From the air, the Grand Valley Water Users Association canal — 10 feet wide and 8 feet deep — tracks a serpentine 55-mile-long path across the mountain-ringed landscape of Mesa County, Colorado. It’s a line that separates parched, hard-baked desert and an agricultural nirvana of vast peach and apple orchards and swaying fields of alfalfa.

The future of this thin brown line that keeps the badlands of the Colorado desert at bay, however, is growing more uncertain by the day.

Since 2000, the snow that blankets the Colorado Rockies each winter — the source of most of the river’s water — has tapered off considerably. Last year it was less than half of normal. So far, the farmers here have gotten their share of water, but this year could bring the first emergency declaration by water administrators. That would mean that some “junior” water users — those whose allocations came later — may have to forego their share in favor of senior users.