Ecological capability assessment of watershed hydrological units to prioritize watershed management executive operations using Fuzzy_TOPSIS approach (Case study: Mokhtaran Plain Basin, Birjand, Iran)

Watersheds are considered as the main unit of planning for sustainable development in many management issues. Evaluating the ecological capability of watersheds and their ranking according to different ecological criteria for prioritizing water management operations is one of the important issues in watershed planning and management. In this study, the Fuzzy-TOPSIS integration method, was chosen to be usen in the Mokhtaran watershed. In this work, 13 environmental criteria, including water resources quantity, flood intensity, soil conservation, surface water quality, groundwater quality, forage production, potential evapotranspiration, groundwater quantity, upstream resources, vegetation composition, water erosion, wind erosion, grazing capacity and groundwater quality of upstream resources were estimated and used. The study area was divided into three blocks of northern heighlands, southern highlands and plain. Each of them has its own criteria, according to the characteristics and potentials of each block. Then, the criteria of each block were weighted by AHP method and each of the 13 environmental criteria was fuzzified. After the fuzzification of the criteria and the weighting of the criteria of each block, the main problem of each sub-basin was determined according to previous studies in the watershed. Then, accordingly, the sub-basins were grouped in each block. Moreover, based on the Likert spectrum, the relative importance of options (sub-basins) was identified as triangular fuzzy numbers relative to each criterion. Finally, by entering all of the inputs in Fuzzy Topsis Solver 2013, the coefficient of proximity of each sub-basin was estimated and based on the nearest coefficient, the priority map of the watershed management plan for the watershed of Mokhtaran was extracted. According to this map, the sub-basins M8, M13, M15, M16, M21, M22, M25, M26, M28 (in the northern heights of the area), M2, M42, M43, M51 (within the southern heights of the area), M32 , M34, M46, M'13 and M'14 (within the plain of the basin) were considered to be in the highest priority and as critical hydrological units. The sub-basins M4, M5, M'4, M'5 (in northern highlands) and M1 (in the plain) were placed at the lowest priority over the study watershed.