CHENNAI: The combined storage in the four reservoirs supplying water to Chennai rose to 55% as on Saturday. Brisk rainfall in the past few days has helped in increasing the levels in the reservoirs.
A senior PWD official said the storage in Poondi reservoir was 1,477mcft, Cholavaram 138mcft, Red Hills 2,207mcft and Chembarambakkam 2,429mcft on Saturday. The full capacity of the reservoirs are 3,231mcft, 1,081mcft, 3,300mcft and 3,645mcft respectively.
Considering the storage levels in the reservoirs on the same day last year, the officials are much relieved.
Except Poondi and Cholavaram, the other reservoirs - Red Hills and Chembarambakkm - had only 988mcft and 271mcft respectively. On that day the combined water level was only 3,009mcft, said the official.
A senior official said after a heavy spell of rain, various factors contribute to the filling of reservoirs. These include water percolation, evaporation levels, and run-off water.
"These factors play a vital role for any reservoir for its level to increase after a rain. A short spell for a few days will not help in bringing water to the reservoir, as it will percolate into the ground quickly. Similarly, one has to account for the run-off water, which is another major factor. Calculating all these factors will result in the actual realisation after rain," he said.
Considering the current water storage position in each reservoir, the rainfall has to be in continuous spells for at least four days. These spells have to be intense, only then the realisation in the reservoirs can be substantial, said the official.
At present each reservoir should get 120mm to 150mm of intense rainfall for at least two days. Such a downpour will help in bringing more water to the reservoirs.