Tamil Nadu’s reservoirs only a third full, against 92% a year ago; Mettur may last a week

Tamil Nadu could face a serious water shortage unless the northeast monsoon picks up. The State’s 15 major irrigation reservoirs hold only about a third of their capacity, against about 92% at this time last year.

The Mettur dam on the Cauvery, which waters the delta’s paddy crop, can supply water for only about another week, according to a report on 8 November, leaving delta farmers anxious about the samba season. Across the larger set of reservoirs the State monitors, only three were full and 43 held less than 25% of their capacity in early November.

Rain has come, but not enough. The State has received about 240 mm since the monsoon set in, slightly more than expected for this point, but needs about 260 mm more this month to avoid shortages. The outlook is not encouraging: the India Meteorological Department expects November rainfall over Tamil Nadu to be below normal, under 77% of the long-term average of 118.7 mm, partly because of El Niño conditions in the Pacific.

Help from upstream is limited too. The Cauvery Water Management Authority has ratified a recommendation that Karnataka release only 3.88 tmcft of water, against the 20.7 tmcft Tamil Nadu asked for.

Why it matters

Tamil Nadu depends on the northeast monsoon, from October to December, for nearly half of its annual rain, and on Cauvery water from Karnataka for its rice bowl in the delta. Last year, Mettur filled to capacity three times. A dry November now would hit the samba crop first, and then drinking water supplies in the towns that draw on these reservoirs through the summer.

What’s next

Rain is forecast across much of the State until 12 November, with heavy spells in the delta and the south, which could ease the pressure on the reservoirs.