This document summarizes key information about managing drought and shortage in the Colorado River Basin. It discusses significant reservoirs like Lake Powell and Lake Mead, the 2007 Interim Guidelines for managing the reservoirs and allocating shortages, and how Arizona, Nevada, and Mexico share in shortages. It also outlines factors that influence lower basin shortages, like basin hydrology and upper basin uses. The near-term outlook presents current status of shortage and probabilities of future shortage. It concludes by discussing current adaptation strategies like storage, conservation, efficiency, augmentation, and potential partnerships.
4. Interim Guidelines (2007)
• Basin States agreement in 2006 on conjunctive
management of Lakes Powell and Mead and shortage
sharing in the Lower Basin
• Adopted by Secretary in
2007
• Effective through water
year 2026
• Renegotiation to start by
2020
5. Shortage Sharing
• Arizona and Nevada share Lower Basin shortages
under the 2007 Guidelines
• Mexico voluntarily agreed in Minute 319 to accept
reductions in its deliveries at the same elevations
Lake Mead
Elevation
Arizona
Reduction
Nevada
Reduction
Mexico
Reduction
1075’ 320,000 AF 13,000 AF 50,000 AF
1050’ 400,000 AF 17,000 AF 70,000 AF
1025’ 480,000 AF 20,000 AF 125,000 AF
• No reductions to California under 2007 Guidelines
6. What Influences Lower Basin Shortage?
1. Colorado
River Basin
Hydrology
2. Uses in the
Upper Basin
3. Colorado
River
Reservoir
Operations
4. Lower Basin
Uses and the
Structural
Deficit
9. Current Status: Shortage
Lake Mead is at elevation
1080 feet = 39% capacity
• 2015 – No shortage
• 2016 – No Shortage
• 2017 – 18% probability
• 2018 – 52% probability
(Before May precipitation:- 2016: 33%, 2017: 75% probability)
10. Risk to All Colorado River Users
Without equalization or corrective
action, Lake Mead could fall below
elevation 1000’ in 5-8 years
If Lake Mead is below elevation 1000’:
• Impacts SNWA ability to withdraw
water
• Less than 4.5 MAF left in storage in
Lake Mead
• Reduced power generation and
efficiency at Hoover Dam, potential
cavitation or vibration damage
11. Current Adaptation Strategies
• Storage:
– CAP and Arizona Water Bank stored water underground for future
recovery during shortages (3.7 MAF – over twice of CAP's annual
diversions from the Colorado)
• Conservation/Efficiency
– System Conservation
• Pilot System Conservation Agreement (targets 75 KAF)
• Pilot Drought Response Actions MOU (targets 740 KAF)
– Brock Reservoir water savings (100 KAF/year)
– Workgroup exploring options to address bypass and excess flows to
Mexico
• Augmentation
– Weather Modification projects in the Upper Basin (2006-present)
– Desalination studies for the Lower Basin (desalination is "drought
proof")
• Potential partnerships for Seawater Reverse Osmosis with Mexico and other U.S.
Users
In 1922, the states and the federal government created the Colorado River compact, which divided the basin in upper (Wyoming, Utah, Colorado, and New Mexico) and lower (Nevada, California, and Arizona) basin, each one receiving 9,251 million of cubic meter (MCM) (7.5 million acre-feet (MAF)) of water rights entitlements. In the lower basin, Nevada, California, and Arizona are entitled, respectively, to 370.0 MCM (0.3 MAF), 5,427.3 MCM (4.4 MAF), and 3,453.8 MCM (2.8 MAF). Mexico and the US signed the 1944 treaty to share waters of the Colorado and Rio Grande Rivers. Mexico is entitled to 1.5 MAF per year, or lower during extraordinary drought conditions (Christensen et al. 2004; Central Arizona Project 2012b).
Arizona, Nevada and Mexico will limit their use of Colorado River water when Lake Mead falls below identified elevations.
The April 24-Month study includes the most probable, minimum probable, and maximum probable inflow scenarios for Lake Mead elevation. The May 24-Month study only includes the most probable inflow scenario.