TN officials say this can be done without affecting its irrigation needs

Despite the Karnataka Government’s claim of its inability to release any more Cauvery water, Tamil Nadu strongly believes that the neighbouring State can very well make good the shortfall of 47 tmcft (thousand million cubic feet) without affecting Karnataka’s irrigation requirements.

This case was presented by Tamil Nadu a week ago during discussions with Central officials led by Union Water Resources Secretary Dhruv Vijai Singh.

The shortfall of 47 tmcft has been arrived at, using a distress sharing formula worked out by the Central Water Commission and finalised by the Cauvery Monitoring Committee. In its submission to the panel, Tamil Nadu argued that the water requirements of Karnataka had been calculated at approximately 70 tmcft.

Taking into account the decision of the Cauvery River Authority (CRA) that the area under cultivation in Karnataka was about 75 per cent of the area [8.71 lakh acres] allowed as per the final order of the Cauvery Water Disputes Tribunal, for the total area to be served by that State’s major reservoirs of Krishnaraja Sagar, Kabini, Hemavathy and Harangi, the requirement would be 96.4 tmcft, which would come down to around 70 tmcft at 75 per cent coverage.

While making this calculation, the Tamil Nadu authorities omitted the coverage under Rabi semi-dry crop as the cultivation would normally be done during the northeast monsoon (October-December) for the Cauvery basin.

According to the Tamil Nadu Government, Karnataka had utilised 66.7 tmcft as on September 30. So, it would require 3.3 tmcft more.

As at the end of September, the net storage of 68.9 tmcft was available with Karnataka. Going by the 29-year-long [1974-75 to 2002-03] average flows, the anticipated further inflow from October to January would be 60 tmcft. It has also been assumed that this year’s northeast monsoon would be normal.

After deducting the requirement of Karnataka of 3.3 tmcft, the available balance quantity would be 125.6 tmcft. Easily, the Tamil Nadu’s shortfall of 47 tmcft could be made up.

Up to the end of September, the Mettur dam realised around 28 tmcft whereas it should have got 75 tmcft even as per the distress sharing formula.

Requirement for crop

As regards Tamil Nadu’s requirement for samba crop over 15 lakh acres, it would require 145 tmcft from the middle of October till the harvest in mid-February. Deducting the likely quantity of 35 tmcft to be saved during the northeast monsoon, the figure of net supply required would be 110 tmcft. The total requirement would go up to 114 tmcft, including four tmcft for evaporation loss and drinking water supply.

This could be met if Karnataka wiped out the shortfall of 47 tmcft and released 44 tmcft more from October 16 to January as per the Tribunal’s interim order. For the remainder, the authorities would manage with the quantity of water available at Mettur.

On Wednesday morning, the level of Mettur stood at 71.13 ft (full level: 120 ft) and storage was 33.7 tmcft (capacity: 93.47 tmcft).