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Changing rainfall pattern in India & its impact on food and water security

A changing rainfall pattern in India is of huge concern as the country’s water and food security stand on risky ground. In the last decade (excluding 2020), 50% of the rainfall over the 122-day monsoon was seen on an average of 40.4 days. However, there has been a transition in intensity as in the present fewer episodes of rain, when it rains, it hits hard.

June 20, 2021: Those staying  in West Bengal, Uttarakhand, Northeast, Arunachal Pradesh or Bihar are no longer enjoying the rain. The incessant rainfall has thrown life out of gear with flood-like situations in Bihar, Arunachal Pradesh and parts of Bengal. If we notice the rainfall pattern in India, then we would realise rainfall happens only for about three to four months from June to mid-September and is characteristically uneven, unreliable and erratic.

Image: Rainfall

Rainfall pattern in India: Monsoon hits hard

At the advent of the rains, it pours heavy and gushingly, giving rise to its label the burst of monsoons.

However, monsoon rainfall in India has been displaying a gradually decline since the 1950s.

If we look at the rainfall pattern in India during monsoon, then there has been a transition even in the intensity of the rains inclining towards the higher side. Meaning there are fewer episodes of rain, but when it rains, it hits hard.

2019 recorded heavy and extreme intensity rainfall which was the highest since 1901.

This steep graph line in total rainfall has accompanied another trend: the decrease in the number of days on which at least half the rain falls.

For instance, in the last decade (excluding 2020 to venture a pattern over the entire monsoon season), 50% of the rainfall over the 122-day monsoon was seen on an average of 40.4 days.

It proved was the fastest in the 12 decades since 1901. Noteworthy, the corresponding time for 75% of rainfall and 90% was only the fourth highest (70.6 days and 94.3 days respectively), although the long-term trend for those higher shares of rainfall is also the same: it takes fewer days now.

Narrowing down the range of sight to the all-India numbers, a significant regional variation in this pattern is observed. Let us take the instance of Delhi receiving 50% of its total monsoon rainfall in 2011-19 in just 83 days while the number was 30 for Karnataka.

In 2018, according to the Hydromet Division of the IMD, between June 1 and June 22, several meteorological sub-divisions in the northwest, northeast and east India have reported deficient (minus 59% to minus 20%) and large deficient rainfall (minus 99% to minus 60%).

Looking into the specific directional parts of the states, East Uttar Pradesh, West Uttar Pradesh, East Rajasthan and West Rajasthan have reported a rainfall departure of minus 63%, minus 43%, minus 52% and minus 54%, respectively. Bihar, Jharkhand and Odisha, too, have had minus 38%, minus 49% and minus 31% deficient rainfall, respectively.

Scenarios appeared bleaker in the meteorological sub-divisions of Saurashtra and Kutch, and Gujarat region, which have reported rainfall departure of minus 97% and minus 91%, respectively.

Overall, up until June 22, only 10 states and union territories reported normal rainfall (minus 19% to plus 19%) in the country. Eleven of them reported deficient rainfall and three are in the category of large deficient.

Meanwhile, eight states and UTs had excess (20% to 59%) and three had large excess rainfall (60% or more), respectively.

Image: IMD

Rainfall pattern in India: Long-term stats in sight

The three IMD scientists – Surinder Kaur, Sumant Kumar Diwakar and Ashok Kumar Das – studied long-term trend of annual, seasonal rainfall, rainfall pattern in India over different districts and meteorological sub-divisions of the country between 1961 and 2013.

Along with it, they also carried out annual rainfall trend analysis between 1961 and 2013.

Studying a total of 632 districts and 34 meteorological sub-divisions and daily rainfall records from 6,995 rain gauge stations across the country was collected.

Andaman and Nicobar Islands, and Lakshadweep were excluded from the study.

Based on this district-wise trend in annual rainfall between 1961 and 2013, (Mausam Quarterly July 2018) the researchers gathered that between 1961 and 2013, 64 districts (10.1%) showed an increasing trend of annual rainfall, whereas 85 districts (13.4%) made a decreasing trend.

