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…
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