Abstract: In this paper, the spatiotemporal change of groundwater level in the Ejin Basin is analyzed based on the long-term monitoring data of groundwater level during the period from 1988 to 2006 and the groundwater level survey data in recent years using the geostatistical analysis method, the geostatistical characteristics and heterogeneity of groundwater depth are discussed, and the geostatistical model is used to fit the heterogeneity of groundwater depth. The results show that a continuous decline of groundwater level in the Ejin Basin had occurred since the 1940s, and it was more serious in the downstream area than that in the upstream area; the phreatic water level has started to rise again along with the increase of river discharge in recent years, but the deep confined water level is continually dropped, and the annual fluctuation range of phreatic water is higher than that of confined water. Spatially, groundwater depth increases at first and then decreases from the south to the north and decreases gradually from the west to the east. The groundwater level elevation decreases gradually from the south to the north, and it is U-shaped from the west to the east, that is the groundwater level elevation decreases at first and then increases. There is holistically a moderate spatial correlation of groundwater depth in spatial distribution, but there is a strong spatial correlation at four different directions in the Ejin Basin. The variable range of groundwater depth is 0.406° (longitude and latitude unit, about 33.7 km), that means there is a spatial autocorrelation in such variable range of groundwater depth.

Key words: groundwater level, spatiotemporal change, geostatistical model, heterogeneity, confined water, phreatic water, Ejin Basin