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Saturday, September 18, 2021

Rains and reservoirs: Normal monsoon, with some erratic features

The 2016 Southwest monsoon season officially ends today. 2 years of drought are over, reservoirs are full, and the sown area under kharif is more than last year. But rain has been neither consistent nor uniform.

Written by Amitabh Sinha |
Updated: September 30, 2016 7:50:08 pm
monsoon, monsoon in india, monsoons, india monsoon, rainfall, rainfall in india, monsoon 2016, normal monsoon, southwest monsoon, southwest monsoon season, southwest monsoon season 2016, end on monsoon, monsoon ends, drought, drought in india, marathwada drought, maharashtra drought, best monsoon, mumbai, rain, hyderabad rain, delhi rain, El Niño phenomenon, what is El Niño phenomenon, La Niña, what is La Niña, cauvery water dispute, indian express news, india news The eastern and northeastern parts of the country have been the only regions to have seen some consistency in the rainfall they received. (Express Photo by Pavan Khengre)

The 2016 monsoon season — which officially ends on Friday — will be remembered as one that produced 97% of normal rainfall, and will be categorised as a “normal” monsoon year. The overall number does not, however, reveal how erratic the rainfall has been this season, both in terms of geographical spread and time.

Even during the best monsoons, rainfall is never uniform over the entire country. Some areas get very good rain, while others are dry — just as in the worst of droughts, some pockets receive excess rainfall. This year, the same areas had alternating spells of excessive rainfall and extremely dry days. Madhya Pradesh faced flooding in August, for example, but has had very little rain in the last one month. Parts of Andhra Pradesh and Telangana, which are under water right now, thanks to a deluge in the last few days, had remained practically dry since the end of July.

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The eastern and northeastern parts of the country have been the only regions to have seen some consistency in the rainfall they received. After good rainfall in July, the region had a 15% to 20% deficiency in almost every week that followed, before it started to pour last week — like in many other parts of the country.

Deviation from forecast

The 97% rainfall (compared to the average of 1951-2001, called Long Period Average or LPA) at the end of the season is far less than the 106% that the India Meteorological Department (IMD) forecast in April, and re-stated in July. The forecast for specific regions too was off by several percentage points (See table above right).

The good thing, however, was that there was enough rain in every region at the time when it mattered the most, ahead of the sowing season.

The impact of deficient rainfall towards the latter half of August and first half of September was, therefore, not felt very strongly. Latest Agriculture Ministry data show that area sown with kharif crops this year has been 1,060.81 lakh hectares — about 8 lakh hectares more than the previous year.

“We must look at two things while assessing whether a monsoon has been good or bad. First, whether sowing of crops has been normal, and second, the situation of storage in our reservoirs. On both these fronts, we are in a very comfortable position this year. There is no crop stress, while the reservoirs, after providing for irrigation needs during the season, are still filled to about 97% of their normal levels at this time of the year,” IMD Director General K J Ramesh said.

No La Niña

The lesser-than-expected rainfall, especially the deficiencies in the second half of the season, is being attributed to the absence of the La Niña phenomenon in the equatorial Pacific Ocean that is known to help the Indian monsoon. Ahead of the start of the season, all global climate models, including that used by IMD, were predicting the development of a La Niña, which refers to the unusual cooling of sea surface temperatures in the Pacific Ocean. La Niña is a sort of opposite of the El Niño phenomenon that had ruined the Indian monsoon in the previous two years.

“This year’s negative temperature anomaly in the equatorial Pacific was not strong and the geographical area covered was not as high as expected. No model predicted the actual pattern of sea surface temperature that was observed. We do not know why,” J Srinivasan of the Divecha Centre for Climate Change at the Indian Institute of Science, Bangalore, said.

Late surge fills reservoirs

Heavy rainfall in most of the country over the past week has boosted reservoir levels. The 91 major reservoirs in the country currently hold a total of 117.202 billion cubic metres of water, as per Central Water Commission figures updated until Thursday. This is about 74% of their total storage capacity.

The current position is much better than last year, though slightly less than what is normally expected during this time of the year. 21 reservoirs are filled to their full capacities, including three in south India which finally received very good rainfall after being mostly dry from the middle of July. Two of the four reservoirs in the Cauvery basin, Kabini and Harangi, have also reached their near-normal levels. Karnataka and Tamil Nadu are currently engaged in a bitter fight over Cauvery waters.

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