Rising mercury fast drying up Chennai’s reservoirs, caution experts
They also point out that prevention of water depletion at reservoirs would help the groundwater level to recharge.
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CHENNAI: The rate of evaporation at reservoirs in Tamil Nadu is speeding up, thanks to the surge in the mercury level. “Since the water bodies in the city and suburbs are shallow, the amount of water evaporating is significantly more than previously thought, and at least one of the reservoirs has lost half the amount of water to evaporation this summer,” a senior official with the Water Resources Department (WRD) told DT Next.
While experts have come out with various options to prevent water loss from water bodies, including installing floating solar panels that could also generate green power, the State has failed to explore any viable alternative so far, experts opine.
They also point out that prevention of water depletion at reservoirs would help the groundwater level to recharge.
“The water level loss due to evaporation has been monitored by the department. During summer, at least 20 cusecs of water get reduced in a reservoir. The depletion vary from reservoirs and lakes due to capacity differences. Despite the surge in temperature impacting water level, it has not affected the water supply in the city,” said a senior WRD official.
The water discharged from the reservoirs for drinking purposes takes into account water loss including evaporation and seepage. If the WRD discharges 100 MLD of water depending on the current storage capacity of the reservoirs, the department would calculate the evaporation and other water loss and then discharge the remaining water to the Metro Water board.
Talking about the measures taken by the government to prevent water reductions because of evaporation, an officer recalled that a few years ago, the then-minister tried a new method by floating thermocol on canals.
Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) officers said the reservoirs are vast areas and they have tried various ways to prevent water evaporation, including using chemicals that form a layer on the surface. However, it was not successful. Another method was using balls to slow evaporation, but it will not spread over the entire area.
“The water bodies are in the custody of PWD. They should take necessary steps. But no new techniques were initiated. Despite the maximum temperature continuing to increase and crossing 40 degrees Celsius there is more demand for drinking water in the city,” said an official with Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB).
Experts opined that though there is evaporation in the reservoirs it would manage because it has larger storage capacity compared to lakes and ponds in the city and outskirts. In addition, the soil conditions should be considered when talking about water absorption.
“The reservoirs are filled with sandy, silty and clay soil, of which the sandy soil would absorb more water during the summer whereas the clay will have less absorption. As part of ways to prevent evaporation, the government has suggested installing solar panels and planting saplings near the water bodies because the oxygen would help prevent intense heat in water bodies,” explained hydrologist Dr T Sivasubramanian.
L Elango, visiting professor of hydraulic and water resources engineering at IIT Madras, suggests that the government should direct water to abandoned quarries because the depth of water will help reduce the scale of evaporation.
