Beijing Non-point Source Pollution Of Small Watershed BMPs Risk Assessment And Selection

Beijing’s main drinking source, Beijing Miyun Reservoir’s eutrophication Index has reached moderate eutrophication level. The proportion of non-point source pollution has been larger than other pollutant, then became the major source of pollution which threats to surface water quality. Therefore, targeted governances should being implemented to the critical source areas (CSAs), which have high-risk of non-point pollution producing ability.In this study, three small watersheds have been chosen as study area, two in the upstream of Miyun reservoir and one in the upstream of Huairou reservoir. The non-point source pollution risk evaluation system has been construed by three factors named Land-use factor, Runoff factor and Distance factor, which referred from Phosphorus Index (PI) and Pollution Potential Index’s (PPI). Take study areas as example to evaluate the risk of non-point source pollution risk, and then make risk partition to determine the CSAs. As the meantime, a Best Management Practices (BMPs) archive has been established by collected domestic management practices. The BMPs selecting program has been written based on MFC platform of Visual C++6.0. Then take CSAs of Shicheng watershed as example to make BMPs selection.The main conclusions are as follows:(1) The database establishment of the three watersheds, including land use patterns, soil type, slope, and river networks and others. The identification of non-point pollution risk evaluation basis has been created;(2) The evaluation system has been constructed by Land-use factor, Runoff factor and Distance factor, which belongs to the "black box" model, data acquisition and processing procedure are uncomplicated. The calculation method of weight of the factors using Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) to reduce human interference. The objection of the evaluation system has been enhanced;(3) Non-point source pollution potential risk evaluation of the study area proved that the potential of non-point source pollution are closely related with land-use patterns affected by human activities; (4) A BMPs archive has been established on the basis of data collection, which mainly including engineering management practices and their attributes such as name, classification, the reduction ratio of TN, TP, suspends particle and runoff. Then programmed the BMPs selecting program based on MFC platform of Visual C++6.0.Using conservation choice method and fast choice method to select BMPs for E zone of Shicheng watershed, which has been taken as an example, and simulated the effect of selected BMP. The result shows that selected BMP reduce the risk of non-point source pollution potential indeed.