Assessing Hydropower Potential in Nepal’s Sunkoshi River Basin: An Integrated GIS and SWAT Hydrological Modeling Approach

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This study assessed the hydropower potential of a mountain watershed within the Sunkoshi River basin in Sindupalchok, Nepal, utilizing Geographic Information Systems (GIS) and the Soil and Water Assessment Tool (SWAT) hydrological model. Topographical, soil and land use, meteorological, and discharge data were employed to characterize the study area. SWAT facilitated the delineation of the Sunkoshi basin into 23 sub-basins, generating a river network with attributes such as stream link, stream order, stream length, and slope, and subsequently simulating river discharges. Calibration and validation of the hydrological model are critical steps when simulating water balance components in watershed systems. The Sequential Uncertainty Fitting Version 2 (SUFI-2) algorithm within the SWAT Calibration and Uncertainty Program (SWAT-CUP) was used to calibrate and validate the model, involving 25 selected parameters. Model performance was evaluated using three well-established efficiency criteria: coefficient of determination (R² = 0.79), Nash-Sutcliffe efficiency (NSE = 0.73), and Percent Bias (PBIAS = 17.59). The study identified 36 sites across streams of order 3, 4, and 5 as having potential for hydropower generation.  The impact of other development projects and environmental factors were also evaluated. The hydropower potential at each identified site was calculated using estimated stream flow and topographical head at various Probability of Exceedance (PoE) levels (40%, 45%, 50%, and 60%). The aggregate hydropower potential of the basin was quantified, yielding a potential of 371.30 MW at a 40% PoE. The findings suggest that an integrated approach combining digital elevation models, stream network data, and a hydrological model like SWAT within a GIS framework can accurately assess a river basin's hydropower potential.

Binaya Kumar