Tamil Nadu’s Mettur Reservoir Fills Early, Transforming Irrigation
The Stanley Reservoir in Mettur reached its full reservoir level (FRL) of 120 feet in June—only the second time this has occurred since its construction in 1934. Fueled by intense rainfall in Karnataka’s Cauvery catchment areas, this June overflow marks a significant moment for Tamil Nadu’s irrigation prospects, especially for the water-dependent Cauvery Delta region.
The Stanley Reservoir, Tamil Nadu’s largest dam, achieved full reservoir level at 120 feet on June 29, a phenomenon unseen in June since 1957. This rare occurrence was triggered by consistent rainfall in the upstream catchments of Karnataka. With inflows exceeding 57,000 cusecs and outflows surpassing 58,000 cusecs, the dam has reached its 94 tmcft capacity. The development has prompted advisories in 11 downstream districts vulnerable to potential flooding. Typically, Karnataka releases water towards the end of June, aligning with the southwest monsoon’s arrival. However, this year, upstream reservoirs were already full, pushing early releases into Tamil Nadu. The unseasonal full capacity has heightened flood preparedness in districts like Salem, Trichy, and Thanjavur, where residents in low-lying areas have been advised to shift. Authorities stress the importance of sustained inflow patterns to support both kuruvai and samba crop seasons.
The Mettur dam is crucial to Tamil Nadu’s agriculture, serving as a lifeline for farmers in the Cauvery Delta. Historically, water release for cultivation begins on June 12, but this schedule is often missed due to inadequate inflow. Officials highlight that reaching FRL in June could significantly improve irrigation consistency. Maintaining the current flow trend could ensure uninterrupted water supply until December, critical for short- and long-term cropping cycles. Constructed during the British era, the Stanley Reservoir is among India’s largest masonry gravity dams, built where the Cauvery River enters the plains. With a catchment area of over 42,000 sq km, the dam has been filling more frequently in recent years due to climate-induced rainfall shifts. This year’s early FRL highlights both climatic unpredictability and the dam’s enduring relevance to Tamil Nadu’s agricultural economy and inter-state water dynamics.
The early filling of the Stanley Reservoir signals a changing climate pattern and an opportunity for Tamil Nadu to optimise water usage in agriculture. As inflows continue and irrigation plans are set in motion, the focus shifts to managing excess water and ensuring equitable distribution. This event may reshape irrigation timelines and trigger discussions on better water-sharing frameworks between riparian states in future monsoon seasons.
