Abstract: By the GIS technology,this paper studied the impact of groundwater resource temporal-spatial change in the lake area of Minqin Oasis on the ecological security of irrigation region landscape.The results showed that the depth of groundwater was descending continuously,the velocity of groundwater line change in the center of irrigation region was faster than that in the edge region,and consequently,the area of the descending funnel of groundwater line was enlarged.From 1987 to 2001,the area with a groundwater depth deeper than 3 m was increased from 81.2% to 97.4%.The descending of groundwater line due to soil water reducing was the main reason that resulted in the destruction and deadness of forests.When the depth of groundwater was deeper than 8m and soil water content was less than 12%,the die-back rate of tree was morn than 90%,and that of shrub was more than 50%.Impacted by the descend of groundwater depth,the area of forest land,shrub land and open-canopy land was decreased by 67%,54% and 31%,and the number of their patches was decreased by 35,42 and 50,respectively.The mineralization degree of groundwater in northern irrigation region increased obviously,and changed the safe pattern of crop growth.The benefit of agriculture decreased,and the adjustment of planting construction was restricted seriously,which became the main impact factor on the ecological security of irrigation region.Reasonably distributing water resource between upper and lower river basin,reducing unreasonable land use,decreasing farmland area,and constructing safety landscape pattern could lead to the balance between the exploitation and replenishment of groundwater resource,prevent the descend of groundwater depth and the increase of groundwater mineralization,and improve the ecological security of the irrigation region.

Key words: Ground water, Ecological security, Minqin oasis