The Colorado River is an economic, environmental and cultural lifeline of the southwestern United States, and the allocation of its scarce waters are a source of ongoing controversy. This year marks the 50th anniversary of the Supreme Court decision in Arizona v. California. While the case was an important landmark in the still-evolving relationship between these two Lower Basin states, it remains most relevant today by the way in which it clarified federal rights and responsibilities. This is especially true in the areas of federal (including tribal) reserved rights, the role of the Interior Secretary in Lower Basin water management, and the ability of Congress to allocate/reallocate water. It also modified the Upper Basin/Lower Basin relationship in important ways, especially in the treatment of Lower Basin tributaries. Moving forward, several types of potential management innovations—in areas such as governance and water transfers—will hinge on the framework outlined by this decision
