Quantifying agricultural drought in the Koshi River basin through soil moisture simulation

Abstract

Study region: The Koshi River Basin (KoRiB), one of the headwaters of the Ganges in Eastern Nepal. Study focus: The mesoscale hydrological model (mHM) is applied to assess the historical spatio-temporal hazard of agricultural drought using soil moisture index (SMI) in the KoRiB. New hydrological insights for the region: The research indicates that KoRiB was most severely impacted by drought from 1976 to 2000, with the two major droughts occurring in 1982–1989 and 1991–1996. Both events had an average duration of over 12 months and affected more than a quarter of KoRiB’s area. Notably, between 1951 and 1975 and 2001–2020, the regions of elevated drought hazard shifted from the middle-eastern to the western area of the KoRiB. Previously, droughts were largely the result of precipitation shortfalls, but in the 21st century, rising temperatures have emerged as a significant factor, accompanying the ongoing precipitation deficits. This underscores the imminent occurrence of such compounded effects and emphasizes the importance of monitoring systems to anticipate and mitigate such events.

Keywords

• Drought
• Hazard assessment
• Koshi River Basin
• MHM
• SMI