The Colorado River system

Lake Powell and Lake Mead are the Colorado River's two great savings accounts — together they hold the majority of the system's stored water and drive every operating decision on the river. Wondering about next year's water? See the winter outlook.

The system at a glance

Each marker shows today's pool elevation; red names are lower than a year ago. Click any reservoir for its full page. Basemap: USGS The National Map; dam locations from USBR's hydrodata site map.

Combined storage, 1963–present

The 2027–2028 operating rules

The 2007 Interim Guidelines, which set Powell release tiers and Mead shortage levels for two decades, end with operating year 2026. In August 2026 Interior signed a Record of Decision for 2027–2036 and issued the first two-year Operating Guidelines under it, after the seven Basin States did not reach a consensus agreement (ROD §1). Lake Powell's water year 2027 falls in the Low Elevation Infrastructure Protection Range, with an expected release of 6.0 to 7.0 maf and operations aimed at holding 3,510 ft; Lake Mead's 2027 is a flat 1.25 maf shortage for the Lower Basin (USBR 24-Month Study, September 2026). Details on the Lake Powell and Lake Mead pages.

Where Lake Powell is headed

Where Lake Mead is headed

Runoff outlook

NOAA Colorado Basin River Forecast Center monthly outlook (50% exceedance ESP values), issued 10/1/2026, fetched at build — cbrfc.noaa.gov. Unregulated inflow is what would flow into Lake Powell absent upstream operations; it drives USBR's projections above.

Every tracked reservoir

Sources and computation rules: data & methodology.