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Laguna Division Conservation Area
History and Background

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The Setting

The Laguna Division is a developed reach of the lower Colorado River near Yuma, Ariz., that extends from Laguna Dam (RM 43.2) to Imperial Dam (RM 49.2).

Laguna Dam was constructed between 1905-1909 to provide water from the lower river to the growing agricultural industry in Yuma, Somerton and Gadsden, Arizona, and Bard and Winterhaven, Calfornia. High river sediment loads contributed to rapid silt build-up upstream of the dam, so starting in 1948, irrigation water for the areas was diverted at Imperial Dam. Laguna Dam now serves as a regulating structure for sluicing flows from Imperial Dam.

Today, Colorado River water is diverted into the All-American Canal (to California) and Gila Gravity Main Canal (to Arizona) for agricultural or domestic purposes at Imperial Dam, with the exception of sluicing flows and a small inflow into Mittry Lake, a water body along the southeastern edge of the area. Mittry Lake provides significant recreational opportunities, and riparian and marsh habitat.

The Laguna settling basin is located within this reach, downstream of the Imperial Dam. Sediment from the Parker, Palo Verde, Cibola, and Imperial divisions accumulates at the upstream face of Imperial Dam, and at the headworks for the All-American and the Gila Gravity Main canals. The sediment is then sluiced into the Laguna settling basin from where it is periodically dredged and disposed of in the adjacent uplands.

Conservation Partnership and Plan

About 1,800 acres of the Laguna Division to the east of the Laguna settling basin has potential for large scale riparian and marsh restoration and enhancement, and in 2007, the Laguna Division Planning Group was formed of representatives from the:

to identify potential restoration projects within the area. The group also ensures any actions taken to develop the project do not affect other potential restoration projects or ongoing river operations, including water delivery, sediment removal, and power generation.

These agencies evaluated several conceptual designs for an enhanced riparian/marsh area based on technical feasibility, water availability and cost effectiveness. Developed by Natural Channel Design and Fred Phillips Consulting, these designs incorporate a variety of native plants and structural materials to help restore natural stream channels and habitats.

The Results

The preferred alternative (selected in 2010) will create, restore and enhance approximately 1,200 acres of riparian and marsh/open water habitat in Arizona and California. Most of this area is currently covered wtih dense stands of saltcedar that thrive in remnants of former river meanders.

The project will shape and contour multiple meandering channels to supply varied water levels to cottonwood-willow, honey mesquite, marsh and backwater land cover types. A pipeline will also be constructed to bring a reliable supply of water to the site from the Gila Gravity Main Canal forebay. The area will also provide new opportunities for low impact recreation and environmental education, preserve cultural sites, and develop new habitat for resident birds and mammals, and for several endangered or threatened species.

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Updated: April 2011