Journal of Range and Watershed Managment

Abstract Knowing the amount of runoff and sediment generated from different lands is an important step in land use management. Since it is not always possible to measure these values, modeling parameters, will be a way to achieve watershed comprehensive management. Beheshtabad watershed in Chaharmahal & Bakhtiari province with different land uses such as range land, agriculture, gardens and urban area is an important part of Northern Karun Basin. In order to simulate the amount of runoff and sediment generated in different land uses, SWAT model was used. Discharge and sediment data of weather and hydrometric stations located in the area was used for sensitivity analyses and then to calibrate and validate model by SUFI-2 algorithm. NS and R² coefficients obtained for runoff calibration are respectively 0.69, 0.71 and for runoff validation are 0.65, 0.67 and for sediment are 0.72, 0.73 in calibration, and 0.66, 0.71 in validation, that confirmed model ability to accurately estimate of flow, runoff and sediment in the study area. The results showed that dry farming lands with average runoff and sediment of 190 mm, 24.5 tons per hectare per year respectively, has the highest and gardens with an average of 80 mm runoff has the lowest sediment yield of 1.63 tons per hectare in the year.

Abstract Soil erosion along environmental problems. The consequences of soil erosion can be examined from a variety of perspectives.the cost of soil erosion is divided into two categories of on-site and off-site costs. Soil erosion affects the production cycle and economics directly and indirectly. The purpose of this study was to estimate and compare direct and indirect economic losses of soil erosion in different land uses in the Beheshtabad Basin.To achive this, first sediment production by each landuse was initially determined by using SWAT model. NS and R² model coefficients for calibration were 0.72,0.73, and 0.66,0.71 for validation. Then direct loss of erosion was calculated based on the method of replacing the main soil organic fertilizer (NPK) by chemical fertilizers and indirect loss of erosion based on the loss caused by sedimentation behind the check dams inside the basin and reservoir dams outside the basin. According to the results, the highest amount of economic loss of soil erosion was related to rainfed farms equivalent to 56 million Rials per hectare Due to the fact that these lands are located on high slopes and also incorrect agricultural operations .The least amount was related to gardens,equal to 4.5 million-rials/hectare that indicated the importance of trees crown covering and observing the proper slope in the construction of gardens in the soil conservation. In this basin,excess grazing and improper utilization of rangelands have led to high erosion rate and sediment production in upstream rangelands and 3.33 million-Rials/hectare economic losses of erosion in this land use.