Assessment of Landuse Change and Its Impact on Watershed Hydrology Using Remote Sensing and SWAT Modeling Techniques—A Case of Rawal Watershed in Pakistan

Assessment of hydrological effects of the landuse transformations on both water yield and flow regimes is an imperative aspect in watershed management. Dealing with water management issues requires analyzing of different elements of hydrologic processes taking place in a watershed area. In the present study, hydrological response of the Rawal watershed (located in the sub-Himalayan region) was studied to historical landuse evolution and variable landuse change scenarios using SWAT -Soil and Water Assessment Tool model. The temporal analysis of LANDSAT TM (1992) and LANDSAT ETM plus (2010) image data revealed a decrease of over 16% in the scrub forest coverage while built-up land increased three folds during 1992-2010 period. Major part of the scrub forest had converted into agriculture and built-up land besides rangeland in some areas. The landuse changes resulted in an increase of about 6.0% in the water yield and 14.3% in the surface runoff of the watershed. The scenario of extreme deforestation likely due to growth in urbanization, exhibited a decrease of about 0.4% in the water yield and an increase of about 122% in the sediment yield from base conditions of 2010 period. In case of an afforestation scenario (e.g. increase of scrub coverage to about 76%), the sediment yield decreased by about 11.4%. Appropriate soil conservation measures based on suitable afforestation techniques can prove influential in mitigating the risk of soil erosion in this fragile mountain ecosystem of the Himalayan region.