An Erodability Assessment of a Cropland and a Grassland on the Khangah Sorkh Watershed, Urumiah Using a Rainfall Simulator

Water and soil are the most important natural resources of every country. As soil is a vital resource for food production and environmental regulation, its deterioration affects the human wellbeing. This research was carried out with the aim of assessing the effect of land use on runoff and sediment production in the Khangah Sorkh Watershed in Urmia. Two slopes of 13 – 0 and 25 – 13 percentage gradient were selected from the DEM map of the region considering the requirements for the setting of rainfall simulator. Also, by investigating the intensity-duration-frequency of the rainfall of the region, two intensities of 40 and 50 mm/h were selected, corresponding to the return periods of 50 and 100 years, respectively. Two cropped fields and two grass-covered rangeland were selected randomly and the rainfall simulation was conducted on each of them for 15 minutes per experiment using the factorial design. The results showed that there was no significant difference in runoff production in the grassland, but there was a significant difference in its sediment production. There was a significant difference between the different levels of slope gradient and the rainfall intensity in the runoff production in the cropland, but there was no significant difference in the sediment production. There was no interaction between the rainfall intensity and slope gradient in either of the land use systems at the 5% confidence level. However, both the volume of the runoff and the rate of erosion were higher for the cropland.