Tamil Nadu's July Cauvery water share hits 50-year low at 0.698 tmcft

Chennai: Tamil Nadu's realisation of its share of Cauvery river water in July this year has dropped to its lowest in five decades, according to official data. The state received only 0.698 thousand million cubic feet (tmcft) against the stipulated 31.24 tmcft for the month, marking the worst July performance since 1974.

The measurement was recorded at Biligundulu, the designated monitoring site for inflow since the enforcement of the Cauvery Water Disputes Tribunal's final award in 2013. Prior to that, the Mettur dam served as the reference point. For Biligundulu, the previous lowest July figure was 2.441 tmcft in 2003. At Mettur, the lowest July realisation was also recorded in the same year at 1.5 tmcft. Other notably poor years include 1987 (Biligundulu: 3.392 tmcft, Mettur: 2.286 tmcft) and 2012 (Biligundulu: 4.153 tmcft, Mettur: 1.033 tmcft).

The data comes from a study by the High Level Technical Team on Cauvery, constituted by the Supreme Court in 2016. The study shows that for July, Mettur's 25-year average realisation was 33.7 tmcft and the 42-year average was 36.2 tmcft. For Biligundulu, the respective averages were 36.871 tmcft and 39.087 tmcft. The team considered these two periods because 2016 marked 25 years since the tribunal's interim order in June 1991, and 42 years since certain clauses of the 1924 Cauvery Accord between the Madras Presidency and the princely State of Mysore came up for review.

According to an application filed by the Tamil Nadu government before the Supreme Court on Monday, the cumulative realisation at Biligundulu as of August 2 was 3.687 tmcft, comprising 2.915 tmcft in June, 0.698 tmcft in July, and 0.074 tmcft in August. For the first two months of the water year, the state should have realised 40.43 tmcft as per the tribunal's final award, which has been amended by the Supreme Court.

The low inflow has raised concerns over water availability for irrigation and drinking water supplies in the Cauvery delta region. The state government has sought early hearing of the matter by the Supreme Court, which has agreed to consider the plea. The development underscores the continuing challenges in managing interstate river water sharing, particularly during years of deficient rainfall in the catchment areas.