In view of the heavy rainfall in several districts of Tamil Nadu and Pudducherry, and the reservoirs in the region getting heavy inflows, the Central Water Commission (CWC) on Thursday issued an advisory for the dam operators to keep strict vigil and release water carefully.

The heavy rainfall is a result of the depression over Bay of Bengal, off north Tamil Nadu coast that moved with a speed of 23 kmph on Thursday morning and lay centred at about 250 km from Chennai, 220 km from Puducherry and 210 km from Karaikal.

Filephoto of heavy rainsIANS

Meanwhile, the India Meteorological Department (IMD) has issued flash flood warnings for Tamil Nadu, Andhra Pradesh and Pudducherry. Its Land Surface Model have shows as high as 95-100 per cent saturation in few watersheds of southern parts of Rayalaseema, southern parts of Coastal Andhra Pradesh & Yanam adjoining to North Tamil Nadu and Tamil Nadu, Pudducheery & Karaikal subdivisions of IMD and up to 80-85 per cent saturation in few watersheds of Rayalaseema and Kerala IMD subdivision.

The depression is very likely to continue to move, and cross north Tamil Nadu & adjoining south Andhra Pradesh coasts between Puducherry and Chennai early Friday morning, the India Meteorological Department (IMD) said.

"The depression is not deep. But the rainfall is expected to be high mainly because the north-east monsoon is active and hence the moist north-easterly winds converging along Tamil Nadu coast would bring in copious amounts of rainfall," said IMD's senior scientist Sunitha Devi.

IMD has already issued a forecast of high rainfall of more than 250 mm in the next 24 hours.

There has been heavy rainfall activity in the districts of Cudallore, Villupuram, Thiruvannamalai, Peralambalur and Kallakuruchi in Tamil Nadu and Puducherry, because of which water levels in the rivers in the regions - South Pennar, Palar, Gedilam, Varahanadi, Velhar, including Gomukhi and Manimuktha, - are likely to rise significantly creating flood type situation and inundation till November 20, the CWC said.

"Reservoirs such as Sathanur dam and Veedur dam are likely to get significant inflows. Releases, if any, may be done as per standard operation procedure after alerting the downstream stakeholders," the CWC advisory from its Hydrology Division in Chennai said.

Tamil Nadu rains
Several parts of Chennai were inundated after heavy rainfall.Twitter

Similarly, due to ongoing heavy rainfall activity in basins of Kosasthalai, Araniyar, Adayar, smaller rivers in Thiruvallur, Vellore, Ranipet, Kanchipuram, Chengalpattu districts, water levels in rivers are likely to rise significantly creating flood type situation and inundation from Thursday till November 20.

"Reservoirs in these basins in Pichatoor dam (Araniyar river in Andhra Pradesh), Poondi reservoir, Chembarambakkam reservoir and other dams are likely to get significant inflow, strict vigil may be kept and releases may be made carefully keeping in view the downstream level conditions," the CWC said.

Authorities concerned may monitor the situation with caution and are advised to be in high alert and also alert the downstream areas for increase in river levels, the advisory said.

Besides, the IMD has issued a Persistent Flash Flood Threat (PFFT) applicable till Thursday evening with moderate to high threat likely to occur over few watersheds and neighborhood of Kadapa, Chittoor districts of Rayalaseema, Nellore, Prakasham districts of coastal Andhra Pradesh & Yanam, Kanchipuram, Villupuram and Puducherry, Ariyalur, Perumbulur, Tiruchirapally, Salem, Dharmapuri, Karaikal, Krishnagiri and Cuddalore districts of Tamil Nadu, Puducherry & Karaikal met subdivisions by Thursday evening.