As Colorado River Basin representatives begin negotiations for a new or modified set of operating criteria and associated agreements to manage uses of water in the Colorado River system, several long-standing sources of controversy among the basin interests are likely to emerge. This working paper identifies six such potential sources of controversy and provides the background necessary to understand why these issues present challenges to reaching agreement on next steps in basin water management. At base, these disagreements turn on longstanding assumptions about water uses that are no longer tenable from the shrinking water supply.