Colorado River Basin

Tuesday, June 9, 2026

Colorado River Basin

Water, law & hydrology

Reclamation's June 24-Month Study Holds Lower Basin in Tier 1 Shortage for 2027

The Bureau of Reclamation released its June 24-Month Study, projecting Lake Mead's January 1, 2027 elevation below the 1,075-foot Tier 1 threshold under the most-probable inflow scenario. Arizona again absorbs the largest share of Lower Basin reductions under the 2019 DCP schedule.

The study lands as the seven states continue post-2026 guideline negotiations without a consensus alternative, and Reclamation's modeling assumptions are themselves a live point of dispute between the basins. (Sample content.)

Why it matters

This is the number every Lower Basin water manager budgets against. A third consecutive Tier 1 year hardens the negotiating positions on post-2026 guidelines — and the longer the states bargain inside a declared shortage, the more leverage shifts to whoever can credibly walk away.

U.S. Bureau of Reclamation ↗

Upper Basin States File Joint Modeling Critique with Reclamation

Colorado, Utah, Wyoming, and New Mexico submitted a joint technical memorandum challenging the inflow assumptions Reclamation is using to evaluate post-2026 operating alternatives, arguing the most-probable traces overweight the 20th-century record. (Sample content.)

Why it matters

Fights over modeling assumptions are fights over the allocation baseline by other means. If the Upper Basin wins a drier baseline, every alternative on the table gets re-scored — and the Lower Basin's structural deficit gets bigger on paper.

Colorado River Authority of Utah ↗

Cross-filed from other sections

Crossfile · AI & Technology

Arizona Regulators Open Docket on Data-Center Tariff Class

The Arizona Corporation Commission opened a docket to consider a dedicated tariff class for data-center load above 50 MW, including minimum-take provisions and transmission cost allocation. Intervenor deadlines fall in August.

The docket follows a wave of state-level bills nationally aimed at insulating residential ratepayers from AI-driven load growth. (Sample content.)

Why it matters

This docket decides who pays for the grid the AI buildout needs — shareholders, hyperscalers, or everyone's utility bill. It's also a template: what Arizona adopts, neighboring commissions will cite. Water and power for compute are becoming one conversation.

Arizona Corporation Commission ↗

Crossfile · AI & Technology

TSMC Arizona Fab 3 Pulls Schedule Forward on 2nm Demand

TSMC moved up the equipment-installation timeline for its third Arizona fab, citing 2nm demand from U.S. customers. The acceleration adds near-term construction labor and water-supply commitments in the Phoenix metro. (Sample content.)

Why it matters

Every accelerated fab is a multi-decade water and power commitment in a basin already negotiating scarcity. The semiconductor buildout and the Colorado River story are the same story on different timescales.

TSMC ↗