| The study researches on rainwater infiltration, runoff and convergence in urban underlying surface. Through study on the rainfall in different recurrence interval which lasted 2 hours, the relevant parameters of rainwater utilization in new building subdistrict in Beijing were gotten.By studying on pluviometric runoff coefficient of different underlying surfaces in different recurrence interval, it is found that when rainfall lasted 2 hour and recurrence interval was 1 year,2 years,3 years,5 years,10 years, the coefficient would be 0.32, 0.45,0.50,0.55,0.61 in new residential area, and it would be 0.55,0.63,0.67,0.70,0.74 in new finance and office area.The net rainfall process line was obtained by runoff coefficient method and early-last loss method, and results were coinciding, thus pluviometric runoff coefficient was reasonable. Then discharge hydrograph was inquired by isochrones method and instantaneous unit hydrograph method, it is found that when the time parameters K of instantaneous unit hydrograph method was half of inlet time of isochrones method, the two lines were mostly coincident and peaks were basically same.According to the discharge hydrograph, the study got corresponding detention volume,combined with relations of rainwater control rate and control rainfall as well as rainwater efflux target runoff coefficient. According to the rainfall characteristics of Beijing, rainwater reuse volume should be calculated by 5 days. The rainwater utilization principle is that rainwater control rate should be 90% and rainwater efflux runoff coefficient should be less than 0.4. In new residential area, when rainwater utilization pattern is collection and reuse, detention volume of detention facility should be 120 m3 per hectare; when rainwater utilization pattern is detention and controlled discharge, detention volume of detention facility should be 30 m3 per hectare; and reuse volume should be 70 m3 per hectare. In new finance and office area, when rainwater utilization pattern is collection and reuse, detention volume of detention facility should be 190 m3 per hectare; when rainwater utilization pattern is detention and controlled discharge, detention volume of detention facility should be 75 m3 per hectare; and reuse volume should be 40 m3 per hectare. |
