New Delhi: With the India Meteorological Department (IMD) predicting a heavy rainfall at isolated places of Tamil Nadu and Kerala over the next 24 hours in view of Cyclone Ockhi, the Central Water Commission (CWC) on Friday said the pouring might trigger a rapid rise in the water level of the rivers in Tamil Nadu, Kerala.

The CWC also asked authorities in Tamil Nadu to closely monitor the Ponnaiyar river for the next five-seven days after a shutter of the Krishnagiri dam got damaged recently, forcing release of water downstream, and in view of Cyclone Ockhi.

The reservoir on the river is located near Periyamuthur village, about 10 km from Krishnagiri town in the state’s Krishnagiri district. The dam reached its full reservoir level (FRL) in September this year due to “very heavy rainfall" in the upper catchment of the Ponnaiyar river in Karnataka and Andhra Pradesh.

A CWC advisory said the west-flowing rivers in Thiruvananthapuram, Kollam, Pathanamthitta, Idukki, Kottayam, Alappuzzha and Ernakulam in Kerala were likely to rise over the next 24 hours and then, slowly fall as the rains reduced.

However, the rivers in Tamil Nadu’s Kanyakumari were likely to remain in a “high flood" situation during the period, the advisory said, adding that the water level in these rivers was expected to dip as the effect of the rainfall reduced.

The Papanasam and Manimutharu dams in Tamil Nadu were likely to get heavy inflows due to the rainfall for the next 12 to 24 hours.

The east-flowing Tambraparani river was likely to rise all along its course in Tirunelveli and Thoothukudi districts of the state during the next two-three days, the advisory said.

Similarly, the Vaigai river was likely to rise and a “significant inflow" was expected to be added to the Vaigai dam during the period, it added.

“However, as there is a sufficient cushion, the releases may not immediately be required," the advisory said.

The CWC said the Amaravathi and Bhavani rivers and their tributaries in the Cauvery basin were also expected to receive sufficient flows, increasing the water levels in the Amaravathy, Moyar, Pilloor and Bhavanisagar dams in the Nilgiris, Coimbatore and Erode districts of Tamil Nadu.

The rainfall was also likely to cause a rise in the water level of the Gomukhi and Wellington dams in Villupuram and Cuddalore districts of the state respectively, the advisory said.

“The lakes around Chennai are also expected to get sufficient inflows during the period between 2 and 6 December," the commission said.

“The release from the Sathanur dam has to be accordingly monitored, in view of the developing situation in association with the well-marked low pressure in the Bay of Bengal which is likely to become a depression and move towards the North Tamil Nadu-South Andhra Pradesh coasts," it added.

The Somasila and Kandaleru projects in Nellore district of Andhra Pradesh were also likely to receive “significant inflows" due to the depression, which was likely to affect the southern parts of the state from 5 December onwards.

“There is a likelihood of a rapid rise in the water levels of the Suwarnamukhi and Kalingi rivers in Chittoor and Nellore districts," the commission said.