Deficit northeast monsoon a “correction”
A dry field at Perambalur district symbolises poor monsoon in many parts of the state. | Photo: M.Srinath

Tamil Nadu’s seven-year-long dream run in the form of higher rainfall during the northeast monsoon (October-December) has come to an end with the State recording 16 per cent less rainfall than the normal in the last three months and raising grim prospects for the summer months ahead.

Not only did the State record a negative departure of rainfall for the overall season this time but also 21 out of 32 districts received deficit rainfall.

The underlying message: the possibility of water shortage looms large over different parts of the State this summer.

A senior official of the Tamil Nadu Water Supply and Drainage Board, which handles water supply for the State except Chennai, does not see any problem till March end, given the fact that several combined water supply projects are dependent on sub-surface flows.

Chennai may not have major problems on the water front as there is sufficient water in the Kandaleru reservoir, the terminal storage point in Andhra Pradesh under the Krishna Water Supply Project.

Besides, Chennai reservoirs have water to the tune of nearly one half of their capacity.

Between October and December of 2012, the State registered 37 cm rainfall against the expected amount of 44 cm, a shortfall of 16 per cent.

According to meteorological standards, normal rainfall is regarded if the deviation from the anticipated rainfall is in the range of minus 19 per cent to plus 19 per cent. For excess, the deviation has to be 20 per cent and more while, for deficient, it has to be in the range of minus 20 per cent to minus 59 per cent.

Since 2004, the State recorded excess rainfall in five years – 79 per cent in 2005; 21 per cent in 2007; 31 per cent in 2008; 42 per cent in 2010 and 23 per cent in 2011. In the other two years, the State registered normal rainfall – one per cent in 2004 and 15 per cent in 2006.

Among the 21 deficit districts this time are Chennai – (actual rainfall: 57 cm, deviation: minus 28 per cent); Madurai – (22 cm, minus 47 per cent) and Tiruchi – (29 cm, minus 25 per cent).

Both Thanjavur and Nagapattinam, forming part of the Cauvery delta, registered deficit rainfall - minus 20 per cent each with 44 cm and 75 cm rainfall.

Only Tiruvarur recorded a normal rainfall of minus eight per cent with 66 cm. Referring to the under par performance of the northeast monsoon compared to the rainfall received last year, a senior meteorologist describes it as a “correction” as no region can go on receiving copious rainfall.

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