| Watershed management has been considered to be the best way for the realization of resource utilization and environmental protection. Developed in the early 1970s, extensive research has been carried out in the field of watershed management and non-point source pollution control. More complete management system and the technical norms have now established in developed countries. Best Management Practices (BMPs), which based on the Total Daily Maximum Load Plan (TMDL), is the most representative. Recently, a new type of BMPs technology LID (Low Impact Development) is also in development.In China, point source pollution has been under control in watershed management; therefore, the problems of non-point source pollution control are highlight important. Contrast to point source pollution, non- point source pollution is characterized by strong randomness, the distribution of a wide range, multiple impact factors, the complex formation mechanism, strong hysteretic nature. So, it is difficult to monitor, control, treat and manage the non-point source pollution. At present, the research on non-point source pollution control is just getting start in China, deep theoretical research and engineering control manual have not formed yet.Xikeng Reservoir is an important reservoir for drinking water source storage at Shenzhen, the water quality not only relates the health of local residents, but also affects the sustainable economic development of Shenzhen city. In this study, in view of the reservoir water quality issues, a pilot project is implemented for non-point source pollution control. Specific watershed management requirements and the local conditions of Xikeng Reservoir catchment, such as landscape and climate, were considered. Two locations were chosen for BMPs design, implementation, monitoring, and evaluation. One is BMPs train system (including wetland, pond, and swale) at the reservoir, and the other is LID (including planter box and biobox) at reservoir administration building area. Project budgetary and cost-efficiency were estimated too.Eight representative rain storms were selected for on-site monitoring in this study. Pollutant removal efficiency was evaluated by the event mean concentration method (EMC); statistical methods (Box-and-Whisker Plot, normal distribution) were used for data analysis. Biobox model was designed preliminarily too. Data show that: (1)Under normal conditions (storm precipitation is 20mm～40mm), the removal efficiency of BMPs train on TSS could reach 70%～90%; BOD5 removal efficiency was 20% to 50%, and nutrients removal efficiency was between 30% and 70 %;(2) The pollutants removal efficiencies of planter box and biobox were relatively high. TSS removal efficiency was 70%～90%, BOD5 removal efficiency was 60% to 70% and the removal efficiency of nutrients was 40%～70%;(3) Heavy rain conditions, BMPs on pollutant removal efficiency decrease. Aiming at the situation of Xikeng Reservoir, a series best management practicesand proposal have been put forward, including structural management practices and non-structural management practices. Non-structural BMPs include land-use planning and management, pollution management and agriculture, forestry, land management measures; Structural BMPs are mainly targeted at concentrated residential areas, distributed residence, bare land at the reservoir area , orchards and agricultural land, small industrial sites. Bio-retention pond, detention pond, wetland system, vetiver grass strip systems and erosion control blankets and other control measures are suggested. This study provides experience for non-point source pollution control and the application of BMPs in China. |
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