21 Dec 2022

Dr. Nora Casson studies how environmental pressures affect water quality. Dr. Darshani Kumaragamage research focuses on the environmental impacts of agricultural practices. Together, they are working on understanding how climate change and human activities are affecting the Lake Winnipeg watershed.

On this episode the research question is, “how do we improve the water quality of Lake Winnipeg?”


KENT DAVIES: Lake Winnipeg, one of the largest freshwater lakes in the world. For many, Lake Winnipeg is an extremely valuable resource. A hotbed of aquatic life and biodiversity, the lake supports both commercial and angling fisheries as well as the traditional livelihoods for many Indigenous communities. Lake Winnipeg beaches are important for tourism, attracting visitors, and residents alike during the summer months. Lake Winnipeg is also a significant part of Manitoba’s Hydroelectric system. The lake’s regulated outflow is essential in the producing electricity for the province. But Lake Winnipeg needs help. For decades, the health of the lake has been seriously affected by harmful algal blooms that have increased in size and frequency, reducing water quality, impacting aquatic species, contaminating beaches, and threatening the viability lake activities, industries, and communities.[i]

NORA CASSON: If you look at a watershed, which is an area of land that drains into a stream or a lake, anything that happens in that watershed is going to influence the chemistry and the biology of the lakes and streams at the bottom of it.

KENT DAVIES: Meet Dr. Nora Casson, an associate Professor in the Department of Geography at the University of Winnipeg and Canada Research Chair in Environmental Influences on Water Quality. Casson researches environmental pressures, including climate change, and how it impacts water quality?

DARSHANI KUMARAGAMAGE: I have the advantage of the location. Manitoba is right at the centre of North America. So, that kind of makes it easy to collaborate with the other researchers.

KENT DAVIES: That’s Dr. Darshani Kumaragamage, Chair of Department of Environmental Studies and Sciences at the University of Winnipeg. Her research is aimed at increasing soil productivity and minimizing environmental pollution stemming from agricultural activities.

Together, they are working on understanding ways in which agricultural activities and climate change are impacting Lake Winnipeg and what can be done to improve its health.

DARSHANI KUMARAGAMAGE: University of Winnipeg is at an advantage, in kind of a location for this type of research. We have a lot of land, agriculture lands and then we have this Lake Winnipeg, the sixth largest lake in North America and we do see these algal blooms coming. So, the problem is right there.

KENT DAVIES: On this episode the research question is: how do we improve the water quality of Lake Winnipeg? From the University of Winnipeg Oral History Centre, you’re listening to Research Question- amplifying the impact of discovery of researchers of the University of Winnipeg.


KENT DAVIES: Dr. Nora Casson has always felt a strong connection to lakes.

NORA CASSON: I grew up mostly in southeastern Ontario, in a town called Kingston, but with a really strong connection to central and northern Ontario, particularly the lakes and the forests in that region. My dad’s family has a cabin on one of the lakes that they’ve had for eighty years. And so, my brothers and sisters and I all grew up spending the whole summer on the lake, canoeing, catching frogs, exploring the forest. So, I really grew up with a with a strong connection to the land.

KENT DAVIES: Dr. Darshani Kumaragamge shares a similar passion with the land where she grew up.

DARSHANI KUMARAGAMAGE: The soil has always fascinated me because I’m like, I mean, in Canada we are mostly see kind of the dark coloured soil. But in Sri Lanka you do get these different coloured soils and sometimes red, yellow, brown and sometimes very dark brown. And then that was something that fascinated me when I was a child.

