Research On Vegetation Evolution Risk Assessment Based On Groundwater Development In Inner Mogaolian Energy Basement Of Ordos Basin

Inner Mongolia Energy base is located in the Ordos Basin,and with the characteristics of arid and semi-arid climates. Due to the shortage of surface water, groundwater resources plays an important role for planning and construction of the energy base. For the fragile of ecological environment, large-scale exploitation of groundwater will impact on the vegetation. Thus the government is very concern how to evaluate the risk of vegetation damage, and whether the damage is acceptable or not.Through interpretation of remote sensing NDVI vegetation index, and combined with a typical field vegetation sampling survey, the interannual temporal and spatial characteristics of vegetation is analyzed detailedly. Then the vegetation is classified into four kind of zonal wegetations (Meadow steppe, typical steppe, desertification steppe, steppe desert) and two kind of azonal vegetations (Saudi, wetlands). The distribution of vegetation is macroscopically controlled by precipitation. The micro-topography such as wetlands, depressions, ridge also play an important control role on the growth of vegetation. The analysis of water content in three kinds of major unsaturated zone (sand, aeolian sand-covered weathered bedrock, clay and silt) indicates that aeolian sand vadose zone structure is favour of water conservation,and is very important for vegetation growth in arid areas.The sandy vegetation in regional zonal vegetation has little to do with groundwater depth, however the wetland vegetation in azonal vegetation is much related to groundwater. The relations of the water table, soil salinity and groundwater salinity to vegetation are analyzed detailedly in two typical water resource areas, one is the Hatucaidang water sources area in Salawusu Formation, and another is the Haolebaoji water resource in the Cretaceous strata. Integrated the above study, the sensitivity analysis of vegetation based on groundwater is carried out, the study area is divided into sensitive areas and non-sensitive areas. The sensitive areas are further divided into primary, secondary and tertiary sensitive areas.A numerical model of groundwater in the study area is built using GMS software, the area is 62,000 km~2 descretized 322 rows and 249 columns, the grid size is 1000×1000m, and the number of active cells is 62848. Based on the exploitation of groundwater in 2006, the groundwater table is predicted after exploitation of 10, 20, 30 and 50 years, respectively. The contour map of groundwater depth in Jun of 2006 is interpolated into raster data by using ArcGIS and to discrete vegetation coverage with the same image element unit 236×236m grid. The quantitative correspondence between the groundwater table and vegetation coverage is established statistically. By coupled analysis of the predicted groundwater water table and vegetation coverage in different time, the change feature of vegetation coverage under groundwater development is assessed. The results show that under the groundwater pumping conditions, the sensitive area will reduce the 12500 km~2, the vegetation coverage in the southeast of the study area and the lake area will be significantly reduced.