缓坡畦灌地表储水形状系数对入渗参数估值的影响

Effect of Surface Shape Factor on Infiltration Parameters Estimation in Border Irrigation

Maheshwari法在估算入渗参数时取地表储水形状系数为定值,但已有研究表明该值并不恒定,针对这个矛盾,分析了地表储水形状系数随水流推进距离的变化规律,研究了畦灌地表储水形状系数对Maheshwari法入渗参数估值的影响.利用水位传感器观测地表水深沿畦长方向的分布,计算对应不同水流推进距离的地表储水形状系数;设定不同的地表储水形状系数,分析Maheshwari法入渗参数估值对地表储水形状系数的敏感性.结果表明,地表储水形状系数随水流推进距离增加而增加,但在推进距离大于50m时,增大趋势渐缓;其不同取值对入渗参数估值的影响显著,随着地表储水形状系数取值的逐渐增大,Kostiakov入渗模型的入渗系数逐渐减小,入渗指数逐渐增大.因此,地表储水形状系数取值对Maheshwari法入渗参数估值的影响不可忽略,对于缓坡畦灌,应用Maheshwari法估算入渗参数时,水流推进距离不应小于50m.

The effect of surface shape factor on infiltration parameters estimation in border irrigation is investigated using the Maheshwari approach. Water-level probes were systematically installed along an 80m border to measure the distribution and variation of surface-water depth. The variation of surface shape factor with water advance distance was analyzed, and then a sensitivity analysis was carried out to investigate the effect of surface shape factor on parameters estimation using the Maheshwari approach. The results indicate that the surface shape factor increases when water advance distance increases, and the increase trend becomes slower when the water advance distance is longer than 50m. The surface shape factor has significantly impacts on estimation of soil infiltration parameters： the Kostiakov infiltration coefficient decreases gradually while the Kostiakov infiltration index increases along with the increase of surface shape factor. Therefore the impact is not ignorable on infiltration parameters estimation by using different values of surface shape factor, the water advance distance should be longer than 50 m when estimation infiltration parameters using the Maheshwari approach in mild-slope border irrigation.