Principal Research Analyst
Water Shortage Declared
On August 16, 2021, the U.S. Bureau of Reclamation (Reclamation) declared the first-ever official water shortage on the Colorado River. This declaration triggered the largest mandatory water cuts in the Colorado River Basin to date.
While Kansas is not part of the Colorado River Basin, it does have a vested interest in Colorado’s water supply issues, as the state relies on Colorado suppling an adequate amount of water each year.
The Colorado River
The Colorado River runs 1,450 miles from its headwaters in Colorado and Wyoming to its terminus in the Gulf of California. The river travels through seven states (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming) and Mexico. The Colorado River Basin spans 246,000 square miles, or about 8.0 percent of the continental United States. Water from the Colorado River is used to irrigate 5.5 million acres of agricultural land and to provide municipal and industrial (M&I) water supplies to 40 million people. Water from the Colorado River is regulated by dams and stored in reservoirs. Two major dams along the Colorado River are the Glen Canyon Dam and the Hoover Dam. Each of these dams has an associated storage reservoir. Lake Powell, associated with the Glen Canyon Dam, has a storage capacity of 26.2 million acre-feet (MAF). Lake Mead, associated with the Hoover Dam, has a storage capacity of 26.1 MAF.
The Law of the River
The laws and agreements governing Colorado River operations are referred to collectively as “The Law of the River.” The cornerstone of the Law of the River is the Colorado River Compact of 1922.
This agreement divided the Colorado River Basin into the Upper Basin (Colorado, New Mexico, Utah, and Wyoming) and the Lower Basin (Arizona, California, and Nevada) and apportioned the River’s water supplies between these two basins. Each basin was apportioned 7.5 MAF per year for beneficial consumptive use.
Problems Facing the Colorado River
Supply and Demand Imbalance
When the Colorado River Compact of 1922 was approved, the appropriations of water supply made were based on the average flows during the preceding ten year period, which included several wet years.
The data from this period indicated the average annual flows of the Colorado River totaled 16.4 MAF. But historical data collected by Reclamation from 1906 to 2020 shows that natural flows averaged closer to 14.7 MAF annually. Thus, water supplies were over-allocated and subject to overuse. Even though this accounting error has been identified, the problem of overuse is likely to persist. Water use increased steadily over the course of the 20th Century and will most likely continue into the future. By 2050, Reclamation estimates demand for water from the Colorado River will increase to 18.1 MAF to 20.4 MAF per year, and the number of people who rely on the Colorado River is projected to double by 2060.
Volume of the Colorado River by Region
In addition to the growing demand for water, a study conducted by the U.S. Geological Survey revealed natural flows from the Colorado River have declined approximately 20.0 percent over the last century. Between 2000 and 2020, flows averaged about 12.4 MAF annually. Reclamation found the current drought (2000 to 2021) has been the driest 22-year period on record, and it has resulted in 8 of the 20 driest years on record.
The drought has negatively affected water storage operations along the Colorado River. According to Reclamation, in fall 2021, Lake Mead was about 35.0 percent full, and Lake Powell was about 32.0 percent full. In June 2021, modeling completed by Reclamation showed there is a 17.0 percent chance that Lake Powell could sink so low by 2024 that hydroelectric generation at the Glen Canyon Dam would become impossible, and there is a 20.0 percent chance that the water in Lake Mead will fall to 1,000 feet above sea level by 2025, which is only 50 feet above the minimum elevation needed to allow the Hoover Dam to generate electricity.
The affected states and Mexico have been working to combat the declining natural flows and elevations of Lake Mead and Lake Powell. Mitigation techniques include using alternative water sources, like aquifers, changing landscaping regulations to incentivise lower water use, investing in waste water treatment and reuse, and studying the potential of desalination plants to transform saltwater into freshwater.
Due to Reclamation’s water shortage declaration, mandatory water cuts have been triggered beginning January 1, 2022. Arizona will see an 18.0 percent reduction, Nevada will see a 7.0 percent reduction, and Mexico will see a 5.0 percent reduction. Future water cuts in the Lower Basin are expected if Lake Mead’s water levels continue to fall.
The Future of the Colorado River
Over the next few years, the states, Mexico, Native American Tribes, and the federal government will be negotiating a new framework to determine how to distribute water supplies, as the current guidelines expire in 2026.