城市扩张下的北京平原区降雨入渗补给量变化

结合WetSpass模型与地理信息系统(geographic information system，GIS)、遥感(remote sense，RS)技术分析了城市扩张引起的土地利用类型变化对北京平原区降水入渗补给量的影响.在估算出1982年和2007年降水入渗补给量的基础上，将2007年土地利用类型还原成1982年的情景重新估算，利用转移矩阵分析两年土地利用类型的相互转化关系，同时，基于GIS空间数据统计功能，计算出不同土地利用类型下的地下水补给量.结果表明，1982年至2007年，研究区内水浇地减少874 km2，其中517 km2转变为城镇建设用地.相对于1982年，2007年城镇建设用地扩张了831 km2，区内降水入渗补给量减少约3 000万m3.研究成果可以为北京平原区的地下水资源保护及土地资源配置提供较为科学的参考. 

Precipitation Infiltration Change in Beijing Plain in the Context of Urbanization

The WetSpass model is used to analyze the impact of urbanization on precipitation infiltration recharge in Beijing Plain combined with the technology of GIS (geographic information system) and RS (remote sense) in this paper. Based on the simulated precipitation infiltration in 1982 and 2007, the influence of land use changing on the precipitation infiltration is quantitatively analyzed by assuming the land-use type in 2007 was the same as that in 1982, and re-running WetSpass model with other input data in 2007. The transfer matrix is used to analyze the mutual transformation relationship of land-use types in the above-mentioned two years, and the statistical function of GIS is used to calculate the groundwater recharge under different land-use types. Results show that the area of irrigable land decreased by 874 km2 from 1982 to 2007, among which 517 km2 turned to the central urban land. The central urban area increased by about 831 km2. The increasing urban area and the decreasing crop area eventually lead to the reduction of the average groundwater recharge. The groundwater recharge decreased by about 3×107 m3 in 2007 compared with the value under the simulated condition. The precipitation infiltration changed obviously in the region around Chaoyang and Fengtai districts characterized by significant urban expansion. This study can be a scientific reference for the groundwater resources protection and city layout of Beijing Plain.