基于约束非线性最小化法的时段单位线优化估计

Optimal Estimation of T-hour Unit Hydrograph Based on Constraint Nonlinear Minimization Method

时段单位线被广泛应用于模拟流域中的地面径流过程。用传统方法(如最小二乘法)推求时段单位线,容易产生锯齿状振荡,并且所得单位线径流深不等于10 mm。为克服此现象,应用数学规划中的约束非线性最小化法来优化单位线的推求过程。为比较该方法的应用效果,最小二乘法也被应用于本研究中。采用两个案例进行分析,结果显示采用约束非线性最小化法能够有效抑制时段单位线锯齿状现象的产生,单位线总量亦等于单位净雨量10 mm,用两种方法得到的地面径流计算值与观测值之间的吻合度是近似的。

The T-hour Unit Hydrograph is widely used in simulating the surface runoff processes. Traditional methods of deducing the T-hour unit hydrograph, such as the least-square method, are prone to create zigzagged oscillations of the resulting hydrographs, and the surface runoff depth is hardly equal to the net rainfall. To tackle this problem, the nonlinear constraint minimization method is used here to optimize the T-hour unit hydrographs. To compare the effectiveness of this method, the least-square method is also used in this study. The hydrological data used are from two research areas. Results show that the nonlinear constraint minimization method can effectively restrain the occurrence of zigzagged oscillation in the resulting T-hour unit hydrographs. The runoff depth is precisely equal to the net rainfall and the observed and calculated surface runoffs deduced from the two hydrographs are similar.