极值降水对雄安新区年径流总量控制率的影响研究

Effects of Extreme Rainfall on Volume Capture Ratios of Annual Rainfall of Xiongan New Area

径流总量控制是低影响开发雨水系统构建的重要控制目标之一。为研究极值降水对年径流总量控制率的影响,首先对雄安新区雄县、容城、安新三个站点年径流总量控制率对应的设计降雨量进行推求,分析设计降雨量与控制率的关系并对雄安新区雨水径流源头控制效果分区进行验证,再利用广义帕累托分布和轮廓似然法估计3个站点不同重现期的降水值以分析极值降水与年径流总量控制率的关系。结果表明:设计降雨量随着控制率增大而增大且设计降雨量增大速度高于控制率的速度,雄安新区雨水径流源头控制效果处于中量低率区;一年里超过设计降雨量的日数在0~10d范围内且2d概率最大;对应一定设计降雨量值每年的控制率会随降水丰枯、极值降水的日数量级的变化而变化;极值降水发生极有可能造成年控制率低于设计值,控制率还受超设计降雨量降水的日数、年降水总量的影响;极值降水虽然发生的日数少但是对排放量的贡献率大,并且随着极值降水重现期增加对控制效果的削弱影响增大;极值降水的日内降水分布不均匀,有可能造成低影响开发(LID)措施达不到设计目标。

In order to study the effects of extreme rainfall on volume capture ratios of annual rainfall,this paper computed the design rainfall corresponding to volume capture ratios of annual rainfall of Xiongxian,Rongcheng and Anxin stations in Xiongan New Area,analysed the relationship between the design rainfall and capture ratios and verified the rainfall runoff source control effect subarea of Xiongan New Area.GPD distribution and contour likelihood estimation were used to estimate the rainfall values of three stations at different return periods and the relationship between extreme rainfall and total annual runoff control rate was analysed.The results show that the design rainfall increases with the volume capture ratios of annual rainfall increases and the design rainfall increases faster than the capture ratios and the rainfall runoff source control effect in Xiongan New Area is in the area of medium quantity and low rate.The amount of daily rainfall which excesses design rainfall in one year within 0-10 and highest probability is 2 days.Corresponding to a certain design rainfall value,volume capture ratios of each year due to the abundance and lack of rainfall and the scale of extreme rainfall events.Extreme rainfall is likely to cause volume capture ratios of that year is lower than the design value and is also influenced by the number of daily rainfall excesses design rainfall and total annual rainfall.Although the amount of extreme rainfall is less,the contribution on emission is large,and with the increase of extreme rainfall return period,weakening influence on the control effect increases.The distribution of intraday precipitation of extreme rainfall is not uniform which may cause LID measures to fail to meet the design goal.