Change in monsoon rainfall in North Eastern Region

In general, the average amount of monsoon rainfall has decreased from 900-3000 mm (1951-90) to 850-2350 mm (1991-07), indicating an average reduction of 18% rainfall in the recent period. The study indicates significant (P<0.01) decrease of amount of rainfall in Ukhrul and Senapati districts of Manipur and Phek, Zunheboto and Wokha districts of Nagaland.

Similarly, the range of rainy days got reduced from 65-91 days (1951-90) to 57-85 days (1991-2007) indicating an average reduction of 9% rainy days over the region.The reduction is significant (P<0.01) for all the districts of Nagaland; upper Assam districts of Tinsukia, Dibrugarh; and Tirap, Changlang, Lower Dibang valley districts of Arunachal Pradesh.

The traditionally wet north eastern region has shown a tendency of moving towards a drier monsoon regime in recent period as evidenced through standardized precipitation index. More locations in the region moved to the negative side of SPI indicating water stress of varying degrees during kharif season.

Preliminary crop modeling study suggests increase in upland rice productivity at Umiam, Meghalaya and Lamphalpet, Manipur by 6-7 and 3-4.5%, respectively if maximum temperature rose by 2 0C and level of CO2 concentration increased to 450 ppm. For the purpose, two locally developed and commonly cultivated high yielding rice cultivars viz. Bhalum-1 (145-150 days duration) and RCPL 1-142 (115-120 days duration) were used after calibration. Both the cultivars have potential to produce over 4 t h^-1 a of grain yield.

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