75 m no-construction buffer around the lakes plus 50 m around rajakaluves.

The surviving fragments of Kempegowda I's mid-16th-century interconnected kere system in old Bengaluru. Kempegowda laid down the city's original ridge cascade in 1537, with each tank's surplus feeding the next downstream. Most of the chain is gone: Dharmambudhi tank (drained 1950s for Majestic bus stand), Sampangi tank (Sri Kanteerava stadium), Karanji Anjaneya (Bishop Cotton playing fields), Akkithimmanahalli (hockey stadium), Domlur (BDA layout). Today only Kempambudhi (Kempegowda's family-deity tank, ~7 ha, severely reduced, operationally a sewage-receiving body) and Ulsoor / Halasuru (38 ha, expanded under Kempegowda II in the 1550s and formalised in the 1809-1811 British Cantonment) remain identifiable as lakes. Together they bookend the heritage chain - upstream-most and downstream-most surviving Kempegowda-era kere in the old city core.

The colonial-era BWSSB drinking-water spine. Hesaraghatta Lake (600 ha full pool, on the Arkavathy river) was constructed in 1894 by the Madras Engineering Group to supply Bengaluru's first piped water - and remained the city's sole drinking source until Tippegondanahalli reservoir (TG Halli, 1932) and the Cauvery stages (1974 onwards). Today Hesaraghatta is operationally near-dry: upstream urbanisation and a collapsed Arkavathy catchment have ended its role as a drinking source. The Vrishabhavathi river it drains into now carries primarily sewage and industrial effluent through west Bengaluru. The 2021 Karnataka tourism / film-city proposal on the Hesaraghatta grasslands was paused after civil-society pushback citing lesser-florican habitat and Arkavathy recharge functions.