I’m originally from Sri Lanka. And. Yeah, I was born there and I went to high school and university. When I think about my childhood, I was brought up in an environment totally different to what you see in Canada, like very resource limited country, agricultural country. That really kind of got me interested in agriculture. So, I got a bachelor of science in agriculture, from the University of Peradeniya. I did my master’s, too, in agriculture, specializing in soil science. But by then, in the university system in Sri Lanka, you can get a faculty position soon after graduation if you kind of get very good grades. So, I was hired as a lecturer and then I got a Canadian commonwealth scholarship to come to Canada. To do a Ph.D. degree, and I could have gone to any university in Canada and my first preference was Manitoba because I knew this is an agricultural province and also soil science was strong. I finished my Ph.D. in soil physical chemistry in 1991. But at that point, I didn’t even think of staying in Canada because I thought I should go and serve the country. So, I went back to Sri Lanka and I became a professor working at the University of Peradeniya in Sri Lanka until 2005. So, it after fifteen years, for one thing, because at that time there was a war in the country and I have two sons so thinking of their education I returned to Canada and then ended up— I started as a research associate at the University of Manitoba. And then I got this position as the Director of Environmental Studies and Sciences at the University of Winnipeg.

NORA CASSON: When I was in university, I worked as a canoe tripping guide. So, I spent a lot of time paddling around the wilderness. And then I was doing my undergrad and I was not sure what I was going to do with my life. And I got a summer job as a research assistant working at a long term research site in a forest near Saint Marie, Ontario. And my supervisor handed me a moisture probe and a temperature probe and she said, okay, your job for the summer is to walk around these forests, take measurements to help us understand how the water moves through these forests. And I thought, “woah, this is my job? You’re going to pay me for this? This is this is amazing.” So, the field work and the chance to spend time outside was how I first got into things. And then as I continued on, I did an undergraduate research project and a master’s and a Ph.D. and I discovered I really loved two things. I loved figuring out the puzzle of how ecosystems work because they’re incredibly complex. And you have to draw on a whole bunch of different disciplines and sets of knowledge to understand how they function. And also, I became really interested in understanding the ways in which our activities as humans are impacting these systems and how that understanding can help us manage the systems in a way that’s that sustainable and preserves them for generations to come.

A lot of my work is looking at patterns of stream flow and stream chemistry, looking at how those patterns have changed over time, and using other pieces of data to try and explain what’s driving those, what’s driving those changes. A lot of what we do is to understand how these processes work in pristine systems that that aren’t influenced by people very much so that when we move to a system that’s more heavily impacted by human activity directly, we understand the controls on the process. And then we understand where they’re sensitive, what makes them sensitive to climate, what makes them sensitive to land use change. And that helps us develop management strategies.

KENT DAVIES: A major focus of Casson’s research is on finding ways on how to limit the spread of cyanobacteria, otherwise known as blue-green algae in Lake Winnipeg.[ii] Blue-green algae are not really algae but are a phylum of photosynthetic bacteria that live in moist soils and water.[iii] Over the years, certain environmental conditions have driven blue-green algae growth, causing toxic algal blooms to occur.[iv] Since the late 90s, Lake Winnipeg has been under siege by harmful algal blooms which in some years has covered more than fifty percent of the lake’s surface. In order to understand the enduring spread of blue-green algae we must first understand what’s fueling their growth, phosphorus.[v]

DARSHANI KUMARAGAMAGE: Okay, so phosphorus is essential for life. It is an essential element because for example, our DNA, phosphorus is a constituent of DNA, and it is that involved in all the energy transfer reactions within the cell. So, we cannot do without phosphorus. And for plants, phosphorus is essential. Plants will grow if there is not enough phosphorus. That is the reason why we do apply phosphorus as fertilizers to crops because a lot of soils are deficient of phosphorus. And when farmers apply phosphorus, usually they apply the phosphorus in the form of fertilizers. Sometimes you do apply it in all that as organic farms do with like manure. To feed the growing population it is needed. However, when it gets lost from soils and ends up in waterways, that becomes a threat to the environment. The reason is the algae that sometimes grows in some of these water bodies and those algae also needs phosphorus for their growth. Phosphorus is the limiting nutrient for algae. And if it is not limiting, these algae will grow like crazy. And that is what we sometimes see in Lake Winnipeg. It is not when they are growing, but when those algae die and then it starts decomposing. The bacteria uses up all the oxygen. So, the water gets depleted of oxygen and that results in fish kills. And some of these some of these algae are harmful algae. They can produce toxins. And when they produce toxins that could threaten wildlife, that could threaten even livestock. And if we ingest some of this water, that it could it could affect our health as well.

