Variation And Influencing Factors Of Groundwater Storage In The Yellow River Basin Based On GRACE Products

Groundwater is an important part of the earth’s water resources,and is the main source of water for industry,agriculture and residential life.Due to climate change and human overexploitation,groundwater reserves in the Yellow River Basin have been greatly reduced.The number of groundwater monitoring Wells in the Yellow River Basin is limited and unevenly distributed,and the regional representation is insufficient,which makes the evolution law of groundwater reserves in the Yellow River Basin lack a comprehensive understanding.GRACE（gravity recovery and climate experiment）gravity satellites have the advantage of continuously monitoring terrestrial water reserves in a large range,and can effectively invert the changes of groundwater reserves,so as to provide a scientific basis for the rational development and utilization of groundwater resources.Based on GRACE satellite data products and GLDAS hydrologic simulation data,this paper verified the applicability of three GRACE data products in the inversion of groundwater reserve changes in the Yellow River Basin by comparing the measured groundwater level data,analyzed the spatial-temporal characteristics of groundwater storage changes in the Yellow River Basin,and discussed the influencing factors of groundwater storage changes.The results show that:（1）GRACE satellite product data is feasible for retrieving groundwater storages in the Yellow River Basin.Among CSR,GSFC and JPL GRACE products,CSR Mascon data has the best applicability in the Yellow River Basin.（2）The groundwater storages in the Yellow River Basin showed a very significant downward trend from 2003 to 2021,with an average decrease of-0.62 cm a^-1;The overall performance of the changes within the year is a downward trend in groundwater storages from September to June of the following year,and an upward trend from June to September of the following year.From 2003 to 2021,the downward trend of groundwater storages in the upper reaches of the Yellow River was relatively slow,and the changes in groundwater storages in the middle and lower reaches showed a continuous downward trend.The average decrease in groundwater storages in the middle reaches was-0.77 cm a^-1,while the average decrease in groundwater storages in the lower reaches was-1.12 cm a^-1.The decrease in groundwater storages in the lower reaches was 31.25%greater than that in the middle reaches.The spatial distribution is characterized by higher changes in groundwater storages in the upstream region and lower changes in groundwater storages in the middle and downstream regions;The proportion of significantly reduced regional area in terms of spatial change is 96.4%,and the proportion of significantly reduced regional area is 76.1%.（3）There is a significant negative correlation between vegetation restoration and changes in groundwater storages,concentrated in the middle reaches of the Yellow River Basin.Vegetation restoration has increased rainfall infiltration,significantly reduced river runoff,and reduced groundwater recharge.At the same time,vegetation restoration consumes a large amount of rainfall infiltration through evapotranspiration,and in addition,the impact of groundwater consumption shows a downward trend in groundwater storages.The results of random forest show that vegetation restoration is the main factor affecting the decline of groundwater storages in the Yellow River basin,with a contribution rate of 65.03%.The net recharge of groundwater P-ET and vegetation restoration are important influencing factors for the GWSA of groundwater storage changes in the western section of the Yellow River Basin,with contribution rates of over 40%;Vegetation restoration is the main influencing factor for changes in groundwater storages in the central section of the Yellow River Basin,with an average contribution rate of 56.37%;The contribution rate of groundwater consumption to GWSA in the eastern section of the Yellow River Basin is the highest（78.26%）,significantly higher than the net groundwater supply P-ET and vegetation restoration.