The temperature had finally dropped below 100 degrees as Juan Butrón and Alejandra Calvo set out toward the bank of the Colorado River, about 10 miles south of the Mexican border town Algodones.
They’re recording data from one of the transects scientists have set up to measure the effects of the “pulse flow,” as it’s called, the rush of water sent down the river valley over a two-month period this spring.
The water was released from Morelos Dam on the U.S.-Mexico border to mimic the spring floods that used to flow into the vast Colorado River Delta annually.
At the height of that flow, Calvo told me, water in the dry, sandy spot where I’m standing would have come up to my waist.
She and Butrón check a seed trap for cottonwood and willow — native trees that used to flourish along the now largely desiccated, tamarisk-choked riverbanks. Tamarisk, also called salt cedar, is an invasive shrub that thrives in poor soil with subpar water conditions.
Data from this and dozens of other sites around the Colorado River Delta will help scientists and policymakers determine how well this binational restoration experiment is working.
“This is a big opportunity to learn how to best use water for restoration,” said Karl Flessa, the University of Arizona professor who heads the team of scientists studying the effects of the pulse flow.
“Let’s face it, we all have to use water more efficiently. It has to be done on the farms, it has to be done in the cities, and it has to be done in restoration efforts.”
The once biologically rich Colorado River Delta has shrunk by an estimated 90 percent since dams and diversions siphoned off most of the water upstream. In an historic agreement signed by the U.S. and Mexico in 2012, water was allocated for habitat restoration in the delta for the first time in history.
Now that the pulse flow is over, conservation groups are charged with maintaining a base flow of water to keep seedlings alive at key restoration sites through the long, hot dry season.
They’ve launched a fundraising campaign — featuring Robert Redford and Will Farrell — to help pay for the water rights.
Non-governmental organizations play a huge role in this experiment in restoring the delta. They’ve been pushing Mexican and U.S. authorities to release water into the Colorado River Delta for more than two decades.
“We want to give a lot of credit to the NGOs,” said Sally Spener, foreign affairs officer for the International Boundary and Water Commission. That's the joint U.S.-Mexican agency that negotiates management of the Colorado River and other major rivers that cross the border. “It is safe to say, I think, that we would not have had this type of agreement without their support and active involvement.”
Minute 319, the agreement that made the pulse flow possible, expires in 2017 and will have to be renegotiated between the two countries.
The success of the experiment will help determine the future of habitat restoration in the Colorado River Delta.
