With about 20 thousand million cubic feet (tmc ft) falling short in the realisation of its share of Cauvery water in the last two months, Tamil Nadu is banking on this month’s rainfall in the river’s catchments in Kerala and Karnataka.

This month, the quota for Tamil Nadu is 45.95 tmc ft.

Unless the State receives a substantial flow in the coming weeks, managers of Mettur dam, which is the primary point of Cauvery water storage, will find it difficult to continue water release for more than a month.

The reason is the depleting storage. As on date, the dam has about 27.7 tmc ft.

Given the present rate of discharge, the storage can last for 29 days, after allowing 5 tmc ft each for dead storage and drinking water requirements.

In June and July, the State should have received a total of 40.43 tmc ft. Instead, it got only around 20 tmc ft.

Karnataka’s reservoirs, too, received a little more than one-third of what they should have got in the two months.

As against 120 tmc ft, they got around 45 tmc ft.

Recalling that in August last year, Tamil Nadu got around 92 tmc ft, the managers are expecting similar realisation this time.

The major difference is that water release commenced in August 2019 after the dam began getting a heavy flow, whereas it started on June 12 this year.

In fact, about 2.4 lakh cubic feet per second (cusecs) was recorded by the dam on August 12, 2019, the day before the dam was opened.

But on Saturday morning, the inflow was a mere 4,118 cusecs.