Characterization of drought in a hill city- Shillong using standardized precipitation index

Abstract

The water stress situation in a high rainfall hill city- Shillong, Meghalaya during 1983 to 2010 was investigated using standardized precipitation index (SPI). The SPIs were computed on sliding timescales of 1- and 2- months to represent short term moisture stress (STMS); 3- and 6- months to represents agricultural drought and 12-, 24- and 36- months to represent hydrological drought. Yearly and monsoon droughts as well as drought spells were also determined. The monsoon months in the area contributes more than 75% to the annual rainfall and droughts during monsoon months are well correlated with annual droughts. Frequency of drought events and drought durations indicated are inversely proportional and directly proportional to the timescale of SPI, respectively. The study revealed that STMS ranged from 1 to 11 months, agricultural droughts ranged from 1 to 13 months and hydrological droughts ranged from 11 to 62 months. Among the STMS indicator, the SPI2 has shown longest drought spell of 11 months between July, 1990 and May, 1991. Similarly, for agricultural drought, the longest drought spell was given by SPI6 which was started in the month of June, 1998 and lasted till June, 1999. Further, hydrological drought given by SPI24 that starts on July, 1995 and lasted until September, 2000 for over 5 years was of the extreme nature. The authors however, concluded that, water crisis in Shillong is manageable with proper soil moisture conservation and water harvesting techniques.