All-American Canal

The All-American Canal brings Colorado River water to the Imperial Valley in California. The canal is the valley's only source of water. It replaced the Alamo Canal, which was located mostly in Mexico. The All-American Canal provides drinking water for 9 cities and irrigates over 500,000 acres (2,000 km²) of farmland. It is the largest irrigation canal in the world, carrying up to convert|26155|cuft|m3 per second of water. The canal was built by the United States Bureau of Reclamation in the 1930s and was completed in 1942. The Bureau of Reclamation owns the canal, but the Imperial Irrigation District operates it. Water for the canal is diverted at the Imperial Diversion Dam. The All-American Canal feeds, from east to west, the Coachella Canal, East Highline Canal, Central Canal and the Westside Main Canal. These four main branches of the canal and a network of smaller canals gradually reduce the flow of the All-American Canal until it ends at a small drop in the western Imperial Valley where it drains into the Westside Main Canal. The main canal is 82 miles (132 km) long, has a total drop of 175 feet (53 m), a width of 150 to convert|700|ft|m and a depth of 7 to convert|50|ft|m The canal gets smaller as it runs west because it carries less water.

Although not part of the All-American Canal System, Senator Wash Reservoir serves as an off-stream regulating reservoir for the canal. It is located two miles (3 km) above Imperial Dam and can store 13,800 acre-feet (17,000,000 m³) of water. Water is pumped into the reservoir when the flow at Imperial Dam exceeds diversion requirements. In addition to Senator Wash, the Imperial Irrigation District has ten other regulating reservoirs with a combined capacity of 3,300 acre-feet (4,000,000 m³). Imperial Dam's reservoir was not intended for water storage and filled with sediment soon after it was built. Currently, it can only hold about 1,000 acre-feet (1,200,000 m³) and requires periodic dredging to keep the diversion channel open. The Colorado River carries an enormous amount of sediment. The sediment is removed at desilting basins so that it will not fill in the canal.

Eight hydroelectric power plants have been constructed along drops in the All-American Canal system. Drops 1 through 5, Pilot Knob, East Highline and Double Weir are located on the All-American Canal. Another power plant, Turnip, is located on the Central Main Canal branch. The power plants are all relatively small and have a combined capacity of 58 MW. Electricity generation is dictated by water delivery needs. There is also a 7.2 MW pumped storage plant at Senator Wash Dam. Water from the Senator Wash Reservoir is released when water needs exceed flows at Parker Dam.

Runoff from the farmland irrigated by the All-American Canal make up most of the flows in the Alamo River and New River, both of which drain into the Salton Sea, providing 85% of its water. The rest is from smaller rivers and drainage systems. If not for the All-American Canal, the Salton Sea would have dried up long ago, returning to its natural state. Unfortunately, the runoff carries fertilizers, pesticides and salts into the sea and creates an unstable ecology.

External links

* [http://www.iid.com/Media/All-American-Canal-Map.jpgIID - All-American Canal map]
* [http://www.usbr.gov/dataweb/html/allamcanal.html USBR - All-American Canal]
* [http://www.usbr.gov/dataweb/dams/ca10185.htm USBR - Senator Wash Dam]