High Line Canal

The High Line Canal is a man-made waterway, used for irrigation and recreation, that serves the Denver-Aurora Metropolitan Area. The High Line Canal (HLC) begins at a diversion dam on the South Platte River, some 1.8 miles (2.9 km) above the mouth of Waterton Canyon. From its headgate, the HLC runs 66 miles (106 km) to Green Valley Ranch, passing through Douglas, Arapahoe, and Denver Counties.

Origin of the name

The High Line Canal is not the only one so named. Others in Colorado include the Farmer’s High Line (which flows from Golden passing through Westminster and Thornton); the Government High Line (which irrigates Grand Junction and the surrounding Grand Valley); and the Rocky Ford High Line (located near Manzanola). Elsewhere in Colorado and in other western states, there are a number of additional canals named "High Line" or "Highline".

High Line canals are named after the engineering principle by which they are designed. The "high line principle" calls for a canal to follow the contours of the terrain, with a minimal drop in elevation per mile along its course. Thus the canal follows the line of highest possible elevation that allows its flow to be driven by gravity (so that neither pumping nor electricity is required for transporting the water). As a result, High Line canals typically have many twists and turns as they maintain elevation by traversing natural valleys first in an upstream direction, then back down the opposite side, then around dividing ridges, and so on.

A view along one of the narrow portions of the High Line Canal in Denver, Colorado

Construction

The High Line Canal was conceived in 1870 by Scottish businessman and early Colorado resident James Duff, who attracted English investors with his vision of turning the arid plains south and east of Denver into profitable agricultural land. For this reason, in its early years the HLC was sometimes referred to as the "English Ditch". It was constructed by the Northern Colorado Irrigation Company, and it was the first large irrigation canal built for the purpose of transporting and selling water to landowners who had purchased water deeds. Construction began in spring 1880 and was completed before November 30, 1883, at a cost of $650,000 dollars.

Wherever the path of the HLC intersected a perennial stream, a means had to be devised that would allow the two watercourses to cross (because the water in the streams was already allocated to other users). In most instances the original solution was to build a flume to carry canal water over the streambed. Some of these old wooden flumes are still in use: the Cheese Factory Flume over Lee Gulch, the Bennett Flume over Dad Clark Gulch, and the flume over Marcy Gulch. But over time many other flumes became unstable or were destroyed by floods. The HLC originally used flumes to cross over Plum Creek, Little Dry Creek, Cherry Creek, Sand Creek, and First Creek; but these flumes have since been replaced by gravity siphons (which carry canal water under the streambed).

The High Line Canal was originally 71 miles (114 km) long, with an average width of 30 feet (9.1 m). The HLC begins at an elevation of 5,542 ft (1,689 m), and terminates at an elevation of 5,410 ft (1,650 m), descending two feet every mile on its way to the plains, for a total drop of only 132 ft (40 m). The builders accomplished this by aligning the HLC with the elevation contours of the land through which it passes. As a result of its curvy path, the endpoints of the HLC are only about 30 miles apart on a straight line, while the actual length of the canal is over twice that distance. The benefit, however, was that the HLC could transport water from its point of beginning on the river to an area which lay approximately 350 feet higher than the nearest point on the same river. Theoretically then, any land situated between the canal and the river could be irrigated.

Developmental struggles

The company originally intended to place about 50,000 acres under cultivation, but it had difficulty securing sufficient water because earlier ditches held irrigation rights based on prior claims. Court cases regarding water rights dragged on for years. Because the High Line Canal's water rights were junior to 74 other canals in the South Platte watershed, it was frequently dry. Although the agricultural development that the HLC was meant to spawn never fully materialized, the canal nevertheless nourished the growth of both Denver and its eastern suburb, Aurora. In 1924, Denver Water took over the canal.

Irrigation

The HLC was designed to carry nearly three-quarters of a billion gallons of water per day, but actually averages only 71 million gallons. The canal today has a water capacity of 600 cu ft/s (17 m³/s). When the Rocky Mountain Arsenal was built in 1942, a lateral was built off the HLC (at about mile 64) in order to supply water to the chemical weapons manufacturing center, and until about 2008, the Rocky Mountain Arsenal National Wildlife Refuge was the furthest-downstream customer that was still taking water delivery via the HLC. However, the canal does not provide a very efficient method of delivering water; Denver Water estimates 60-80% of water in the canal is lost to seepage and/or evaporation. As a result, the Arsenal is now provided with recycled water instead of canal water, and as of 2011, the HLC's last customer is Fairmount Cemetery (at about mile 48). However, Denver Water still occasionally sends water further downstream, in order to water the trees that line the canal's bank. Denver Water has vacated the HLC downstream from mile 66.3 in Green Valley Ranch, and today there is very little visible evidence of the additional five miles that historically extended beyond that point.