Uttar Pradesh (UP) having maximum number of districts (32) showed a decreasing annual rainfall trend. These districts include Agra, Aligarh, Etawah, Firozabad, Gorakhpur, Kanpur, Mathura, Unnao, etc.

While on the Eastern side, Odisha having a maximum of 12 districts highlighted an increasing trend, such as in Cuttack, Kalahandi, Koraput, Mayurbhanj, Puri, etc. Area wise, 97,663.9 sq. km area in Uttar Pradesh has a declining trend in annual rainfall, whereas 68,846.9 sq. km area in Odisha has an increasing trend.

According to the trend analysis of annual rainfall 2017, the inference drawn was, “…the sub-divisions of West UP, East UP and Arunachal Pradesh are showing significantly negative trend in rainfall whereas the sub-divisions Odisha, Coastal AP (Andhra Pradesh) and Konkan and Goa are showing significantly positive trend at 95% (confidence level)”.

From an all round track, at national level, 10.3% area in the country (except Leh and Ladakh district, Andaman & Nicobar and Lakshadweep) has reported an increasing trend in annual rainfall between 1961 and 2013; and 8.03% area has reported a decreasing trend in annual rainfall during the same time period.

Besides the annual rainfall trend, the IMD scientists have also studied monsoon rainfall between 1961 and 2013. And, the analysis shows: “The sub-divisions of West UP and East UP are showing significantly negative trend in monsoon rainfall whereas the sub-divisions Jammu & Kashmir, Odisha, SI (south interior) Karnataka and Konkan and Goa are showing significantly positive trend in monsoon rainfall at 95% (confidence level)”.

There is not a single district that showed an increasing trend in rainfall in Uttar Pradesh, Uttarakhand, Delhi and Puducherry in both the periods.

Image: Down to Earth

Impact on food and water reserves

This sway in the Indian rainfall pattern is a huge concern as the country’s water and food security stand on risky ground. The specifics of a 2017 document of the Indian government’s think tank NITI Aayog, Revitalising Rainfed Agriculture in India, say that India is already water stressed. Almost 52% of its cropped area remains without irrigation and some areas are chronically water stressed.

The share of canal in net irrigated area has declined from 39.8% to 23.6%, whereas groundwater sources has increased from 28.7% to 62.4% between 1950-51 and 2012-13. Because of lack of irrigation, a large number of farmers depended on monsoon rainfall to practice agriculture. For instance, as per the NITI Aayog document, of the total pulses, oilseeds and cotton produced in the country, 80% pulses, 73% oilseeds and 68% cotton come from rain-fed agriculture.

Image: Blog

The net potential effect of severe changes in rainfall pattern is the disruption in crop production leading to food insecurity, joblessness, and poverty. The annual demand for cereals, pulses, edible oils, vegetables and fruits is increasing at a rate of 1.3%, 3%, 3.5%, 3.3% and 5%, respectively. The fluctuation on rainfall pattern can put a spanner in India’s food security.

Researchers of the IMD study warned, “Changes in climate over the Indian region, particularly during the SW [southwest] monsoon, would have a significant impact on agricultural production, water resources management and overall economy of the country.” Such climatic changes would also mean an increase in extreme weather events, droughts and floods.

Also read: Odisha, West Bengal brace for severe cyclonic storm Yaas, NDRF deploys 115 teams in 5 states

To back it, let us consider the case of northeast India, which is facing destructive floods. As of June 22, Manipur had a rainfall departure of minus 60% (classified as large deficient), but thereafter faced a fury of floods. As against the normal rainfall of 315 mm, Assam has so far received only 254.1 mm rainfall this southwest monsoon (minus 19%, on the borderline of normal category), but 14 people have lost their lives in flash floods and rainfall-induced landslides, whereas more than half a million people in the state have been affected by the floods.

By Arpita Patro


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