基于水量平衡原理的畦灌下渗水形状系数变化规律研究

Study on variation of subsurface shape factor of border irrigation based on water balance principle

以往水量平衡模型应用中,通常认为在同一次灌水过程中的下渗水形状系数为恒定值,使模型精度受到一定影响。基于此,本试验以水量平衡原理为基础,结合量纲分析,研究了畦灌过程中的下渗水形状系数变化规律并提出了估算其值的经验计算式。结果表明,同一次畦灌过程中下渗水形状系数并非恒定值,而是随灌水时间和水流推进距离等因素变化的。结合已有文献资料验证,结果表明采用水量平衡模型模拟畦灌水流运动过程,同时考虑动态的地表储水形状系数和下渗水形状系数取值,可有效提高模型的计算精度。同时也表明采用本文所建经验计算式估算畦灌下渗水形状系数值是可靠的。

In the traditional water movement models of border irrigation based on the principle of water volume bal-ance ,it was usually supposed that the subsurface shape factor was a constant value in the same border irrigation ,which affected the precision of models .Based on the principle of water volume balance and combined with dimensional analy-sis ,the variation of subsurface shape factor was studied and an empirical formula that could be used to compute the value of subsurface shape factor was proposed .The results showed that the subsurface shape factor was not a constant value in the same border irrigation ,but it was variable along with the change of irrigation time ,water advance distance and other factors .The validity of the proposed method was verified by some existing literatures .The results showed that the preci-sion of water volume balance model could be improved in simulating water movement process of border irrigation when the variation of surface shape factor and subsurface shape factor was considered .The results also showed that the proposed empirical formula was reliable in computing the subsurface shape factor of border irrigation .