by Chuck Cullom, Colorado River Programs Manager
8/14/2019

Today, the U.S. Bureau of Reclamation issued its August 24-Month Study Report, a two-year outlook projecting water supply and operating conditions in the Lower Colorado River Basin..


The August Report defines, among other things, the operating conditions for Lake Mead for 2020, and includes the recently enacted Lower Basin Drought Contingency Plan (DCP). At the end of 2019, the projected Lake Mead elevation – the measuring stick for whether there is a shortage declaration on the river for 2020 – is just shy of 1090’. And, for the first time, the Lower Colorado River Basin will formally implement reductions outlined in the DCP at the new Tier Zero beginning January 2020.

What does this mean?

In short, it shows that in its first year, DCP is already working.

While the Basin experienced a stellar snowpack year and subsequent phenomenal run-off, because Lake Mead is projected to end 2019 below elevation 1090’, the Lower Basin States (Arizona, California and Nevada) will be in a DCP Tier Zero shortage condition next year. Under Tier Zero, Arizona’s Colorado River supplies will be reduced by 192,000 acre-feet; Nevada’s will be reduced by 8,000 acre-feet; and California takes no reductions. In addition, Mexico will reduce its water use by 41,000 acre-feet, due to Minute 323, an agreement under the 1944 Treaty for water users in both countries. Because of Arizona’s Colorado River priority system and agreements amongst water users, the Central Arizona Project (CAP) will take 100% of Arizona’s reductions under Tier Zero. CAP’s supplies will be reduced by 192,000 acre-feet, representing 12% of its normal annual Colorado River water supply.  For CAP customers, this means eliminating the water that would have been available for underground storage, banking and replenishment. Water going toward CAP agricultural uses will be reduced by about 15%.

The Tier Zero reduction to CAP, while significant, is largely equivalent to the amount of Colorado River water CAP has been leaving voluntarily in Lake Mead since 2015 as part of our Lake Mead Conservation ProgramIn essence, CAP and its water users have been planning and preparing for Tier Zero reductions for the past five years. The difference is that those previous contributions were voluntary – now, under DCP, these contributions are mandatory.

Through the DCP, Arizona continues to prepare for a drier future. This year, CAP, along with the Gila River Indian Community and the Colorado River Indian Tribes, is contributing and storing 236,000 acre-feet in Lake Mead. Next year, even with the Tier Zero reductions, these same water users, along with the Mohave Valley Irrigation and Drainage District, will continue to conserve and store additional water in Lake Mead. These efforts are part of Arizona’s plan to implement DCP developed collaboratively by the Arizona water community and legislative leaders. The plan balances the impacts of DCP amongst water users and provides additional protection to the Colorado River system, giving us a road map to follow for the next several years.

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