Water reserves in the six major reservoirs supplying drinking water to Chennai are nearly 50 per cent lower than a year ago, despite heavy rain over the past three days increasing inflows and raising hopes of replenishment during the northeast monsoon, IANS reported on Thursday.

Source: IANS

The six reservoirs — Poondi, Puzhal, Chembarambakkam, Cholavaram, Kannankottai-Thervoy Kandigai and Veeranam in Cuddalore district — have a combined capacity of 13.222 thousand million cubic feet (tmc). As of Wednesday morning, their combined storage stood at 5.139 tmc, compared with 9.738 tmc during the corresponding period last year, a decline of about 47 per cent, leaving them at just under 39 per cent of capacity.

5.139 tmcChennai's combined reservoir storage now
9.738 tmcstorage on the same day last year
13.222 tmccombined full capacity of the six reservoirs
39%of capacity currently filled

Among the reservoirs, Puzhal recorded an inflow of 1,126 cubic feet per second (cusecs) on Wednesday morning and held 2.248 tmc against its 3.3 tmc capacity. Chembarambakkam received 555 cusecs and held 1.435 tmc of its 3.645 tmc capacity, while Poondi recorded an inflow of 520 cusecs and Veeranam received 340 cusecs, according to the IANS report.

The shortfall is not limited to Chennai. Official daily data for October 22 show the 18 reservoirs in the southern districts of Tirunelveli, Tenkasi and Kanyakumari together hold 4,573.03 million cubic feet, or 20.7 per cent of their capacity, down sharply from 12,702.26 million cubic feet on the same day last year. Papanasam recorded an inflow of about 1,828.6 cusecs, yet many southern reservoirs remain very low, and officials say recovery will depend on catchment-area rainfall in the coming weeks.

Source: Particle News (official daily data)

Yaani — in plain terms

One tmc is about 28 arab (2,800 crore) litres. Chennai's 5.139 tmc therefore works out to roughly 14,500 crore litres in storage — barely half of what the city's reservoirs held at the same time last year.

The northeast monsoon has gathered strength over Tamil Nadu since last week, bringing heavy showers to Chennai and its suburbs. Rain across the catchment areas has increased inflows into several reservoirs, but officials say the improvement has yet to bridge the large gap with last year's levels.