� In Colorado, more than two dozen ditches or pipelines provide nearly 500,000 acre-feet of water annually by transmountain diversions. By basin, here are the major importers:

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South Platte River Basin: About 350,000 acre-feet annually from the West Slope, and about 20,000 from the Arkansas Valley. The Big Thompson Project, through the Adams Tunnel, brings in more than 200,000 acre-feet. Denver's Moffat and Roberts tunnels bring in more than 100,000 acre-feet annually. Aurora brings in about 25,000 acre-feet per year through Homestake and other Colorado River projects, with another 20,000 from Arkansas River basin water rights purchases. The Grand River Ditch adds about 18,000 acre-feet annually, for agricultural use. Arkansas River Basin: About 130,000 acre-feet annually from the West Slope. The largest diversion is for the Fryingpan-Arkansas Project through the Boustead Tunnel, about 55,000 acre-feet per year. About 38,000 acre-feet come annually through Twin Lakes, with another 25,000 acre-feet through the Homestake Tunnel. The Busk-Ivanhoe, shared by Pueblo and Aurora, brings more than 5,000 acre-feet, and Pueblo's Ewing and Wertz ditches bring about 3,700 acre-feet. Pueblo sold the Columbine Ditch, 1,300 acre-feet, to Aurora and Climax Mines last year. While all of those diversions come from the Colorado River basin, the Larkspur Ditch, being purchased by the Lower Arkansas Valley Water Conservancy District, brings about 200 acre-feet annually from the Gunnison River basin. Two small diversions, the Medano and Hudson ditches, have brought in about 1,000 acre-feet annually from the San Luis Valley into Huerfano County. Rio Grande Basin: Eight mountain ditches bring about 2,500 acre-feet of water into the Rio Grande basin each year, from the Dolores, San Juan and Gunnison basins.

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An acre-foot of water is 325,851 gallons and can support two to three homes for a year or about one-half acre (consumptive use) for crops.