KENT DAVIES: Agricultural activities, untreated human sewage, and even common household products have all contributed to phosphorus loading. However, it’s the size of Lake Winnipeg’s watershed, an area roughly forty times larger than the lake itself that has become the biggest challenge when it comes to limiting phosphorus.[vi]

NORA CASSON: Lake Winnipeg is at the bottom of the continent. We are like the bathtub drain of a really, really big part of North America. The watershed of Lake Winnipeg extends well beyond Manitoba. It goes into Saskatchewan and even a bit into Alberta. It crosses the border down into the United States. The problem is, in the last fifty or sixty years, the loading of nutrient pollution has really, really increased into the lake. This is a real agricultural area. So, there’s lots of different kinds of agriculture crops that have fertilizer, applied; animals that produce manure. There’s lots of cities and urban developments in the watershed. And so, all of the activities that occur across that really broad watershed are impacting what happens in Lake Winnipeg.

KENT DAVIES: Unfortunately, climate change is also exacerbating the problem.

NORA CASSON: Winters are getting shorter. Which is shifting the snow melt that happens at the end of the winter. And that snow melt is usually the main source of water to all of the lakes in the watershed, including Lake Winnipeg. Summers as a consequence are getting longer, meaning the ice free season is longer and the water temperatures are perhaps a little bit warmer. And then on top of that, the types of precipitation that we’re seeing are changing. The storms that we see during the summer are becoming more frequent and more intense. And those are different for the lake because it’s a big delivery of water and nutrients at a time when it’s not the normal snowmelt that that usually occurs. So, all of those climatic pressures are layered on top of this nutrient pollution issue, which makes it even more complicated to unravel what we can do on the landscape to mitigate the issue.

KENT DAVIES: Examining snowmelt runoff is an important part of research into phosphorus loading. Part of that research involves collecting extensive snowmelt samples in watershed areas, a task that can be challenging and requires a lot of coordination.[vii]

DARSHANI KUMARAGAMAGE: We had to transport runoff boxes to the fields and we had to rent two U-Hauls. I wasn’t comfortable driving the U-Haul and I got my son to drive it for me. And I don’t think I have ever transported that much of a kind of a huge items to the fields and installing that took like two or three days with about maybe twelve people. That is why we had a lot of collaborators and, and we had some students and postdocs, but they all were there. Every day we had to collect the snowmelt. So that snowmelt collection period was pretty intense. As soon as we collect the snowmelt, we record, the volume, get a subsample and some subsamples gets back to the lab and there has to be another team in the lab to analyze it. So, this had been going on for about fourteen days but it was rewarding though.

KENT DAVIES: Some of the samples end up here at the Soils and Vegetation Lab, part of UWinnipeg Physical Geography Lab Complex.[viii]

NORA CASSON: So, we use the lab for a variety of things, which is sometimes not the way in which people who just work in labs use labs, because we go out in the field and we collect these really messy samples. We collect bottles of water from streams and lakes. We collect cores of soil from the ground and we bring them back to the lab. And we look at all kinds of chemical and physical properties in the lab. We have instruments that measure very, very low concentrations of nutrients like nitrogen or phosphorus. The other thing we do in the lab is experiments where we bring these samples from the environment into the lab and we subject them to different treatments. And in the lab, we’re able to control conditions like the temperature, like the moisture. And so that that lets us investigate the processes in detail in a way that it’s difficult to do in the field because you don’t have any control over how hot it is.

In our lab a variety of students at different stages, ranging students who are kind of early in their undergrad, who are interested in gaining some exposure, upper level undergraduate students and master’s students who have research skills and are applying them in research projects that they direct independently. And then we have postdocs who are people who have finished their PhDs, who are coming to our lab to run their own research projects in collaboration with the rest of the people in the lab.

