Imperial Dam is a concrete slab and buttress, ogee weir structure across the Colorado River on the California-Arizona border, northeast of Yuma. Completed in the 1938, the dam retains the waters of the Colorado River in the Imperial Reservoir before desilting and diversion into the All-American Canal, the Gila River, and the Yuma Project aqueduct. Between 1932 and 1940, the Imperial Irrigation District relied on the Inter-California Canal, the Imperial Canal, and the Alamo River.