Staring at driest-ever August: Breaking down El Nino impact on the monsoon

But this August is set to go down as the driest since 1901, from when rainfall records of the India Meteorological Department are available. By Tuesday morning, the country as a whole had received only 160 mm of rainfall this month. That means a deficit of about 33 per cent for the month. Never has the country received less than 190 mm of rainfall in August (see accompanying charts).

States like Gujarat and Kerala have had a deficit of nearly 90 per cent for the month so far. Karnataka, Telangana and Andhra Pradesh also have more than 50 per cent deficiency. Tamil Nadu, which receives a bulk of its rainfall during the winter months, has a shortfall of about 23 per cent.

“The influence of El Nino is very clearly visible now. We were lucky to have good rainfall in July, otherwise we would have been staring at a very difficult situation,” M Rajeevan, former Secretary in the Ministry of Earth Sciences, said.

El Nino impact

El Nino refers to the unusual warming of the equatorial Pacific Ocean off the coast of northwest South America, which influences weather events across the world. Over India, it has the effect of suppressing the monsoon rainfall. A similar phenomenon in the Indian Ocean, called the Indian Ocean Dipole (IOD), was expected to turn favourable for the monsoon rainfall this year, but did not have much impact, Rajeevan said.

“It is only now that the IOD is getting into a positive phase. But the relationship of the IOD with the Indian monsoon is not as well established as El Nino’s. It is futile to expect that IOD would compensate for El Nino. In fact, there is some evidence to even suggest that it is the monsoon that affects the IOD, and not the other way. This is not yet a settled question,” Rajeevan said.

The only regions that received good rainfall in August were east and northeast India. Incidentally, these parts had remained significantly dry in June and July, showing a deficit of 15 per cent and 32 per cent in those respective months. August rainfall brought welcome relief in this region, but even though the monthly rainfall in most of these states has been more than normal, it has not been sufficient to wipe off the seasonal deficit.

“The impacts of El Nino unfold in such a manner that rainfall over almost the entire country, barring the east and northeast, is suppressed. And that is exactly what we have seen in August. Beyond El Nino, there are some other systems that can also bring about short spells of rain. Many of these were favourable during July, but unfortunately, none in August. For example, except for one feeble low-pressure event that brought some rains over Madhya Pradesh, there was a complete absence of low-pressure systems in August,” D Sivananda Pai, a senior scientist with IMD, said.

Both Rajeevan and Pai said there were chances of a revival of the monsoon in the first or second week of September.

“A strengthening of monsoon activity is expected around the first week of September and it is likely to last for a week or 10 days, but it is uncertain how much rainfall this will result in. As of now, under the influence of El Nino, September is expected to be deficient too,” Rajeevan said.

Dropping reservoir levels

Since the four-month monsoon season brings about 75 per cent of India’s annual rainfall, the storage of water in reservoirs for use during the rest of the year is crucial. As of now, water levels in the major reservoirs of the country are not bad. The combined storage in 146 major reservoirs of the country, as per data till last week, was about 94 per cent of the normal. This is likely to see a drop when the latest data is released later this week.

But in several states, reservoirs are already running at very low levels. In Kerala and Tamil Nadu, reservoirs are holding only 50 per cent of the water that they normally have during this time of the year, while in Bihar, reservoirs levels are at only 12 per cent of the normal. States like Uttar Pradesh, Jharkhand, Odisha, Andhra Pradesh and Telangana are also not doing very well. A dry September can exacerbate this situation.

There are concerns for the winter crops as well. Even the standing kharif crops, which benefited from plenty of water during the sowing time in July, are feeling the stress now. The Soybean Processors Association of India said in a statement on Tuesday that the crop required an immediate bout of rains to sustain itself. Soybean is not even a highly water intensive crop.

“Any delay in rains will be detrimental to the soybean crop in the entire country. The extent of yield loss will depend on the revival of rains and it is premature to predict the overall crop today. All will depend on how the monsoon behaves in the next 45 days,” the statement said.