The Colorado River
The Colorado River is the lifeline for the arid
Southwest U.S. It provides water and electricity for people throughout
the region, including residents of Los Angeles, Phoenix, Tucson,
Las Vegas, Denver, and Albuquerque. Throughout its 246,000-square-mile
(637,000 sq. km) basin, Colorado River water is also used extensively
for agriculture, irrigating over 3 million acres (1.2 million
ha) of crops and pasture. Along its route, the Colorado River
has carved the Grand
Canyon and other geologic spectacles, and provides abundant
recreational opportunities for rafting, fishing, boating, and
hiking. The river and its riparian areas also serve as habitat
for a multitude of fish and wildlife species, including several
endangered native fish.
Streamflow in the Colorado River comes mainly
from winter storms from the Pacific Ocean that build snowpacks
in the high mountains of western Colorado, western Wyoming, and
northeast Utah. Most of the annual flow in the mainstem river
occurs between April and July as these snows melt. The frequency
and moisture content of the winter storms is strongly influenced
by atmospheric circulation patterns and sea-surface temperatures.
While El
Niño-Southern Oscillation (ENSO) strongly influences
precipitation in the lower basin, its influence on the upper basin
snowpacks is much weaker, so ENSO's overall effect on streamflow
in the Colorado River basin is modest, except during very strong
El Niño events.
As the atmospheric flow of moisture from the Pacific
Ocean shifts from year to year, the flow of the river varies up
to fivefold, necessitating storage reservoirs in order to deliver
a consistent water supply to users. Two huge reservoirs, Lake
Powell and Lake Mead, are the linchpins of an elaborate system
of reservoirs, canals, and tunnels (see map below) that distribute
water and generate hydropower. In total, these facilities can
store about four years of average flow. The U.S.
Bureau of Reclamation operates the major reservoirs, with
many state and local entities contributing to the overall operation
of the system.
Map of the Colorado River
basin (click on map for larger image) showing the locations
of major dams and reservoirs.
Map
courtesy of the U.S. Bureau of Reclamation. |
The pages that follow describe
the legal basis for management of the Colorado River and the importance
of Lees Ferry and its gaged streamflow record.
The Compact and
Lees Ferry
The Lees Ferry gaged
flow record
