With Water, Life Returns to the Colorado River Delta
December 23, 2014
Seeds of a riverbank willow wait to be released by the wind along the Colorado River. An experimental pulse of water during the spring of 2014 was designed to regenerate habitat in the Colorado Delta. Cheryl Zook/National Geographic
Last spring, on the eighth day of the release of Colorado River water into its channel at the US-Mexico border – an event known as the “pulse flow” – I witnessed something extraordinary.
Like most mornings, I headed out with my National Geographic team before dawn to find the leading edge of the river as it slowly made its way toward the sea.
This pulse of water, made possible by a historic agreement between the US and Mexico, was sending water through the Colorado Delta for the first time in many years. Once a 3,000 square mile (7,770 square kilometer) expanse of wetlands, lagoons and cottonwood-willow forests, the Colorado Delta was now a desiccated place due to a century of dam-building to supply water to burgeoning cities and farms in the American Southwest.
That morning, as often happened during those days tracking the river, I ran into a group of scientists who were studying this grand ecological experiment.
Along with Karl Flessa, professor of geosciences at the University of Arizona in Tucson and Co-Chief Scientist of the monitoring team for the pulse flow, were freshwater biologist Rebecca Lester and marine ecologist Jan Barton from Deakin University in Victoria, Australia. They were kneeling and staring hard into the dark green rim of the river’s edge as it inched its way along the channel.
“Copepods,” they told me excitedly.
These microscopic crustaceans had lain dormant in the desert sands for a decade or more. The females lay a kind of leathery egg that can remain viable through extreme dryness for years and years.
Within a couple days of being wetted by the pulse flow, billions of tiny copepods had hatched. Some were now feeding on algae along the river’s fringe.
As I was taking in this mini miracle, Lester exclaimed, “Dragonflies are coming!”
And sure enough, scooting atop the river, drawn to the water to breed, were these big-eyed, winged, aquatic insects. Dragonflies eat copepods, and they were on the hunt.
Carp coming down the river were after the dragonflies. And Lester had also seen fish larvae eating the copepods.
“This is exciting,” she said. “You can see the food web developing within minutes of the water arriving.”
For me, it was the most literal and powerful experience of the “water is life” maxim one could imagine.
It was also a sign of what could be achieved by returning water regularly to the Colorado Delta, once one of the most biologically diverse desert aquatic ecosystems on the planet.
Water Brings Life
The pulse flow is part of a large-scale experiment in ecosystem restoration made possible by the landmark agreement between the US and Mexico known as Minute 319, signed in November 2012 and to be carried out over five years. It is the first time two countries have joined together to give water back to a river they share.
Minute 319 returns less than 1 percent of the Colorado’s historic flow to the delta—about two-thirds released during the pulse and another third in the form of sustaining base flows after the pulse. Strategically timed and placed, the water is sufficient to restore crucial habitat for the hundreds of species of birds and wildlife that historically called the delta home.
On another morning, I ventured out into the upper reaches of the river by canoe with Osvel Hinojosa Huerta, a wetlands conservationist with ProNatura Noroeste. Osvel can identify some 350 birds just by their sound.
Here, the river was flowing full from the pulse and even spreading onto its floodplain, nourishing native cottonwoods and willows that hadn’t had a good drink in quite some time.
We watched as the wind sent their seeds aloft. Many landed on the water’s surface to hitch a ride downstream. Eventually some would nestle into a moist bank to germinate. The hope was for thousands of new cottonwoods and willows to spring up as a result of the pulse flow, although non-native salt cedar would benefit from the slug of water, too.
As Osvel and I paddled down river, we eyed three muskrats along the bank. Ducks flew overhead, while rails and bitterns appeared to be looking for places to nest. It was migration time for warblers, sparrows and thrushes, and they were following the corridor of trees alongside the river.
“They react to cues,” Osvel said. “They see green and structure, and know it’s good.”
While canoeing 10 miles (15 kilometers), we saw or heard forty different species of birds – including white-tailed kite, ash-throated flycatcher, belted kingfisher, and four varieties of heron. It was music to an ecologist’s ears – and another sign of water bringing life to the Delta.
Stepping Stones of Habitat
The ultimate goal of the restoration underway is to create what Osvel calls “stepping stones” of habitat so that birds and wildlife can find enough places across the delta to feed, breed, rest and nest.
Two sites actively being restored by conservation groups – Miguel Alemán and Laguna Grande – are critical components of that habitat connectivity.
At Miguel Alemán, located in an old meander of the Colorado River, Pronatura Noroeste has overseen the planting of thousands of cottonwoods, willows and mesquite trees, grown from seed in a nearby nursery. A pipe carries water from an irrigation canal over to the site to irrigate the seedlings.
Further downstream at the Laguna Grande restoration site, workers overseen by the Tucson, Arizona-based Sonoran Institute planted tens of thousands of trees during 2014; the plan is to plant 200,000 more in 2015. To survive and grow, at least until the roots of the young trees can reach groundwater, these restoration sites need irrigation water, as do the little cottonwoods and willows that emerged as a result of the pulse flow.
Those sustaining “base flows” are provided through the Colorado River Delta Water Trust, which purchases both temporary leases of water and permanent water rights from delta farmers desiring to sell their water. The trust then delivers that water through irrigation canals to the areas targeted for restoration.
Change the Course, the water restoration initiative led by National Geographic, the Bonneville Environmental Foundation and Participant Media, has provided about 1 billion gallons of these base flows to date, with more planned for 2015.
Scientists Weigh In
Last week, the International Boundary and Water Commission released the early scientific findings from monitoring of the pulse flow. These findings only cover the period up to July 24, 2014 – four months after the water releases to the delta began.
Although preliminary, the results show beneficial recharge of groundwater, the successful delivery of flows to restoration sites, an increased number of migratory birds in open-water areas, and an overall green-up of vegetation.
Scientists used imagery from Landsat 8, a joint satellite project of NASA and the US Geological Survey, to compare changes in “greenness” between August 2013 (before the pulse) and August 2014. They calculated a 43 percent increase in green vegetation along the route wetted by the flow, and a 23 percent green-up of the riparian (or riverbank) zone.
It will take more study to know what types of vegetation benefited most from the pulse flow, and what impacts on wildlife the green-up will have.
Much work remains to be done to capture and assess the full ramifications of last spring’s pulse flow and the ongoing base flows that are re-shaping the delta landscape.
But if water continues to flow to the new islands of green in the delta, it’s hard to imagine that a diversity of life will not follow.
Help restore water to the Colorado River Basin by joining Change the Course, a project of National Geographic and partners. To return 1,000 gallons to the watershed, sign up online or text “River” to 77177.
Originally posted at National Geographic Newswatch