The Watershed Planning Subcommittee (WPS) meets once per quarter with additional meetings scheduled as needed. Representatives from jurisdictions and various interest groups, including the University of Arizona and water companies, can be members.

The committee has identified a series of water-related issues as part of the Environmental Planning Advisory Committee strategic planning process and each meeting either focuses on one of these issues or tackles a topic that is of timely importance to members.  The purpose of the committee is to provide information to and coordinate among members and to advise and respond to the EPAC on regional water issues.

Other related committees include the Stormwater Management Working Group, the Statewide Water Quality Management Working Group and 208 Planning Task Forces, which are formed as needed to provide a public comment venue.