Koyna dam storage down to 16.15%; power generation curtailed

Kolhapur: Water levels in Koyna, Maharashtra’s largest dam, have dropped sharply with its live storage down to 11.30 TMC out of 100.12 TMC, exhausting the reserved quota for hydroelectric power generation and prompting authorities to curtail output.

As of Friday, the dam had 16.15 TMC gross storage—about 15.34% of its total capacity—lower than 18.58% during the same period last year, sources in the water resources department said. Including dead stock, the dam’s total capacity is 105.25 TMC.

An official said the depletion has effectively exhausted the western hydropower quota of 67.50 TMC, of which 67.48 TMC has been used. “Despite this, power generation will continue at a reduced level as it is not technically feasible to abruptly halt operations,” an official said.

“The dam currently has 11.30 TMC usable water and 16.15 TMC gross storage. Power generation will continue on a limited scale,” said Ashish Jadhav, sub-divisional engineer at Koyna dam. He said the energy department has sent a proposal seeking approval for additional water usage.

The technical water year ends on May 31, after which the reserved allocation for power generation lapses, offering operational flexibility. Authorities expect approval for additional usage, citing precedents from previous years.

Engineers said the available storage was expected to meet both irrigation and reduced power generation needs until the end of June. On average, around 6 TMC is used for irrigation and 5 TMC for power generation.

Koyna received 188.45 TMC inflow last monsoon. Of this, 67.48 TMC was used for western power generation, 32.87 TMC for irrigation via the eastern canal, 14.53 TMC in backwater irrigation, and 6.91 TMC through emergency releases. Reduced demand from the Sangli irrigation department has led to lower emergency outflows.

Historical data shows that current levels, while low, are not unprecedented. In June 2023, gross storage had dipped to 10.71 TMC—among the lowest since June 1996, when it stood at 10.66 TMC. A similar situation was seen in June 2019, when storage fell to 10.75 TMC. The lowest inflow recorded was in Sept 2013 at 65 TMC, even lower than 89 TMC during the drought-stricken year of 1972.

Despite IMD forecasting below-normal rainfall amid El Nino conditions, officials said there was no immediate cause for concern. In a normal year, Koyna receives 180-200 TMC inflow—far exceeding its storage capacity—forcing release of 50-60 TMC and often triggering floods in downstream districts such as Satara, Sangli and Kolhapur.

Authorities said even with slightly below-average rainfall, irrigation and power generation were unlikely to be disrupted.

Groundwater conditions in parts of Satara district, however, indicate an emerging stress. A survey of 106 wells by the Groundwater Directorate Of Surveys & Development Agency found overall (groundwater) levels stable at 7.27m — above the five-year average — but declining in drought-prone Man and Khatav talukas.

Groundwater levels in Man stood at 8.73m and 8.35m in Khatav, signalling growing water scarcity. The administration has deployed 78 tankers to supply water to 1.14 lakh residents across 89 villages in the region.

Officials said while the reservoir situation remained manageable in the short term, declining groundwater levels "highlight increasing pressure in vulnerable pockets ahead of monsoon".