Colorado River Structural Deficit
Levels at Lake Mead are rapidly dropping, in part, because the water stored in this reservoir is over allocated to the states that share it. This puts the stability of the Colorado River system and reliability of Arizona’s Colorado River supplies at serious risk.
Structural Deficit Infographic
Less water flows into Lake Mead than is taken from it— about 1.2 million acre-feet less annually. The result is a “structural deficit” that causes Lake Mead’s elevation to drop about 12 feet every year, drought or no drought.
Lake Mead is the largest reservoir in the United States and a key component of the Colorado River system. It is the reservoir level of Mead that determines shortage conditions on the Colorado River. The lake supplies water to three states and Mexico, serving 20 million people and supporting extensive agriculture. Water from the lake accounts for 34 percent of the supply portfolio of the AMWUA members.
The Colorado River is over-allocated. More water is committed to the states and Mexico that rely on the river than is actually available in an average year. In years with normal inflows, Lake Mead declines twelve feet in elevation. This imbalance between inflows and diversions is known as the “structural deficit.” Seventeen years of drought have exacerbated the problem, hastening the decline of Lake Mead.
Water managers are well aware of the deficit and have planned for shortages. In 2007, the seven states that share the river, the federal government, and Mexico agreed to interim guidelines that determine how Lake Powell and Lake Mead are managed and how shortages of supplies will be shared. Since that time, it has become clear that there is increasing probability of deeper shortages, sooner, and there is an unacceptable risk of catastrophic declines in Lake Mead.
Innovative system conservation programs have helped avoid shortages to date and have bought precious time to develop more comprehensive solutions.
The Pilot System Conservation Program, a cooperative effort between Upper and Lower Basin water users, has demonstrated the viability of jointly funding cooperative, voluntary projects to conserve water to increase storage levels in Lake Mead and Lake Powell. The fact that the water saved through the program remains in the Colorado River system and is not allocated to any state, agency, or water user is unprecedented.
A Memorandum of Understanding (MOU) signed in 2014 enabled a new approach to reduce the risk of shortage. The agreement between the Bureau of Reclamation, Arizona Department of Water Resources (ADWR), Central Arizona Water Conservation District (CAWCD), Metropolitan Water District of Southern California, Southern Nevada Water Authority, Colorado River Board of California and Colorado River Commission of Nevada, identifies voluntary actions to develop from 1.5 to 3 million acre-feet of new water for Lake Mead by the end of 2019. CAWCD's goal is to store 345,000 acre-feet of water – or approximately four feet of elevation – in Lake Mead between 2014 and 2017. The combined benefit of this agreement may result in a 10-foot elevation boost to the lake.
Drought Contingency Proposal
Over the course of the past several years, the seven Colorado River Basin states, the federal government, and Mexico have developed a proposal that will protect Lake Mead from dropping to critical levels and improve the health of the river system. The Drought Contingency Plan (DCP) proposes sharing reductions among Arizona, California, Nevada and the United States, while still honoring previous agreements. The reductions to Arizona’s and Nevada’s Colorado River supplies will be earlier and deeper than those agreed to in 2007. Under this plan, California, for the first time ever, would agree to take reductions in Colorado River deliveries if Lake Mead drops to specified elevations.
There is consensus among the parties as well as the broader water community that the plan is necessary and practical. It will provide much needed certainty regarding the longer-term reliability of Colorado River supplies.
There is a hurdle remaining, however. The deeper and earlier reductions to central and southern Arizona’s water supplies will affect water users sooner than previously anticipated and the impacts aren’t equitable. If all of the stakeholders aren’t on board, it will be impossible to pass legislation to enable the state to enter into the DCP agreement.
Testifying before the U.S. Senate Subcommittee on Energy and Natural Resources, ADWR Director Buschatzke stated, “Collaboration and an all-hands-on-deck approach is the future of the Colorado River.” Credit: Ben Moffat/Cronkite News
To secure support for DCP, the Director of ADWR is leading an effort among leaders in the water community to create a plan—known as DCP Plus—to mitigate or delay the impacts of DCP imposed reductions in water allocations to water users within Arizona. AMWUA is an active participant in these discussions. AMWUA has also facilitated discussions among its members regarding opportunities to help shore up Lake Mead levels in advance of DCP and DCP Plus.
In a step toward proving the potential for a DCP Plus Plan, the Bureau of Reclamation, the State of Arizona, the City of Phoenix, the Walton Family Foundation, and the Gila River Indian Community have entered into a historic, $6 million, five-party agreement that will enable the Gila River Indian Community to leave 40,000 acre-feet of its 2017 allocation in Lake Mead.
AMWUA and its members strongly support efforts to stabilize Lake Mead, improve the resiliency of the Colorado River system, and ensure the certainty and reliability of Arizona’s Colorado River supplies.
Colorado River Shortage Preparedness Workshop
Top water resource managers from ADWR, Bureau of Reclamation, and CAP provide the latest information on drought status, shortage probabilities, and anticipated shortage impacts at public meetings. Credit: CAP
What You Can Do
All of us who rely on the Colorado River must take rapid, substantive action to protect the river system and the communities that rely on it. We encourage residents and businesses to become more familiar with these issues. Attend ADWR shortage briefing meetings, and subscribe to the ADWR newsletter.
Let your water providers, agencies, and elected officials know it is imperative that they make wise decisions that ensure the long-term reliability of our water supplies. Lend your support when necessary to ensure necessary policies and investments are made.
Resources and Additional information: