Arizona Environmental Water Needs Assessment (AzEWNA) Report: Considering environmental water needs alongside human demands is an emerging paradigm in water policy. The science of environmental water needs (or e‐flows) is ever growing and evolving. And yet, no compendium of efforts to define e‐flows in Arizona had been compiled,until now. This Assessment Report describes the geographic location and focus of nearly 100 studies of environmental water needs in Arizona, using all relevant sources. It identifies environmental water needs for some rivers and denotes the Arizona rivers where we know little. Defining environmental water needs is the first critical step in the broader process of securing and addressing environmental flows. Revised 2012.