EarthCache: Monitoring and Restoring the South Saskatchewan River—Urban Watershed Science in Action

EarthCache Question 1:
What is the scientific term for the process by which pollutants are carried from urban surfaces to natural water bodies via rain or snowmelt?
EarthCache Question 2:
Why are pollutants from storm drains particularly harmful to aquatic organisms?
EarthCache Question 3:
What are two responsibilities Saskatoon residents are encouraged to adopt to help reduce river pollution?
Earth Cache Question 4: 
Visit the coordinates provided and examine the stormwater outfall area. Describe the types of typical litter or runoff that could enter this outfall.  Identify any infrastructure visible at the site that help prevent or reduce pollution.
Photo requirement: 
Take a photo of yourself or your GPS etc. near the Trash Trap with the sign, or the river in the background (stay safe). Face not required.

You may post this log with the photo when you arrive on-site along the  Meewasin trail designed for walking, running, cycling, and enjoying the natural beauty of the river valley, however, If I don't receive the required information from you within 24 hours, I'll have to delete your log.  

DO NOT POST ANSWERS IN YOUR LOG BUT PLEASE ADD YOUR PHOTO TO THE LOG.   Please don’t provide the answers in when logging the cache online, but use “Send answers” feature or geocache email the cache owner.  Please remember to answer to the best of your ability. As long as you give it your best effort, we'll be happy to accept your responses.  You will probably find the answers you are looking for in this description page or the interpretive sign on site!

Location: Outfalls near Pembina Avenue (this location) and Prince of Wales Avenue, Saskatoon, Saskatchewan, Canada
Themes: Urban Hydrology | Watershed Management | Polluted Runoff | Restoration Ecology | Environmental Geography
Have you ever wondered where rainwater goes after it hits the ground in your neighbourhood? Let’s follow the journey of water—and the pollution it can carry—through a city and into the beautiful South Saskatchewan River.

I. Introduction: A Living Laboratory for Urban River Health

The South Saskatchewan River is one of the most significant freshwater systems in western Canada. Originating in the Rocky Mountains via the Bow and Oldman rivers, the South Saskatchewan flows eastward through southern Alberta and central Saskatchewan before joining the North Saskatchewan River at the Saskatchewan River Forks. The resulting Saskatchewan River continues eastward through Manitoba, eventually discharging into Lake Winnipeg. This river network constitutes part of the larger Nelson River watershed, which ultimately drains into Hudson Bay.

The South Saskatchewan River serves as a critical ecological, hydrological, and socio-economic resource. It supplies drinking water to major prairie cities including Saskatoon and supports diverse aquatic habitats, agricultural irrigation, hydroelectric generation, recreation, and traditional Indigenous land-use practices. However, anthropogenic pressures from urbanization, agriculture, and climate change have increasingly threatened water quality and aquatic ecosystem function.

South Sasaktchewan River and watershed courtesy Shannon1 CC1.2

This EarthCache introduces a pilot urban hydrology and pollution mitigation initiative taking place in Saskatoon, Saskatchewan. The project involves the deployment of engineered trash trap nets at key stormwater outfalls to prevent solid waste and contaminants from entering the river. Earth cache participants will explore the scientific and civic responses to non-point source pollution, a critical issue in modern watershed management.

Urban Hydrology: How Water Moves Through a City

II. Urban Hydrology and Polluted Runoff: Pathways to River Contamination

In natural environments, precipitation infiltrates soils, recharges groundwater, and is gradually released into streams and wetlands. In contrast, urban environments are dominated by impervious surfaces—pavement, rooftops, and compacted soils—which limit infiltration and accelerate overland flow. This results in stormwater runoff: the rapid movement of rainwater and snowmelt across the landscape into storm drain systems.  When rain or snowmelt flows over streets, parking lots, and rooftops, it picks up pollution along the way. This fast-flowing water often carries things with it—candy wrappers, pet waste, oil from cars, and more which  is scientifically known as polluted runoff or stormwater runoff, and it’s a major pathway by which urban pollutants reach rivers and other natural waters and is a big challenge for city rivers.

As this runoff travels over urban surfaces, it mobilizes various pollutants—oil and grease from roads, microplastics, metals, sediment, fertilizers, pet waste, and litter. These pollutants are conveyed untreated into storm sewers that discharge directly into natural water bodies. In Saskatoon, this includes numerous outfalls into the South Saskatchewan River.

III. Project Description: A Science-Driven Approach to Urban Water Quality

A watershed is like a giant bowl. All the rain and melted snow in the area flows and drains into a common water body, such as a river That means what happens on land—like spilling oil, littering, or using too much fertilizer—affects the water.  Activities anywhere in the watershed can impact water quality downstream.

In a collaborative initiative between the University of Saskatchewan (USask) and the City of Saskatoon, researchers have installed two large-scale trash trap nets on storm drain outfalls near Pembina Avenue and Prince of Wales Avenue. Each trap costs $15,000 and was funded through a $30,000 NSERC (Natural Sciences and Engineering Research Council of Canada) Alliance Grant.

The objective is to capture and analyze debris and particulate matter to better understand the composition, source, and volume of urban pollutants entering the river system. The trash trap project was created—to understand how land use in Saskatoon affects river health. This empirical data will support future urban water management policies and inform decisions about the scalability of this technology.

