SOIL LOSS ESTIMATION USING THE INTERO MODEL IN THE S1-2 WATERSHED OF THE SHIRINDAREH RIVER BASIN, IRAN

UDK 631.459(55 Shirin-Dareh Basin) Soil erosion is one of the main problems of land degradation of agricultural land, especially in the mountainous areas. This negative process is one of the key problems to the environment and water resources in Iran. Using the computer-graphic modelling, we calculated sediment yield and peak discharge of the S1-2 catchment, of the Shirin-Dareh Basin of the Caspian Sea watershed. The area characterized cold winters (the minimum of 24.4°C) and warm, dry summers (the absolute maximum air temperature of 34.6°C; the average annual precipitation of 328 mm). The coefficient of the region's permeability, S1, is calculated on 0.84. The structure of the river basin, according to water permeability, is the following: f0, poor water permeability rocks, 53%; fpp, medium permeable rocks, 41%; fp, very permeable products from rocks: 6%. The most common soil type in the studied area is Inceptisols with Calcic horizon. The river basin is under the mountain pastures (51%) and the rest (49%) is the ground without grass vegetation and plough-lands. The coefficient of the river basin planning is calculated on 0.75. The coefficient of the vegetation cover is calculated on 0.9. We calculated the soil losses from the S1-2 catchment on 20404 m3 yr-1 and the peak discharge on 209 m3s-1 (for the incidence of 100 years). The value of the Z coefficient of 0.917 indicates that the river basin belongs to the second destruction category, where the strength of the erosion process is high. With this study we provided new information about the recent state of the sediment yield of the S1-2 catchment, of the Shirin- Dareh Basin in the North Khorasan province of Iran in formats that can simplify the management in the watersheds, demonstrating the possibility of Soil Loss Estimation using the IntErO Model.