Phytoremediation of Calgary Stormwater

Filtering pollutants and toxins from Calgary's rivers, by building constructed wetlands in the river, where the outfalls come out (the phytoremediation process).
Isabelle Klaassen
Grade 8


Concern for polluted stormwater going into Calgary rivers got me thinking of ways to filter pollutants and toxins out.

Polluted stormwater negatively impacts rivers, by introducing and spreading pollutants and toxins throughout the downstream environment. Contaminated rivers affect the living conditions of fish, plants, and other wildlife that use that water as their drinking source or habitat (, why is stormwater a problem, N.D.). Humans are also affected by polluted rivers in many ways, including contaminated drinking water, food supplies and even air quality.

In some Calgary communities, there are effective stormwater treatment designs built into the landscape. For 20% of total stormwater volume, these designs provide natural filtration using wet/dry ponds, rain gardens, and wetlands. However, where 80% of stormwater drains directly into rivers (Green Calgary. N.D.), that is the focus of this innovation project.


After understanding how mother nature works so well in naturally filtering/cleaning water, and observing how constructed wetlands are already used for filtering 20% of Calgary’s stormwater, it makes sense to expand this approach for the other 80% of stormwater that remains unfiltered. However, the challenge was to find an effective solution that can be easily installed and require minimal maintenance over time. 

The best solution considered was to build small scale, constructed wetlands in the rivers where stormwater is released through outfalls. This would work well in providing easy access for construction and maintenance, and is likely cost effective when compared to possible alternatives. An important aspect of this approach is that it uses natural materials and processes to replicate nature's own defenses, such as aeration and phytoremediation. The natural appearance of these constructed wetlands is another appealing factor.

This innovation starts on the shores of the Bow and Elbow Rivers. Polluted stormwater enters the rivers from the 800 outfalls within the city, where large rocks are arranged to control the flow of river water through the wetland, and allow for the gradual mixing of fresh water with stormwater as it flows downstream through six stages of each constructed wetland. This intentional mixing of water is necessary to maintain regular flow through the wetlands when there is little or no stormwater present.

STAGE I - Deep Pool: Similar to how a catch basin works, a deep pool (e.g. 2 M deep) will slow the water flow, and let heavy sediment and other pollutants settle at the bottom.

Source: City of Calgary. Pathway and river cleanup. 2020. Pathway and River Cleanup (

STAGE II - Medium rocks/rapids: Medium rocks will provide the opportunity for aeration to begin refreshing the stormwater. This will allow the water to absorb oxygen and release carbon dioxide and hydrogen sulfide.

Source: Living Water Aeration. What does aeration do to water? N.D. What Does Aeration Do to Water? – Living Water Aeration.

STAGE III - Aquatic plants: A combination of small and large aquatic plants provide phytoremediation, which absorbs chemicals in the water, and breaks them down so they are less harmful to the environment as organic material. These plants also provide habitat for small/micro organisms which contribute to water filtration and overall biodiversity.

Source: (Dordio, Palace, & Pinto, 2008).

STAGE IV - Small rocks/rapids: A mix of small and medium rocks will provide additional aeration of the water, allowing for oxygention and helping to cleanse the water further.

STAGE V - Deep Pool: A second deep pool allows the aerated water to calm down, and let any remaining sediments settle to the bottom.

STAGE VI - Aquatic plants: In this last stage, water flows through a dense area of small and large aquatic plants that absorb remaining toxins and pollutants, and provide additional habitat.

Constructed wetland dimensions

The proposed measurements of an initial pilot constructed wetland, is 50 meters in length and 10 meters in width. Making for a total footprint of 500m2. This was estimated to be a practical size and proportion for the Bow River, after walking along the shores and across bridges in making this observation.

This innovation is very adaptable, because it can be scaled for any location.


The following analysis has observations and learnings made during this project. It also provides thoughts about important information to obtain and planning to be done, in the next phase of developing this innovation to become reality.

Because this innovation has a flexible design, it can be scaled to adapt to any physical setting and should be very cost efficient. This means that constructed wetlands are likely possible at most outfalls in Calgary, and beyond!

To understand how well each pilot wetland site is working to remove pollutants, scheduled testing of stormwater would be required before and after flowing through the site. Regular river water quality at each site would also need to be measured for comparison.

Once a constructed wetland has been built, it should be monitored for a period of time to ensure the plants become well established and to adjust for any seasonal impacts (changes due to winter conditions, heavy storms, etc).

After the pilot sites have been working for several years, and test results have been analyzed, then the most effective site design can be installed on more outfalls throughout the city (and include the Elbow River).

