Controlling depth of groundwater tables along mainstream and in downstream tributary-intensive areas of Ejina River

In order to probe the ecological groundwater table along the mainstream and in the downstream tributary-intensive areas of Ejina River, GPS, RS and GIS technology were applied to analyze the interactions between ground water table and different plant communities based on the data of observed long-term groundwater tables. The single point method was used in analysis of east-west river mainstream areas and west river downstream. The method of overlay between the groundwater table and the plant communities was used for analyzing east river downstream tributary-intensive areas. The results showed that the ecological ground water table was changed in different areas. It was estimated as 2.14 to 2.27 m in the east-west mainstream areas with a variable range of 0.61 to 1.14 m, 2.52 to 3.88 m in the west river downstream areas with a variable range of 0.90 to 1.09 m, and 2.48 to 3.39 m in the northern Andou Grassland areas with a variable range of 0.26 to 0.33 m. The different ground water depth associated with different plant communities in the tributary-intensive areas of the downstream of east river. Populus euphratica community appeared in the areas where the groundwater table was less than 3.0 m with a variable range of 0.51 to 1.41 m. Tamarix ramossima community appeared in the areas where the groundwater table was 3.0 to 6.0 m with a variable range of 0.85 to 1.94 m, and weed habitat appeared in the areas where the groundwater table was 3.0 m with a variable range of 1.41 to 2.46 m. The results are helpful for the allocation of surface water in Ejina eco-irrigation district.