The All-American Canal delivers Colorado River water to the Imperial Valley, sustaining a desert valley that is one of the most productive agricultural regions in the world. The canal, about 80 miles long, joins the Imperial Dam (and its desilting works) and the 123-mile-long Coachella Canal to complete the All-American Canal System. This system irrigates as much as 600,000 acres of land in the Imperial and Coachella valleys, producing about one-half of the nation’s annual lettuce crop, among other vegetables and fruit.

BACKGROUND

Rainfall is scarce in the desert region at less than three inches per year and groundwater is of limited value. Water was essential if the desert was to bloom.

As early as 1853 the Colorado River was viewed as a source of water to irrigate land in the Imperial Valley, but early efforts to build and operate a canal were beset by financial and operational problems. By the early 1900s a canal mostly situated in Mexico was delivering water to the Imperial Valley. But water destined for the Imperial Valley did not always make it there, and the lack of complete United States control was a sore point for some in the valley.

In 1928, after more than a decade of lobbying by Imperial Valley interests, Congress authorized construction of the All-American Canal as part of the Boulder Canyon Project Act. The act also authorized Imperial Dam near Yuma, Arizona, and Hoover Dam near Las Vegas.

The All-American Canal – finished in 1940 – runs west from Imperial Dam on the Colorado River and roughly parallels the international Mexico border, giving it its name. The canal supplies about 3.1 million acre-feet (more than 1 trillion gallons) each year to nine cities and 500,000 agricultural acres.  Eight hydroelectric plants have been built along the canal since its construction. It was built by the U.S. Bureau of Reclamation and is operated by the Imperial Irrigation District.

CHALLENGES AND CONTROVERSIES

When it was first built, the canal was unlined and leaked badly in the section that passed through sand dunes. In 1988, Congress authorized lining portions of the All-American and Coachella canals but did not fund it and the project lay dormant. 

The lining project gained new momentum in the early 2000s. California was under pressure to reduce its use of the Colorado River and urban Southern California water agencies were interested in funding on-farm water conservation measures in exchange for the water that was saved. After some complicated negotiations as part of the 2003 Quantification Settlement Agreement, San Diego County Water Authority and the state of California funded lining portions of the All-American Canal to reduce the annual 67,700 acre-feet of seepage. Portions of the Coachella Canal running along the east side of the Imperial and Coachella valleys also were lined, saving about 26,000 acre-feet of seepage.

The All-American Canal lining project, however, caused tension in relations between the United States and Mexico because the canal’s seepage had helped to recharge Mexico’s groundwater basin. Mexico protested the lining, but a court decision and Congressional approval allowed the lining project to go forward. 

Along with the lining project, a small holding reservoir – called Brock Reservoir – was built alongside the All-American Canal to capture excess water that otherwise would flow to Mexico. Completed in 2010, the reservoir allowed Colorado River water that was ordered from Hoover Dam but later deemed unneeded to be held for later use.

LOOKING AHEAD

Historic drought and a warming climate have significantly diminished Colorado River flows and reduced water levels in the river’s two largest reservoirs, Lake Mead behind Hoover Dam and Lake Powell behind Glen Canyon Dam. How that will affect water deliveries through the All-American and Coachella canals – and the farm to urban water transfers that helped fund the canal lining projects – remains to be seen.

Updated February 2026