Climate change effects on hydrology of the Tawi basin in Western Himalaya

Abstract

This study has been conducted to assess future climate change impacts on hydrology of the Tawi River Basin using Soil Water Assessment Tool (SWAT). Model parameters were identified using sensitivity analysis and long-term calibration procedures, which enabled the historical behaviour of the catchments to be reproduced. Following validation, the parameters were used to simulate the effects of climate change on future streamflow. During the model development, 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. The reanalysis data of NCEP has been used for setting up the downscaling model for GCM. Future daily time series of precipitation, maximum and minimum temperature have been downscaled from the HadCM3 GCM using the multiple linear regression based statistical downscaling model SDSM for the medium-high (A2) and medium-low (B2) SRES mission scenario, as drivers of the hydrological simulations during the future scenarios. Changes in streamflow were in general agreement with the projections of daily precipitation and temperature fields. It has been found from the model results that the average annual streamflow might increase in the 2020s, 2050s and 2080s of the century. The results also indicate that streamflow in future may widely spread in the months as compared to the past which will ensure the good quantity of flow in the river for more months in a year, but there will be decrease in lean season flows due to the projected future climate change.