Overland flow, terrestrial runoff, polluted runoff or stormwater runoff (flooded streets during a rainstorm event)

IV. Restoration Ecology: Scientific Frameworks for River Recovery

This pilot program is led by two researchers from USask with specialized expertise in environmental toxicology and engineering:

• Dr. Markus Brinkmann, Director of the USask Toxicology Centre and Lead Principal Investigator

• Dr. Kerry McPhedran, Associate Professor in Civil, Geological, and Environmental Engineering and Co-Principal Investigator

Their research teams examine the contents of the trash trap nets and perform water quality assessments to identify chemical, physical, and biological pollutants. Then, they analyze the contents and test the stormwater to find out what types of pollution are entering the river—and where it’s coming from. The broader aim is to generate actionable knowledge that guides ecological restoration efforts and minimizes anthropogenic stress on aquatic systems.  

Why does this matter? Polluted water makes life harder for fish and aquatic insects. Trash, chemicals, and oil can hurt their gills, eggs, and food supply. Some pollutants are even toxic, poisoning the water and the creatures living in it. Aquatic fauna—including fish, benthic invertebrates, and amphibians—are sensitive to changes in water quality. Pollutants can interfere with reproduction, respiration, and trophic interactions, while solid waste can damage habitat and obstruct mobility. Many of these pollutants are bioaccumulative and persist in sediment and biological tissue.

Importantly, the trash traps are designed with a secondary anchoring system, preventing the net from detaching or releasing waste into the river, even under high-flow or high-volume conditions. This ensures mechanical integrity under variable weather and hydrologic scenarios.

Precipitation washing contaminates into local streams diagram courtesy Rowan Andrews CC4.0

V. Community Stewardship: Seven Practical Steps to Support River Health

Science and infrastructure alone are not sufficient to maintain the health of urban rivers. Public engagement and behavioural changes at the household level are equally essential. Residents of Saskatoon can support water protection efforts by adopting the following these actions:

1. Secure garbage bins to prevent windblown litter

2. Properly dispose of hazardous chemicals and household waste

3. Clean up after pets to reduce pathogen load in runoff

4. Use organic or low-impact fertilizers in landscaping

5. Maintain vehicles to prevent fluid leaks

6. Minimize the use of road salt and de-icing agents

7. Participate in community cleanups or river stewardship initiatives

VI. Geographical Significance of the South Saskatchewan River

The South Saskatchewan River plays a foundational role in shaping the Prairie landscape. The river cuts through glacial tills and Cretaceous bedrock, with significant geological exposures in areas such as the Meewasin Valley. Its flow regime is regulated by upstream infrastructure, including the Gardiner Dam and Lake Diefenbaker reservoir, which influence sediment transport, nutrient cycling, and seasonal hydrodynamics.

Downstream ecosystems—including the Qu'Appelle River basin and ultimately Lake Winnipeg—are influenced by nutrient and pollutant loading from upstream sources. Polluted runoff from Saskatoon therefore has cascading ecological impacts far beyond city limits, contributing to algal blooms, hypoxia, and water quality deterioration in distant parts of the watershed.

Stormwater carrying street bound pollutants to a storm drain for river and watershed discharge. Diagram courtesy TyDelargy cc4.0

VIII. Conclusion: Science-Based Stewardship of Urban Rivers

This EarthCache underscores the importance of evidence-based interventions in managing urban watershed systems. By integrating environmental engineering, toxicology, and public education, projects like this serve as blueprints for other cities seeking to safeguard river health. Through applied science, civic engagement, and responsible governance, we can reverse the trajectory of ecosystem degradation and protect freshwater resources for future generations.

If you are a student or researcher in environmental sciences, geography, urban planning, or ecology, consider how your academic training could contribute to similar interdisciplinary watershed initiatives.

Remember:
"Only rain should go down the drain!"

What can you see in the trash trap, or what would you think would end up in the trash trap? Photo of trash trap not required.  Remember safety first, and do not get too close to this stormwater drain, stay on the upper or top side of the fencing or railing please.  The railing is there for a good reason.

Infrastructure definition: The system of public works of a country, state, or region also : the resources (such as personnel, trash trap net, signage, sediment control signs, buildings, storm drain grate,  or vegetative buffers, equipment) required for an activity.

Bibliography:

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City of Saskatoon. (n.d.). Storm water system. Retrieved July 2, 2025, from https://www.saskatoon.ca/services-residents/power-water-sewer/storm-water/storm-water-system

ESEmag. (n.d.). USask, Saskatoon capture & analyze waste entering river. Retrieved July 2, 2025, from https://esemag.com/stormwater/usask-saskatoon-capture-analyze-waste-entering-river/

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SaskToday. (n.d.). Saskatoon, USask project to stop debris from flowing into river. Retrieved July 2, 2025, from https://www.sasktoday.ca/central/local-news/saskatoon-usask-project-to-stop-debris-from-flowing-into-river-6980772

University of Saskatchewan—College of Engineering (SENS). (2023). University of Saskatchewan teams up with Saskatoon to trap & analyze trash headed for river. Retrieved July 2, 2025, from https://sens.usask.ca/news-articles/2023/university-of-saskatchewan-teams-up-with-saskatoon-to-trap-analyze-trash-headed-for-river.php

University of Saskatchewan—Global Institute for Water Security. (2018). GIWS progress report 2017–18 [PDF]. Retrieved July 2, 2025 from https://water.usask.ca/documents/GIWS%20Progress%20Report%202017-18%20Final-web.pdf

Wikipedia. (n.d.). Saskatchewan River. Retrieved July 2, 2025, from https://en.wikipedia.org/wiki/Saskatchewan_River