This document is part of an effort to define a set of ecosystem flow requirements for the Bill Williams River (BWR) downstream of Alamo Dam in western Arizona (fig. 1), one of the U.S. Army Corps of Engineers (USACE)/TNC focus rivers. In addition to USACE and TNC involvement, the BWR effort is being undertaken by a multiagency/entity group (the Bill Williams River Corridor Steering Committee) that meets on an approximately quarterly basis to coordinate resource management and prioritize research needs associated with the BWR. In the context of the BWR and Alamo Dam, the focus of both the steering committee and the technical and resource support made possible by the USACE–TNC agreement is to use the definition of flow requirements as a means to (1) assess current dam operations and their effect on the downstream aquatic and riparian ecosystems and (2) identify changes in reservoir management that will restore and protect downstream ecosystems. By design, this work to define ecosystem flow requirements will also advance the steering committee’s firm commitment to develop and implement an adaptive management and monitoring plan. This plan will be used to evaluate ecosystem response to current and future management of Alamo Dam.