July 18, 2017
By Liz Clift
One of the easiest ways to get water from one place to the next is to let gravity do the work. While on the extreme end, this creates waterfalls, if the change in elevation is more gradual, it can create a meandering waterway. This is also the principle behind high line canals. The canals are constructed on the high line of elevation, and often meander to simultaneously follow the higher points of elevation while incurring only a small change in elevation over the course of a mile.
Construction on Denver’s High Line Canal (HLC) was originally completed in 1883, a mere 24 years after the gold rush that sparked white settlement in the Cherry Creek and South Platte River area. The original canal covered 71 miles, in what is now Douglas, Arapahoe, Denver, and Adams counties, and irrigated 20,000 acres. The canal loses about two feet of elevation for every mile it covers. Denver Water took over the canal in 1924, and maintains management of the canal.
Now, the canal covers 66 miles. Alongside most of the canal is a popular recreation trail. Although some areas of the canal are currently inaccessible to the public, the High Line Canal Conservancy is working with Denver Water and others to improve connectivity along the entire trail while preserving the natural character of the trail. Part of the vision planning, according to the High Line Canal Conservancy website, includes development work that is aimed toward increasing the amount of water the canal can hold and convey. The canal was designed to convey 750,000 million gallons of water a day, but currently only moves about 71 million gallons. There are multiple factors weighing into this lower-than-planned conveyance, loss to seepage and evaporation.
In fact, the canal is often dry. This is because Denver Water operates the canal only intermittently, to deliver water to the last remaining HLC customer, and to nourish trees that thrive on more water than is typical for this arid region.
There are plans to further develop and manage the HLC, including developing continuous trail connectivity* and temporarily detaining higher flows a bit longer through segmenting berms, which will provide some water quality improvements. This change may also alter the ecology of the canal slightly by shifting which soils are wet longer, although these higher flows are not expected to be a regular event. Vegetation that could be supported includes cottonwood (Populus deltoides), which provide broad and dappled shade to the canal, the adjacent recreational trail, and human and non-human (such as deer and foxes, as well as aquatic animals like crayfish!) users of the trail and the canal, as well as native shrubs like snowberry (Symphoricarpos albus) and willow (Salix spp.) which provide shelter and forage for many species of bird.
The canal also provides a nesting spot for turtles. A friend of mine was recently walking along the HLC, and came across a young painted turtle (Chrysemys picta). This is where I fully disclose that I love turtles, and seeing her picture on Facebook of the baby painted turtle made me want to immediately hop on my bike and start cruising along the trail in hopes of finding one also.
Painted turtles thrive in habitats with slow moving waters and soft bottoms with ample basking spots (such as partially submerged branches), which pretty much describes the HLC, when it has water, perfectly. They consume aquatic vegetation, small fish, insects, and crustaceans. As a child, I caught baby painted turtles with a net. They would often be basking on top of pockets of algae, their hind legs stuck straight out behind them, as though they were flying. I loved noticing the differences in their plastrons which range from pale yellow to red with dark markings in the middle. I loved that if the baby turtle was especially young and its shell hadn’t begun to harden, that I could feel its heart beating on my palm.
The increased connectivity proposed for HLC could provide more access for those who live along, or near, HLC—or have access to it from other Denver-area trails that intersect it—the chance to experience more of the biodiversity along the canal. Although in this post, I only talk about a couple of plant species, and turtles, the canal is an important migration corridor for a variety of animals, and also hosts many different plant species.
In addition, increased connectivity of the trail could increase beneficial health outcomes for those who access the trail. Daily physical activity, including biking, walking, and horseback riding (all of which are activities people engage in on portions of the trail) is linked to physical health benefits, as is general contact with green space, which more studies are indicating benefit our overall well-being. In The Nature Principle, Richard Louv writes, “In wilderness, and in natural cases or even natural urban parks, we find our senses….” He puts forward the idea that being in nature, and being present in nature (rather than still engaging in technology) helps nourish our deeper senses, and the very essence of our human intelligence.
Updates on the progress of the HLC can be found through the City & County of Denver and the High Line Canal Conservancy websites.
*The City & County of Denver has made conceptual designs of some of this increased connectivity available through public meetings and its website.
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