An Analysis on the Inter-annual Spatial and Temporal Variation of the Water Table Depth and Salinity in Hetao Irrigation District, Inner Mongolia, China

Long-term Yellow River irrigation and the unique natural conditions in the Heitao Irrigation District (HID) Inner Mongolia, China, has led to serious environmental problems such as the shallower groundwater table and soil secondary salinization, etc. The conflicts among socio-economic development, water shortage and environmental degradation have become increasingly critical. By using the statistical methods, geo-statistical methods and ArcGIS9.0, we analyze the temporal and spatial variation of depth to water table (DWT) and groundwater salinity in the three different irrigation seasons in 2001, 2002 and 2003 respectively. The results show that DWT and groundwater salinity has formed a ribbon distribution after the long-term Yellow River irrigation. DWT is medium spatial correlative and the average spatial autocorrelation distance is 18.5km; the groundwater salinity is strong spatial correlative and the average spatial autocorrelation distance is 12.5km. The inter-annual distribution of DWT and groundwater salinity in 2001 is quite similar with it in 2002 and 2003. The DWT in western area, eastern area and a small part of middle area are shallower than other area in HID. The average DWT in March reached maximum and its minimum is in November each year. There are two high salinity degree zones ( M>5000mg/l and even some other M>30000mg/l). The shallower groundwater salinity in the southeast and northwest are higher than that of in the middle part of HID. The shallower water table depth is, the higher the salinity of groundwater will be; the deeper water table depth is, the lower the salinity of groundwater will be.