Climate changehas impactedrainfalldistribution during monsoon months innortheasteven as the total amount of rain remains mostly unchanged. On the eve ofWorld Environment Day, experts said this lack of uniform distribution of rainfall throughout the monsoon months has resulted in prolonged consecutive dry days and shorter wet days.
Research on rainfall patterns atAssam Agricultural University(Aau) revealed a decreasing tendency of annual rainfall by 66.4 mm/decade during 1986-2015 over theBrahmaputra valleyof Assam. This decrease of annual rainfall in the valley was mainly contributed by the decrease in monsoon rainfall by 53.4 mm/decade, with statistically significant decrease of September rainfall in the upper (39 mm/decade) and central (35 mm/decade) parts of the valley and July rainfall in the lower (77 mm/decade) part of the Brahmaputra valley.
The annual Average rainfall over northeast is 2162 mm, which varies from 4275 mm (Meghalaya) to 2250 mm (Nagaland). The annual rainfall in Assam is about 2352 mm. Monsoon season contributes the highest amount of annual rainfall (65%) while pre-monsoon, post-monsoon and winter seasons contribute about 25%, 7% and 3% to the annual rainfall of the region respectively.