Climate response of the Naumure Multipurpose Project: assessing water availability and irrigation demand

ABSTRACT

Climate change poses significant challenges to water resource management for multipurpose projects in Nepal. This study aims to evaluate the impacts of climate change on water availability and irrigation water demand for the Naumure Multipurpose Project (NMP) located in the West Rapti Basin (WRB) using a multisite calibration approach in Soil and Water Assessment Tool (SWAT) and CROPWAT8. SWAT-CUP with SUFI-2 algorithm was utilized for model optimization and performing sensitivity on WRB along with manual calibration. The bias-corrected ensemble of future projected climate data from five different climate models projected that maximum and minimum temperatures increase by up to 4.05 and4.96 °C, respectively, under the SSP5-8.5 scenario in the far future (FF), with a 10–48% increment in precipitation from the near future (NF) to FF in WRB. The future annual average flow is projected to increase by 33–51% under SSP2-4.5 and 33–77% under SSP5-8.5 at the Naumure Main Dam site, with a similar increment at the Lamatal regulatory dam site. For Banke and Kapilvastu irrigation schemes, the demand decreases by up to 17 and 13%, respectively, under SSP2-4.5 to 23 and 20% under SSP5-8.5 scenario. However, for Kapilvastu, demand continues to increase in the mid-future and FF compared with NF but does not exceed baseline demand in the high-emission scenario. The total annual irrigation demand for each of the command areas of NMP does not exceed the baseline under any future scenarios, which highlights that the projected hydrological changes are unlikely to adversely affect hydropower production and irrigation reliability at NMP.