Hydrological responses to climate change in a central Himalayan basin: insights from snow and glacier runoff modelling

Abstract

Assessment of the impacts of climate change on central Himalayan hydrology is vital for the sustainable management of downstream water resources under recent CMIP6 climate projections. We focused on the hydrological processes and water components of the Ghaghara River basin (GRB), particularly on snow- and glacier-melt runoff under projected CMIP6 scenarios. The Spatial Processes in Hydrology (SPHY) model was calibrated and validated for the baseline period (2001–2010), achieving good-to-excellent performance at daily and monthly scales. In the baseline scenario, snow and glacier melt contributed 13.17% and 6.09% of total runoff, respectively. The snowmelt runoff declined by up to 5.49%; however, glacier melt increased by up to 6.13% under the high-emission scenario (SSP5-8.5) compared to the baseline. Rainfall-runoff is expected to increase by ~8% relative to the baseline period. Snowmelt runoff anomalies are expected to decrease after mid-century, particularly under high-emission scenarios, due to reduced snow cover during melt periods. The findings suggest that incorporating climate projections and their associated uncertainties is important for regional water management and planning.