A trickle of water might save an estuary
The Colorado River Delta was once a watery labyrinth of willow thickets, mesquite and cottonwood, bigger than the state of Rhode Island and teeming with bird and animal life. Today it is a barren expanse of salt-stained mudflats where the river used to meet the sea south of Yuma.
About 90% of the delta’s wetlands and natural habitat dried up over the last half century, as water from the Colorado was captured in reservoirs and diverted to farms and cities from Las Vegas to Mexicali.
For more than a decade, conservation groups in the U.S. and Mexico have tried unsuccessfully to restore North America’s largest desert estuary. Now the Sonoran Institute is warning that unless restoration is undertaken before a prolonged dry spell, which many scientists are predicting, it could be too late.
In its forthcoming analysis of the delta, the nonprofit Arizona institute paints a dire picture of the once-vibrant ecosystem. But it also puts forth a proposal for replenishing much of the area by replacing a tiny fraction of the river water that once flowed through the delta, saying it would be enough to restore much of the area’s natural wealth.
Under the institute’s plan, the delta would get about three-tenths of a percent of the river’s historic annual flow, making it one of the more modest claims on a river that serves 30 million people. But even that amount could be a hard sell.
Eight years of drought in the Colorado watershed have raised the likelihood of shortages in the near future, and as officials in the U.S. and Mexico look for creative ways of limiting future cutbacks, every drop will count.
The river’s annual flow has fallen as low as 25% of normal since 2000, and some scientists have predicted that with the growing influence of climate change, flows will average 50% to 60% of normal over the next 50 years.
Later this year, Interior Secretary Dirk Kempthorne is expected to announce the first-ever guidelines for managing reduced water deliveries from the Colorado in the event of shortages. Officials say a shortage will be declared when the water level at Lake Mead drops 36 feet below its current level, a change that is expected within the next few years.
As the government draws up plans for dealing with a reduced water supply, environmentalists believe restoration must be made a priority or the delta will be doomed.
“If we fail right now, we might really fail, as the shortage becomes a reality and discussions about saving water for conservation become a lot harder,” said Jennifer Pitt, a policy analyst with the group Environmental Defense, which works closely with the Sonoran Institute.
Advocates for the delta have little legal leverage.
Neither the 1944 treaty that allocates Colorado River water to Mexico nor any environmental law in that country mandates water for the delta. Late last year, in support of efforts by California to reclaim water that has been seeping across the border and nourishing crops and wetlands in the delta, Congress passed legislation barring the use of U.S. environmental laws to protect Mexico’s interests.
But the Sonoran Institute contends that there is still nearly enough unclaimed water in the river to revive the delta without impinging on any existing rights on either side of the border.
“What we are talking about is the slop, leakage and waste discharges, " said Peter Culp, a lawyer who represents the institute. It’s the water that slips past Mexico’s Morelos Dam after a storm or that trickles back to the river from irrigated fields.
For 30 years, the crown jewel of the delta’s remaining wetlands, the 40,000-acre Cienega de Santa Clara in Sonora, Mexico, has relied entirely on brackish discharges from a nearby irrigation district.
The problem with such releases, however, is that they can’t be counted on forever and don’t always occur when nature needs them. To ensure timely flows, the institute has proposed amending the 1944 treaty to allow Mexico to bank water in the U.S. and participate in a bi-national water market.
“There are significant human benefits to the proposal,” said Mark Lellouch, one of its authors. About 200,000 people live in scattered communities in the delta, Lellouch said, and restoration would provide more sustenance and more jobs.
Even now, nature tourism is a going concern. Visitors from the U.S. and Mexico are drawn to the Cienega de Santa Clara and other destinations by the estimated 350,000 birds that still nest and feed in the delta.
“There are a number of stakeholders in Mexico interested in that environment,” said Steve Smullen, principal engineer for the International Boundary and Water Commission, the agency that administers water-rights treaties between the United States and Mexico. But he said the institute’s plan “works against agricultural interest, conservative interest and the interests of large communities” vying for the water.
“If there’s enough will, you can make anything happen,” he said. “But it’s an uphill battle.”