Tucson group helping to restore Colorado River tributary
By Sophie J Everatt
In the distance, smoke rises from bonfires burning remnants of the salt cedar trees that previously inhabited the site. Salt cedar, considered an invasive species that was introduced for erosion control, currently dominates the sides of the Colorado River and its tributary, the Rio Hardy. The restoration plan involves replacing some of the salt cedars along the Rio Hardy with native willow and cottonwood trees.
“As a whole, it will enhance the ecological condition of the whole (riparian) corridor,” explained Francisco Zamora, the director of the Upper Gulf of California Legacy Program with the Tucson-based Sonoran Institute. A non-governmental organization, the institute describes itself as helping communities conserve and restore natural and cultural resources and manage growth and change.
“Birds are one of the main motivations” of the restoration project, he said.
Riparian areas of lush willow and tall cottonwoods once lined the banks of the Colorado and Hardy rivers, providing a safe haven for more than 371 species of migrating birds.
Zamora hopes the network of restoration sites the Sonoran Institute and others are creating – at a minimum rate of about 50 acres a year – along the Colorado River in Mexico will help the native cottonwoods and willows reclaim some of their lost land.
The Rio Hardy, or Hardy River, is a tributary that feeds into the dwindled lower course of the Colorado River, adding a little water to the dry riverbed. The Colorado once ran all the way to the ocean, but many dams and reservoirs along its route have diminished the flows.
The Hoover Dam was finished in 1935, creating Lake Mead, and the Glen Canyon dam was completed in 1963, creating Lake Powell. Between them, there is enough capacity to hold four times the annual average flow of the Colorado. The Colorado is now a decimated river that does not reach the ocean in most years.
The Rio Hardy exists now because of residual agricultural flows in the Mexicali Valley. The riparian corridor of the Hardy River is 80,000 acres. Its 16-mile stretch has eight tourist camps on it, drawing birdwatchers and hunters. One of these private tourist camps became the first restoration project on the Rio Hardy, with help from the Sonoran Institute and the Mexican conservation organization Pronatura.
Bird watching is popular along the Rio Hardy, but the birds in the riparian area have declined with the salt cedar infestation and lack of water. For instance, the Yuma Clapper rail, a large-footed marsh bird, has been listed as endangered since 1967, with no critical habitat designated.
Many people would “love to see, or at least hear, a Yuma Clapper rail,” said Karl Flessa, a “geoscientist turned conservation biologist” who heads the University of Arizona’s Department of Geosciences. He has been working with Zamora on riparian restoration and the issue of Colorado River water making it to the sea. He thinks that this is “an extremely resilient system” that has been abused, but would recover with even a little water permanently back in the Colorado River system.
Duck hunting also has been a popular draw to the area, but it has declined with the lack of water. If the Rio Hardy restoration helped revive the sport, this would increase tourism and have positive effects on the economy, Zamora indicated. As it is, at least one unemployed hunting guide is working on the restoration project.
Zamora, an oceanographer and coastal manager, has been working on community based restoration projects for more than 10 years now. Edith Santiago and Karen Schlatter, both with the Sonoran Institute, also work on the Upper Gulf of California Legacy Program.
In this particular 45-acre restoration project, the Sonoran Institute is combining forces with Pronatura Noroeste and the Mexican section of the International Boundary and Water Commission as well as with the U.S Bureau of Reclamation and Geosystems Analysis Inc., a private consulting firm.
GSA has been working on the seed germination of cottonwoods and willowsand on habitat restoration and revegetation. The firm used cuttings on the 1.5-acre site, but the plan calls for using seeds in the next 5-acre project, Santiago said. Cuttings produce identical genetic reproductions of their source tree, while seeds can create original combinations of genes.
“They (cuttings) still get germinated by wind, but genetic diversity is affected,” said Matt Grabau, an agricultural engineer and restoration scientist with GSA. Among other things, he is supervising the harvesting, storage and planting of cottonwood and willow seeds.
The willow seeds are like “grains of pepper” and are easy to collect, Grabau said. But they have no internal energy storage, so they must be planted on the surface to sprout. The cottonwood seeds are “fluffy,” he said, noting that the best way to prevent re-infestation of salt cedar is to plant cottonwood seeds close together. This mimics natural seed fall. Grabau said a density of one tree per square foot of land can create a canopy that can outcompete salt cedar.
Another facet of the Sonoran Institute’s work with the Upper Gulf Program is to secure “water for nature” throughout the Colorado Delta system. According to Zamora, “farmers are willing to sell their right to use the water” because they remember the days when the Rio Hardy flowed and understand “that water will benefit the river.”
The plan is to run the water secured by the institute across 300 meters (roughly 1,000 feet) from the irrigation canal to the site. They will have to construct a tube to carry the water uphill to the rest of the site. The restoration sites are areas of high groundwater, Zamora said. This way the trees, once established, will be able to continue growth without irrigation.
Local people are provided employment in the restoration programs, whether it is helping to clear the fields, maintain the irrigation ditches or plan the installation of the irrigation tube.
When a local engineer arrived, Zamora and his team gathered in the dusty field that would one day be a cottonwood/willow forest. They met for about two hours in the vast expanse of cleared land discussing the details of how to move the water uphill.
Local schools and tourism camps actively participate in the Adopt-A-River Program. More water in the river means increased access to recreation and fishing. This would have positive effects on the local economy and “both countries (would) benefit,” Zamora said.
Zamora sees the Rio Hardy restoration project as one piece of the Colorado River Delta restoration. Ultimately, Zamora said, “I want to be able to see the river connecting to the ocean again.”
Sophie J. Everatt is a graduate student in Geosciences whose primary interests are in ocean science and science translation.