High Line Canal, National Recreation Trail and waterway in Denver metropolitan area, Colorado.

The High Line Canal is a man-made irrigation waterway and National Recreation Trail running about 66 miles (historically 71) from a diversion dam on the South Platte River above Waterton Canyon northeast through Douglas, Arapahoe, Denver and Adams Counties. It follows the contours of the land so gravity alone moves the water, which is why it twists through valleys and around ridges. A low dark metal footbridge with an arched top rail crosses the shallow channel between grassy banks.

The canal was built to irrigate about 50,000 acres, but its water rights ranked behind 74 other canals in the South Platte watershed, so it often ran dry. Denver Water took over the canal in 1924. In 2024 it transferred a 45-mile segment to Arapahoe County, with a conservation easement held by the High Line Canal Conservancy.

The canal path connects various communities and serves as a shared space where local residents regularly walk, cycle, and ride horses together. It runs through both residential areas and open spaces, becoming part of the daily rhythm of the Denver region.

Multiple entry points line the canal route, making it easy to access for hiking, cycling, and horseback riding activities. Maps and detailed information about conditions are available from the High Line Canal Conservancy.

The canal loses 60 to 80 percent of its water through seepage, unintentionally creating wetland areas alongside the path. This loss has inadvertently supported wildlife and shaped local ecosystems in unexpected ways.