Abstract:
Runoff is a key component of hydrological cycle and it is relevant for the basin planning and management
programme for conservation and development or natural resources. This implies the need to develop and
test hydrological models for understanding the hydrological characteristics of the region of interest for
appropriate mitigation and adaptation measures to cope with future water demands. Soil and Water
Assessment Tool (SWAT) is a physically based semi-distributed hydrological model, which has been
developed to predict runoff, erosion, sediment etc. and it employs the hydrological response unit (HRU)
as the basic unit of the basin. In the present study, SWAT was applied to the Tawi River Basin of Western
Himalayan region of India. Tawi is a forested mountainous basin with geographical area of 2167 km2.
Model parameters were identified using sensitivity analysis and long-term calibration procedures, which
enabled the historical behavior of the catchment to be reproduced. Following validation, the parameters
were used to simulate the streamflows. In order to establish the effectiveness of model to simulate
hydrological responses to climatic variations, the simulated values were subjected to rigorous calibration
with observed runoff data on a monthly time scale. Fifteen-year monthly rainfall and runoff data were
used to simulate the hydrological behavior of the basin for the study. During the simulation, the monthly
observed stream flows matched well with simulated flows with Correlation coefficient and Nash-Sutcliffe
coefficients values of 0.72, 46% during calibration (1983–1992) and 0.92, 84% during validation (1993–
1997) respectively, suggesting a better parameterization and simulation performance. Since the database
on SWAT model's potential in simulation performance on Himalayan basins is scanty, this paper is
successful in showcasing the potential of SWAT in simulating the runoff of Western Himalayan basins.
