Spatial And Temporal Variations Of Groundwater In Northwest China Were Monitored Using GRACE And GLDAS Data

Northwest China is short of water resources and has a fragile ecological environment.As an important part of water resources,groundwater is the main source of water for domestic,industrial and agricultural irrigation in northwest China.Real-time dynamic monitoring of groundwater change in northwest China is of great significance to local economic development and ecological protection.Based on the 2002-2016,GRACE RIL06 data inversion of land reserves change water in northwest China,and combined with the global land data assimilation system GLDAS data,in removing soil moisture changes in terrestrial water reserves,snow water equivalent change,canopy water changes obtained on the basis of the research area of groundwater reserves,and compared with the measured data of ground water level,wa,ter land reserves in the study area,the spatial and temporal evolution regularities of the variation of the groundwater and characteristics;Combined with TRMM rainfall data,NDVI data,evapotranspiration data,soil moisture content,surface runoff,drought and other natural factors and human factors such as population data,GDP,urbanization level,etc.,the driving force of groundwater change in northwest China was discussed and analyzed.The results showed that:(1)from 2002 to 2016,the land water reserve in northwest China showed a declining trend as a whole,with a change rate of-0.0088cm/a and a cumulative decrease of 0.3800cm water column height.In space,the land water reserve of central Xinjiang decreased significantly,with a decrease speed of 0.4180cm/a.The land water reserve of central Xinjiang,the junction of western Gansu and Xinjiang,eastern Gansu,central Ningxia and northern Shaanxi showed a decreasing trend,and the maximum decrease was 1.68cm/a.The land water reserve in Qinghai showed a significant increasing trend,with an increase rate of 0.3094cm/a.The land water reserve in western and southern Gansu,southern Shaanxi,northern Xinjiang and the boundary of Southern Xinjiang and Tibet and Qinghai showed an increasing trend,with the maximum increase of 0.77cm/a.(2)The groundwater reserves as a whole show a declining trend,with a rate of decline of 0.0097cm/a and a cumulative decrease of water column height of 3.16cm.In space,the groundwater reserves in western and central Xinjiang are significantly reduced,with a reduction rate of 0.5498cm/a.The groundwater in northwestern and southern Gansu,Ningxia and central and northern Shaanxi also shows a decreasing trend.Groundwater reserves in most areas of Qinghai increased significantly,with an increase speed of 0.3391cm/a.Moreover,groundwater reserves in the junction of Xinjiang,Tibet and Qinghai,northern Xinjiang,and the junction of southern Shaanxi and Sichuan,Henan and other regions also showed an increasing trend.Based on the data from 8 observed groundwater level monitoring points,the measured data of groundwater level are significantly correlated with most of the inversion results,which indicates that the inversion results have certain reliability.(3)nine kinds of factors such as rainfall,vegetation change correlation size of Soil moisture content(Soil)>surface runoff(Qs)>rainfall(TRMM)>population(TPOP)>evapotranspiration(EVAP)>NDVI>GDP>urbanization level(DMSP)>drought degree(TVDI),it is concluded that the main factor affecting the groundwater reserves decline of Soil moisture,surface runoff,precipitation and other natural factors,only surface runoff from 2002 to 2016 showed a trend of decrease,the other factors are increased,geographical probe further proved that the conclusion;Comprehensive factor of east-central and southwest of the northern xinjiang,qinghai,gansu,shaanxi central and southern regions such as the groundwater reserves have obvious role in promoting,northern and central to xinjiang,Tibet and qinghai province at the junction,west of Inner Mongolia and shaanxi and ningxia border region groundwater reserves have obvious effect of consumption.