PNNL

Abstract

Agriculture accounts for 90% of global freshwater consumption and it is expected to intensify in the future. Thus, quantifying future global agricultural green and blue water consumption is key to evaluate and cope with future water scarcity conditions. Climate and land use change are two major factors affecting these consumptions, and in this study we explicitly consider the effects of land use change in a consistent manner with climate change that previous studies were not able to. This study addresses two important research questions: 1) How will global crop green and blue water consumption evolve over time under future climate and land use changes; and 2) what are the relative impacts of climate and land use changes on future crop green and blue water consumption? To explore possible changes in future global agricultural green and blue water consumption under climate and land use conditions, a crop water use module is developed and validated based on the Global Change Assessment Model (GCAM) and its hydrology module (i.e., Xanthos). Crop specific green and blue water consumption are then calculated on monthly time step at global 0.5°×0.5° grid scale, and results are validated against historical estimates. Results show that global crop green water consumption increases by 12% by the end of century when compared with that in 1971-2000, where climate change dominate over land use change in determining the trend of global crop green water consumption. However, expansion in global irrigated area dominates the changing trend of global crop blue water consumption which increases 70% by the 2090s, especially in regions with significant irrigated land expansion (e.g. northern Africa, central Asia, China, Mexico, the Middle East, Russia, southern Asia, and Argentina). Furthermore, global crop blue water dependency will increase under climate and land use changes, especially in arid regions. This study estimates global future crop green and blue water consumption under harmonized climate and land use change scenarios, which could inform water managers to optimize the planning of adaptation strategies for the sustainable use of agricultural water and cope with future water scarcity.