Widespread rainfall lashed several parts of Tamil Nadu in the early hours of Wednesday, with a few coastal areas experiencing intense downpours, under the influence of a prevailing weather system over the Bay of Bengal. Heavy rainfall is expected to continue over many districts this week.

The strengthening of easterly/northeasterly winds over the region signals the impending arrival of the Northeast monsoon. The Regional Meteorological Centre (RMC) said the simultaneous withdrawal of the Southwest monsoon and onset of Northeast monsoon was likely on Thursday.

An upper air cyclonic circulation over coastal Tamil Nadu and adjoining Comorin area is cited as one of the reasons for wet weather in the State. In its bulletin, the RMC forecast wet spell to continue till October 21.

On Thursday, four districts, including Tirunelveli and Ramanathapuram, may receive very heavy rainfall. Heavy rain is likely in 22 districts, including Virudhunagar, Villupuram and the Nilgiris. Many coastal districts, including Chennai and neighbouring districts, are likely to receive intense rainfall.

In 24 hours ending at 8.30 a.m. on Wednesday, Ennore in Chennai recorded very heavy rainfall of 14 cm. Kathivakkam (10 cm), Manali New Town in Chennai and Kodanad in the Nilgiris district (9 cm each), Wimco Nagar in Chennai (8 cm) also reported heavy rainfall. Several other districts received light to moderate rainfall.

Water release

Meanwhile, the Water Resources Department (WRD) released about 700 cubic feet per second (cusecs) of water from the Poondi reservoir, and 200 cusecs from the Red Hills reservoir on Wednesday as a precautionary measure.

Officials of the WRD said the water released into the Kosasthalaiyar river will reach the Tamaraipakkam anicut. From there, it would be diverted to Cholavaram tank for storage.

The shutters of the Poondi reservoir were opened as it received heavy inflow of 2,260 cusecs from catchment areas, the Kesavaram anicut, the Illupur check dam, and the Kandaleru-Poondi canal.

According to the WRD's compendium of rules, the reservoir water level must be maintained at 33 ft. in October. However, the water level now stands at 34.30 ft., requiring it to be diverted to the Cholavaram tank for storage.

Officials said the floodgates of Red Hills reservoir, one of the major drinking water sources for the city, were also opened as the storage was 3,006 million cubic feet against 3,300 mcft.

"We have to maintain the water level two feet lower than full level in October, ahead of monsoon. The reservoir storage will be stepped up to full capacity by December. The water level was at 19.97 ft against full level of 21.20 feet, leading to the precautionary measure of opening shutters," an official said.

Intense rainfall over many parts of Tamil Nadu to continue this week