Space–time variability in soil moisture droughts in the Himalayan region

Abstract. Soil water is a major requirement for biomass production and, therefore, one of the most important factors agriculture productivity. As agricultural droughts are related to declining soil moisture, this paper examines moisture drought in transboundary Koshi River basin (KRB) central Himalayan region. By applying J2000 hydrological model, daily spatially distributed derived entire over 28-year period (1980–2007). A multi-site and multi-variable approach – streamflow data at station evapotranspiration three stations was used calibration validation model. In order identify conditions based on simulated deficit index (SMDI) then calculated, considering derivation actual from long-term weekly timescale. To subdivide variations river partitioned into distinct geographical regions, namely trans-Himalaya, mountains, plains. Further, SMDI aggregated temporally four seasons winter, pre-monsoon, monsoon, post-monsoon wetness dryness patterns observed study area. This has enabled us look magnitude, extent, duration drought. The results indicated that model can simulate processes with good accuracy. Considerable variation physiographic regions across due high precipitation temperature conditions. year 1992 driest 1998 wettest scale both magnitude duration. Similarly, also highest number weeks under Comparing standardised (SPI) suggested reflect higher than SPI. Our occurrence severity have increased last 3 decades, especially winter pre-monsoon seasons. insights provided frequency, spatial coverage, provide valuable contributions towards an improved management resources greater productivity