Groundwater Storage Variation In Anhui Province Using GRACE Time-varying Gravity Field Combined With Multi-source Data

In recent years,due to the rapid economic development and the continuous increase of human production and life,groundwater resources have been overexploited for a long time,and groundwater quality has been deteriorating continuously,leading to frequent environmental geological problems such as land subsidence and karst collapse,which has brought great threats to the social economy and people's life.The effective monitoring of groundwater reserves is an important basis for regional water resources management,but the limitation of traditional monitoring methods makes it difficult to realize it.This paper presents a method to estimate the variation of groundwater reserves in Anhui Province based on the water balance equation using GRACE(Gravity Recovery and Climate Experiment)gravity satellite data combined with GLDAS(Global Land Data Assimilation Systems)data in the same period.At the same time,combined with the regional precipitation and surface temperature data,the time series analysis and spatial variation analysis of the above inversion results were carried out,respectively,in order to obtain the spatial and temporal distribution characteristics of groundwater reserve change in Anhui Province.Finally,the feasibility and effectiveness of the inversion method of groundwater reserve change in Anhui Province are verified by the measured groundwater data in this paper.The following are the main research contents of this paper:1.The principle and data processing method of inversion of surface quality anomaly by GRACE time-varying gravity field are summarized,and the filtering principles and effects of different filters such as Gaussian filter,Swenson filter,Duan filter and PNMM filter are emphatic analyzed and compared.At the same time,the advantages and disadvantages of scale factor method and spatial domain method in signal leakage error correction are compared.2.A piecewise average method is proposed to determine the time series of land water storage change in Anhui Province from 2002 to 2017.According to the difference volatility of the inversion results of different GRACE data products,the segmentation interval was determined,and the average value of the time series with less difference in the inversion results within the corresponding interval was taken as the final result.The results show that the land water storage in Anhui Province shows a decreasing trend,the decreasing speed is 1.1mm/a,and there are obvious periodic fluctuations.3.Use GLDAS hydrological model data to obtain the change of surface water reserves in Anhui Province,and obtain the change of groundwater reserves in Anhui Province based on the simplified regional water balance equation.The results show that the overall groundwater reserves in Anhui Province show a decreasing trend with a decreasing rate of 5.6mm/a,which is mainly affected by precipitation,and is very similar to the spatial distribution of land water reserves in the region.4.By comparing and analyzing the interannual variation of groundwater reserves and the measured results of groundwater resources in Anhui Province,the correlation coefficient is 62.5%,which proves that the method of inversion of regional inland groundwater reserves based on GRACE gravity satellite data and GLDAS hydrological model data in this paper is feasible and effective.