Impact of revegetation and agricultural intensification on water storage variation in the Yellow River Basin

The Yellow River Basin (YRB) is experiencing a critical water resource shortage due to climate change and human activities. Thoroughly understanding water resource dynamics under the dual pressures of revegetation and agricultural intensification presents significant challenges. Development of satellite-based observations for vegetation and water storage has greatly facilitated large-scale and high-resolution watershed analysis, and enables understanding their dynamics. In this study, the effects of revegetation and agricultural intensification were assessed by incorporating multiple vegetation indices and phenological methods. Regression models were developed to determine how much water variation could be attributed to vegetation change driven by these human activities, using an expanded set of vegetation features to analyze seasonal water storage variation. The results indicate that both revegetation and agricultural intensification played important roles in the decline of water storage in the YRB and showed significant heterogeneity across the basin. In semi-humid and semi-arid regions, revegetation can explain over 60% of groundwater reduction throughout the year, while in arid areas, the primary impact was particularly revealed in summer soil moisture, with the explanation rate reaching 70%. Water storage in the downstream croplands decreased at a rate of 18 mm·yr-1 due to a combination of intensified irrigation and reduced precipitation. In the upstream croplands, crop structure changes and irrigation reduction led to a reduction in spring and winter water storage at a rate of 2 mm·yr-1. Consequently, the security of water, food, and ecosystems is challenged. This study benefits sustainable management of the YRB by providing comprehensive vegetation features and their impact on water storage.