Characteristics and Influencing Factors of Spatial-temporal Variation of Land Water Reserves in Songhua River Basin.

The Songhua River Basin is an important grain production base and ecological region in China, and studying its water supply and water quantity changes is of great significance for achieving scientific water allocation and ecological environment protection in the basin. This study employed the CSR RL06 Mascon data products derived from the GRACE and GRACE-FO gravity satellites from 2003 to 2020. For the missing data between GRACE and GRACE-FO, published reconstructed data were used to fill the gaps. The accuracy of the data in the study area was validated through comparison with GLDAS simulated water storage data. Based on this, the spatial and temporal variation characteristics of terrestrial water storage in the basin were analyzed using a combination of Theil-Sen and Mann-Kendall trend tests. Additionally, the Pearson correlation coefficient and geographical detector methods were utilized to delve into the influence of various factors, including precipitation (Pre), evapotranspiration (ET), population density (POP), normalized difference vegetation index (NDVI), ecological zones (Ez), and digital elevation model (DEM), on terrestrial water storage. Furthermore, aiming to address the issue of errors introduced by resampling when performing correlation analysis on remote sensing data of different resolutions, the traditional raster data resampling method was optimized. The research findings indicate the following: 1 The GRACE data products exhibit good accuracy in the study area, and the linear trend range of their changes exhibits a high correlation with GLDAS data. 2 The optimized resampling method is more suitable for spatial studies similar to Pearson correlation analysis, and it significantly improves the accuracy of most data compared to directly using raw data. 3 The water storage in the Songhua River Basin has shown an increasing trend during the study period, with a noticeable increase in the extreme value ratio. By the end of the study period, the spatial distribution of water storage in the region tended to stabilize, exhibiting a basic pattern of more water in the northeast and less in the southwest. 4 The primary individual factors causing changes in water storage in the basin are precipitation and evapotranspiration, and the combined effects of most factors manifest as nonlinear enhancement. [ABSTRACT FROM AUTHOR]