Spatio-temporal patterns of green and blue water scarcities in agriculture

Agricultural areas are increasingly experiencing green water stress – i.e. soil moisture limiting crop growth – due to rising water demands of an expanding world population as well as climate change. While irrigation has the potential to mitigate this stress, its effective implementation is often challenged by blue water scarcity and lack of irrigation infrastructure. In this study, we apply a newly developed plant physiological index of green water stress, modeled by the global dynamic vegetation model LPJmL, that accounts for both soil moisture limitation and atmospheric water demand of major agricultural crops. By analyzing the spatial-temporal patterns of green water stress globally and over the past decades, we identify current hotspots of green water stress which are mainly located in India and Pakistan, Southern Europe, northern Sub Saharan Africa, southern Africa and Mexico and are characterized by a high seasonal variability. We also map blue water stress relating to human water use (withdrawals for households, industry and agriculture) and demonstrate the extent to which sufficient blue water resources are available to buffer green water stress in agriculture. By focusing on the interconnectedness between green and blue water stresses through the implementation of irrigation, this study contributes to a more profound understanding of sustainable water use in agriculture.