Simulation of runoff, sediment and soil erosion by EUROSEM model in Tange-Ravagh sub basin, South Karun watershed, Kohkeiluieh-Boyer Ahmad Province

To perform soil and water conservation programs in watersheds, a model is required to predict runoff, sediment and soil erosion spatially and temporally. This research was conducted in order to evaluate EUROSEM model in estimating runoff and soil loss in Tangh-Ravagh sub-basin of south Karun watershed. The study area covered 1 ha, was divided into nine units according to EUOSEM users guide manual. Soil and plant cover parameters and geometrical characteristics of the sub-basin were collected and measured, then parameterization, calibration and validation processes were done in 7 separate events. The calibration of hydrograph was performed by decreasing saturated hydraulic conductivity and capillary drive and increasing soil moisture. The calibration of sedigraph was done by decreasing detachability of soil particles and increasing Manninmg’s n and soil cohesion. Validation results showed that EUROSEM model provides a good simulation of the total runoff, total soil loss and peak runoff discharge, but it could not simulate well the time of runoff, time to peak discharge and the peak of sediment discharge. Comparisons of measured capillary drive and soil cohesion in the study area based on the values provided by EUROSEM manual, showed significant differences. Therefore, the tables are not recommended to be used in evaluating these parameters that should be adjusted locally.