西庄流域土地覆被变化及其水文响应模拟研究

Land Cover Change and Its Effect on Hydrological Process in Xizhuang Watershed

自20世纪80年代以来,随着滇西南农业综合开发造林项目建设、退耕还林、天保林工程的建设,滇西南的土地利用格局发生明显改变,尤其是山区流域林地覆被明显增加,耕地减少,分析这种变化趋势对水文水资源的影响很有必要。本文选取怒江水系中山小流域西庄流域为例,以遥感影像为主要信息源,利用GIS分析了1982、1991、1999和2004年的土地覆被变化,然后以分布式水文模型SWAT为研究工具,用1998～2002年流域实测降雨及径流资料对模型进行率定,然后固定气候因子(1998～2002年实测气候资料),模拟分析了不同土地覆被情况下的水文响应。研究结果表明,自1982年至2004年,森林覆被面积增加44%,草地面积减少28.6%,耕地面积减少16.1%;相应的流域地表径流减少21.3%,年径流减少2.0%,雨季径流量减少2.7%,枯季径流量减少0.2%,年蒸发增加4.8%,雨季蒸发量增加5.0%,枯季蒸发量增加3.9%。合理规划流域土地利用格局对于流域综合水资源管理具有重要意义。

Two programmes, the Natural Forest Protection Programme （NFPP） and Sloping Land Conversion Programme （SLCP）, were implemented following the floods in 1998 in China. Land use and land cover （LULC） of southwest of Yunnan Province has been changing. The forest cover rate has increased apparently special for mountain watershed. It is necessary to analyze the interaction between the land cover change and hydrology. Xizhuang Watershed was selected as a study case. Firstly, four times＇ land use and land cover map （1982, 1991, 1999 and 2004） were interpreted based on the satellite data by using RS＆GIS. Secondly, SWAT model was calibrated and validated by using the measured data （1998-2002）. Then hydrological process was simulated under different land use and land cover scenarios. The results show that during the period of 1982 to 2004, forest cover rate increased by 44%, grassland cover rate decreased by 28.6%, and agriculture cover rate decreased byl6.1%; Consequently, annual surface flow decreased by 21.3%, annual total water yield decreased by 2.0%, wet seasonal total water yield decreased by 2.7%, dry seasonal total water yield decreased by 0.2%, annual actual evapotranspiration increased by 4.8%, wet seasonal actual evapotranspiration increased by 5.0%, and dry seasonal actual evapotranspiration increased by 3.9%.