These constructed wetlands should be included in annual river cleanup events.


The research indicated that constructed wetlands for treating stormwater is a practical approach, and it’s effectiveness should be evaluated in a realistic application. This was confirmed by the subject matter expert (retired Civil Engineer). Therefore, the conclusion is that additional planning is worthwhile to pursue, in establishing a pilot.

In order to evaluate and optimize effectiveness, it is proposed that three pilot outfall wetlands be constructed along the Bow River in Calgary: one downtown, one in the north-west, and one in the south-east. This is to allow for trial and error in finding what and where works best. Each of these sites should be designed a little differently, to test various combinations of stages and components. For example: different pool depths, rock sizes and spacing, plant types and spacing, overall dimensions. Consultation with water management experts (e.g. City of Calgary, University of Calgary) would be necessary in order to accurately determine these factors.

In the next stage of development (e.g. grade nine science fair), the following additional details should be figured out:

  • Specific rock types and sizes.
  • Aquatic plant combinations.
  • Cost calculations (e.g. materials, equipment, labour).
  • Dimensions and proportions of stages.
  • Effective water quality testing program (before/after wetlands).
  • Strategic locations and number of sites.
  • Consultation with the City of Calgary Stormwater Management department to help coordinate the pilot and obtain approval to proceed.

Upon the advice of my teacher, I will be submitting my innovation to the 2021 ‘Caring for Our Watersheds’ contest for Southern Alberta.

My goal is to eventually see constructed wetlands located at outfalls along the Bow and Elbow Rivers throughout Calgary, making our downstream water supply cleaner and healthier!


STORMWATER ISSUES: Why stormwater is a problem

Why is Stormwater a Problem? (n.d.). Department of Energy & Environment. Retrieved on 2020 December 05, from

EXISTING STORMWATER MANAGEMENT IN CALGARY: Storm drains in Calgary Stormwater management Storm ponds in Calgary Water treatment online tour

Storm drains in Calgary (2020). City Of Calgary. Retrieved on 2020, November 25, from

Stormwater management in Calgary (2020). City of Calgary.  Retrieved on 2020, November 25, from

Storm ponds in Calgary (2020). City Of Calgary. Retrieved on 2020, November 25, from

Water treatment online tour in Calgary (2020). City Of Calgary. Retrieved on 2020, December 04, from


Stormwater Management in China's Cities (2020). The Nature Conservancy. Retrieved on 2020, December 06, from

Denmark demonstrates footprint-free stormwater treatment method (2019). Stormwater Report. Retrieved on 2020, December 06, from

South Korea Waterworld (2020). WaterWorld. Retrieved on 2020, December 06, from

Sources and Solutions: Stormwater (2019). United States Environmental Protection Agency. Retrieved on 2020, December 06, from

STORMWATER TREATMENT CONCEPTS/IDEAS: Storm drain filters (Green Calgary (NA))

Water Treatment Solutions (2018). Lenntech. Retrieved on 2020, December 05, from

Ultra-Storm Drain Filters (2020). GEI Works. Retrieved on 2020, December 07, from


Pathway and River Cleanup. City of Calgary. (2020). Retrieved December 16, 2020, from

Splichal, A. (1970, May 09). What Does Aeration Do to Water? Retrieved December 16, 2020, from

Pariona, A. (2018, April 24). What Is Stormwater Pollution? Retrieved December 16, 2020, from

Invasive aquatic plants. (2020). Alberta. Retrieved December 16, 2020, from


Chazarenc, F., Gagnon, V., Comeau, Y., & Brisson, J. (2009). Effect of plant and artificial aeration on solids accumulation and biological activities in constructed wetlands. Ecological engineering, 35(6), 1005-1010. Retrieved on Dec.16.2020 from Effect of plant and artificial aeration on solids accumulation and biological activities in constructed wetlands - ScienceDirect.

Dordio, A., Palace, A. J., & Pinto, A. P. (2008). Wetlands: Water Living Filters?. Retrieved on Dec.16.2020 from Repositório Digital de Publicações Científicas: "Wetlands: Water Living Filters?", (


I would like to acknowledge my father, Paul Klaassen, for his encouragement and support in helping me develop my idea to build this project. I would also like to thank my Opa, Hugh Klaassen (retired Civil Engineer) for being my consulting expert.

Of course, it also goes without saying that my teachers and Principle at RT Alderman, have provided constant support and assistance along the way for which I am very grateful.

Lastly, I would like to thank the CYSF judges for taking the time to review my innovation!