Calgary Unearthed: Understanding our Water

Posted on May 28, 2024

Storm sewers and the Calgary storm sewer network are surprisingly easy to learn about. A quick internet search using the terms "Calgary" and "storm sewer" leads immediately to a large number of high-quality, varied, and related topics. One’s immediate impression is that we, and by extension our municipal government, are highly concerned with storm sewers and drainage.

First, let’s adjust our terminology. The City of Calgary website uses the terms “storm drains” and “catch basins” to describe the metal gratings embedded in our streets and sidewalks, and “stormwater system” to refer to the network as a whole. There are approximately sixty thousand drains in the system, most of which are designed to channel and transport water off the streets and properties that cover the city’s terrain. Some of these drains are designed to create holding ponds on specially selected streets, intersections, and public spaces to prevent the system from being overwhelmed in the case of a deluge. In short, the stormwater system exists to prevent flooding and property damage. However, to truly understand what this system does for us, it is helpful to wind back the city’s development to the distant but still historic past.

Let us begin by imagining the land around us as a vast rectangle covering about a thousand square kilometers, its long side stretching north to south and centered on the confluence of the Bow and Elbow rivers. This terrain is characterized by rolling hills and river valleys on the western side and flatlands, prairie, and the occasional ephemeral lake and wetland on the east. Prior to the arrival of Europeans, the short-grass prairie plant community (hardy, fire/winter/drought-resistant, soil-generating, carbon-sequestering, and able to withstand regular grazing by enormous herds of bison) spread widely across the landscape. This land was a grassy domain, an important thing to remember when considering storm drains. Grasses absorb water, and ecosystems based on grasslands are some of the most fertile and biologically productive habitats we have yet encountered. Urbanization largely does away with grasslands and their benefits, replacing them with a very different environment of concrete and pavement over which water moves easily but into which it is not easily absorbed. The water still flows, and as a result, we have to devise a system to ensure it doesn’t flow into our homes and businesses, hence the stormwater system.

Another habitat or natural water-processing system that urbanization disposes of is wetlands. The development of Calgary eliminated several wetlands, but the large one that was nestled on the benchlands of the Nose Hill escarpment in the city’s northwest comes readily to mind when considering the nature of water flow in our present situation. Wetlands process and purify water, provide enormous biodiversity, and (once again) mitigate flooding by absorbing and storing water. Vestigial remains of this wetland can be seen in Confederation Park, Confederation Golf Course, and the “wild” portions of West Confederation (formerly Canmore Park). These parks are well worth visiting for observation as well as for recreation. Homeowners and business proprietors in the lower areas of adjacent districts are understandably mindful of flooding concerns as a result. The buildup of the city replaced this functioning and important ecosystem, as well as its incipient water-processing capabilities, with a stormwater system that is actually part of the problem it is supposed to solve. The stormwater system moves dirty and polluted water swiftly to local rivers, and there is no question that the wetland it replaced was ecologically and economically superior, dispensing aforementioned benefits free of charge.

This is a familiar story but also incomplete. To finish our summary, we must mention, albeit briefly, the effect of dams, large-scale water storage, and diversion. This story is short but recounts a powerful effect. Calgary, particularly at the meeting of the Bow and Elbow rivers, was a city that flooded regularly until the major dams were constructed on regional waterways during the 1930s, 40s, and 50s. Flood prevention altered the ecology of the riparian (adjacent to river) lowlands and encouraged urbanization. Before the dams, the river valley looked quite different, most notably lacking tall trees, particularly near Prince’s Island and surrounding districts, and functioned differently. The silt and downwashed materials from the mountains and foothills are no longer deposited, and the rivers flow more slowly and scour their beds more deeply because of it. Fish are less numerous and smaller than they once were, and the grasses and smaller wetlands that filtered the overland flow of water feeding the rivers have largely been removed. Every so often, the river rouses itself, as we saw in 2013, reacquainting us with its power and function. But for the most part, we humans have control of it. Perhaps we should replace the word “control” with “responsibility” as it would be more accurate.

The waters still flow and bring us things we’d rather not think about and responsibilities that we’d prefer to leave to someone else. Yet the control and responsibility can be a source of satisfaction and an opportunity too. Every green space we curate functions to cleanse and absorb water; every tree we plant holds water in its root systems, branches, and leaves. When we collect rainwater and use it for the garden and plants, we participate in the flow, the cycle of water. Examples of responsible participation in the water cycle are all around us if you look for them. Understanding what the urbanization process has done to the natural operation of that cycle is key to realizing our place within it. We have to care for our city to live in it, and that means caring for the waters that flow through it as well.



Shawn Mueller

Communication Team Volunteer 

Green Calgary Association