Post-2026 Draft EIS Alternatives

Basic Coordination Alternative

This alternative is designed to be implementable absent new agreements among Basin water users. Lake Powell releases would primarily be 8.23 maf, with some releases above and below 8.23 maf, and minimum releases of 7.0 maf. Lake Powell elevations could be increased by releases from CRSP Upper Initial Units within their respective RODs to protect infrastructure at Glen Canyon Dam. Reclamation would identify triggers for when additional Upper Basin actions are needed to protect critical infrastructure. Lower Basin shortages up to 1.48 maf would be triggered based on Lake Mead elevation and distributed consistent with priority system. Existing ICS would be delivered in accordance with existing agreements, but there would be no new delivery and storage mechanisms.

A curve of Lake Mead elevations (in feet) as a function of the Lower Basin CY Shortage (in million acre-feet) that provides the shortage guidelines to reduce deliveries from Lake Mead, under the Basic Coordination Alternative. A curve of Lake Powell elevations (in feet) as a function of the Lake Powell WY relsease (in million acre-feet) that provides a coordinated operation guideline for Lake Powell and Lake Mead, under the Basic Coordination Alternative.

Shortage Guidelines to Reduce Deliveries from Lake Mead³

  • Shortages based on Lake Mead elevation up to 1.48 maf
  • Shortages distributed based on priority
  • Identify conditions when additional reductions may be needed to avoid reaching critically low elevations

Coordinated Reservoir Operations (Lake Powell and Lake Mead)

  • Lake Powell releases are determined based on Lake Powell elevation unless equalization releases are required
  • Releases range from 9.5 to 7.0 maf, unless more is required for equalization releases
  • Identify conditions when additional action may be needed for infrastructure protection

Storage and Delivery of Conserved System and Non-system Water (Lake Mead and/or Lake Powell)³

  • No new storage and delivery mechanism to replace ICS
  • Delivery of existing ICS in accordance with existing agreements

Surplus Guidelines to Increase Deliveries/Releases from Lake Mead³

  • Surplus determinations limited to 70R (spill avoidance strategy) and Flood Control conditions

Additional Activities Above Lake Powell

  • Releases from CRSP Upper Initial Units within their respective RODs and contingent on hydrologic conditions to protect infrastructure at Glen Canyon Dam
  • Identify conditions when additional Upper Basin actions may be needed for infrastructure protection

³ These operational elements contain modeling assumptions for water deliveries to Mexico. Shortage volumes include assumptions related to reductions in water deliveries to Mexico. Lake Mead storage volumes for the Storage and Delivery of Conserved System and Non-system Water include assumptions related to storage available to Mexico. Surplus Guidelines include assumptions related to increased deliveries to Mexico. Appendix A provides additional detail. Reclamation's modeling assumptions are not intended to constitute an interpretation or application of the 1944 Water Treaty or to represent current United States policy or a determination of future United States policy regarding deliveries to Mexico. The United States will conduct all necessary and appropriate discussions regarding the proposed federal action and implementation of the 1944 Water Treaty with Mexico through the IBWC in consultation with the Department of State.