FLOOD FURY
TN in troubled waters without restoration of its tanks, rivers
People Died, Crops Were Destroyed And Roads And Bridges Crumbled In Recent Rain That Put Rivers In Spate. Experts Say Loss Of Water Bodies Will Make Situation Worse
Team TOI
27.11.2021
The administration and people of Tamil Nadu have been living a life of self-deceit in handling issues concerning ecological degradation. The state creates its own comfort zone by viewing extreme weather systems as aberrations.
The 2015 Chennai floods was viewed as a once-in-a-century phenomenon, which may not recur for a couple of generations. Chennai got flooded again, twice this year, but thankfully Adyar and Cooum did not wreak havoc by overflowing into human settlements. If they had, none had any solution on hand.
Except for very few rivers like the Cauvery, other rivers in the state will overflow if reservoirs connected to them let out water to their full capacity. Adyar, for instance, gets water from close to a dozen sources including Chembarambakkam reservoir and Athanur lake. The river cannot carry more than 60,000 cusecs (cubic feet per second) water, whereas more than one lakh cusecs was released into the river in November-December 2015, resulting in inundation of many parts of Chennai for about a week.
Thanks to the drive carried out by the then Kancheepuram district collector against encroachers, Adyar can carry more water now. It may not be enough though. Kosasthalayar, which draws water from Red Hills and Poondi reservoirs, can carry up to 70,000 cusecs of water. However, the release from the reservoirs exceeded the river’s carrying capacity in the recent rains, resulting in flooding of Manali Pudhu Nagar and surrounding areas.
S Thirunavukkarasu, former assistant executive engineer of PWD, said that water flow can be better regulated if one more reservoir with 1tmcft capacity is constructed upstream of Poondi reservoir.
Creating more water bodies many not be the right solution. Climate patterns are fast changing and they will no longer remain aberrations. Global warming causes faster evaporation of seawater – even at 24ºC-25ºC– and the water molecules that escape have to come down as rain. The stark difference is that a week’s downpour now matches the rainfall of a month in previous years. “The state should acknowledge that going forward, cyclones and storms will become severe and super cyclones will be a routine affair. Business as usual will not work. If the 1,076 km coastline gives huge growth prospects to Tamil Nadu, it will also bring in incessant rains during every weather formation. Apart from receiving about 930mm of average annual rainfall, Tamil Nadu is also a natural drain for Kerala, Karnataka and Andhra Pradesh to let out excess water. Tamil Nadu governments, in the past, have been demanding water from its neighbours. It has never thought of what to do if there is excess release from those states. Our solution has been letting out excess flow into the sea as runoff, without bothering to store it,” said S Janakarajan, former professor of Madras Institute of Development Studies.
Tamil Nadu has compounded the problem by indiscriminate denudat cover. “Let us not hide beh change for all our past blu Janakarajan. “Madhav Ga shows three-fourths of our cover in the Western Ghats our water tower – is lost. Th made disaster. And strangel putting brakes on it,” he said The state has enough nat man-made waterways and o storage structures. It has grouped into 17 major basins basins. There are 90 reservoirs with a combined storage capacity of 224tmcft water. There used to be 42,000 tanks, big and small, but the numbers have been revised to 39,000 by government agencies. Only about 30,000 of them are effective though. Others have been lost to development and encroachments. There are close to 1,000 tanks below the Grand Anicut in the Cauvery delta districts. Sadly, even after sinking several thousand crores of rupees in the name of ‘kudimaramathu’ schemes over the past many years, none of the waterbodies in the state has been restored to its previous glory. “Our reservoirs, lakes, tanks and rivers are heavily silted. Most reservoirs including Mettur and Vaigai have lost more than 30% holding capacity owing to silting. If storage, water catchment area and foreshore area of existing water bodies are restored, much of our problem will be solved,” said Janakarajan.
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