Recreation

Although the HLC was originally built for the purpose of irrigation, today it is better known to Colorado residents as a source of recreation. The canal itself (and the water flowing through it) is owned by Denver Water, and the adjoining maintenance road was entirely closed to the public until 1970. Today it remains closed to all unauthorized motor vehicles, but approximately 60 miles (97 km) of the road have been improved for use as a recreational trail open to non-motorized users. Designated a National Landmark Trail, it is a popular destination for Denver’s outdoor enthusiasts and is open all year to hikers, bikers, joggers, and (along some segments) equestrians. The High Line Canal Trail is shaded for much of its length by mature cottonwood trees, and the surface of the pathway ranges from hard-packed dirt to concrete. The HLC Trail is maintained with the help of five other agencies:

Agency	Approx. distance	Description	Comments
Douglas County	8.7 miles (mile 1.2 to 8.9)	From Waterton Road to the west bank of Plum Creek.	This segment of the trail has a dirt surface, with some sandy and/or thorny sections. Heading upstream, the trail west of Waterton Road runs through a short section of private property before dead-ending at mile 1.2, where a fence blocks public access along the canal the rest of the way to its beginning. Heading downstream, the trail ends just beyond the gravity siphon on the west bank of Plum Creek. The next .4 miles of the HLC run through private property, and there is no direct connection to the trail on the east side of Plum Creek.
(private property; unmaintained)	1 mile (mile 8.9 to 9.9)	From the west bank of Plum Creek to the private Acequia bridge.	The canal runs through private property from mile 8.9 to 9.3, and there is no maintained trail access between there and the bridge at mile 9.9.
Highlands Ranch Metropolitan District	7.1 miles (mile 9.9 to 17)	From the north side of the private Acequia bridge to the south side of County Line Road.	The short segment of the trail on the west side of Santa Fe Drive has a dirt surface (mi. 9.9 to 12.5), while on the east side of Santa Fe the trail is hard-pack gravel. However, between mile 14.7 and 16.7, the HLC trail is coincident with the Centennial Trail, which has a concrete surface.
South Suburban Parks and Recreation District	19 miles (mile 17 to 36)	From the north side of County Line Road to the south side of Hampden Avenue.	Primarily this segment of the HLC trail has a hard-pack gravel surface.
(Wellshire golf course)	.9 mile (mile 36 to 36.9)	From the north side of Hampden Avenue to the west side of Colorado Boulevard.	The canal runs through a golf course, and this segment is not open to recreational users. This section can be easily bypassed using public roads (Jefferson Avenue and Colorado Boulevard).
Denver Parks and Recreation Department	13.2 miles (mile 36.9 to 50.1)	From the east side of Colorado Boulevard to the west side of Havana Street.	This segment of the trail is primarily surfaced with asphalt.
Aurora Parks and Open Space	13.7 miles (mile 50.1 to 63.8)	From the east side of Havana Street to Green Valley Ranch near 40th Avenue.	From Havana to Springhill Golf Course, the trail is primarily surfaced with concrete (to about mile 60.5). North of Springhill, there is no direct way to cross Sand Creek, and the remaining three miles of Aurora's portion of the trail (through mile 63.8) has two inaccessible segments and is generally not maintained for recreational use.
Denver Parks and Recreation Department	2.5 miles (mile 63.8 to 66.3)	From Aurora city limit near 40th Avenue to the west side of Picadilly Road.	The HLC runs through Green Valley Ranch, thus re-entering Denver city limits. This entire segment of the trail is surfaced with concrete.

In January 2009, The Trust for Public Land helped place a conservation easment on 20 acres (81,000 m²) of land adjacent to the popular High Line Canal Trail.

Wildlife

Deer, ducks, geese, turtles, hawks, herons, pelicans, raccoons, fox, coyotes, mountain lions, and various other animals have been spotted on or around the canal and surrounding trails. Three juvenile skunks, and two adult rabbits were observed on the Canal in June 2012 (personal observation).

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External links

• Denver Water: High Line Canal (official)
• Denver Water: High Line Canal (map)
• Douglas County: Open Space, High Line Canal Trail
• Trails.com summary of Highline Canal Trail
• City of Littleton: Irrigation Projects
• Detailed interactive map showing trail conditions, milepost locations, photos, etc.