Gunnison, river, 180 mi (290 km) long, rising in W central Colo. and flowing SW, W, and NW to the Colorado River at Grand Junction. It flows through magnificent canyons, notably the Black Canyon of the Gunnison, a national park. Gunnison Tunnel, c.5 mi (8 km) long, was built between 1905 and 1909 to divert the river's water to the Uncompahgre Valley for irrigation.
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