Abstract
The present work proposes to improve estimates of snowpack and snowmelt and their assessment in the steep Himalayan ranges at the sub-catchment scale. Temporal variability of streamflow and the associated distribution of accumulated snow in catchments with glacier presence in the Himalayas illustrates how changes in snowpack and snowmelt can affect the water supply for local water management. The primary objective of this study is to assess the role of elevation, temperature lapse rate (TLR), and precipitation lapse rate (PLR) in the computation of snowpack (or snowfall) and snowmelt in sub-catchments of the Satluj River basin. Modeling of snowpack and snowmelt was constructed using the Soil Water Assessment Tool (SWAT) in both historical (1991–2008) and near-time scenarios (2011–2030) by implementing real-time hydrometeorological, snow-hydrological parameters, and Global Circulation Model (GCM) datasets. The modeled snowmelt-induced streamflow showed a good agreement with the observed streamflow (~60%), calibrated and validated at three gauges. A Sequential Uncertainty Parameter Fitting (SUFI2) method (SUFI2) resulted that the curve number (CN2) was found to be significantly sensitive during calibration. The snowmelt hydrological parameters such as snowmelt factor maximum (SMFMX) and snow coverage (SNO50COV) significantly affected objective functions, such as R2 and NSE, during the model optimization. For the validation of snowpack and snowmelt, the results have been contrasted with previous studies and found comparable. The computed snowpack and snowmelt were found highly variable over the Himalayan sub-catchments, as also reported by previous researchers. The magnitude of snowpack change consistently decreases across all the sub-catchments of the Satluj river catchment (varying between 4% and 42%). The highest percentage of changes in the snowpack was observed over high-elevation sub-catchments.
Highlights
Perennial streamflow in river basins in India such as Ganga, Indus, and Brahmaputra originate from the Himalayan glaciers
More than 30 different soil parameters associated with each soil category, such as soil texture, available water content, hydraulic conductivity, bulk density, and organic carbon content, were used to setup Soil Water Assessment Tool (SWAT) simulation
The average curve number (CN) has been computed around 80 in the catchment, though it varied from lower sub-catchment to upstream sub-catchment as per the unique combination of land use/land cover (LULC), slope, and soil
Summary
Perennial streamflow in river basins in India such as Ganga, Indus, and Brahmaputra originate from the Himalayan glaciers. As per the Intergovernmental Panel on Climate Change (IPCC), temperature increase is the main cause of precipitation alteration in the Himalayan regions [1,5]. Some of these changes can be reflected in the spatial distribution and temporal variability of rainfall and snowfall, which at the same time can drive streamflow generation in large catchments in the Himalayas [6,7,8]. As in other regions around the world, the shift in runoff generation regimes may increase flood risk, affecting food, energy, and urban security downstream of the catchment areas [11,12,13,14]
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