KENT DAVIES: According to Casson, her favourite part of her job is mentoring the next generation of environmental scientists.  

NORA CASSON: I have a really strong belief that you cannot have good science without good training and you can’t have good training without good science. The two things go hand in hand. And so, it’s absolutely my favourite part of my job to get to work with undergraduate students and graduate students and postdoctoral fellows to help them develop research skills as well as to work in collaboration with them on important and novel research projects that are that are going on. Students are the people who are going to go on to save the world, they’re going to solve climate change and protect our lakes. And they need those collaborative skills. So they need to be built into undergraduate and graduate curriculum.

KENT DAVIES: For Casson, Manitoba is the ideal place to study water quality, where research can lead to action.

NORA CASSON: It is a really good place to study water quality because we have a lot of water quality problems. And so, we’re located in a place where, where we see the impacts of our activities on our streams and lakes and where people are concerned about them. And also that means that we’re in the place where we can change our behaviours, whether that’s through government policy, whether that’s through different practices in agricultural systems, whether that’s through changing the way we deal with sewage. We have a lot of ability to, to make changes to our behaviour which could improve water quality. So, it’s a great place to study this.

KENT DAVIES: Manitoba is also in close proximity to the Experimental Lakes Area, one of the most important freshwater research stations in the world. Experiments at the research site were critical in understanding the connection between phosphorus and blue-green algal blooms.[ix]

NORA CASSON: So, the Experimental Lakes area was originally set up as a government research station in the sort of sixties and seventies, and a lot of the original work that was done there was around the problem of algal blooms. So, in a really famous experiment, they took a lake, divided it in half with a big, heavy curtain. They added phosphorus to one side and nitrogen to the other side. And the side that had phosphorus turned green demonstrating that that phosphorus was the nutrient most responsible for these algal blooms that were that we’re worried about. And so, they’ve done all kinds of these experiments over the years but in addition to all this amazing and important experimental work, they have done something that’s really difficult to do, which is quietly maintained records of really boring things. For decades and decades, they’ve monitored how much water is in all the streams and all the lakes. They’ve monitored the chemistry of the streams in the lakes, they’ve monitored the rain and the temperature. And as a result, we have this incredibly rich and very unique data set that lets us look at long term trends in streams and lakes and climate. And it’s three and a half hours from Winnipeg. We’re incredibly lucky to be here and to be able to work there and to have all of the world class scientists who do those experiments are either based in Winnipeg, where they come to Winnipeg in order to get to the site. So that is really cool.

KENT DAVIES: So, back to the research question, how do we improve the water quality of Lake Winnipeg?

NORA CASSON: So, I think the first thing I like to say is these we have identified these water quality problems in Lake Winnipeg and there has been, especially for the last fifteen or so years, lots of research activity directed at solving this question. So, we have learned a lot about what’s going on in the watershed and why we have so much phosphorus in the lake. And it’s a complicated answer, but it’s not just one thing, but a big thing that we’ve learned is if you have water that’s moving quickly over the landscape to the stream and ultimately to the lake, that water carries with it a lot of phosphorus. If you’re able to hold that water back on the landscape and just slow it down, then you can stop some of that phosphorus from getting into the lake. So, there’s a few different ways you can do that. The first thing you can do is to protect the natural wetlands that exist in the watershed, because that’s what those wetlands do naturally. And in fact, we used to have many more wetlands all across the landscape that would hold the water back. It would move slowly through the wetlands and the nutrients in the water would feed the cattails and the vegetation that grows in in wetlands. We can also do other mitigation measures like constructing wetlands. And in particular, we can use what we’ve learned about the landscape to put our resources around constructing wetlands in the place where you’re going to get the best bang for your buck. There are other, more technical things that can be done. There are improvements that can be made to the way sewage is handled, both from big municipalities like Winnipeg and upgrades to our sewage treatment plants, as well as in small communities that have sewage lagoons that release their sewage lagoons into the streams a couple of times a year. And then finally, there’s a set of research looking at what we can do in agricultural fields to help hold the phosphorus back. The farmers will apply phosphorus to the field because it’s a fertilizer and plants need it to grow. But it’s often applied in excess and then that excess runs into the runs into the stream. And so, some of the mitigations are behavioural. You can figure out what the best time and the best place and the best way to apply the fertilizer is so that you don’t have too much running off into the stream. You can make modifications to the to the landscape that that slow the water down as it moves from the field to the stream. And then you can also do stuff in the field itself. So, you can do things like change your tilling practices, or you can do the types of stuff that Darshani and I are investigating around chemicals that you can apply to the field that will help hold the phosphorus back.

