The Colorado River system in charts

The Colorado River supplies about 40 million people across seven states and Mexico, and almost all of its stored water sits in two reservoirs: Lake Powell behind Glen Canyon Dam, and Lake Mead behind Hoover Dam. Powell is the upper basin's bank, Mead is the lower basin's, and between them they hold the large majority of the system's storage. Watch those two lines and you are watching the river.

The 1922 split, and the math problem inside it

The 1922 Colorado River Compact divided the river between an upper basin and a lower basin, 7.5 million acre-feet each per year, with 1.5 million acre-feet later guaranteed to Mexico by treaty. Add those up and the paper allocation comes to 16.5 million acre-feet. The trouble is that the river has often produced less than that, and less still in the dry decades since 2000. The system was promised more water than it reliably yields, and Powell and Mead have absorbed the difference by drawing down.

The two banks, live

The charts above are Powell then Mead, current storage against their normal-for-the-date bands. The two move together because they are one plumbing system: Glen Canyon releases from Powell flow downstream to refill Mead. When people talk about the Colorado River crisis, this pair of lines is the crisis, measured.

The elevations that make headlines

The alarms on the Colorado are written in feet of surface elevation. At Lake Powell, minimum power pool is elevation 3,490 feet, the level below which Glen Canyon Dam can no longer generate hydropower, per Reclamation. Below that, water can leave only through the river outlet works, and dead pool, near elevation 3,370 feet, is where even gravity releases become uncertain. At Lake Mead, Reclamation puts dead pool at elevation 895 feet, with the Hoover Dam power pool historically at 1,050 feet, now extended lower with wide-head turbines. This site tracks storage volume rather than gauge elevation, so read these thresholds as the danger marks and the charts above as where the water actually sits. For the pool vocabulary in full, see the full pool and dead pool guide.

A system in renegotiation

The rules that govern shortage on the Colorado, including the tiers that cut deliveries as Mead falls, are being renegotiated for the post-2026 period. The Waterline reports the framework and the storage as published by Reclamation and the basin states. It does not predict how the negotiations will land.