Research And Application Of Clean Small Watershed In The Agricultural Compound Pollution Area Of ??plain River Network

With the comprehensive control of industrial point source and urban non-point source pollution,rural and agricultural non-point source pollution become the primary limiting factor for improvement of the water environment quality of the Taihu Lake Basin.The construction of the ecologically-clean small watershed promoted by the Ministry of Water Resources achieves remarkable results in the protection of water quality of water sources,soil erosion control,non-point source pollution control in mountainous.However,rainfall runoff and production and domestic drainage are the main forms of non-point source pollution in plain river network areas,soil erosion is the main form of non-point source pollution in mountain areas.Therefore,we need to innovate in the theory and practice of clean small watersheds.This article integrated ecologically clean small watersheds and related theories to propose the connotation,governance model,and evaluation index system of clean small watershed in the compound pollution area of plain river network.Moreover,we chose the Xiaoqiaobang small watershed in the west of Taihu Lake for verification.There are main results:(1)The study put forward the connotation of clean small watersheds in agricultural compound pollution areas of plain river networks: taking small watersheds as a unit,based on the carrying capacity of water environment,applying the whole process control strategy of non-point source pollution to rural production,living and habitats,implementing unified comprehensive management of water,forests,fields,grass,ponds,villages,and establish a long-term management mechanism,finally to achieve the water quality of small watersheds meet the requirements of the water function area,the virtuous cycle of the ecosystem,and the economic and social sustainable development.We divided small watersheds into clean living areas,clean production areas and clean habitat areas.The clean small watershed construction measure system was equipped with the ideas " Sources reduction and Ruse-Resources utilizationEcological restoration-Management mechanism-Engineering protection ".(2)The evaluation index system of clean small watersheds in agricultural compound pollution areas was divided into target layer(A),criterion layer(B),element layer(C),and indicator layer(D)four levels.The evaluation index system had 9 elements and 25 indicators,which were attributed to 4 aspects for clean life,clean production,clean habitat and long-term management.We determined the basic steps of the hierarchical-fuzzy comprehensive evaluation method(AHP-FCE),and the indicators were divided into "very clean","clean"," general",and "unclean" four levels,and the clean classification standards were determined.(3)Example verification of Xiaoqiaobang small watershed.We used the analytic hierarchy to obtain the weights.The weight ranking of the four aspects is: clean production(0.362)> clean habitat(0.3263)> long-term management(0.1632)>clean life(0.1485),which indicated that clean production areas and clean habitats were the essential construction content of clean small watershed.The fuzzy comprehensive evaluation results show that the Xiaoqiaobang small watershed improved from the unclean state before construction to the clean state after construction,with the clean indexes of 0.413 and 0.790,respectively.After construction,the Xiaoqiaobang small watershed reached the clean level in four aspects.However,there was a slight unclean state in clean living and long-term management.In the future,the small watershed needs to strengthen village sewage treatment and its resource utilization,and increase the enthusiasm of the residents to participate in clean construction.According to the actual situation,the water environment quality of Xiaoqiaobang small watershed significantly improved,and the ecological circular agricultural chain formed,the administrative village where it is located rated as " National rural governance model village ".The effects achieved in the construction of clean small watersheds were consistent with the evaluation results,which indicated that this indicator system had a certain rationality and expandability.