Assessment and modelling of hydro-sedimentological flows of the eastern river Dhauliganga, north-western Himalaya, India

Assessment and modelling of hydro-sedimentological flows of a high-altitude river system is a critical step for developing and managing sustainable water resource projects and best management practices (BMPs) in the downslope regions of the Indian Himalayan Region (IHR). A field study was carried out to measure the hydraulic parameters such as water pressure, water flow rate, and stage of the 6th order glacier-fed river to quantify hydro-sedimentological flows using area-velocity and vacuum filtration method for 3 successive years during 2018-2020. Further, a process-based hydrological model: Soil and Water Assessment Tool (SWAT), is used to simulate the hydro-sedimentological flows. The statistical indices such as coefficient of determination (R-2), Nash-Sutcliffe efficiency (NSE), and percentage bias (PBIAS) attain higher values during both calibration and validation periods. The snowmelt and rainfall contributions to the total streamflow range from 17-35 % and 27-34 %, respectively. The measured and modelled hydro-sedimentological flows show high variability with a high coefficient of variation (COV > 1). However, the mean suspended sediment load (SSL) carried by the river was low compared to the other glacier-fed rivers. The physical weathering rate (PWR) dominates the chemical weathering rate (CWR) for the study years. This might be due to higher crushing of the region and weathering of base rock materials. The PWR and CWR of the basin are less than that of the western Himalayan regions. This study also underscores the necessity of basin management plans in the Himalaya, emphasizing erosion identification, snowmelt and glacier melt in streamflow, and customized groundwater recharge strategies through GIS mapping, providing essential insights for sustainable land and water resource management in changing climatic conditions.