Research of Spatial-Temporal Variation and Correlation of Water Storage and Vegetation Coverage in the Loess Plateau

As a region with functions such as energy production and as an ecological barrier, the Loess Plateau plays a vital role in China. This study examines the spatiotemporal changes in water storage and vegetation cover and their correlations. The changes in water storage were calculated using GRACE data and the GLDAS-NOAH model, while vegetation changes were derived from MODIS data. The results showed that the groundwater inventory decreased by 7.80 mm/a and the land inventory decreased by 9.72 mm/a. Surface water storage capacity increased by 1.92 mm/a. From west to east, terrestrial and groundwater storage decrease, reflecting overall losses, but surface water storage remains positive. By analyzing the FVC, it can be observed that since 2006, vegetation coverage has shown an overall increasing trend, with the highest value occurring in 2018. There has been a remarkably increase in vegetation coverage in most areas, while there was a decrease in vegetation coverage along the borders of Qinghai Province and northern Shaanxi Province. By conducting a correlation analysis, it can be found that the correlation coefficients between terrestrial water storage, surface water storage, and groundwater storage changes and vegetation coverage are −0.85, 0.60, and −0.93, respectively, indicating that increased vegetation coverage leads to reduced groundwater and terrestrial water storage. The results also indicate that there are significant spatial differences in the monthly correlations and maximum lag months between water storage and vegetation coverage. In addition, through discussing the driving factors of water storage changes in the Loess Plateau, we consider that the Grain for Green Project and mining activities may be the two major drivers of these changes. This study is highly important and valuable to the study of changes in water reserves in the Loess Plateau, as well as ecological protection and environmental assessment in the Loess Plateau.