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Zusammenfassung:
Precipitation partitioning into blue (runoff) and green water (transpiration) flows is a fundamental hydroecological process shaping freshwater availability across vegetated and hydrologically active land areas. This partitioning is determined by interactions among climatic conditions, land surface characteristics, and vegetation dynamics, which change with rising temperatures and CO2 concentrations. Yet, future global shifts in blue–green water partitioning, their controlling factors, and their broader implications remain uncertain. We address this knowledge gap using Earth system model simulations and define the Blue–Green Water Share (BGWS) metric to quantify changes in the relative partitioning of precipitation into runoff and transpiration. Here, we show that projected BGWS changes are spatially heterogeneous rather than dominated by a uniform global shift. Increases in extreme five-day precipitation are most strongly associated with these changes, favouring larger blue water shares. This effect is independent of mean precipitation increases and occurs under both drying and wetting conditions. Additionally, increases in leaf area index tend to favour larger green water shares and counteract the blueward influence of stronger precipitation extremes. Our results provide a process-based perspective on projected blue–green water partitioning and its hydroecological implications.
