For the first time in six decades, Mettur Dam, the lifeline of the Tamil Nadu agrarian belt, will be thrown open for irrigation much before the customary opening date of June 12. The Cabinet on Sunday decided that the dam's gates would open this year on June 6. It will irrigate about six lakh hectares of land in the districts of Salem, Namakkal, Karur, Tiruchi, Pudukottai, Thanjavur and some parts of undivided South Arcot.
Though it has been customary to open the dam, called Stanley Reservoir, on June 12, it could not be done so due to poor storage for 52 years in its 77-year-old history. The Public Works Department has virtually made it mandatory to open the dam only when storage level of water touches 90 ft. It was opened as late as October 7 in 2003.
Its sluice gates were opened for irrigation on June 12 on 15 occasions. And this year would be the 11{+t}{+h} time that it would be opened ahead of June 12. Conventionally, the dam is closed on January 28.
The dam, built in 1934, has a maximum capacity of 93.4 thousand million cubic feet (tmcft) and its maximum level is 120 feet. The reservoir level at 4 p.m. on Sunday was 113.63 ft and its storage was 83.675 tmcft. According to PWD sources, the current storage would be sufficient for 80-90 days' supply and if the southwest monsoon proves to be normal as forecast, it would be a comfortable year for agriculture in terms of irrigation.
The dam helps generate power too. While the dam and tunnel powerhouses can generate 250 mega watts, its barrages can generate 150 MW. Thus, when the dam is thrown open for irrigation, the power generation in the State can be augmented by 400 MW.
Whenever rains lash the Wayanad region in Kerala and Coorg in Karnataka, under the influence of the southwest monsoon (June-August), and as soon as the Kabini reservoir starts surplussing, the Mettur Dam will start getting substantial inflows. There have been years — such as 1961 — when the inflows touched a rate of 3.61 lakh cubic feet per second (cusecs). In recent times, it was in 2005 that the reservoir received water at a maximum rate of 2.41 lakh cusecs.
But whenever the monsoon fails and the Mettur Dam level looks bleak, Tamil Nadu agriculture, especially that of delta, is in trouble. ‘Kuruvai,' the short-term crop, is the worst hit. There have been years when the entire kuruvai has been lost because of poor storage in the dam. But the State has somehow been managing the long-term ‘samba' paddy crop with the help of northeast monsoon (October-December).
The opening of this dam on the customary date has been a major worry for the State government every year for the past four decades because the inflows have been poor. However, farmers will have much cause for cheer this year.
