CALCULATION OF SOIL EROSION INTENSITY IN THE S1-6 WATERSHED OF THE SHIRINDAREH RIVER BASIN, IRAN Morteza BEHZADFAR, Natural Resources and Watershed Management Head Office, Iran Nevenka DJUROVIC, Faculty of Agriculture, University of Belgrade, Serbia Ivan SIMUNIC, Faculty of agriculture, University of Zagreb, Croatia Milica FILIPOVIC, Plantaze A.D., Podgorica, Montenegro Velibor SPALEVIC*, Institute of Forestry, Montenegro *Corresponding author: velibor.spalevic@gmail.com Soil erosion on agricultural land with steep slopes and dry ones is the main problem in Iran and is a threat to soil quality and to the ability of soils to provide agricultural services and may cause to endanger food security. The negative on-site and off-site impact of sediments on the environment and water resources is widely acknowledged with many watercourses in Iran. In this context rapid risk-assessment procedures using of computer-graphic methods have been introduced in the Shirindareh region of Iran to help policymakers to recognise sites where either certain crops should not be grown or anti-erosion measures are required. We used modelling of sediment yield and runoff for calculation of soil erosion intensity for a S1-6 watershed. Physico-geographical inputs, which are the basis for the calculation of soil erosion intensity, are included in the IntErO simulation model, with the Erosion potential analytical method of Gavrilovic embedded in the algorithm of this computer-graphic method. Our results shown that the net soil loss was calculated on 8437.09 m³ per year, specific 200.88 m 3 km -2 per year. The results of this study are the determination of erosion processes such as type and strength in the studied watershed; new information about the recent state of the runoff and a sediment yield in formats that can facilitate its efficient management and protection, illustrating the possibility of modelling of sediment yield with such approach. Key words: Erosion, Soil erosion assessment, watershed, Land use, IntErO model. Introduction Soil erosion is often regarded as one of the main processes of desertification. This has led to the use of various desertification indicators that are related to soil erosion. Most of these indicators focus, however, on small spatial units, while little attention has been given to the amount of sediment exported at the catchment scale. Such a small spatial unit approach neglects the transfer of sediment through catchments as well as the scale-dependency of erosion processes. Furthermore, this approach does not consider important off-site impacts of soil erosion, such as sediment deposition in reservoirs, as well as ecological impacts (Vanmaercke et al, 2011). Land degradation caused by soil erosion is especially serious in Iran. Soil erosion by water (water erosion) affects agricultural productivity in a number of ways, either directly or indirectly. The off-site impacts of runoff, sedimentation, loss of reservoir capacity is increasing in this Region. It diminishes soil productivity by reducing topsoil depth (Lal et al., 2000); availability of water (Bossio et al., 2010); nutrients (Li et al., 2013) and organic matter (Fenton et al., 2005), as well as by restricting rooting depth (Vaezi and Bahrami, 2014). Quantitative information on soil loss and runoff is needed for erosion risk assessment. This requires collection of field data and observations, various measurements by estimating the sediments accumulated in reservoirs or using suspended sediment yield data of rivers (Bagarello et al., 2011; Della Seta et al., 2009; Zeng et al., 2009; de Vente et al., 2008; van Rompaey et al., 2005), laboratory experiments (Leone and Sommer, 2000), as well as processing of those data through the predictive models.