Officials say that the likelihood of a repeat of 2015 is small. This is mainly due to the fact that the rains have not been as severe as in 2015.

With 286 mm of rainfall on average over seven days, Chennai was battered by rains in December 2015. The city also recorded the highest single-day rainfall in a century with 494 mm in Tambaram. In November 2015, the total rainfall recorded was 1018 mm, the highest since the year 1918.

In contrast, the average per-day rainfall brought in by Cyclone Nivar is estimated to be around 110 mm. Rains are heavy but they are also intermittent, unlike in 2015.

As on November 25, the Chembarambakkam reservoir is at 21.55 feet of storage. The total storage capacity is 24 feet. Public Works Department officials have decided to begin releasing water from the reservoir on the afternoon of November 25 at the rate of 1000 cusecs.

The Adyar river’s carrying capacity is 60,000 cusecs. Currently, the river is carrying about 4000 cusecs of water and from noon, will carry an additional 1000 cusecs of water which will be released from Chembarambakkam.

Contrast this with 2015, when the level of water in the reservoir was at 22.08 feet and outflow was steadily increased to 29,000 cusecs by the evening of December 01.

The Adyar, in 2015, carried a massive one lakh cusecs of water, as against its capacity of 60,000 cusecs. Inflows from others drains, tanks and lakes as well as rainfall made the Adyar swell and inundate its flood plains which have been built upon.

Seeking to allay the fears of Chennai’s residents, Additional Chief Secretary with the Revenue Department, Atulya Misra told The Lede, “The outflow is being closely regulated considering inflow, rainfall in catchment areas, water level in feeding water bodies and capacity of Adyar river. Zones 11, 12, 13, 9 and 5 are on high alert and people living in vulnerable areas are being shifted to relief camps.”

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Manasa Chennapragada

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