The world’s wettest place is witnessing a decline in rainfall

A recent analysis of 119 years of rainfall measurements at different rain gauge stations across North East India, has revealed a decreasing trend in summer rainfall since 1973, including in rainy Meghalaya, reputed for hosting the world’s wettest place.

• Parts of India, especially Northeast India, one of the wettest places on the Earth, are facing a severe impact of the climate crisis with reduced rainfall and increase in dry, or no rain, and heavy rain days.
• The monsoon, which generally begins in June and retreats by September, delivers around 70% of India’s annual rainfall.
• The monsoon is key to replenishing reservoirs, groundwater and addressing water shortages.
• However, the current study has shown significant decreasing trends in Meghalaya, where Cherrapunji is known as one of the places with the highest precipitation globally.
  • Climate change is bringing erratic weather—flood and drought, sometimes in the same area (for example-Kerala (2018).
  • The monsoons now bring less rain in total, while the demand for water increases as the population, economy, and industry grows.
  • The rains come in increasingly violent deluges, but with little storage options, most of the rainwater is lost as run-off.

Assessing North East India on the rainfall track

• North East India is mostly hilly and is an extension of the Deccan plateau.
• The region is highly sensitive to changes in regional and global climate.
  • Northeast India has the highest vegetation cover in India and included in 18 biodiversity hotspots of the world, indicating the importance of the region in terms of its greenery and climate-change sensitivity.
• Pre-monsoon and monsoon are the rainy seasons of North East India.
• Rain-bearing summer air currents (the Bay of Bengal branch of monsoons) that move north from Bangladesh’s hot and humid floodplains hit the funnel-shaped relief of the Meghalaya hills with deep valleys and gorges.
• The steep parallel mountains (Garo, Khasi and Jaintia hills) in Meghalaya block the movement of the clouds to the north; they are squeezed in through the gorges and then forced to ascend the steep slopes and shed most of their rainfall in the region.

 Key-highlights of the Study

• According to the study, most stations in North East India show negative trends in rainfall, with the largest decreasing trends in rainfall in summer and the lowest in winter.
• The annual mean rainfall for the period 1973–2019 showed decreasing trends of about 0.42 mm per decade.
  
  
  • The reduction in winter rainfall is statistically significant at North Lakhimpur, Pasighat and Shillong.
• These long-term rainfall changes in the region are responsible for the observed shift of the world’s wettest place from Cherrapunji to Mawsynram (separated by 15-km) in recent decades.
  • Mawsynram receives an average annual rainfall of 11,871 mm while Cherrapunji braces for torrential rains every year with an annual average at 11,430 mm.

• Variation in temperature of water bodies: The decline in rainfall is driven by changes in the Indian Ocean temperature and Arabian Sea.
• Human factor: Population growth and human activities such as agriculture have caused deforestation and reduction in ice and snow in northeast India. This has increased water bodies, and urban and built-up lands between 2001 and 2018.
• Climate change: Human-induced climate change has been causing widespread changes to weather patterns in India. 
• Conversion of forestlands: It is also due to conversion of forestlands and vegetation cover to croplands in the last two decades.
  • The analysis also showed reductions in vegetation with 104.5 sqkm lost per year.
  • On the other hand, there were significant increases in crop-land (182.1 sqkm per year) and urban and built-up lands (0.3 sqkm per year) during the period 2001–2018.
• Fragmented forests: The fragmentation and isolation of once contiguous forests because of infrastructure projects is also why a fourth of Meghalaya’s forests are now vulnerable to climate
• It is also due to change in moisture content in air due to changes in vegetation pattern.

To sum up, changes in land-use patterns, coupled with variations in temperature in the Indian Ocean and Arabian Sea, remarkably contributed to a decreasing trend in rainfall.

Implications

The changing climate in Meghalaya would have widespread implications for forests, water resources, biodiversity, agriculture, livestock and human health.

• Forest fire, landslides & siltation of water bodies: Due to significant rise in temperature, forest fires may go up while extreme rainfall events will increase risk of landslides in high altitude areas causing siltation of water bodies downstream.
• Threat to flora and fauna: The rise in temperature will also threaten endemic plant species many of which are already on the verge of extinction.
• Adverse effects on agriculture: Rain-fed agriculture in the state will be adversely hit with crop yields and production declining.

• In North East India, long-term, dense and reliable daily rainfall data from IMD is infrequent due to remoteness of the region with low population density, extended periods of regional conflicts and environmental disasters and change in location of the observatories in some stations within the same locality resulting in fragmented or inconsistent data series.
• A better understandingof the physical mechanisms of the NEI’s rainfall variability is crucial for developing advanced projections of future rainfall variability.