Spatial variation of ground water in middle stream of the Heihe River basin during past two decades

Middle stream of the Heihe River basin(HR-MR),located in northwestern China,was selected as the study area.On the basis of long-term observated groundwater level data in 1985 and 2005,Geographic Information System(GIS) and geostatistical method were applied to synthetically analyze the spatial distribution of groundwater table during the past 20 years.The results showed that changes of groundwater level occurred in the study area during the past 20 years.The auto-correlation between groundwater tables become weaker.Groundwater connectivity become stronger and the vulnerability of groundwater increased.Groundwater level in the middle and upper reaches of the alluvial fan decreased obviously(5~15m),while that in lower reach of the alluvial fan and the river valley plain exhibited an increasing trend.Therefore,more rational water resources management in the study area is required for maintaining sustainable development,especially for more reasonable measures to mitigate geological disasters in arid inland river basin.