Thanks to record summer rains, Kerala's dams are more filled than during the year of the deluge

A rainbow forms near the Idukki arch dam reservoir. Photo: Reju Arnold

Something unprecedented had happened in Kerala in the three summer months between March 1 to May 31. There was relentless flood-scale summer rainfall all over Kerala. Not a single district that had less than 75 percent excess rainfall. Half the districts had witnessed more than 100 percent excess rainfall.

And the southwest monsoon has not yet arrived. But once it does, what will happen to Kerala's already water-fattened reservoirs, whose sudden opening in 2018 had caused the great deluge.

At this point, Kerala's reservoirs hold more water than at the start of monsoon in 2018, the deluge year. The figures put out by the Central Water Commission show that major dams in Kerala, at this point, hold nearly 75 percent more water than is normal. On May 31, 2018, they had held only 43 percent more than normal.

Dam levels: 2021 and 2018

Take for instance the largest dam, Idukki, the shutters of which were opened in 2018 leading to widespread destruction. On June 1, this year, the water level in the reservoir was at 2339.78 feet. Three years ago on June 1, 2018, it was lower at 2323.23 ft.

Now take Idamalayar. On June 1, this year, the water level in Idamalayar touched 138.49 metres (454.53 ft). On June 1, the deluge year, it was only 129.58 metres (425.13 ft).

Here are the two water levels for Kakki dam: 962.56 metres or 3158 ft (June 1, 2021) and 952.12 metres or 3123.75 ft (June 1, 2018).

Here are the comparative levels for Periyar reservoir: 865.38 metres or 2839.17 ft (June 1, 2021) and 860.77 or 2824.04 ft (June 1, 2018).

Here are the pre-monsoon water levels in Malampuzha: 103.85 metres or 340.72 ft (June 1, 2021) and 103.02 metres or 338 ft (June 1, 2018).

Below alarming levels

Nonetheless, top officials at the Disaster Management Authority assure that there is nothing to worry. “None of our major dams have filled to a level that warrants even the lowest alert,” a top official said.

Take Idukki dam for instance. At the moment, the water level in the reservoir has touched 2339.78 ft but for even the blue alert, the lowest level of alert, to be sounded, the level has to be 2392.03 ft. The highest red alert is issued when the level touches the 2399.03 ft mark, which is just below the full reservoir level of 2403 ft.

Measured water release

These permissible limits were set after the 2018 floods. Jolted by the deluge, the KSEB had developed what is called a 'rule curve' system that determined the safe water levels in reservoirs for each day. “This has helped the KSEB to closely monitor rising water levels in reservoirs. If the level rises beyond the permissible limit on any given day, we will release the waters in a limited way,” the KSEB official working in the generation wing of the company said.

Such incremental release of water from the dams will also do away with the panic lifting of shutters that was witnessed during the 2018 floods. “You don't wait for the dams to get dangerously full before the shutters are lifted. The rule curve system has now allowed us to time the release of water in a measured way. When water is released in small doses it will not create floods downstream either,” the KSEB official added.

Forever rising waters

This assurance, nonetheless, can get drowned under the unrelenting rains.

The massive inflow into the dams caused by the incessant summer rains hint that the danger levels could be crossed in no time. The inflow into the reservoirs, thanks to the tireless summer rains, is as high as 18.1 million units. In 2018, the inflow was less than 10 million units.

“The inflow is high but we stabilise the water level in our reservoirs by increasing hydel production,” a top KSEB official said. If the inflow is 18.1 million units, the average daily hydel production is over 24 million units.

Hydropower solution

To keep the water level low in its reservoirs, KSEB has stepped up daily hydel generation. Thanks to the constant rain and COVID-induced lockdown, the overall power consumption in Kerala has cooled. If daily consumption was over 70 million units during the last week of May 2018, it is far lower at 65-68 million units during the last week of May this year. Yet daily hydel production is higher this May (25 million units) when compared with 2018 May (22 million units).

A sign that KSEB is working overtime to keep its dams safe during the monsoon. That the monsoon will be lower than normal this time has also come as a relief to KSEB planners.

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