The Colorado River Compact

What it is

The Colorado River Compact is an agreement among Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming, signed at Santa Fe, New Mexico, on November 24, 1922. Congress approved it in the Boulder Canyon Project Act of 1928, and it took effect in 1929 on the approval of six of the seven states. Colorado's copy is in state law at C.R.S. 37-61-101.

Instead of dividing water state by state, the compact split the river system into two groups at Lee Ferry, a point on the river in northern Arizona, below Glen Canyon Dam:

• Upper Division states: Colorado, New Mexico, Utah and Wyoming.
• Lower Division states: Arizona, California and Nevada.

The key terms

• Article III(a) apportions to each basin the exclusive beneficial consumptive use of 7,500,000 acre-feet of water per year.
• Article III(b) lets the Lower Basin increase its beneficial consumptive use by up to 1,000,000 acre-feet per year.
• Article III(c) deals with water owed to Mexico, which a 1944 treaty later set at 1.5 million acre-feet a year in normal years.
• Article III(d) says the Upper Division states will not cause the flow at Lee Ferry to be depleted below 75,000,000 acre-feet in any period of ten consecutive years.

Article III(d) is the clause most discussed in Colorado. It is written as a limit on depletion by the Upper Division over rolling ten-year periods, which is why Upper Basin water planning watches the ten-year total at Lee Ferry.

Colorado's share: the 1948 Upper Basin Compact

The 1922 compact did not divide water among the Upper Basin states. The Upper Colorado River Basin Compact of 1948 (C.R.S. 37-62-101) did: after 50,000 acre-feet a year for the part of Arizona in the Upper Basin, it apportions the Upper Basin's use by percentage — Colorado 51.75%, Utah 23%, Wyoming 14% and New Mexico 11.25%. Because the share is a percentage of what is available, not a fixed volume, Colorado's entitlement shrinks when the river does. The 1948 compact also created the Upper Colorado River Commission.

Where it matters in Colorado

Water Divisions 4 (Gunnison), 5 (Colorado), 6 (Yampa and White) and 7 (San Juan and Dolores) lie in the Colorado River system. So do the sources of most transmountain diversions that carry West Slope water under the Continental Divide to the Front Range and the Arkansas Valley. Inside Colorado, water is still administered by prior appropriation; the compacts set limits on the state's total use, they do not rank one Colorado ditch against another.

The compacts also shape planning inside the state. Colorado's water plan and the basin roundtables on the West Slope weigh any new use of Colorado River water against the risk that the Upper Basin could someday have to cut back use to keep the Lee Ferry commitment.

Why it is in the news

The compact's numbers were set after a run of wet years. Flows over the following century have averaged well below what the negotiators assumed, and storage in Lake Powell and Lake Mead fell sharply after 2000. The 2007 Interim Guidelines for operating those reservoirs run through 2026, and Reclamation and the seven states have been working on the rules that follow them. Because these negotiations move quickly, check Reclamation and the Colorado Water Conservation Board for the current status rather than relying on any summary — including this one.

How to follow it in BasinMind

The live box above shows today's flow on the Colorado River in Division 5 with its percent of the median for the date. On the Reservoirs page you can follow storage in the division, and Ask BasinMind can pull compact records, river forecasts from NOAA's Colorado Basin River Forecast Center and Reclamation data for a specific question. BasinMind does not interpret compact compliance; that is for the states, the commissions and, in disputes, the courts.