The Bureau of Reclamation released a Final Environmental Impact Statement establishing an adaptive decision framework for managing Lake Powell and Lake Mead through 2036 on July 31.
The document is the most consequential water policy action for the American West in years, governing allocation across seven states that depend on the river: Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming, according to the Interior Department.
The Colorado River supplies water to approximately 40 million Americans and irrigates roughly 5.5 million acres of farmland. Lake Powell and Lake Mead, the nation’s two largest reservoirs, have experienced dramatic declines in water levels over the past two decades due to a megadrought that scientists have described as the worst in at least 1,200 years.
The adaptive framework outlined in the EIS is designed to allow water managers to adjust allocation decisions based on changing reservoir conditions rather than relying on fixed rules that may not account for worsening drought, according to Reclamation.
The plan affects municipal water supplies for major cities including Phoenix, Las Vegas, Los Angeles, and Denver, as well as agricultural operations across the region and hydroelectric power generation at Glen Canyon and Hoover dams.
Tribal nations with water rights claims on the Colorado River also have significant stakes in the outcome. A Record of Decision formalizing the management framework is expected to follow the EIS publication.