典型流域土地利用/覆被变化及对水质的影响--以太湖上游浙江西苕溪流域为例

利用1985、1995和20D0年的TM数据及水质资料，运用GIS和水质指数法研究西苔溪流域的土地利用／覆被变化及其水环境效应。结果表明：流域内耕地不断减少，建设用地持续扩大，林地前期减少后期缓慢增加；林地和耕地是流域内的主要土地利用类型，二者面积之和占流域面积的比例在三个时段均在92％以上；空间集中性及斑块碎化是土地利用空间格局变化的主要表现，建设用地斑块数量增多且斑块面积明显增大，饼地面积减少但斑块数量增多。研究时段内流域水质在时间上呈逐步恶化趋势，在空间上则表现为自上游至下游逐渐下降，其中，1996-2000年，研究河段内水质指数下降幅度达30％左右；只治理点污染源仅使水质指数增加6．5％左右，表明影响水质的主要因素是土地利用变化导致的面源污染。

LAND USE/COVER CHANGE OF CATCHMENT AND ITS WATER QUALITY EFFECTS--A CASE OF XITIAOXI CATCHMENT IN ZHEJIANG PROVINCE

The environment effects of land use/cover change will become the focus in the future.Based on remote sensing images and water quality dataset of Xitiaoxi Catchment in1985,1995and2000,land use/cover change map and land use matrix were made.This paper analyzes the temporal-spatial regulation of land use/cover change over the last15years followed by the analysis of the correspondence relationship between the land use/cover change and water quality change.The area of arable land decreased continuously while the constructive area expanded all the time.The woodland area increased slowly after a period of going down.The variation trends of landscape structure are patch-fragmented and types of landscape simplified.The land use/cover change of Xitiaoxi Catchment has caused distinct water environmental effects by Nonpoint pollution source while the point source only increase6.5%of water quality.The water quality gradually deteriorated along the river from upper reaches to lower reaches mainly due to the land use change.So,in the future,the highest priority measure to improve water quality of Xitiaoxi Catchment should be controlling Nonpoint pollution resources.