Estimation of soil erosion by using RUSLE and GIS for small mountainous watersheds in Pakistan
2006
Nasir, A. (University of Agriculture, Faisalabad (Pakistan). Dept. of Structures and Environmental Engineering) | Uchida, K. (Kobe Univ. (Japan). Dept. of Agricultural and Environmental Engineering) | Ashraf, M. (Pakistan Council of Research in Water Resources, Islamabad (Pakistan))
Soil erosion has become a very serious problem in Pakistan. Deforestation, overgrazing and improper land use practices have reduced natural vegetation, leading to increased surface runoff causing soil erosion. About 65 percent of the Pothwar area have been severely eroded resulting in loss of fertile land and deposition in the downstream dams and reservoirs. A study was carried out to evaluate soil erosion by using Revised Universal Soil Loss Equation (RUSLE) with GIS at a sub-watershed of Lake Rawal (Satrameel) during 1989-96. Digital elevation data were used to develop contour and drainage maps of slope steepness and slope length based on digital elevation model (DEM). Moreover, rainfall erosivity factor was also determined by using erosivity models compared with rainfall. The monsoon rainfall was not uniformly distributed within and between seasons. Soil erosion risk was found to be the highest from July to September compared to other month s. Annual runoff measured by a H-type flume, averaged 2.3 cm depth across the watershed. Over 203 runoff events were observed in which 131 runoff events had more than 25mm rainfall. The predicted soil loss ranged from 0.1 to 28 t/ha/yr averaging 19.13 t/ha/yr. Combining the RUSLE with GIS tools was found useful for estimating soil loss on small size watershed for soil conservation and land use planning.
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