The Department of the Interior’s Bureau of Reclamation has released a revised draft Supplemental Environmental Impact Statement (SEIS) as part of the ongoing, collaborative effort to update the interim operating guidelines for near-term operation of Glen Canyon and Hoover dams to address the ongoing drought and impacts from the climate crisis.
To protect Glen Canyon and Hoover dam operations, system integrity, and public health and safety through 2026 – when the current interim guidelines expire – an initial draft SEIS was released in April 2023. After a historic consensus-based proposal secured in partnership with states – which committed to measures to conserve at least 3 million-acre-feet (maf) of system water through the end of 2026, enabled by funding from the Investing in America agenda – Reclamation temporarily withdrew the draft SEIS to allow for consideration of the new proposal.
The revised draft SEIS includes two key updates:
The Lower Basin states’ proposal as an action alternative
Improved hydrology and more recent hydrologic data.
The release of the revised draft SEIS initiates a 45-day public comment period.
“The Colorado River Basin’s reservoirs, including its two largest storage reservoirs Lake Powell and Lake Mead, remain at historically low levels. [This] advancement protects the system in the near-term while we continue to develop long-term, sustainable plans to combat the climate-driven realities facing the Basin,” said Reclamation Commissioner Camille Calimlim Touton. “As we move forward in this process … we are also working to ensure we have long-term tools and strategies in place to help guide the next era of the Colorado River Basin.”
Reclamation conducted updated modeling analyses using June 2023 hydrology for the No Action Alternative, Action Alternatives 1 and 2 from the initial draft SEIS, and the Lower Division proposal. Results of that modeling indicate that the risk of reaching critical elevations at Lake Powell and Lake Mead has been reduced substantially. As a result of the commitment to record volumes of conservation in the basin and recent hydrology, the chance of falling below critical elevations was reduced to 8% at Lake Powell and 4% at Lake Mead through 2026. However, elevations in these reservoirs remain historically low and conservation measures like those outlined by the Lower Division proposal will still be necessary to ensure continued water delivery and to protect the long-term sustainability of the Colorado River System.
Based on these modeling results, Reclamation will continue the SEIS process with detailed consideration of the No Action Alternative and Lower Division Proposal. The revised SEIS designates the Lower Division Proposal as the Proposed Action. Alternatives 1 and 2 from the initial SEIS were considered but eliminated from detailed analysis.
This process is separate from recently announced efforts to protect the Colorado River Basin starting in 2027. The revised draft SEIS would inform Reclamation’s ongoing efforts to set interim guidelines through the end of 2026. The post-2026 planning process recently advanced will develop guidelines for when the interim guidelines expire.
