一种时变分布式单位线计算方法

A method of deriving time- variant distributed unit hydrograph

为了解决由降雨强度引起的径流汇流的非线性问题,提出一种基于SCS(United States Department of Agriculture-Soil Conservation Service)流速公式的时变分布式单位线计算方法。引入参考雨强表征SCS公式中流速系数对应的水力条件。由降雨过程的时段雨强与参考雨强的比值构成一个量纲一因子,将该因子加入SCS公式后使其能够考虑降雨对流速的影响。改进后的流速公式用于计算一次降雨过程中不同降雨时段对应的时变分布式单位线,时变分布式单位线与新安江模型的产流模块构成降雨径流模型,将模型用于裴河流域率定参考雨强。率定后的模型用于谭家河流域进行应用检验,结果显示,确定性系数大于等于0.9的洪水场次,由时不变单位线的42%增大为83%。提出的方法能够显著提高流域水文模型的降雨径流模拟能力。

In order to solve the nonlinear problem of runoff concentration caused by excess rainfall intensity,a method deriving time-variant distributed unit hydrograph(TVDUH)based on the SCS′s velocity equation was presented in this paper.A reference rainfall intensity is introduced to represent the hydraulic conditions corresponding to k values.A dimensionless factor formed by the ratio of duration excess rainfall intensity to reference rainfall intensity is added in SCS′s equation to make up a new velocity equation that can take into account of the influence of excess rainfall intensity on flow velocity.The modified SCS′s equation is used to derive the TVDUH of each rainfall duration during a rainfall event.A rainfall-runoff hydrological model is constructed of TVDUH and the runoff generation module of Xin′anjiang model.The rainfall-runoff hydrological model is used in Peihe River basin to calibrate the reference rainfall intensity.Application is performed in Tanjiahe River basin for validation.Results show that the number of events whose coefficient of efficiency being greater than or equal to 0.9 increases from 42%of time-invariant unit hydrograph to 83%.It is concluded that the presented method can contribute to increase the rainfall-runoff simulation capabilities of watershed hydrologic models observably.