Graduation Term

Summer 2026

Degree Name

Master of Science (MS)

Department

Department of Geography, Geology, and the Environment

Committee Chair

Wondwosen Seyoum

Committee Member

Lisa Tranel

Committee Member

Jonathan Thayn

Abstract

This study investigates long-term changes in terrestrial water storage and their impact on hydrological processes in glacier-fed regions of Nepal. The study focuses on the central to eastern Himalayan region, including major river basins within the Koshi system. Multiple datasets, including the Gravity Recovery and Climate Experiment (GRACE) and GRACE follow-on (GRACE-FO) missions satellite data, the Global Land Data Assimilation System (GLDAS) products, and in situ streamflow data, were used for the period 2002–2019. Terrestrial Water Storage Anomaly (TWSA) derived from GRACE data shows a strong decreasing trend over time, indicating significant water storage loss across the study area. Soil Moisture Anomaly (SMA) derived from GLDAS also shows a consistent decline, suggesting progressive drying of the land surface. Surface Storage Anomaly (SSA), defined as the difference between TWSA and SMA, shows a substantial reduction in surface and glacier-related water storage, with stronger depletion in the eastern region than in the western region. Time-series and seasonal decomposition analyses indicate that water storage decline is consistent across all seasons, although seasonal variations are influenced by monsoon rainfall. Streamflow analysis shows variable responses across river basins, with some showing increasing discharge while others exhibit declining or stable trends. Cross-correlation analysis indicates a positive relationship between SSA and streamflow with short time lags of approximately 1–2 months, suggesting a delayed hydrological response. The long-term depletion of water storage could be driven by glacier mass loss, increased evapotranspiration, and changing climate conditions. Although increased melting currently sustains river flow in some basins, this condition is not sustainable in the long term. This study highlights the importance of understanding water storage dynamics for improving water resource management and planning in the Himalayan region.

Access Type

Thesis-Open Access

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