| چکیده انگلیسی مقاله |
Soil and water resources are the most important components of nature that play a critical role in achieving sustainable development goals. Accelerated erosion is one of the most important factors destroying soil resources and polluting water resources in the world. Erosion reduces soil fertility by removing fertile and nutrient-rich topsoil and, on the other hand, causes environmental problems by transporting eroded material to water sources. Therefore, controlling erosion so that both soil and water resources are preserved is one of the main goals of soil conservation programs. A fundamental question in this case is to what extent soil erosion needs to be controlled to ensure the sustainable preservation of these two important sources? In other words, how much erosion is allowable without damaging soil productivity and environment quality? To answer this question, a concept called tolerable erosion has been proposed, which is a basic indicator for knowledge and judgment about the status of soil erosion and the extent of potential economic, social and environmental hazards. Despite the importance of tolerable erosion, it has not received much attention in soil conservation programs, probably due to the lack of a comprehensive, standard and practical methodology for determining and using it. Because several definitions and methods have been provided for tolerable erosion. Initial definitions of the tolerable erosion concept were mainly based on soil productivity and soil formation, and environmental issues were added to it with rising environmental concerns in recent decades. According to the latest definition, tolerable erosion is equal to the maximum amount of erosion that, in addition to maintaining soil productivity in the long run, also ensures the health of the environment. However, so far no methodology has been proposed that can take into account all three criteria of soil formation, soil productivity and environmental health in determining tolerable erosion. In this paper, based on the new definition and considering both on-site and off-site effects of erosion, a comprehensive framework is proposed for protection of soil and water resources. The results of a case study in Gorganrood basin showed that the amount of subbasins-based soil loss was between 0.2 to 17 ton. ha-1 yr-1 and the amount of sediment yield was between 0 to 11 ton. ha-1 yr-1. Tolerable soil loss was between 5 to 10.5 ton. ha-1 yr-1 and tolerable sediments were determined between 2.2 to 2.8 ton. ha-1 yr-1. Using the proposed framework, about 30% of the total area of the basin was under threat of erosion and needs protection measures. Of this area, about 9% only needed measures to reduce soil loss, 13% only needed measures to reduce the sediment delivery ratio, and 8% needed measures to reduce both erosion and sediment delivery ratio. |
