Abstract:
Tarbela Dam sub-watershed located 90 km upstream of Dam is considered as the most vulnerable to soil water erosion and dump heavy load of sediments in the Tarbela Dam. Due to heavy sedimentation of Tarbela Dam its storage capacity has reduced over past few decades. This research aims to assess soil erosion hotspots and risk areas in the Tarbela sub-watershed. Revised Universal Soil Loss Equation (RUSLE) was used to get the results that consider the six factors named as cover management, practice management, rainfall runoff, erodibility, slope length and slope steepness. Rainfall data of 25 years (1985 - 2009) was used to calculate the rainfall factor and soil maps were used to extract the information for erodibility factor. Satellite image of SPOT-4 were used to extract the land use/ land cover of the area and NDVI for the cover management and practice management factors. DEM was used to calculate the slope length and slope steepness for area. Finally all these maps were multiplied to generate the potential erosion map. The results indicate that 22, 18.9, 38.3 and 14 percent of study area were under minimal, low, moderate and high erosion risks respectively. 6.4 percent area (192 sq km) is under extreme erosion and requires urgent attention. The annual soil loss predictions range between 0 and 506 tons ha-1. Average soil loss was highest (165 tons ha-1 year-1) in agriculture area and lowest soil loss rate was found in forest area (0.99 tons ha-1 year-1). This research can be helpful in improving land management and soil conservation for the areas of high erosion risk. Soil water erosion is becoming a serious problem in rain fed areas of Tarbela watershed. Tarbela Lake, a major source of water supply for Pakistan and biggest water reservoir for water storage and agricultural use in the country is undergoing
