An update on how climate patterns are changing in India's northeast, changing rainfall dynamics too
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India's northeast faces climate crisis - Monsoon variations
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- The story: Over the past century or so, rainfall in the northeast region of India, along with the flood-drought cycle, has changed a lot. Rainfall patterns over the region are resulting in its overall drying up. Till August 27, 2021, several states in the northeast were suffering from high deficits in rainfall.
- Statewise: Manipur had the highest deficit, with 58 per cent less rains than normal. Mizoram recorded a deficit of 28 per cent; Nagaland and Arunachal Pradesh received 23 per cent and 21 per cent less rainfall than normal. Other states fared better only marginally.
- What a change: The trend becomes starker when data from the last few decades is compared. The northeast hosts some of the rainiest places on Earth, with rainwater being the major source of water there. Other sources of water, such as glaciers that feed rivers in other mountain regions of India, are not as common in the North East. Glaciers in Arunachal Pradesh cover 223 square kilometres of a total land area (83,473 square km). In Himachal Pradesh, they span 4,500 square km out of a total land area (55,673 square km).
- The dynamic: The rain and snow feed mountain springs, which feed the tributaries that join either the Brahmaputra, Barak as well as rivers in Manipur. All these together water the region. If the rainfall decreases and the flow of the springs diminish, the rest of the water systems also get disturbed. Almost 27 per cent villages in northeast India are watered directly by the springs. NITI Aayog published a report on the inventory and revival of springs published in August 2018.
- Around 70 per cent of the region’s area lay in the catchment of the Brahmaputra river and its major (41) and minor (121) tributaries as well as numerous streams. This dependency on rainfall makes the region highly vulnerable to climate change.
- Northeast normally receives heavy rainfall during the monsoon months (June-September), which replenishes the rivers every year. Over generations, people have learnt to reclaim and cultivate the soils brought in by the rivers. Now they have become uncertain about their knowledge.
- Droughts and floods: The probability of drought occurrence in the region was 54 per cent during 2000-2014, found a research paper published in journal Current Science in January 2015. Western India too faced high chances of drought, but they were half of what northeast India experienced.
- There had also been two major flood years — 2007 and 2010 — in the Brahmaputra in the same period
- The river gets flooded every year, a natural process that has shaped the land in most of North East India for millions of years. Major floods in the Brahmaputra, therefore, are known to cause inundation for more than 10 days at a stretch.
- In Assam, 86 per cent of the rural population practices agriculture, according to the state’s action plan on climate change. The state is also highly prone to flooding every year as most of its area is drained by the Brahmaputra.
- Analysing rainfall trends over different periods of time and to different geographical extents yield slightly different results but with a clear imprint of changing patterns indicating a change in climate.
- Rainfall in north east India was reliable in the past, till as recent as 1951. It varied at an average of 15-20 per cent from one year to the next from 1901-1951, according to a research paper by P Jagannathan and HN Balme from the Indian Institute of Tropical Meteorology (IITM), Pune.
- A 115-year (1901-2015) monsoon rainfall analysis by India Meteorological Department (IMD) in 2018 found a significantly declining trend in Arunachal Pradesh and Nagaland, Manipur, Mizoram and Tripura (NMMT) subdivisions (meteorological geographical categories as defined by the India Meteorological Department). Another rainfall analysis for India from 1871-2005 found that the NMMT subdivision witnessed a decline in monsoon rainfall by 135 millimetres in total — the third-highest decline in the country after Chhattisgarh and Kerala, according to a research paper published in the Hydrological Sciences Journal in May 2010. The total annual decline was around 85 mm. Annual rainfall in Assam and Meghalaya subdivision decreased by 0.53 mm every year amounting to a total decrease of almost 72 mm. The decrease in monsoon rainfall for the two states put together is even starker with an annual decrease of 0.64 mm a year, which amounts to over 86 mm in total.
- Sunspot epochs: Sunspot epochs are alternating periods of increased and decreased activity on the Sun’s surface that influence the climate of Earth. Researchers found that during the monsoon, rainfall patterns in North East India differed significantly from one sunspot epoch to another, suggesting differential intensification of the seasonal trough of low pressure over the country. During 18 of the last 19 years (2001-2019), North East India received monsoon rainfall less than normal with an exception of 2007 (110 per cent of normal), according to an IMD report from 2019.
- EXAM QUESTIONS: (1) Explain the general trends being observed in northeast India, in rainfall patterns. What policy measures can help minimise the pain created by it? (2) What are sunspot epochs? How to they influence rainfall patterns? Explain.
#Rainfall #Northeast #SunspotEpochs #ClimateChange
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