The results from series analysis of changes in precipitation，surface runoff，groundwater regime and groundwater storage show that the Chaobaihe alluvial-diluvial fan region has undergone a marked change in groundwater. Among the reasons for water table decline and storage reduction，decrease of precipitation accounts for approximately 24％ while human activities are responsible for the other 76％. The impact of human activities on groundwater is remarkable based on groundwater monitoring. Changes in groundwater storage have been calculated based on the monitoring data of groundwater table and specific yield. The study gives a potential method based on water mass balance to differentiate the impact of climate change from human activities on groundwater system to promote the sustainable groundwater management and utilization.