Read in : தமிழ்

Share the Article

After the annual monsoon’s closing act on December 30-31, emptying 201.2 mm of rainfall on the city and drowning New Year’s Eve, the average Chennaiite would want a respite—to recover from a deluge year. For Chennai’s water supply, however, it would be a different story.

Because last year’s Monsoon officially ended only on January 22 this year, the Tamil Nadu government has only a few months left to prepare for the next one. Perhaps this time it could ensure that the excess floodwater does not just drain into the sea but is stored better.

The year 2021 was to have been one of promise. Extensive vaccination would rein in COVID-19, new jobs and restored salaries would spur economic activity, and a normal monsoon predicted by the India Meteorological Department’s (IMD) would bring gains to the farmer and urban dweller alike with good farm productivity and lower consumer prices.

But 2021 did not live up to it.

A year of peak rain spells disrupted life in Chennai and key cities such as Coimbatore. The Margazhi season’s classical music brought brief relief, but the Omicron wave ended it early in the new year. However, some welcome sounds continue to enthuse: the small waves lapping the edges of Chennai’s brimming drinking water reservoirs.

Music to a city’s ears

On January 21 this year, the city’s major lakes that bring precious Metro water to house taps were almost full, just as they were when 2021 began. The total volume of water in the five lakes sustaining Chennai stood at 10,842 mcft, just a small dip from last year’s 11,070 mcft. The total storage capacity of the reservoirs is 11,757 mcft.

Chennai recently got a third government Doppler radar for better weather data collection for the IMD although it will take more improvements to modelling of monsoon patterns to produce accurate short- and long-range forecasts. But no weather forecast could predict what happened to Chennai on December 30.

Sathyamurthy Sagar, the giant waterbody familiar to many as the Poondi reservoir across the Kosasthalaiyar river, had a near-full storage of 3,073 mcft out of a capacity of 3,231 mcft. The much smaller Cholavaram retained 881 mcft (against 1,081 mcft) while Red Hills, which primarily brings water to the city, had a healthy 3,072 mcft out of 3,300 mcft.

Chennai should be happy with the smart recharge that the rains brought to Kannankottai Thervoy Kandigai, a more recent addition to the reservoir system, and, of course, to the giant back-up plan, Chembarambakkam lake: at 500 mcft and 3,315 mcft, both could keep things going for several weeks when the others start running out.

Clouds of uncertainty

Chennai recently got a third government Doppler radar for better weather data collection for the IMD although it will take more improvements to modelling of monsoon patterns to produce accurate short- and long-range forecasts. But no weather forecast could predict what happened to Chennai on December 30. Clouds driven by easterlies from the Bay of Bengal, buttressed by a sudden accumulation of moisture overland in the city, brought a torrent of rain and flooding.

Chennai flood 2021

It came during a year of cooler Pacific Ocean winds thanks to a La Nina phase, which should have cooled off the sea surface. The cooling phenomenon was witnessed for the second year running, as the World Meteorological Organization (WMO) noted. But the WMO also noted that average global temperature was more than one degree C higher than the pre- industrial era average for the seventh year in a row.

So, what could 2022 bring?

The IMD’s and other agencies’ annual monsoon forecasts are still some weeks away.  Available forecasts say La Nina will go on until spring of 2022—up to May. The US. Climate Prediction Center estimates that this will be the case, promising a cooler sea surface environment. But as the WMO notes, the high average global temperature (1.1 degrees C higher in 2021) caused by man-made climate-warming activities may be overriding the benign impact of natural phenomena such as La Nina.

This uncertainty adds a layer of complexity to an already complicated picture for the whole of South Asia. As the climate scientist Roxy Mathew Koll of the Indian Institute of Tropical Meteorology (IITM) notes in an article that the widespread extreme weather events in parts of Central and North India and sections of the Western Ghats from Kerala to Goa had increased over a study period of 1950-2015.

Paradoxically, these flood-causing weather events in a large part of the country—Telangana, Madhya Pradesh, Gujarat and Maharashtra to Jharkhand, Assam and Chhattisgarh—coincided with a long-term declining trend in daily monsoon rainfall. Therefore, it could be proposed, Dr Koll and colleagues say, that the excess moisture for such weather events may be coming from the Arabian Sea, due to a warming of the northern half there.

For Tamil Nadu and Chennai, the concern is on what the impact of continued cool sea wind conditions could be on Monsoon 2022. There could be the additional influence of another weather phenomenon, the Indian Ocean Dipole, on the annual system.

Many water experts think the rated capacity of the reservoirs serving Chennai is merely on paper. Much work needs to be done quickly to deepen them. The city also has hundreds of urban water storage possibilities, such as neglected temple ponds and peripheral lakes, which have been encroached and filled with garbage.

Here, part of the Indian Ocean to the west, extending into the Arabian sea off Africa and India’s western coast, raises convection and moisture in that zone when it warms (while the reverse effect is felt along Indonesia and Australia in a negative year). If more moisture is picked up from the Arabian sea into the Indian mainland in a warming world, it could add to flooding events in many key cities and towns across the peninsula. There are bound to be severe losses.

Can Tamil Nadu profit from rain?

There is little doubt that all good water is blue gold. With only months to go for another possible round of intense rainfall—and more floods—the DMK Government led by MK Stalin barely has enough time to get the crews moving. It has to increase the storage of reservoirs in all districts, particularly Chennai’s big five.

Many water experts think the rated capacity of the reservoirs serving Chennai is merely on paper. Much work needs to be done quickly to deepen them. The city also has hundreds of urban water storage possibilities, such as neglected temple ponds and peripheral lakes, which have been encroached and filled with garbage.

Last year, the city reservoirs got their first notable showers in the third week of June. By November, the lakes were so full that water had to be released to keep the levels down. Can the Stalin government afford to throw away more blue gold in 2022? It has five months to act.


Share the Article

Read in : தமிழ்