Cauvery awards work only during good monsoons: Data

An overview of the water releases month-wise, since 2018, shows that the order was adhered to when rains were bountiful

The Cauvery Water Disputes Tribunal (CWDT)’s prescription of the monthly schedule of the release of water by Karnataka to Tamil Nadu has been a bone of contention since the Tribunal’s interim order in June 1991. Though the CWDT’s final award, delivered in 2007, was modified by the Supreme Court 11 years later to address certain stakeholders’ concerns, the court did not disturb the scheme of the monthly schedule.

Also, considering the growing requirements of Bengaluru city for drinking water, the court awarded an additional 4.75 TMC to Karnataka, along with 10 more TMC. Consequently, Tamil Nadu’s overall allocation went down to 404.25 TMC from 419 TMC, as stipulated in the Tribunal’s final award, and that of Karnataka rose to 284.75 TMC from 270 TMC. Of the total allocation for Tamil Nadu, Karnataka should release water from its reservoirs in such a manner that 177.25 TMC is realised by the lower riparian State annually (June-May) as per the monthly schedule.

The first four months of the water year — June-September or southwest monsoon (SWM) — are crucial for both the principal riparian States of the Cauvery river, Karnataka and Tamil Nadu. It is during the June-September period that the upper riparian State, Karnataka, receives the most rainfall. For Tamil Nadu, these four months account for nearly 70% of the annual quota — 123.1 TMC — of inflows into the State.

This year’s SWM was bountiful for both the riparian States compared to the previous year. Last year, the lack of adequate rainfall led to emotions running high in both States over the lack of water supply for irrigation. This year, however, as the social media handle of the Karnataka State Natural Disaster Monitoring Centre (KSNDMC) revealed, the gross storage of four reservoirs of the Cauvery basin at the end of the monsoon period (September 30) was almost 60% higher than what it was on the corresponding day last year.

In terms of TMC, this year’s storage was about 110.83 TMC against the previous year’s 59.85. This year’s storage amounted to 97% of the gross capacity, 114.57 TMC. Karnataka’s four reservoirs in the basin — Krishnaraja Sagar, Kabini, Hemavathi, and Harangi — received at least 80 TMC more this time compared to the 30-year average of cumulative inflows. According to the KSNDMC, a total of 338 TMC was received by the reservoirs during this year’s SWM. With the bountiful rains and the reservoirs filling up, water supply should not be an issue in the coming months for both agricultural and drinking water purposes in Karnataka.

The story for the lower riparian State, Tamil Nadu also coheres with the above; this year’s figure of Cauvery water realisation exceeded the 200 TMC mark, with nearly 204 TMC released to the State. The receipts are vital as Tamil Nadu’s Cauvery delta relies mainly on water from the upper riparian State during the SWM since the northeast monsoon (NEM) is relatively unpredictable and erratic in terms of rainfall patterns. This is evident in the way the India Meteorological Department views the NEM — as one of large spatial variations.

The eastern part of the Cauvery Delta, also closer to the coast, receives heavy rainfall many times in November and December, but the rest of the State does not receive this frequency of rainfall.