Effects of land use change on groundwater quality in karst watershed-A case study in Xiaojiang watershed of Yunnan province
2004, 19 (6):
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.
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