KENT DAVIES: Working with a variety of groups including farmers, Kumaragamage is conducting comparative research studies of different types of manure, and synthetic fertilizers, to find out which soil amendments suffer the greatest losses and what possible changes can help reduce phosphorus loss during snowmelt.[x]

DARSHANI KUMARAGAMAGE: So, this phosphorus with snowmelt run off stuff started with my NSERC discovery grant. And with that, we got new grants from Environment and Climate Change Canada. And then we had follow up grants from Ag-Action, it is from the government of Manitoba, from Manitoba Agriculture, and that as well as Lake Winnipeg Foundation. So, all that research was focusing on evaluating different soil amendments and how effective they are in reducing phosphorus loss to snowmelt. So, we did laboratory studies at first. And once we found that some of these amendments are very effective, and then we moved our research to the field. So, we have done now two field seasons, but still we feel that we need to do more field seasons to get to some conclusions and one other thing that I am doing in the future is to get these amendments blended rather than just apply a single amendment. And also, we are thinking of doing some kind of a field scale research where we can find from which areas, which kind of soils release more phosphorus to snowmelt. So, if we can do that and make a map of it that might help future research as well as anyone using kind of like using the land.

KENT DAVIES: Kumaragamage, Casson and their research team are continuing to investigate where, when, and how phosphorus loading is occurring in the Lake Winnipeg watershed.[xi] Knowledge that is critical for effectively managing algal blooms in the future and for developing strategies for remediation. Assisting in this endeavor are community groups like the Lake Winnipeg Foundation, who not only advocate for ways to protect Lake Winnipeg from phosphorus loading but also help researchers collect valuable water samples.[xii]  

NORA CASSON: One of the knowledge gaps that we have is we just do not have the person power to look at all of the different streams that drain into the main rivers, that drain into Lake Winnipeg, because there’s a lot of streams and the water is mostly moving in the streams at a time that’s really inconvenient when the snow is melting and the roads are muddy and it’s hard to it’s hard to get out there. So one of the really incredible things that the Lake Winnipeg Foundation has done is set up a whole community of citizen scientists, and they’ve come up with a really simple protocol for people who live near streams or who are interested or concerned about streams, to go out to those streams on a regular basis, sometimes daily, when the snow is melting to collect the water samples to bring back to the lab to see how much phosphorus is in the streams. That’s a really cool approach, both because it solves this problem that we have, which is that we just do not have enough information about all these streams. And also, it engages people in the science, and it helps people feel ownership over the issue and helps them be part of the part of the solution. It’s been it’s been really, really great to be a part of that, both by collaborating with Lake Winnipeg Foundation on some of our work, using their data to frame some of the questions that we have about processes in streams. And also right now, we’re running their phosphorus samples in our lab. So, it’s a partnership where we’re helping each other out.

