Colorado Delta Blues No More

The species homo sapiens can only prosper in the arid West if the Colorado River is healthy. Photographer: Ed Darack/Science Faction via Getty Images

How the Colorado River Delta, once a verdant wilderness south of the U.S.-Mexico border, turned into a brown and salty wasteland is a sadly familiar tale. Remarkably, however, this story is about to run in reverse. Humans, having parched the delta for decades, are about to water it again. The benefits are not just environmental but also political.

In the mid-20th century, when the U.S. began holding the Colorado River back behind a series of dams, the river stopped flooding the delta. Some water from the Colorado still reached Mexico, as nature intended (and as a treaty required), but it was diverted to farms and cities. When the delta dried up, the fish, shellfish and water birds that once flourished there -- along with willow and cottonwood trees, deer and jaguar -- disappeared.

Already, some of the 35 billion gallons earmarked for the delta has begun streaming down from upriver reservoirs. Starting today, the water will be released from the Morelos Dam on the U.S.-Mexican border, and this flow will continue for the next two months -- mimicking, if weakly, the spring floods of years long past.

The hope is that this will revive just a small fraction of the delta: 3.7 square miles of what used to encompass more than 3,000. If it does, it can be used as a model for countless similar challenges around the world, in which people and governments struggle to manage and protect the rivers that sustain them. The importance of preserving essential ecosystems will only grow in an era of unpredictable climate change, which can bring floods as well as drought.

Under a five-year experimental deal between the U.S. and Mexico, the two countries and a collection of conservation groups will provide water for the delta -- the nongovernmental groups will buy water rights from Mexican farmers. After the initial "pulse" flow in the next two months, half again as much water is to be sent downriver over the next few years.

The deal also calls for the U.S., along with regional water agencies in California, Arizona and Nevada, to finance $21 million in improvements to Mexico's irrigation canals in return for some of Mexico's water this year. More important as an exercise in sensible river management, the pact establishes flexible allotments of Colorado water so that the countries can share in both surpluses and shortages. In drier years, less water will be sent to Mexico. In wetter years, Mexico can store some of its water in U.S. reservoirs.

This is in contrast to the usual water-rights approach that apportions fixed quantities of water. North of the border, for example, the upper basin states are required to deliver a set volume of water to the lower-basin states over a 10-year period, no matter how much the rain and snow provide.

With flexible sharing, all players involved benefit -- and in the U.S.-Mexico deal, that includes the environment. The water is expected to lower the salinity of the delta and raise the water table enough to help the willows and cottonwoods that conservation groups have been planting in the area to take root. Hundreds of species of birds and fish are expected to return.

It's not just plants and wildlife that will benefit, of course. The species homo sapiens, which relies on the river for everything from food to electricity, can only prosper in the arid West if the Colorado is healthy. If this delta restoration project succeeds, as scientists expect, it should encourage the U.S. and Mexico to renew the deal in three years for a much longer run.

--Editors: Mary Duenwald, Michael Newman.

To contact the editor on this story:
David Shipley at