Mettur's Stanley Reservoir achieves FRL in June for the second time in its history

Chennai: For the first time since 1957, the 91-year-old Stanley Reservoir in Mettur, Tamil Nadu, has reached its Full Reservoir Level (FRL) of 120 feet in June, thanks to heavy rains in the catchment areas of the Cauvery River in Karnataka.

The reservoir, named after Lt. Col. Sir George Frederick Stanley, who was the Governor of the then Madras State, achieved its FRL on the evening of June 29 -- the last time the dam was full in June was 68 years ago, in 1957.

At 8 am on Monday, the dam’s water level stood at 120 feet, with water storage at 93.470 tmcft. The inflow into the dam was 57,732 cusecs, while the outflow was 58,000 cusecs.

With the inflow increasing and the dam achieving its FRL, an advisory has been issued to administrations in 11 districts in the western and central parts of Tamil Nadu, including the fertile Cauvery Delta region, for whom the Stanley Reservoir is a lifeline.

People living in low-lying areas in Salem, Erode, Namakkal, Karur, Ariyalur, Trichy, Thanjavur, Thiruvarur, Mayiladuthurai, Nagapattinam, and Cuddalore have been cautioned to move to safer places.

This is the 44th time that the Stanley Reservoir has reached its FRL since it was constructed in 1934. Officials said the dam achieving its FRL in June is a rare event, as water from dams in Karnataka is usually released only by the end of June due to the influence of the southwest monsoon, which generally begins on May 31 or June 1.

“Since the dams in Karnataka are already full and excess water is being released, the Mettur reservoir has achieved its FRL in June itself. This trend has to be continued if water release from the dam is to be sustained till December this year for cultivation of kuruvai (short-term) and samba (long-term) crops in the Delta,” a government official said.

The Stanley Reservoir, a giant structure built during the British regime, still serves as the lifeline of lakhs of farmers in the Cauvery Delta region. On August 21, 1934, the sluices of the reservoir in Mettur, 50 km from Salem in Tamil Nadu, were opened for the first time after being built over a period of 10 years.

Named after Lt. Col. Sir George Frederick Stanley, who was the Governor of the then Madras State from 1929 to 1934, the reservoir is one of the largest dams in India, having been constructed in a gorge where the Cauvery River enters the plains.

Over the years, the designated date for opening the sluices of the reservoir was shifted to June 12, keeping in mind the arrival of the southwest monsoon, which hits Kerala on May 31 and Karnataka a little later.

However, the gates of the reservoir have not been opened on the designated date of June 12 for over 60 times since the 1930s due to the non-availability of adequate water.

The dam’s storage depends on water released from reservoirs in Karnataka. While the Full Reservoir Level (FRL) is 120 feet, the total water storage is about 94 tmcft. The catchment area of the Cauvery River up to the dam site is 42,924 sq km, while the project consists of a masonry gravity dam with a length of 1,614.4 m and a height of 65.23 m.

In the past few years, the dam has been attaining FRL quite frequently due to incessant rains in the catchment areas of the Cauvery River in Karnataka.