Provide the public with answers about conditions facing the Colorado River and Lake Mead, the great reservoir from which Arizona, Nevada and California receive much of their river allocations.

Persistent drought and chronic over-allocation of the river’s water is causing water levels at Lake Mead to drop. Hydrologists have identified specific levels beyond which the lake’s health as a functioning reservoir may destabilize. Arizona’s water-resources manager, the Department of Water Resources, and the manager of the state’s Colorado River delivery system, the Central Arizona Project, are taking steps to help assure the lake’s long-term viability.

An important step in that direction is providing timely information to the public.

Here are five issues that were addressed on May 18:

• What is Lake Mead and what purpose does it serve? Along with its up-river complement, Lake Powell, Mead is key to distributing the vast majority of Colorado River water allocated to Arizona, California and Nevada, as well as to Mexico. In order to do its job as a reservoir, Mead needs water to distribute. As a result of drought and over-allocation, it has less of it. In recent years, a lot less of it.

• What does the term “allocation shortfall” mean? The formula for distributing water among the three “Lower Basin” states of Arizona, California and Nevada, as well as to two states in northern Mexico, is complex. Not all rights to Colorado River water are equal. The system has priorities, many of them anchored in decades-old legal agreements. As written, the agreements place most of the responsibility for allocation shortfalls on Arizona’s shoulders. Arizona’s water managers are seeking more equity – more burden-sharing – among the system’s many users.

• What has Arizona done to prepare for potential allocation shortfalls? A top priority of Arizona water management for the last 36 years can be viewed as preparation for this here and now. Legally codified groundwater/aquifer protections, “water banking,” and mandatory municipal drought-response plans have been tools in Arizona’s drought-preparedness toolkit for decades. All of which helps explain why Arizona may face substantial water-distribution challenges, but not a water-supply “crisis” such as what other states now face.

• How has the Central Arizona Project prepared for having less water to deliver to its customers? The 336-mile diversion system delivers up to 1.6 million acre feet of Colorado River water from Lake Mead to customers as diverse as Pinal County farmers and urbanites in southern Arizona. As early as 2018, it may not have sufficient water to fulfill those obligations.

• What is Arizona and its Lower Basin partners doing cooperatively to prepare for potential shortfalls? The goal of the Colorado River-users partnership is a familiar one for states: Come up with an equitable resolution among yourselves before the feds do it for you. Ultimately, the Secretary of the Interior is the arbiter of how best to protect Lake Mead. A cooperative resolution among user-states and their respective stakeholders will be far more preferable than awaiting an edict from on high.

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