| Groundwater resource is the most critical environmental factor for human life in the extremely arid and semi-arid areas in Western China,which plays a very important role in maintaining human survival,activities and development in arid areas.In recent years,with the rapid population growth,rapid economic development,inappropriate land use,instability of surface water resource supply and demand,the pressure that the groundwater resources in oases can carry is growing and the contradiction between the land and water resources will be increasingly prominent,which is the result of inappropriate development and utilization of land resources by human beings for a long time while neglecting harmonious development between the oasis land resources and groundwater resources.Especially with the rapid socio-economic development in arid areas,there is a sharp increase in demand for land-use and the land use changes in a dramatic growing trend,resulting in a sharp fall of the groundwater table.This study tries to explore the reason why the groundwater depth goes down from the perspective of land use,qualitatively and quantitatively analyze interactions between land use change and groundwater table,with a view to facilitating rational land resource development and utilization of groundwater resources.Taking Gaochang District,Turpan City,Xinjiang as an example with the remote sensing interpretation results of 2006,2010 and 2015 in the study area and the groundwater table data collected in this study stage as the basic data,this paper first analyzes change ranges,dynamic degrees and migration characteristics of different land-use types of oasis in Gaochang District during the period from 2006 to 2015,and then fits the temporal-spatial variability of different groundwater tables of 2006,2010 and 2015 in Gaochang District with the semi-variant function model and Kriging interpolation,for overlay analysis and correlation analysis of the relationship between land use types and the groundwater depth.The main work and conclusions of the paper include:(1)Land use is classified into six types including farmland,woodland,grassland,water body,construction land and unused land according to the actual conditions in the study area.With the support of the software RS and GIS,by classifying 2006,2010 and 2015 remote sensing images of the oasis in Gaochang District via supervised classification,the paper gets the land use/land cover data of the oasis phase 3 in Gaochang District and have its accuracy tested.(2)During the period from 2006 to 2015,there have been great changes in land use types in Gaochang District and these six land use type have enjoyed obvious changes in the spatial and temporal scales,featured by expanding trend of the oasis in Gaochang District with an area increased by 246.53km~2.The results of land use dynamic degree analysis showed that,unused land and water were in negative dynamic changes in 2006-2015 but with difference in rate of dynamic change,where the unused land was slowly decreasing throughout the study period while the water bodies was particularly slowly decreasing;the farmland was slowly increasing;both woodland and construction land were very slowly increasing.According to the transfer matrix analysis,the area of the unused and water bodies transferred to other land use types was 246.53km~2 in total,and at the same time,the degraded area of other types of land use was only 45.00km~2,it can be seen that the amount of transferred out land is equivalent to 5.5 times that of the transferred in land.(3)From the dynamic change characteristics,dynamic change characteristics of the groundwater table during the year carried mining dynamic characteristics,the lowest water table appeared in July and August while the highest water table appeared in the next January to March.And the inter-annual dynamic change characteristics took on a continuous declining trend,at an average rate of 0.38m/a.Statistics showed that the spatial distribution of indexes predicted by spherical models in 2006 and 2015 carried medium strong spatial correlation and spatial difference,from which we can see,drivers leading to changes in water table include effects of human activity in addition to natural factors.(4)From the relationship between land use changes and water table,the area of four types of land use including grassland,farmland,construction land and woodland area in Gaochang District was expanding while the area of water bodies was shrinking.The unused land continuously transferredinto other land use types is the main land use type that leads to a continued decline of groundwater table in Gaochang District. |
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