Study On Regulation Of Water Movement In The Vadose Zone Based On Hydrus-1D In Zhongning Plain

The vadose zone is a necessary channel, which associates groundwater with atmosphere and surface water. It is not only a part of the water circulation system in the nature, but also an important link in the soil-plant-atmosphere energy transmission system. Study on migration of water in the aeration zone is of great significance to elucidate the formation of the saturated water and water cycle research.Zhong Ning Plain is a part of Wei Ning Plain, which belongs to the economic zone along the Yellow River, and it is an important grain producing area in Ningxia. Under the influence of irrigation, the groundwater and surface water exchange frequent. Water cycle through vertical exchange, and evaporation is the major route of excretion. So research of vertical groundwater recharge and discharge rules is of great significant for a correct evaluation and rational development of groundwater resources.Based on the understanding of domestic and abroad research methods and progress of moisture migration regularity in the vadose zone and the hydrogeological conditions of the study area, in this paper, the author built the water transport numerical model of the vadose zone using the Hydrus-1D software. This study makes use of soil negative pressure and meteorological observation data obtained from situ tests and the soil physical parameters obtained from laboratory test.The model is divided into four groups, which contains bare land and vegetation group and the simulation period can be divided into 2013 and 2014. The four indicators, the root mean square coefficient, relative error, Nash-Sutcliffe efficiency coefficient and the coefficient of determination, are used to evaluate the fitting effect of a single model and overall. It is thought that the fitting effect is good that simulated values and measured values along with the trend of time variation is close and the model can basically reflect the characteristics of water movement in the vadose zone and the physical properties in the soil.The relationship between surface evaporation and meteorological, vegetation, groundwater level and soil properties is analyses by using the model and it is thought that stronger atmospheric, more vegetation water requirements, higher groundwater level and better soil hydraulic properties makes surface evaporation more intense. The effect of rainfall and irrigation on recharge of groundwater is also discussed in the study and it is thought that small scale rainfall is almost without recharging the groundwater and continuous rainfall, adequate irrigation is the favorable conditions for groundwater recharge. When it is dry and the groundwater level is average, rainfall less than 50mm/day is ineffective for the recharge of groundwater.