基于Ross模型的降雨灌溉入渗补给地下水规律分析

An Analysis of Groundwater Recharge from Precipitation and Irrigation Based on Ross Numerical Models

采用基于Ross方法的数值模型,模拟了华北平原中部典型区降雨灌溉对地下水入渗补给。分别计算了整个土层、根区土层、根区以下土层土壤在强、弱渗透性情况下的入渗通量与地下水潜在补给量,分析了土壤渗透性和地下水埋深对地下水潜在补给的影响。结果显示,大埋深条件下(地下水埋深为30m),在地表以下10m处水分通量过程基本不受上边界年内变化影响;在地表2m以下,年累积通量基本不变,可以将地表以下2m作为潜在补给量的计算深度。根区土层渗透性变化对水分通量与补给量有较大影响,根区以下土层影响较小。渗透性对入渗补给量的影响主要通过根区水量均衡和表层土壤性质控制。地下水埋深大于5m后,埋深的增加对潜在补给没有影响。Ross模型能很好地处理产生干湿交替含水量变化的大气边界,建议采用Ross模型代替传统迭代模型计算降雨灌溉条件下的地下水补给。

A numerical model based on Ross Method is adopted to simulate the groundwater recharge in the middle district of North China Plain. The infiltration of precipitation and irrigation makes up groundwater recharge. Several scenarios are given to illustrate the impact of different hydraulic conductivities and groundwater depths. The hydraulic conductivity variances are over the whole vadose zone, root zone and profile below the root zone. The results show that with deep groundwater level, the alternate drying-wetting process at the upper boundary has no impact on the water flux when the depth is over 10 m. The annual accumulation of water flux at the depth of 2 m remains unchanged, so 2 m can be used as the calculation depth of potential recharge. The hydraulic conductivity variances of root zones have a considerable impact on water flux and recharge, while the variances below the root zones have little influence. The root zone soil property and water balance play a significant role in the relationship between hydraulic conductivity variance and groundwater recharge. When the groundwater depth is more than 5 m, the increase in groundwater depth has no impact on potential recharge. The Ross Model has better performance in simulating the variably saturated flow with atmosphere boundary. It is recommanded that the groundwater recharge by Ross model rather than traditional iterative models should be adopted.