How farmers can help keep salt out of the Colorado River

Water spritzed from sprinkler nozzles suspended a few feet above the ground, wetting the grass below. The spigots dangled from a center pivot — an irrigation structure that rotates around a fixed point — slowly circling a field on Mark LeValley’s family ranch, high on a mesa in western Colorado. Millions of years ago, a vast sea covered this area, creating the layer of salt-rich earth that lurks beneath LeValley’s boots. Talking over the rush of water through the sprinkler, LeValley described what it took to irrigate this field before he and his brother, Hank, installed their first center pivot. Using shovels, dams and ditches, they shunted water from an open canal across the land, flooding it. Excess water ran into the ground, collecting and dissolving salt from the ancient seabed as it trickled toward the Colorado River.

Over the last two decades, the LeValleys have converted about a third of their irrigated hay fields and pasture to sprinkler systems, a more efficient method that helps them grow more hay and doesn’t leave behind much surplus water — or sweep up extra salt. Today there are five center pivots on the ranch, the newest installed last year. They purchased it through a federal cost-sharing program created to help farmers in parts of the Colorado River Basin switch to more efficient irrigation systems. It’s motivated not by water savings per se, but by salt.

Almost 40 million people rely on the Colorado for some or all of their drinking water. The river also supports millions of acres of irrigated farmland in the West, a handful of wildlife refuges and recreation areas, and nearly two-dozen tribal nations as well as farms and cities in Mexico. But its tributaries carry an unwelcome stowaway: salt. So much salt collects in the Colorado that the U.S. sustains hundreds of millions of dollars in crop losses, corroded pipes and other infrastructure woes every year. In 1974, Congress initiated a basin-wide program for dealing with the problem, spurring the construction of a few large projects designed to rein in some of the salt. But the best way to keep salinity in check might involve the combined effect of smaller, incremental changes to irrigation systems, implemented farm-by-farm and ditch-by-ditch, designed to keep salt in the ground and out of the water.

The Colorado picks up about 9 million tons of salt each year by the time it passes Hoover Dam below Lake Mead. Salt springs and rock erosion contribute about half of that. The rest derives from human activities like flood-irrigating fields and running water through leaky ditches, creating seeps that dissolve salt on their way to the river.

More than 800,000 tons of salt per year come from agricultural irrigation in a small area called the Lower Gunnison Basin, where LeValley’s ranch is located. The basin is one of about a dozen places in Utah, Wyoming and Colorado that federal agencies have targeted for salt control, many of which have seen large improvements. Only about 10 percent of the Lower Gunnison’s ditches are lined or piped, and efficient sprinkler or drip systems water only about 5 percent of the basin’s irrigated acres. Relatively inefficient irrigation combined with the region’s underlying layer of ancient, salty seabed make the Lower Gunnison a prime spot for further addressing salt, says Beth Karberg, the state salinity field coordinator for the basin. “We really stand head and shoulders above anybody else,” she says.

As a result, the Bureau of Reclamation and the Natural Resources Conservation Service fund programs to help ditch companies run open canals through underground pipes and farmers irrigate more efficiently. Over the last decade, for example, the Bureau of Reclamation has poured about $60 million into canal improvements in the Lower Gunnison.

But while those changes represent water savings for farmers and ditch companies, they count as losses elsewhere. Water soaking through the ground from canals and flood-irrigated fields recharges aquifers and nourishes plants and wildlife. Those relatively lush ditch-side areas, however, are already altered ecosystems, says Jake Hartter, the watershed coordinator at the Western Slope Conservation Center in Paonia, Colorado. “Cottonwoods don’t really belong on the sides of shale-y mesas in a natural environment,” he says. Canal-piping projects often include money to restore habitat elsewhere. That can be an opportunity to rehabilitate the streamside areas where cottonwoods do belong, Hartter says, where they flourished before water was diverted into ditches.

Shifts in irrigation practices can alter local ecosystems and boost ranchers’ bottom lines — but they also have basin-wide benefits. Every dollar spent reducing salt in the river upstream can save $3 or more in the lower basin, Karberg says. The savings come from averting salt-related costs like replacing corroded household and industrial pipes and appliances, crop losses and the expense of treating water. “The impacts are really significant to the downstream water users,” Karberg says. “Salty water just costs money.”

Note: This story has been updated to reflect the amount that the Bureau of Reclamation has spent on canal improvements in the Lower Gunnison Basin in recent years.

Emily Benson is an editorial fellow at High Country News. Follow @erbenson1

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