Assessment of soil erosion risk using SWAT model

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ORIGINAL PAPER

Assessment of soil erosion risk using SWAT model Manel Mosbahi & Sihem Benabdallah & Mohamed Rached Boussema

Received: 30 May 2012 / Accepted: 10 August 2012 # Saudi Society for Geosciences 2012

Abstract Soil erosion is one of the most serious land degradation problems and the primary environmental issue in Mediterranean regions. Estimation of soil erosion loss in these regions is often difficult due to the complex interplay of many factors such as climate, land uses, topography, and human activities. The purpose of this study is to apply the Soil and Water Assessment Tool (SWAT) model to predict surface runoff generation patterns and soil erosion hazard and to prioritize most degraded sub-catchment in order to adopt the appropriate management intervention. The study area is the Sarrath river catchment (1,491 km2), north of Tunisia. Based on the estimated soil loss rates, the catchment was divided into four priority categories for conservation intervention. Results showed that a larger part of the watershed (90 %) fell under low and moderate soil erosion risk and only 10 % of the watershed was vulnerable to soil erosion with an estimated sediment loss exceeding 10 tha−1 year−1. Results indicated that spatial differences in erosion rates within the Sarrath catchment are mainly caused by differences in land cover type and gradient slope. Application of the SWAT model demonstrated that the model provides a useful tool to predict surface runoff and soil erosion hazard and can successfully be used for prioritization of vulnerable areas over semi-arid catchments. Keywords SWAT model . Semi-arid catchment . Soil erosion . Land cover M. Mosbahi : M. R. Boussema Laboratory of Remote Sensing and Information System for spatial reference, National School of Engineers of Tunis, BP37, Tunis Belvedere 1002, Tunisia S. Benabdallah (*) Center for Water Research and Technologies, BP 273, Soliman 8020, Tunisia e-mail: [email protected]

Introduction Soil erosion constitutes a global environmental and economic problem in Mediterranean region (Terranova et al. 2009). It has long-term impacts as it causes loss of fertile topsoil and reduces the productive capacity of the land and thereby creates risk to global food security. In Tunisia, soils are under a serious risk due to long dry periods followed by heavy bursts of intensive rainfall, falling on steep slopes with fragile soils and low vegetation cover. Twenty percent of the total land area is affected by water erosion, yearly, 15,000 ha of farming arable land and 500 million m3 of runoff water are lost (DG/ACTA 1993). It is the primary environmental issue in the Sarrath river catchment subject for a future dam. This catchment located in north west of Tunisia (1,491 km2) is characterized with heterogeneous soil erosion patterns. Quantification of soil loss is one of the greatest challenges in natural resources and environmental planning (Arekhi et al. 2010). Computer simulation models are becoming increasingly popular in predicting soil loss for various lan