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

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.