Optimization Analysis On Rainwater Utilization Technology In Tianjin Urban District

With the development of urbanization, the problem of water shortage is becoming serious. At the same time, city's underlying surface changes a lot. It results in the increase of the total runoff and peak flow. And then, the burden of urban sewerage system is becoming heavy. Therefore, technology of rainwater collection and utilization should be optimized, in order to utilize rainwater fully and prevent flooding.On the basis of Tianjin's rainfall data, the characteristics of monthly rainfall and annually rainfall are analyzed, and the property of storm is summarized. Then, the feasibility of rainwater utilization is studied.By the investigation of storm models, SWMM(Storm Water Management Model) is applied. The model of storm water on an area in Tianjin is established, and it is used to model rainfall runoff process.Model simulates the generation and transport of runoff flow in the undeveloped and developed states. The results show that flow rate and the total runoff volume in developed states is more than them in undeveloped state, because the impervious area increases and the feature of the underlying surface changes.Base on Tianjin's rainfall data and relevant documents,recurrence period used to design the rainwater utilization scale is 2 years. Then, at the condition of the total runoff volume in developed state less than it in undeveloped state, calculate the volume of storage tank. And then, the rainfall runoff processes in different rainfall levels is analyzed. The result shows storage tank can dramatically decrease the flood peak flow and the runoff volume. In addition, quantity of collecting rainwater by storage tank is calculated.By simulating the effect of grass swale on rainfall runoff process, the depth of the grass swale is calculated. The result shows that grass swale can increase the rainwater utilization rate, and have a more dramatic effect on reducing the flood peak compared with the storage tank.