U.S.-Mexico experiment aims to resurrect the Colorado River delta

The mighty Colorado River, which over millenniums has carved the Grand Canyon, does an unusual thing when it gets south of the Arizona-Mexico border. It dies.

The Morelos Dam — sitting on the international boundary — serves as its headstone, diverting nearly all of the river water into an aqueduct that serves agriculture as well as homes in Tijuana.

South of the dam, the river channel travels about 75 miles to the Gulf of California. Except when filled by rains, the channel is bone dry. But starting Sunday, the river will flow again, part of an unprecedented experiment by U.S. and Mexican officials.

A few days ago, the International Boundary Water Commission, made up of Mexican and U.S. officials, released water from Lake Mead in Nevada to send it toward the Colorado River delta, a region cut off from most of the river’s flow by the dams and diversions constructed in the 20th century.

Although there have been experimental high-flow water releases in the Colorado River, such as one last year from Lake Powell designed to spread sediment in the Grand Canyon, this is the first “pulse” for the delta.

The pulse, in the planning stage for some time, is part of a five-year pilot project designed to reinvigorate the delta environment. It’s a coincidence that it comes when a record drought has increased concerns about the future of water security in the West.

That’s why Mexican and U.S. water authorities, hoping to stem any pushback or last-minute hesitation, met with California and Arizona officials before announcing the pulse to assure them that they would receive their full allotment of Colorado River water this year.

The pulse will start slowly Sunday, when officials lift the gates at the Morelos Dam, west of Yuma, Ariz., releasing about 700 cubic feet of water per second. It will peak Thursday when about 4,200 cubic feet per second will rush through the dam. Over eight weeks, an estimated 105,000 acre-feet will be released. (An acre-foot is the amount water required to cover an acre a foot deep, or about 326,000 gallons — enough to supply two average homes for one year.)

Experts from both countries will study the effects of the release. It’s unlikely the water will reach the Gulf of California and unclear whether it will all soak into the soil or be left standing in parts of the channel.

The pulse is allowed under an amendment approved two years ago to a 1944 treaty governing water use by the two countries. The amendment established new rules for sharing water in times of drought and committed both nations, often at odds over water, to conducting the pulse experiment.

The release is intended to revitalize the delta, help Mexican farmers grow their crops, recharge the aquifer and bring back hundreds of bird species native to the region.

Source: Cindy Carcamo | LA Times

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