5 more die, Assam toll at 127 N-E battles deluge but IMD says monsoon rain declined over 3 decades

NEW DELHI: The flood situation in Assam and Meghalaya continued to remain alarming due to ongoing extremely heavy rainfall in the northeastern states. However, India Meteorological Department (IMD)’S study highlighted that monsoon rainfall over northeastern states has been on a decreasing trend in the past three decades, pointing at changing weather patterns due to climate change.

At least 121 people have died in rain-related incidents since April 1 in Assam with over 2.5 million people still reeling under the deluge, according to a report by Assam State Disaster Management Authority (ASDMA). In neighbouring Meghalaya, several parts of the state were cut off last week when incessant rains caused landslides, mudslides and flooding.

Nearly every year these parts of the northeast suffer deluge during monsoon months. However, IMD’S analysis of ‘rainfall variability and changes over different states’ for the period between 1989 and 2018 for Assam suggests that monthly rainfall for all monsoon months between June and September is recording a decreasing trend.

“Due to heavy rainfall in the eastern Himalayan and other watersheds of the north-eastern parts of India, Assam has extensive river systems consisting of the Brahmaputra, Barak, Burhidihing, Danshiri, Subansiri, Kopili, Dihang and others. All these rivers in Assam are vulnerable to floods, mainly because they receive heavy rainfall within a short time in the state and its neighbourhood where water runs very fast into Assam, which has mostly low elevation,” states IMD’S analysis, also available on IMD Pune’s website.

These rivers are in their early stage of maturity and are very active agents of erosion. “The river water collects a tremendous amount of silt and other debris from the hilly terrains and raises the level of the riverbeds,” said IMD Pune in its rainfall variability analysis.

Apart from the unique geographical position of Assam and Meghalaya, the entire northeastern region is also witnessing a shift in monsoon pattern combined with increase in climate change-induced extreme rain events, experts said.

“Monsoonal weather systems have reduced leading to reduced overall rainfall. Depressions used to form during monsoon months that would bring continuous downpour to this region or usually a trough would form in Bihar and move towards northeast India. We are not seeing these formations anymore. But there is massive rainfall during a short period of time like we saw in Meghalaya and Assam in last two weeks. These short duration heavy rainfall events are expected due to climate change,” Pulak Guhathakurta, head of climate division in IMD Pune.

For northeast and east India, IMD’S normal rainfall calculated for the period from 1961 to 2010 was 1,410.4 mm which came down to 1,367.3 mm in the 1971 to 2020 period. During this year’s monsoon so far between June 1 and June 23, Meghalaya has recorded 150% excess rains, followed by Assam 83% and Arunachal Pradesh 25% excess rain, according to IMD.

Meghalaya — which has a hilly terrain with elevations varying from 150 metres to 1,965 metres above sea level — is also seeing a reduction in seasonal and annual rainfall, according to the IMD analysis.