Vegetation greening promotes the conversion of blue water to green water by enhancing transpiration

Abstract

Despite extensive research examining vegetation effect on hydrological processes, there remains a need for more comprehensive and systematic assessments within the innovative concepts and frameworks of blue-green water resources. Over the past three decades, China has experienced an extensive vegetation greening trend, raisng great concern about understanding the response of blue water (BW) and green water (GW) resources to vegetation change. To explore this, we employed a process-based distributed hydrological model coupled with a remotely-sensed evapotranspiration module. By conducting hydrological simulations with different vegetation change scenarios for 1982–2012, we observed that the increase in LAI led to a rise in GW by about 1.5 mm year^-1 decade^-1 (0.3 % decade^-1, p < 0.01), close to the decrease in BW [-1.4 mm year^-1 decade^-1 (−0.4 % decade^-1, p < 0.01)]. The enhancement of transpiration was the primary driver of GW increase, while concurrent reductions in soil evaporation partially counteracted these effects, resulting in small overall changes in GW. Strong positive spatial correlations (r = 0.59 ∼ 0.93, p < 0.01) between trend of vegetation-induced changes in the green water coefficient (GWC) and trend in LAI across China suggest that vegetation greening promotes the transition from BW to GW. These findings provide insights into blue-green water resources assessment under vegetation change, and emphasize the need for integrated blue-green water management strategies for sustainable development of both human societies and ecosystems.