Drinking water down the drain in Chennai

CHENNAI: A good spell during the monsoon doesn’t always mean a boost to the city’s water supply. Days of heavy rain have eaten into about two thousand million cubic feet (tmcft) of drinking water in the past four days in neighbouring Kancheepuram and Tiruvallur districts.

Authorities were forced to release surplus water from Poondi, Red Hills and Chembarambakkam reservoirs which were fast reaching their full capacities thanks to the spate of showers, a senior engineer from the public works department said.
They began releasing 2,000 cubic feet of water per second (cusecs) from Poondi last week and 2,000 cusecs each from Red Hills and Chembarambakkam reservoirs since last Sunday. The three reservoirs are among the city’s main water sources. The PWD also released 1,200 cusecs of water from Cholavaram reservoir.
But why is surplus water released early and why are reservoirs not allowed to reach full capacity?
The engineer explained that PWD’s Compendium Rules and Regulations mandate that all reservoirs must maintain their water level at a minimum of two feet below its full capacity. This is particularly important during the monsoon.
Former PWD assistant executive engineer S Thirunavukkarasu said an amendment should be brought into this provision in the compendium of rules to increase the storage levels. The reservoirs that supply water to the Chennai should be allowed to maintain levels at 1ft below the full reservoir level. Bringing in this change in the rules will help in reducing the amount of surplus water let out into the sea.
Conducting soil tests based on permeability at the reservoir’s bed and then taking up the desilting can also help in increasing the water storage capacity in each reservoir, he said.