Population and economic growth, as well as climate change, have pushed water crises to the top of the global agenda. Given the scale of the issues, delivering sustainable water management requires rapid mobilization of funding for water-related improvements and more effective use of existing resources. The Achieving Abundance Working Paper proposes a method whereby any decision-maker can calculate the cost required to deliver sustainable water management to a geography. The working paper calculates the cost of action required to close the gap between current conditions and desired conditions to financially compare and prioritize different water-related challenges or different targets of Sustainable Development Goal 6. The paper also estimates the costs of delivering sustainable water management for all countries and major basins—estimated globally as US$1.04 trillion (2015$) annually from 2015 to 2030.