Mettur storage can run out in 16 days, government needs to have a plan, say experts

TIRUCHY: As Mettur storage declines by the day, irrigation experts urge the State government to establish a joint emergency management plan by the Water Resources and Agriculture departments. They suggest field inspections and adopting localised, need-based water release, with the formation of irrigation management zones in the Delta region.

On Saturday, storage at Mettur stood at 27.979 TMC. Of this, 10 TMC is dead storage, and it includes 4 TMC of accumulated silt. While the inflow was unchanged at 1,028 cusecs, outflow was 14,997 cusecs. The substantial difference between inflow and outflow has caused the rapid depletion of reservoir storage.

As the Cauvery delta is entering a critical phase in samba cultivation this year, the success of paddy cultivation in Thanjavur, Tiruvarur, Nagapattinam, Mayiladuthurai and adjoining command areas depends on the availability of irrigation water from the Cauvery system, the timing and distribution of northeast monsoon rainfall, and the ability of farmers to manage water efficiently to prevent the adverse impact of water shortage.

Excluding the dead storage, if the inflow and outflow are unchanged, the reserve storage could be exhausted in approximately 16 days.

"As per the current scenario, the daily inflow into Mettur is estimated at 0.136 TMC while the daily outflow is measured at approximately 1.296 TMC (with 15,000 cusecs outflow) and the net storage depletion is estimated at approximately 1,160 TMC. This is a mathematical projection, not a forecast of actual reservoir operation. In practice, releases would be expected to change as storage declines. Drinking-water requirements, outlet constraints and other operating considerations would influence decisions," said A Meenakshi Sundara Arasu, climate adaptation expert and former faculty member of Irrigation Management Training Institute, Tiruchy.

Arasu pointed out that the reservoir would reach the 10 TMC planning threshold by October 27 under the stated assumptions, and the government should plan accordingly to avoid any adverse impact on cultivation.

The water shortage would certainly have an impact in the tail-end regions. Wary of water availability, farmers in certain areas have not commenced cultivation, and it is up to the government to ensure availability for those who have begun cultivation.

Arasu stressed field-level inspection and localised water distribution so that command areas that are yet to commence cultivation are avoided, and areas where farming is under way are not left out.

“A crop can survive at least for four days with the available water source, and then it starts to wilt and wither away subsequently, and so it is essential to ensure water availability to the crops that are in the flowering stage," Arasu said.

He urged the State government to review daily inflow, storage and forecast conditions and divide the Delta into irrigation management zones with clear priorities for head, middle, tail end and commence rotational water supply. "The Agriculture department should compile crop stage information by village and prioritise water release to save the standing crops and field-specific advice," he said.

Arasu also urged the government to publish a daily water balance showing storage, inflow, outflow, estimated usable storage and the implications for irrigation releases. This would enable farmers and local officials to make informed decisions rather than relying on isolated storage figures.

"The immediate priority should be to protect standing samba crops through a transparent, demand-based irrigation strategy, while preserving sufficient water for essential needs and the remaining cultivation season," he added.