岩溶流域土地利用变化对地下水水质的影响——以云南小江流域为例

Effects of land use change on groundwater quality in karst watershed-A case study in Xiaojiang watershed of Yunnan province

利用1982、2003年土地利用现状图、地下水水质资料和监测数据,在GIS支持下,研究云南小江岩溶流域20年来的土地利用变化及其水文环境效应。结果表明:20年来,流域610.12km2的土地利用面积发生变化;土地利用变化的主要过程是由未利用地向耕地和林地以及林地向耕地的转化;土地利用的空间格局发生很大变化,空间格局指数有不同程度的增加或减少;地下水水质的变化与土地利用变化表现出动态一致性,林地和未利用地转变为耕地后,地下水的总硬度、总碱度、pH值、SO42-、NO3-、Ca2+等离子值明显升高,并形成明显的高值区;1982年流域地下水以I、II、III级水质为主,而2003年流域却以IV、V级水质为主,地下水水质呈明显恶化趋势;流域地下水水质的变化与流域森林质量下降以及耕地扩张带来的化肥污染息息相关。

The environmental effects of land use/cover change will become the focus in the future. Based on 2 times spatial data of land use and water quality datasets of Xiaojiang watershed in 1982 and 2003,land use change map and land use matrix were made,and also a series maps on pH and hydro chemical features of common ions of groundwater and groundwater quality change map were achieved,supported by GIS and comprehensive evaluation of groundwater quality.It indica tes: (1)The transformed area was 610.12km2 or 59% of the total during the past 20 years in Xi aojiang watershed.The unused land transformed into cultivated land and forestland,and forestland transformed into cultivated were most important change,of which the transformed area was 475.29km2 or 77.9% of the total;the spatial pattern of land use in Xiaojiang watershed has changed greatly.With the increase of human disturbances,the diversity index,the homogeneity index and the broken index all increase,especially,the broken index increased by 84.6%. (2)As forestland transformed into cultivated and unused land transformed into cultivated,the total hardness,total alkalinity,pH,SO42-,NO3- and Ca2+ of groundwater increased obviously,and formed the high value zone.The I,II and III grades of groundwater quality area were 943km2 or 91.2% of the total area in 1982,but there were only 434.2km2 or 42% of the total area which were I,II and III grades of groundwater quality area in 2003.Obviously,the groundwater quality became worsened during the past 20 years in Xiaojiang watershed. (3)Changes of groundwater quality are related to the pollution of fertilizer resulting from increase of cultivated land and the degeneration of eco environment due to the worsening of forestland quality.There was a dynamic relationship between the groundwater quality change and the land use change. Therefore,based on the watershed served as research unit,the research of land use change and its effects of hydrogeologic environment are very important for the protection of the resources and environment of the karst region.