Spatial-Temporal Evolution Of Oasis In Hetian-ruoqiang Area And Analysis Of Shallow Groundwater Distribution

The scale of oasis in arid area directly influences the stability of oasis and the development of regional economy.In recent years,human activity has become a more important factor which affects the evolution of oasis.Study on direction and regulation of oasis variation has great significance in promoting the sustainable development of oasis and controlling land desertificaiton.Based on series of image of Landsat satellites and LUCC(Land-Use and Land-Cover Change)data,the spatial evolution of oasis in land use and total area were analyzed by means of transfer matrix of land use and deterioration and expansion model in this paper.In addition,characteristic of land desertification evolution was revealed by extracting vegetation fraction coverage.Several relevant factors were selected based on multi-source data to construct the water distribution probability model which was used to analyze the possibility of shallow groundwater distribution.The results indicated that:(1)Arable land,forest grassland,construction land and salinization area showed an increasing trend,however,the area of gobi and sandy land were declined.(2)Transfer matrix of each partition reflects the transformation between each oasis and other types of land.On the whole,from 1985 to 2005,no change area of oasis was 5548.06 Km2,the expansion area of oasis was 2564 Km2 and the deterioration area was up to 659 Km2.However,the corresponding data between 2005 and 2015 are 6143.53 Km2,2049.24 Km2 and 1741.6 Km2,respectively.(3)From 1985 to 2005,the expansion of the oasis was mainly distributed in the local areas between the MinFeng county and the Aoyiyayilake town,as well as the Qarqan River.However,degradation areas mainly occurred in areas where the depth of groundwater was shallow in the west and northeast of Ruoqiang county.From 2005 to 2015,the expansion area was mainly distributed in the west of Qiemo county,but the degradation was distributed throughout the region,which mainly converted into construction land.(4)Heavy desertification area showed a decreasing trend,moderate desertification area reduced firstly and then increased,while mild desertification and non-desertification areas were on the rise.(5)The arable land had highest mean daily evapotranspiration(ET),the ET of Hetian Oasis could reach 2000 mm,besides,arable lands in Yutian,Minfeng,Qiemo,Ruoqiang and other area had higher ET(1000-2000mm),the ET of the river is also higher,in contrast,sandy land and gobi had the least amount of ET(almost 0mm).(6)There were high possibilities of water near the cultivated land and river,while water-poor areas were mostly distributed in piedmont areas,the specific areas are near the piedmont from Cele county to Yutian county and the west of Qiemo county as well as the piedmont from the east of Qiemo county to Thirty-sixth farm.