With Tamil Nadu’s realisation of the Cauvery river water exceeding the 600-tmc ft-mark on Friday, November 18, 2022, for the first time in the last six decades, the focus is on whether this year’s realisation will surpass an all-time high of about 750 tmc ft (thousand million cubic feet) recorded 61 years ago.
Under normal circumstances, the remaining period of the water year, which ends in May, will experience reduced rainfall in the catchment of the Cauvery. Even if the coming five and a half months witness a repeat of the previous year in terms of realisation, the State may get at best, around 90 tmc ft more which will be 60 tmc ft less than what was realised in 1961-62.
For statistical purposes, the highest realisation as recorded at Mettur between 1963-64 and 2012-13 was 476.65 tmc ft during 1964-65. Tamil Nadu had to wait 11 years to get more than 400 tmcft in a year. During 1975-76, the reservoir recorded around 427.7 tmc ft.
After the publication of the Cauvery Water Disputes Tribunal’s final award in the gazette of the Central government in 2013, Biligundulu has replaced Mettur as the reference point for measurement. Till date, this month, about 28 tmc ft was realised.
Thanks to a huge realisation in the present water year, water level has remained at 120 ft at Mettur reservoir for over a month. Earlier this year too (during July 16- September 23), it was in an identical situation.
Consequent to the release of excess flows from the reservoir for weeks, the Lower Anicut, which is the last measuring point in the State for the Cauvery flow, may have registered the surplus flow of over 450 tmc ft draining to the sea.
Even though the wasted quantity is equivalent to nearly four times the storage of the Mettur reservoir, the topography of the State is such that not much can be done to prevent its occurrence, says a veteran irrigation engineer.