Analysis On Rainwater Utilization And Engineering Decisions In Tianjin Urban District

With the accelerating pace of urban development, the proble m of water shortagein cities is becoming increasingly serious. As a kind of water resources, rainwater hasadvantages such as low cost, easy to direct use. Therefore, rainwater utilization hasattracted more and more attention. Utilization of urban rainwa ter can not only amplifythe urban water resources, but also prevent city floods and recharge groundwaterresources. Raising the rate of rainwater utilization is also an important measure inconstructing water-saving cities.This article mainly researches the rainwater utilization in Tianjin. On the basis ofreviewing large quantity of domestic and international literature and collecting therainfall data of Tianjin, the characteristics of rainfall in Tianjin was summarized, andthe ways and means of urban rainwater utilization was elucidated.By simulates different design frequencies runoff flow in the undeveloped anddeveloped states with SWMM. Proved that stormwater runoff volume and peak flowsignificantly increased in the developed states, and later runoff is obvious. Simulatingthe grass swale on rainfall runoff process with SWMM, showed that the grass swalecan effectively alleviate the general intensity of rainfall runoff. However, due to thevolume limit of the grass swale,in the area of huge rainfall intensity should to buildrainwater utilization facilities with the grass swale to achieve better results.A specific rainwater collection scheme was formulate. The quality of rainwaterfrom different collection points was analysis. Based on the rainfall monitoring ofdifferent monitoring points in2010and2011, it is found that most of rainfall isthunderstorm in Tianjin, the early rainfall intensity is greater and rainfall duration isshorter. The following conclusions can be drawn from the monitoring of rainfallquality:â‘ The rainwater quality from shingle roof is more variations than that fromwatt qualitative Roof;â‘¡The most polluted rainwater runoff of roof generally occurin the first few rainfalls and the period of high temperature in summer;â‘¢For thepavement rainwater, the initial rainfall runoff pollution is the most serious. Thepollutant concentration also decreases in the late of rainfall.Through the study of engineering examples, the analysis of various conditions ofthe urban rainwater utilization engineering was summarized. The calculation methodof proposed water balance was clarified. The calculated of investment in fixed assets and annual operating costs was formulated, so the investment of Rainwater utilizationscheme can be estimated.