| The North China Plain (NCP) is the region that most seriously suffers the shortage of water resource during the economic booming of China. The groundwater level has decreased to below 20m in most places due to continuous over-pumping of groundwater. It's already become an inevitable choice for the sustainable agricultural development of this region to reasonably utilize the local water resource so as to alleviate the trend of groundwater level decreasing. So it will be very significant to study the transformation between rainfall, soil water and groundwater, it searches the process of rainfall infiltration under great buried condition and shows dynamic changing of groundwater water level, so as to provide theory support for reasonable utilization of groundwater resource of this region.Based on the practically available hydrogeologic data from Luancheng Agriculture Experimental Station of CAS, after parameter calibration and numeric model verification, numerical simulation of water movement in the soil of farmland is conducted using SWAP model as an analysis tool. The rule of soil water movement under the condition of rainfall and infiltration replenishment is analyzed primarily from the aspects of soil water content, soil water potential and soil water flux. The transform relation between rainfall, soil water and groundwater is discussed. The main results obtained are as follows:1,There is an obvious hysteresis in the increase of soil water content caused by infiltration under great burial depth of groundwater. If it is no extra influence from infiltration, evaporation, and the change of groundwater level, soil water content will increase with the increase of burial depth.2,Under burial depth, even with the storm rainfall in 1996 (921.8mm), the influence depth of infiltration was only about 11m. The infiltration depth by the end of 1997 was about 17m. Since groundwater level continuously changed, soil moisture in the layer that is 5m above the groundwater table would change rapidly. When rainfall infiltrated into this layer, it's hard to tell when it will arrive the groundwater and the amount of recharge. Under different levels of groundwater level changing, the range of the layer above the water table, which is influenced by the oscillation of water table, would change consequently. 3,According the dynamic change of soil moisture, the unsaturated zone from top to bottom could be divided into four zones: (a) the infiltration zone, or the zone with frequent interaction of evaporation; (b) unsteady infiltration zone; (c) relatively steady zone; (d) the zone influenced by groundwater level change. |
