Patterns of blue and green water in the Yellow River Basin from 1998 to 2020: Influence of climate change and human activity

The Yellow River Basin in China. The hydrological cycle in the Yellow River Basin is undergoing significant changes due to the combined effects of climate change and human activities. Based the simulations of a processed model and observational data collected from official bulletins, this study focused on investigating the spatiotemporal variations of blue and green water in Yellow River basin from 1998 to 2020. Furthermore, the Partial Least Squares Structural Equation Modeling (PLS-SEM) method is used to quantify the respective contributions of climate change and human activities to these observed patterns. During the study period, both blue water volume and green water flow increased overall across the Basin where blue water volume and green water flow were higher in the west than in the east. Water withdrawal (including water consumption and water return flow) showed an increasing trend that mainly concentrated in the Toudaoguai (TDG) area, mainly due to increases in domestic and ecological water consumption, since water return flow showed a decreasing trend (due to decreases in agricultural and industrial water return flow). Climate change affected blue water volume and green water flows mainly through changes of precipitation (the path coefficient β > 0.59). Changes in land cover were able to explain 87 % of the observed variation in water return flow and 95 % of the observed variation in water consumption and subsequently affected green water directly through water consumption (β = 0.515). Changes in land cover indirectly explained 20.9 % and 27.3 % of the variations in blue water volume and green water flow, respectively. Climate change showed greater influences on blue water volume and green water than human activities. These findings highlight the need for efficient water management in the Yellow River Basin. • Patterns of blue water(BW) and green water(GW) were investigated in the Yellow River Basin. • BW increased mainly due to increasing precipitation. • GW flow increased mainly due to increasing transpiration. • Land use cover changes have effects on human water consumption and subsequently on BW and GW flow.