Water security assessment for effective water resource management based on multi-temporal blue and green water footprints

Climate change and land use change have significantly altered the water cycle, thus affecting watershed water security. Quantitative assessment of water security using the water footprint concept can improve water resource management at the watershed scale. Therefore, this study aims to investigate the impacts of climate change and land use change on water security based on the water footprint concept, with the goal of enhancing water resource management at the watershed level. In this study, we employed the Soil and Water Assessment Tool (SWAT) to quantify the spatial and temporal distribution of blue and green water resources in the Weihe River Basin (WRB), China. Multiple water security evaluation indicators, including scarcity and vulnerability, were integrated to quantify water security. Significantly, statistical analysis methods were employed to identify key factors influencing the changes in blue and green water. The results indicate that the interannual and monthly coefficient of variation for blue water is higher than that for green water, with the order being blue water > green water storage > green water flow. Hotspots of the blue water crisis are concentrated from February to July, with agricultural water use exhibiting the highest crisis (BWvulnerability = 0.814), while hotspots of the green water crisis are concentrated from April to October. Blue water is primarily influenced by climate change, particularly precipitation, while the changes in green water flow and green water storage are influenced by the interactive effects of climate change and land use change. Specifically, in the upstream, blue water is mainly influenced by precipitation (r = 0.703), while green water is influenced by precipitation, temperature, and pasture. In the midstream, blue water is mainly influenced by precipitation, temperature, and agriculture, while green water is additionally influenced by forest and pasture. In the downstream, the key influencing factors for blue and green water are similar to those in the midstream, with the difference that blue water is negatively correlated with the population (r = -0.421). Developing water-saving agriculture can effectively improve water security in the midstream and downstream. This study has identified key factors for optimizing the allocation of water resources upstream, midstream, and downstream, providing valuable insights for future research on water security at the basin scale.