Investigating the Status of Some Indicators of Assessment of Watersheds and Prioritizing Sub-Catchments in Terms of Erosion Reduction (Case Study of Karkheh Watershed)

Environmental challenges are increasing day by day which this is a result of the increasing human population and demand for natural resources. Mismanagement of natural resources causes instability in environmental indicators. Degradation of watersheds with soil erosion and sediment yield is one of the most important environmental issues in Iran. Therefore, it is necessary to prepare and complete the spatial information of the natural characteristics of the watersheds and their prioritization. Because it is used in comprehensive watershed management. The purpose of this study was to investigate the status of some indicators and prioritize sub- catchments in Karkheh watershed. So indices of sensitivity of rock units to erosion, modified fournier erosivity index, erosion intensity from EPM experimental model and sedimentation through logarithmic sediment delivery ratio and discharge data were extracted and analyzed. After calculating mentioned indices in the sub-cachtments of Karkheh watershed, the values of each indicator in the basin and sub basins were examined, standardized and compared and then sub- cachtments prioritization were performed. The clustering method was also used to group the sub- cachtments and the above mentioned indices and topographic indices. Investigation of the susceptibility of formations to erosion of Karkheh watershed showed that sensitive class to erosion is the most frequent in this basin (60 %). The largest similar category in sub- cachtments includes nine ones with codes2213, 2214, 2221, 2222, 2223, 2225, 2226, 2227 and 2228 and the coefficients of area and length of flow had the most similarity. The results of rainfall erosivity and average erosion also indicate that very high erosivity class and high erosion class have the largest area (49% and 52% respectively) in this basin which the average erosivity and erosion of the basin were 60.6 mm and 727 m3 / km, respectively. The results of the average ranking of the indicators of geological formation sensitivity, rainfall erosivity and erosion of each sub basin show that sub basins such as 2215 (Karkheh Bala) and 2224 (Khoramabad) are prioritized in terms of planning and practical measurments at the level of the basin at managerial levels and sub- cachtments such as 2211 (Karkheh Payab) and 2227 (Ab Aleshtar) are less priority than other sub- cachtments in the Karkheh watershed.