Manmade flood helps bring life back to the Colorado River delta

Chuck Bednar for redOrbit.com – Your Universe Online
An engineered flood that helped bring water to previously dry reaches of the lower Colorado River delta has resulted in greener vegetation, the germination of new types of plant life along the river, and a temporary increase in the water table.
The flood, which is part of a joint US-Mexico project known as Minute 319, “worked,” said University of Arizona geosciences professor Karl W. Flessa, co-chief of the project’s science team. “A small amount of water can have a big effect on the delta’s ecosystem.”
The team of over 21 scientists released over 130 million cubic meters (more than 105,000 acre-feet) of water into the dry river bed below Morelos Dam, which straddles the border between the US and Mexico just west of Yuma, between March 23 and May 18 of this year.
“The groundwater was recharged, vegetation got greener than previous years and the water helped germinate new native vegetation. As a bonus, the river reached the sea,” Flessa explained, adding that people living along the river also benefited from the artificial flood.
“People in the communities along the river were just overjoyed to see their river again. When the surface water was there, people celebrated. Kids who’d never seen water in the river before got to splash in it,” he added.
Flessa was joined on the project by researchers from the Universidad Autónoma de Baja California, the US Geological Survey (USGS), the US Bureau of Reclamation, The Nature Conservancy, the Sonoran Institute and other universities, government agencies and private-sector organizations. He will present his team’s findings Thursday at the annual meeting of the American Geophysical Union (AGU) in San Francisco, California.
While most of the water soaked into the ground in the 37 miles located below the dam, the surface flow of the river reached regions located farther downstream that had been singled out for restoration, the researchers said.
The increase in groundwater revived vegetation along  the entire 83 mile route to the sea, they added. In fact, a comparison of satellite images captured by Landset 8 in August 2013 with those taken by the probe in August 2014, Flessa’s team calculated a 23 percent increase in the greenness of vegetation in the area between land and the river (also known as the riparian zone).
While the groundwater did eventually recede, the surface water led to the germination of new willows and cottonwoods – plants which typically germinate after natural spring floods, and whose roots are able to grow quickly enough to keep pace with the receding water table. The surface water also reached and helped establish native vegetation in pre-prepared locations.
“So long as the roots get down into the permanent water table, then you have established a new bunch of trees that will then live for 20, 30, 40 years. Those trees will attract birds,” Flessa said, noting that he and his colleagues have already observed an increase in avian numbers there.
The researchers said that learning where the newly germinated plants survived beyond the first summer will help them determine which areas will benefit the most from ecosystem restoration while requiring the least amount of water. They plan to continue monitoring the vegetation and hydrological response of the lower Colorado River Delta to the pulse flow.
Furthermore, the joint US-Mexican research team plans to monitor how the new plant growth will impact both local bird life and those migrating along the Pacific Flyway. They will monitor the environmental results of this engineered flood over the next five years, and their effort is being supported by federal agencies and environmental advocacy groups in both countries.
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