The 15,000-acre ciénega, the largest wetland in the Colorado River Delta, is home to several endangered species and is a major stopover for birds migrating north and south along the Pacific Flyway. It lies within Mexico's Biosphere Reserve for the Upper Gulf of California and Colorado River delta.
The Mexican community of Ejido Johnson operates a small ecotourism business at the wetland. Birdwatchers are attracted by the birds found there, including the Yuma Clapper Rail, listed as an endangered species by the U.S. and as a threatened species in Mexico.
How running the desalting plant would affect the water quality, vegetation and birdlife of the ciénega was not known. The ciénega receives its water primarily from Arizona's Wellton-Mohawk irrigation district –- water that is used by the desalting plant when it operates.
When the plant is running, the water it desalinates is returned to the Colorado River. The remainder, a smaller amount of saltier water, does flow to the ciénega.
Some scientists predicted that having a smaller and saltier portion of water flow to the ciénega would alter the ecosystem, said Karl W. Flessa, the UA geosciences professor who leads the U.S.-Mexico team of researchers that has been studying the ciénega since 2006.
To ensure that the ciénega would continue receiving the same amount and quality of water as before, U.S. and Mexican government agencies and non-governmental organizations from both sides of the border worked together to provide replacement water to the ciénega during the May 2010 to March 2011 pilot run of the Yuma Desalting Plant.
The international agreement was added to the 1944 water treaty between the U.S. and Mexico and represents the first time that water was allocated across the border for environmental purposes.
Chuck Cullom, Colorado River Programs Manager for the Central Arizona Project, said, "This unique and fruitful collaboration exemplifies the new spirit of binational cooperation and collaboration in monitoring and evaluating different environmental resources in the Colorado River system."
As part of the agreement, the researchers monitored conditions in the ciénega before, during and after the plant's pilot run.
"There was no significant change to the ciénega's hydrology, water quality, vegetation and marsh birds," said Flessa. He and his colleagues reported the team's findings in a report released by the International Boundary and Water Commission on June 25.
Cullom said, "The report really represents the most comprehensive monitoring effort to date of the cienega wetland system. It's good work that adds to the body of knowledge about the cienega."
The replacement water was delivered to the ciénega over the period of October 2009 through July 2011. The U.S. contribution was delivered before the pilot run started and another large portion of replacement water was delivered after the pilot run, said Cullom.
"There was fluctuation in water quality and salinity during the pilot run," he said. "However over the course of the monitoring there were no lasting adverse impacts to the ciénega."
Francisco Zamora, who managed the monitoring team, said the times when the plant was running and no replacement water was delivered, the vegetation seemed less healthy. However, it recovered once more water was delivered. He said it's not possible to tell from the monitoring program how long a dry spell the ciénega can recover from.
"The fact the replacement water came at a different time than when the desalting plant ran allowed us to see these short-term changes and learn that the cienega is resilient," said Zamora, director of the Sonoran Institute's Colorado River Delta Legacy Program. "The fact that the cienega can handle these short-term changes is good."
Flessa, who is also director of UA's School of Earth and Environmental Sciences, said, "This tells us they can run the plant and little will happen -- so long as they find replacement water for the ciénega."
However, he had expected changes from the April 4, 2010 earthquake, which occurred just before the pilot run started, and the three-day wildfire that burned about 80 percent of the ciénega in late March 2011.
In both cases, he was wrong – neither the earthquake nor the fire made harmful changes. If anything, the fire burned away accumulation of dead vegetation and returned nutrients to the soil, he said.
"It turned out to be a great way to find out the beneficial effects of fire. The bird populations this year were unaffected, productivity is up, and the ciénega is greener than ever," he said.
The team's report said, "The Ciénega de Santa Clara appears to be an ecosystem that is resilient in the face of short-term disturbances."
The agencies and organizations that forged the agreement to operate Yuma Desalting Plant's pilot run, provide replacement water and to support researchers to monitor the ciénega are: the Central Arizona Water Conservation District, the Southern Nevada Water Authority, Metropolitan Water District of Southern California, U.S. Bureau of Reclamation, the environmental organizations Pronatura, Sonoran Institute and Environmental Defense Fund, CONAGUA, Mexico's national water commission, SEMARNAT, Mexico's ministry of the environment, and the International Boundary and Water Commission.
To assess whether running the desalting plant affected the ciénega, the scientists placed instruments to record water quality and water level every 30 minutes at 20 locations all over the ciénega -- some in open water, some along the edges of the marsh, and others deep in cattail thickets.
Every month, the researchers used small boats to visit every instrument and download the information stored in it. The team also measured water flow into the ciénega from its main sources of water.
The researchers also assessed the bird populations during the breeding season and during the spring and fall migrations. The team used satellite images to measure the extent and health of the vegetation.
The team found the biggest factors affecting the ciénega's water budget are the inflow of water, the evaporation of water, and loss of water from the plants themselves, Flessa said.
During summer months, plants and evaporation consume more water than flows into the ciénega, increasing its salinity. In the winter, about half the inflow water drains through the ciénega to the lower basin. That flushing keeps salinity within the range tolerated by the plants.
During the plant's pilot run, salinity went up when water was diverted to the plant but no replacement water was being supplied. Salinity returned to normal levels when the replacement water was supplied and when the pilot run concluded, the report said. Other aspects of water quality were largely unaffected by the plant's operation.
"This story has a happy ending, and here's why," Flessa said. "It doesn't appear that there's been any lasting harm to the ciénega, and it demonstrates that by working together we can find solutions to tough environmental problems even across international boundaries."
He credits the scientific success of the project to cross-border interactions among scientists that were fostered by the National Science Foundation-funded Lower Colorado River Delta Research Coordination Network that began in 2005.
"It would have been really hard to put this team together on short notice had we not already had a respectful and collaborative atmosphere among the scientists," he said.
Funding for the monitoring project was provided by Central Arizona Water Conservation District, Metropolitan Water District of Southern California and Southern Nevada Water Authority, with additional funding from Mexico's Comisión Nacional de Áreas Naturales Protegidas and the Instituto Nacional Ecología.
The monitoring project was a collaborative effort among the University of Arizona, the Sonoran Institute (Tucson, Ariz.), Pronatura Noroeste (San Luis, R.C., Sonora), the Universidad Autónoma de Baja California (Mexicali campus), and Centro de Investigación en Alimentación y Desarrollo (Guaymas, Sonora) and the Upper Gulf of California and Colorado River Biosphere Reserve.
Researcher ContactsKarl Flessa
Mari N. Jensen | EurekAlert!
Foxes in the city: citizen science helps researchers to study urban wildlife
14.12.2018 | Veterinärmedizinische Universität Wien
Machine learning helps predict worldwide plant-conservation priorities
04.12.2018 | Ohio State University
Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.
Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...
The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.
Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...
What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...
A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.
The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...
A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.
Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...
12.12.2018 | Event News
10.12.2018 | Event News
06.12.2018 | Event News
17.12.2018 | Physics and Astronomy
17.12.2018 | Architecture and Construction
17.12.2018 | Life Sciences