Managing water resources is one of the most pressing challenges of our times - fundamental to how we feed 2 billion more people in coming decades, eliminate poverty, and reverse ecosystem degradation. This Comprehensive Assessment of Water Management in Agriculture, involving more than 700 leading specialists, evaluates current thinking on water and its interplay with agriculture to help chart the way forward. It offers actions for water management and water policy - to ensure more equitable and effective use. This assessment describes key water-food-environment trends that influence our lives today and uses scenarios to explore the consequences of a range of potential investments. It aims to inform investors and policymakers about water and food choices in light of such crucial influences as poverty, ecosystems, governance, and productivity. It covers rainfed agriculture, irrigation, groundwater, marginal-quality water, fisheries, livestock, rice, land, and river basins. Ample tables, graphs, and references make this an invaluable work for practitioners, academics, researchers, and policymakers in water management, agriculture, conservation, and development. Published with IWMI.