河北雨洪模型中下渗公式的一种改进方法

下渗强度的计算是干旱半干旱地区超渗产流计算的关键环节。河北雨洪模型中的流域下渗强度计算公式由两部分组成,一部分为由张力引起的下渗强度,另一部分为由重力引起的下渗强度(稳定下渗能力)。计算以上两部分下渗强度时,公式所用的雨量有重复,致使总下渗强度普遍偏大,从而导致模型模拟的洪水过程的洪量及洪峰偏小。提出一个改进的流域下渗强度计算公式,计算张力引起的下渗时所用雨强为总雨强与稳定下渗能力的差值。利用改进前后的计算公式,分别对2mm/h到10mm/h雨强及0mm到140mm表层土湿条件下的下渗强度进行计算,并对结果进行对比分析。大阁流域的实例应用结果表明,改进后的下渗强度计算公式,对模拟洪水过程的洪量和洪峰流量的增加效果明显,增加值分别为实测值的14.14%和10.08%。

A Method for Modifying Infiltration Equation Used in Hebei Model

The computation of infiltration rate is a key step for estimating the infiltration excess runoff in dry and semi-dry regions. The infiltration equation used in Hebei model is made of two parts, the one is the infiltration rate governed by tension and the other is that governed by gravity (the constant infiltration capacity). Because of the repetition of rainfall rate used to compute the two infiltration rates, the total infiltration rate is always greater than it should be and as a consequence, the runoff amount and the peak discharge of the hydrograph simulated by the hydrological model is decreased. A modified infiltration equation is presented, in which the rainfall rate used to compute the infiltration rate governed by tension is the difference between the total rainfall rate and the constant infiltration capacity. Computation for the modified infiltration equation and the original?one under conditions for rainfall rates ranging from 2 mm/h to 10 mm/h and initial water content ranging from 0 mm to 140 mm are carried out, and the results from the two infiltration equation are compared. It can be seen from the results of the Dage watershed by the modified infiltration equation that the runoff amount and the peak discharge of the hydrograph simulated are increased 14.14% and 10.08% respectively.