The U.S. Bureau of Reclamation (“Reclamation”) published its August 2021 24-Month Study on Monday, effectively declaring a shortage on the Colorado River for the Lower Colorado River Basin. The August study predicts that the elevation of Lake Mead at Hoover Dam will continue to be below 1,075 feet (the level that triggers a Tier 1 shortage) for the foreseeable future and consistently below 1,050 feet (the level that triggers a Tier 2 shortage) by April 2023.
A Tier 1 shortage reduces Arizona’s 2.8 million acre-feet per year (“AFY”) allocation of Colorado River water by 512,000 AFY and Nevada’s allocation of 300,000 AFY by 21,000 AFY. The impacts of a Tier 1 shortage will primarily be felt by farmers in Pinal County, Arizona, who rely on Colorado River water transported through the Central Arizona Project (“CAP”) canal. But the extent of the impact, initially, will be dampened by increased use of non-renewable groundwater supplies.
A Tier 2 shortage would further impact Arizona and Nevada, and even California will begin to share in the reductions when the elevation of Lake Mead goes below 1,045 feet. The August 24-Month Study predicts Lake Mead to be below 1,045 feet by May 2023.
While the states in the Lower Colorado River Basin have been actively planning for this moment for well over a decade, expect to see increased pressure from interest groups and state parties to explore additional measures to address shortage on the Colorado River. The Arizona Department of Water Resources notes that it will continue to work with stakeholders to seek long-term solutions.