Calculation And Spatial Analysis Of Precipitation Infiltration In Beijing Plain Based On WetSpass

Groundwater recharge estimation is an important part of the evaluation of groundwater resources, and accurate quantitative assessment of groundwater recharge is always a very important problem of hydrogeology. In arid and semi-arid areas, precipitation is the main way to recharge groundwater, especially in Beijing Plain, where nearly50%of groundwater recharge from precipitation, bad weather condition and accelerated urbanization decrease the precipitation infiltration in Beijing Plain. It's very essential to evaluate precipitation infiltration for reasonable exploitation and protection measures of groundwater in Beijing Plain.WetSpass model is a precipitation infiltration estimation model, based on water balance, detailed describe the groundwater reserve changes caused by precipitation, and it also consider the impact of various factors to precipitation infiltration, including climate conditions, soil texture, landuse types and other conditions, so that can estimate more accurately of the precipitation infiltration, interception, surface runoff and evapotranspiration under large-scale area. The paper using WetSpass model, with basic data of meteorological data, groundwater depth, soil texture and landuse types, estimated the precipitation infiltration of Beijing Plain, in2007. And combined with GIS spatial analysis function, describe the impact of various factors to precipitation infiltration. Details are as follows:(1) Estimate the precipitation infiltration in study area. The average amount of precipitation infiltration is65.43mm, which only12.23%of the annual precipitation of Beijing Plain in2007. Nearly82.99%of the precipitation returned to the atmosphere through evaporation and transpiration consumption, the rest is consumed by surface runoff and interception. The precipitation infiltration shows a tendency of northeast and southwest of the higher, northwest to southeast lower in spatial.(2) Verify the accuracy of the model. With groundwater monitoring data for2007Beijing Plain, the paper estimates the precipitation infiltration by using the water level fluctuation method. The results show that in regions with shallow groundwater depth, the result from WetSpass model is more accurate; WetSpass model estimation accuracy is lower, where groundwater depth larger, which are related to the operational mechanism. Overall, WetSpass model have better applicability in arid and semi-arid regions, especially to the region with shallow groundwater depth, the model has higher accurate. (3) Evaluate the impact of various factors to precipitation infiltration. Climatic conditions, soil texture and landuse types have an important influence on precipitation infiltration. The precipitation infiltration under the semi-humid climate condition is significantly better than the semi-arid climate; in2007, the descending order of average annual infiltration under different soil texture is:loamy sand?sand?sandy loam?loam?clay?sandy clay loam?silty clay loam? clay loam. The descending order of average annual infiltration under different kind of landuse types in study area is:excavation> beach/dune> shrub-grass mix> rural settlements> non-irrigation cropland> irrigation cropland> paddy field> urban area> shrub> deciduous broadleaf forest> deciduous coniferous forest> mixed forest> lake.