For Hyderabad Metropolitan Water Supply & Sewerage Board (HMWS&SB), which manages the operations and utility of Osmansagar and Himayatasagar reservoirs, the 2025 Hyderabad floods remind the 1960s.
As early as the last week of July, the twin reservoirs were almost full and filling about 100 to 300 cusecs. For a full tank level of 1,790 feet, the water level at Osmansagar was just short of two feet. So was Himayatsagar, at 1,761 feet for its FTL 1,763.
But on September 26 (Friday), at the peak of the season, the recorded reservoir numbers at 10 a.m. appeared to be multiplied by 10. The inflows were 3,000 cusecs and 2,800 cusecs respectively. And the outflows, with two gates lifted to just two feet, were at 460 cusecs and about 2,000 cusecs.
In the next hour, the Board had news. The much-awaited inaugural ceremony of Amberpet sewerage treatment plant by Chief Minister A. Revanth Reddy was being postponed due to heavy rains, it said. But by 12.20 p.m., it had breaking news: “flood warning”, combined discharge from both reservoirs will be at 12,000 cusecs — 5,000 cusecs from Osmansagar and 7,000 cusecs from Himayatsagar.
With incessant rains in the catchment, recording an average rainfall of 130 mm and a maximum of 175 mm rainfall in Vikarabad, the reservoirs kept receiving more volumes of flood, and the numbers grew.
According to HMWS&SB, “the last time 15 gates of Osmansagar were operated for nine feet height was 60 years ago, in 1962 and 1965. And a combined outflow of over 34,000 cusecs too.”
On Friday, the Board had also issued another flood warning at around 5 p.m. and said about 26,000 cusecs will be discharged.
The river’s spate only continued, and at 8 p.m., the total discharge was 29,557 cusecs. A record combined inflow of 40,000 cusecs – 16,000 cusecs at Osman Sagar and 24,000 cusecs at Himayatasagar was at 10 p.m. And at 5 a.m. on Saturday, the outflows breached the 34,000-mark, the maximum.
The gates at Osmansagar remained open to their maximum nine feet till the evening on Saturday, and as at 8 p.m., as per the last available figures, the combined inflows came down to about 12,000 cusecs and the combined outflow was 10,027 cusecs.
A combination of human expertise, advanced technology, and coordination with various departments, the Board said, was on display for the successful operation.
“Such large-scale operation of the gates was not done in the recent past. In 2010, eight gates were raised by seven feet, in 2021, six gates were operated by three feet, and it was 13 gates to a height of six feet in 2022. In 2023 and 2024, six gates were raised by four feet and two feet only,” a senior official citing the records informed.
Water Board officials monitored the flood reaching Osmansagar at Shankarpally bridge, about 25 km away, and at Venkatapur and Amdapur villages in the upstream for Himayatsagar.
“While water level at Shankarpally bridge has not crossed 10 feet in the last 25 years, the Musi stream towards Osmansagar here touched an unusual 16.5 feet height. Also, towards Himayatsagar, the Esi stream at Amdapur touched 18 feet height, replacing the 25-year high of 14 feet height,” this official explained.
Published – September 27, 2025 10:28 pm IST
