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Colorado River Delta
by M. Cohen, courtesy of Pacific Institute for Studies in Development, Environment and Security

The Southwest's Great River

Conservation Priorities: Map of the Delta

Since the dams: Historical ecology of the Colorado Delta, Karl Flessa, et. al., English, En Espanol

Media Articles Related to the Colorado River and Delta

News Flash!

8-10-2001: Colorado River Delta Needs More Water: Stakeholders From U.S. and Mexico Release Principles to Guide Restoration

Scientific Reports

Taxonomic status and distribution of the bivalve mollusk Mulina coloradoensis in the Guld of California, Karl Flessa, 2001

Conservation Implications of the Population Decline of the Colorado Delta Bivalve Mollusk, Mulina coloradoensis, Karl Flessa, 1999

Importance of United States Water Flows to the Colorado River Delta and the Northern Gulf of California, Mexico, Edward Glenn, 1998


The Southwest's Great River

For millennia, the untamed Colorado River flowed from the Rocky Mountains of Colorado to the Gulf of California, nourishing along the way vast wild lands and abundant wildlife. Roughly 90,000 acres of cottonwood-willow riparian forest once covered a massive Colorado River flood plain from the Grand Canyon downstream to what is now the International Border with Mexico, according to the U.S. Bureau of Reclamation. Desert pupfish, Gila chub, and bonytail chub fish once swam the river and its marshes, providing an abundant food supply for migratory birds and the child-sized, top river predator, the Colorado River pikeminnow.

Sediments carved from the Grand Canyon washed downstream in a thick, muddy river, ultimately settling out in the vast delta region where the river meandered over centuries between the Gulf of California and the basin now occupied by the Salton Sea. The nearly 2 million acre delta region was a morass of twisting river channels, marshes, and jungle-like riverside forest vegetation. So much fresh water flowed down the river that the tidal estuary extended an estimated 40 km into the northern Gulf of California. Naturalist Aldo Leopold was enchanted by a 1922 visit the region and later wrote,

On the map the Delta was bisected by the river, but in fact the river was nowhere and everywhere, for he could not decide which of a hundred green lagoons offered the most pleasant and least speedy path to the Gulf. So he traveled them all.... He divided and rejoined, he twisted and turned, he meandered in awesome jungles....

River ecosystem no more

The wondrous Colorado River and Leopold's delta today exists only in historical accounts, a few pictures and memories. Leopold's adoration for the delta stands in stark contrast to his historical peers. In 1932, Herbert Hoover made an unexpected visit to what was then the largest construction project on Earth. Looking across the Colorado River on the Arizona-Nevada border, he declared:

"The waters of this great river, instead of being wasted in the sea, will now be brought into use by man. Civilization advances with the practical application of knowledge, in such structures as the one being built here in the pathway of one on the great rivers of the continent. The spread of its values in human happiness is beyond computation."

Now named after the man who sang its praises, Hoover Dam and a myriad of other dams, diversion canals and channelization have converted much of the river to little more than a conveyance canal for delivery of water to sprawling southwestern cities and big agribusiness. Over years, the federal government has signed contracts and a treaty for delivery of water to river basin states Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming and to Mexico for far more water than actually flows downstream in any given year. So today dust blows where water once flowed in most of the delta region at the river's mouth – in many areas barren salt flats are all that remain.

continued...The River's return

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