Study On The Effect Of Runoff Storage And Pollution Reduction Of Urban Green Space

Problems of water source, flood disaster, and water pollution are the three hydrological responses in urbanization process, also are the main issues in water environment management. Great attention has been paid to efficient runoff management, which is helpful for solving the above water problems. Traditional municipal water and wastewater system has been built to solve the retaining water and water pollution in small-scale areas, however, some faults and drawbacks also have appeared in such systems. This study focuses on the methods for rainwater utilization and treatment which will bring environmental, ecological and economical effect. Therefore, it is of great necessity to study the effect of runoff storage and pollution reduction of urban green spaceThe paper is based on the project Study on the Effect of Runoff Storage and Pollution Reduction of Urban Green Space which sponsored by Science and Technology Commission of Shanghai Municipality (No.04DZ 12024). The data in this paper are based on three ways, including collecting historical literature, selecting the data from related government offices, and field monitoring, etc, both qualitative and quantitative methods are used to analyze the effect of green space for city runoff storage. Empirical work is done to prove the pollution reduction effect of green space, in the same time, some detailed measures and management strategies are approached on how to improve the effect of urban green space for runoff storage and pollution reduction.A review of runoff management and green space building history is made for indicating the importance of urban green space construction for runoff management. The permeability and water holding capacity of green space and its influencing factors have been also analyzed in this paper. The results, in the case study, show that the soil constant infiltration rate of is between 1.53×10^-6m/s and 4.90×10^-5m/s, which is affected by the factors of vegetation arrangement and human-disturbance. The soil water content of green space is much higher than that of uncovered soil, and the main influencing factors are vegetation arrangement and elevation arrangement.The effect of runoff storage effect of green space is proved from three perspectives including regulation of land use, combination of water and green space, and structure of green spaces, .The results reveals that: (1) Based on the analysis of land use regulation effect, the ratio of green space in a given area will result in a change of the area runoff coefficient. When the ratio of green space area in the area is in a difference of 10 per cent, the formation time of runoff peak in the bigger green space will occur 20 minutes later than the smaller one. (2) Taking Changfeng park as a case, it is proved that the water-green system hold a higher storage capacity than pure green spaces. (3) The hollow grassland is different from other ordinary green space in elevation structure. The soil constant infiltration rate, the ratio of green space area and the concave-down depth of hollow grassland are the main influencing factors for the storage effect of green space.The pollution reduction simulation experiments in this paper show that, the pollutants such as COD, NH₄-N, TN and TP can be clearly reduced by green space. Pollution reduction effect of green space is better than that of uncovered soil. The reduction effect for COD and NH₄-N of green space is obvious while the effect for TN and TP is relatively less.The application of management strategy such as building of socialized water management system, designing of water-green ecological system, and comprehensive using of several storage methods, will help to establish ecological drainage systems and improve urban water environment.