Idukki dam is nearly 40% full ahead of monsoon. Does the bell toll for another flood year?

As the southwest monsoon is just about to sweep through the Kerala coast, Kerala State Electricity Board has found itself in as scary a situation as an unlucky soul whose cloth edge gets stuck on the railway track as a train approaches.

On the eve of the monsoon, predicted to be normal to heavy, KSEB has found that the reservoir of its biggest dam, the 780-MW Hydel project in Moolamattom, Idukki, is nearly 40 per cent full. On May 28, it was 38 per cent full.

Ideally, to absorb the massive inflows of even a normal monsoon, the water level in the Idukki reservoir on May 31, the end of a water year, should be kept reasonably low at 704.39 metres. The full reservoir level in Idukki is 732.43 metres.

At the moment, there is water up to 713.37 metres in the Idukki reservoir. In the same period last year, the water level in the Idukki reservoir was 706.35 metres. In 2018, the year of the deluge, the water level during the period was 707.88 metres.

In short, Idukki reservoir now has considerably more amount of water than the two consecutive flood years.

COVID-19 pours cold water on KSEB plans

The virus outbreak has played a huge part in water accumulating in the reservoir. “Power consumption had fallen steeply after the lockdown. With industrial, commercial and business establishments closed, peak hour demand just collapsed,” a top official working in the Dam Safety wing of KSEB said.

During the peak of summer - April and May - daily consumption was generally below 75 million units a day. Last year, daily consumption was over 85 million units almost the whole of May, touching a record of 89 million units on May 23. This May, even the highest consumption on a day was only 77.38 million units, and that too on May 27 when the lockdown was relaxed substantially.

The frequency of summer rains, and also the cyclone-induced rains, during May had also reduced daily power demand in Kerala.

Nonetheless, even when the heat was at its extreme in the middle of April this year, daily consumption did not cross 68 million units. Lockdown effect, obviously.

During the middle of April last year, daily consumption was consistently above 85 million units.

Idukki seriously under-worked

But with the monsoon approaching, KSEB could have still stepped up generation in Idukki. If not required internally, it could have at least sold the surplus power outside. It has not.

Last May, KSEB generated 15-20 million units a day from its Idukki plant. This year, even when there is a need to keep the reservoir space open for the monsoon waters, it could generate not more than 8 million units a day.

Reason: Three of Idukki's six generators, 130 MW each, are dysfunctional. One was closed down for "modernisation and renewal" on September 7, 2019. Two other generators went caput this year, one on February 1 and the other on February 22.

A top official in KSEB's generation wing said one of the faulty generators would resume operations in the first week of June. For the other two – one that is being renovated and the other that had broken down mid-function -- to resume operations, top experts will have to be flown in from outside and foreign equipment from China, France and Germany will have to be imported.

Both will have to wait for COVID-19 to subside.

KSEB's assurances

So, with only four generators – assuming one would be functional by the first week of June -- can the dam do well to manage a possible flood? Top KSEB officials said if at all it was required, dam shutters need to be opened only by the second week of July. “The Idukki reservoir will not be even 70 per cent full by the end of June,” a KSEB engineer said.

If so, the water level will be manageable. This is because the level will be below the prescribed limit as per the lately evolved 'rule curve' – a series of maximum water levels for specific time points.

For instance on July 10, according to the rule curve, there should be a flood cushion or free space of 18 per cent in the Idukki reservoir. If only 70 per cent of the reservoir is filled at the end of June, as the KSEB claims, there would be a flood cushion of 25-30 per cent in the reservoir on July 10.

Why KSEB's thinking could go wrong

Problem is, this is not an usual year for the reservoir. It is already 38 per cent full. This, according to the storage bulletin issued by the Central Water Commission, is 34 per cent more than normal.

What if the reservoir gets filled 80 per cent by the end of June? And what if in another 10 days another 10 per cent is added, chances of which are high because the monsoon intensifies in July?

Then, the water will rise far above the 'rule curve' level and there will only be a 10 per cent flood cushion in the place of 18 per cent. This will force authorities to release water in abundant quantities, endangering the Periyar river basin.

"We are closely monitoring the situation. If there is heavy rainfall, we will make sure that the water is released in small doses. And just because there is a rule curve, it does not mean we will always keep the water at the maximum level," a dam safety official said.

Will 2018 August return to haunt

However, 2018 had shown that the monsoon could catch the state off guard. Take 2018 August for instance. Till then that year, there was 12 per cent excess rainfall in Kerala. But between August 1 and 7 there was a rainfall deficit of 38 per cent.

And just when it was felt the worst was over, between August 13 and 19, as if some curse had befallen Kerala, there was excess rainfall of of 362 per cent. Idukki alone was subject to 800 millimetres of rain in three days in the middle of August.

There was panic opening of dams, and all hell broke loose.

As per the rule curve, only 11 per cent flood cushion is required in the Idukki dam on August 10. Environment experts say this should be at least 25 per cent in August so that if there is sudden and extreme rain there will be no wild release of water to the Periyar river basin.

A top KSEB official said extreme rainfall events of the kind witnessed in 2018 had only a 0.05 per cent chance of striking again in 2020. This is either bold gamble or sheer complacency.