The Calculation Of Water Storage Variation In Northwest China Based On GRACE Satellite Data

The GRACE gravity satellite is the second phase of the new generation of international satellite gravity program.The satellite was launched in March 2003,by recovering the earth's time varying gravity field to estimate terrestrial water storage variations.Since the launch of GRACE gravity satellite,it has gained wide attention from domestic and foreign researchers and has made great progress.At present,the research shows that the accuracy of the equivalent water column height of 1.5cm can be recognized.Northwest China belongs to arid and semi-arid region,where water resource is scarce and the ecological environment is fragile,to study the distribution characteristics of water resources in northwest China is of great significance to economic development and ecological environment protection in northwest China.Because northwest China is vast,and the groundwater level monitoring is limited,the application of GRACE gravity satellite in this area can make up for the lack of spatial and temporal resolution of conventional observation methods,and provide a new method for studying the distribution of terrestrial water storage in northwest China.This paper elaborated on the principle of GRACE gravity satellite and its inversion of terrestrial water storage,and uses GRACE gravity satellite data to invert the changes of terrestrial water storage in northwest China.Combining GLDAS global land data assimilation system data,to remove the changes of soil moisture and snow water equivalent,groundwater storage variations can be computed,which is compared with the measured groundwater level in the study area shows a good agreement.And we collect the information of groundwater extraction and annual precipitation of each province in the study area,which are used to analyze correlation with the groundwater storage variations.The inversion results of terrestrial water storage indicated that averaged TWS in the whole NW China declined with time at a rate of 0.014 cm/month that is equivalent to a reduction of 5.35 billion m~3 per year.Spatially,TWS increased at 2.24 million km~2and decreased at 1.06 million km~2.TWS and precipitation have a similar seasonal variations,indicating precipitation is the most important water sources in NW China.The analysis of the changes of inversion terrestrial water storage indicated that the changes of groundwater storage inverted by GRACE and GLDAS had a consistent trend with groundwater level of monitoring wells,which showed that GRACE gravity satellite has inverted the accurate terrestrial water storage.The groundwater storage variations of northwest region was demonstrated negative correlation with groundwater extraction,and no obvious correlation with precipitation,which showed that increase of groundwater extraction intensifies the consumption of groundwater storage.