Impact of Land Use Change on Groundwater Quality in Oasis

A case study on the impact of land use/cover change on shallow groundwater quality in the oasis over the Sangong River Basin, Xinjiang, China, is carried out by applying RS, GIS and geostatistical analysis. The data used in this study include the TM images in 1987, ETM images in 2004 and test data of groundwater quality sampled from 77 wells in 2004. Results indicate that the hydrochemical characteristics in alluvial-diluvial fans in the upper reaches of the river are predominantly represented by NO₃ ^--SO₄ ^2--Ca-Mg, with showing the mineralization of groundwater generally lower than 800 mg/L. The nitrate content in groundwater is high, its average value is 27.37 mg/L, and groundwater is polluted by nitrate in some areas. The areas with high nitrate content in groundwater, like farmland, land for construction, industry and mining, have been undergoing a long period of land resource exploitation and utilization. The hydrochemical type is SO₄ ^2--CL^--HCO₃ ^--Ca-Na-K-Mg over the alluvial plain in the lower reaches of the river, with showing the mineralization of groundwater usually higher than 1000 mg/L. Groundwater salinity is high in some areas, and it is mainly composed of nitrate and chloride.