流域土地利用变化对径流的影响

Effect of Land Use Change on Runoff in the Liushahe Watershed,Xishuangbanna Southwest China

美国农业部开发的SCS水文模型可以定量反映土地利用／土地覆被变化对径流的影响，是应用较广的模型之一。在GIS支持下，以1965年西双版纳地形图及1988、2003年两期Landsat TM／ETM卫星影像获取的土地利用数据及实地土壤调查资料确定模型参数（CN值），通过分析CN值的变化来反映土地利用变化对径流的影响。研究结果表明，从1965～2003年，土地利用变化使流域径流系数增大，其中旱地、水田、有林地和草地的变化对流域径流的影响较大；人类活动逐渐向水文土壤条件较差的区域扩张，这种土地利用变化趋势使流域CN值增大，下垫面产流能力增强；人类活动干扰程度大的土地利用类型面积增加，这些土地利用方式对流域径流的影响越来越大。流域水田和水域面积减少，对流域径流的调节能力下降，势必影响到流域的水文循环。

The Soil Conservation Service （SCS） Curve Number （CN） rainfall runoff technique is widely used to estimate runoff. Based on GIS and RS, land use data for 1965, 1988, 2003, which were got by digitizing relief map and classifying two landsat TM/ETM images, and soil data by digitizing soil map were used to estimate SCS hydrological model parameter （Curve Number, CN）. And the relationship between CN and land use were analyzed to reflect the effect of land use change on runoff by analyzing variation of the parameter of SCS hydrological model in the Liushahe watershed. The results show that land use change, especially cropland, forest land and grassland, leads to the increase of runoff from 1965 to 2003. And human activity expands to the field that can produce more runoff. The decreasing of paddy field and water area can reduce the ability of adjusting watershed runoff, which will impact water cycle.