Impact of Drought on Crop Yield Across Physiographic Regions of Gandaki River Basin in Nepal

Drought is one of the possible consequences of climate change and it can potentially trigger water related stresses. Meteorological drought is analysed both in time and space by using drought indices based on site-specific precipitation and temperature data. This study focuses on the characterization of meteorological droughts along different physiographic regions (High Himalaya, High Mountain, Middle Mountain, and Siwalik excluding Terai) of the Gandaki River Basin in Nepal. The objective of this study is to assess possible impacts of drought on crop yield along different physiographic regions along this river basin. The intensities, frequencies and trends of drought occurrences were analysed using Standardized Precipitation Evapotranspiration Index (SPEI) for the multiple timescales of 1-, 3-, 6-, 9-, and 12-months and on a seasonal basis (winter and monsoon). The daily precipitation and temperature records for 1984-2011 period were used to determine the SPEI to characterize meteorological droughts (onset, severity, duration, intensity, and withdrawal of drought). It is evident that there are differences in drought characteristics regionally within the river basin. The southern part of the river basin, Siwalik region is more prone to have high frequencies of droughts with incidents of short duration and severe drought events. The High Mountain and High Himalaya are prone to severe level of droughts. Moreover, the results showed that the cropping season precipitation, minimum temperature, and maximum temperature account for 59%, 57% and 52% of the variance in crop yield in Siwalik, Middle Mountain and High Mountain respectively, but not in High Himalaya. Drought prevention and management should therefore be differentiated based on the varying characteristics of drought and effects of climatic factors in different regions. This study could be a first step to make detailed assessment of drought considering more indices for robust conclusion on drought risk management. Keywords: Drought, Gandaki River Basin, SPEI, Nepal, Water Scarcity