KENT DAVIES: The Lake Winnipeg Foundation is also calling for increased wetland protection, the adoption of water-retention practices in agricultural communities and the implementation of upgraded sewage treatment systems to improve the health of Lake Winnipeg. Recently the federal, provincial and municipal governments committed to funding upgrades to the North End Sewage Treatment Plant in Winnipeg, which will help reduce the amount of phosphorus loading from the city’s wastewater.[xiii] However, researchers and advocacy groups alike maintain it’s imperative that all parties who contribute to phosphorus loading, not just those in Manitoba have to work together to minimize their inputs if Lake Winnipeg has a chance at improving water quality in the long term.[xiv]

DARSHANI KUMARAGAMAGE: So, the contribution from Manitoba is estimated to be less than fifty percent. When it comes to agriculture, the estimated contribution is about fifteen percent. So, one thing we have to realize is that one sector alone cannot solve the issue. All sectors have to try to minimize their contribution of phosphorus towards the lake water engagement.


KENT DAVIES: You’ve been listening to Research Question. Research Question is produced by the University of Winnipeg Research Office and Oral History Centre.

The University of Winnipeg is located on Treaty 1 Territory, the heartland of the Metis people.

Written, narrated and produced by Kent Davies.

Our theme music is by Lee Rosevere.

For more on University of Winnipeg research, go to uwinnipeg.ca/research

For more information on the University of Winnipeg oral history centre, and the work that we do, go to oralhistorycentre.ca.

Thanks for listening.


[i]Water Quality Challenges in Lake Winnipeg,” Lake Winnipeg Foundation, July 22, 2019. Accessed November 30 2022; “State of Lake Winnipeg: 1999 to 2007,” Environment Canada, Manitoba Water Stewardship, June 2011. Accessed November 23, 2022.

[ii] Diane M. Orihel, Helen M. Baulch, Nora J. Casson, Rebecca L. North, Chris T. Parsons, Dalila CM Seckar, and Jason J. Venkiteswaran. “Internal phosphorus loading in Canadian fresh waters: a critical review and data analysis.” Canadian journal of fisheries and aquatic sciences 74, no. 12 (2017): 2005-2029; Reducing phosphorus runoff, University of Winnipeg, accessed, January 27, 2023.

[iii] Harmful algal blooms on Lake Winnipeg, Lake Winnipeg Foundation, accessed November 30, 2022.

[iv] Diane M. Orihel, Helen M. Baulch, Nora J. Casson, Rebecca L. North, Chris T. Parsons, Dalila CM Seckar, and Jason J. Venkiteswaran. “Internal phosphorus loading in Canadian fresh waters: a critical review and data analysis.” Canadian journal of fisheries and aquatic sciences 74, no. 12 (2017): 2005-2029.

[v] Vicki Burns, Lake Winnipeg Blue-Green Algae, Save Lake Winnipeg Project, accessed November 30, 2022; Nancy Macdonald, “Canada’s sickest lake,” Maclean’s, August 20 2009. Accessed November 30, 2022.

[vi]Lake Winnipeg: Nutrients and Loads: Status Report,” Manitoba Environment, Climate and Parks, Water Science and Watershed Management Branch, April 2022. Accessed November 30, 2022; “State of Lake Winnipeg: 1999 to 2007,” Environment Canada, Manitoba Water Stewardship, June 2011. Accessed November 23, 2022.

[vii] Kumaragamage, Darshani, Chamara S. Weerasekara, Madelynn Perry, Olalekan O. Akinremi, and Doug Goltz. “Alum and Gypsum Amendments Decrease Phosphorus Losses from Soil Monoliths to Overlying Floodwater under Simulated Snowmelt Flooding.” Water 14, no. 4, 559. January 16, 2022. Accessed November 23, 2022.

[viii]Geography Facilities,” UWinnipeg, accessed November 30, 2022; Reducing phosphorus runoff, University of Winnipeg. Accessed January 27, 2023.

[ix]Exploring Harmful Algal Blooms,” IISD Experimental Lakes Area, April 2, 2016. Accessed November 30.   

[x] Ahmed Lasisi, Darshani Kumaragamage, Inoka Amarakoon, Doug Goltz, Nora Casson, Srimathie Indraratne, and Henry F. Wilson. “Effectiveness of Soil Amendments to Reduce Flooding-Induced Phosphorus Transfer during Snowmelt from Agricultural Soils to Waterways.” In ASA, CSSA, SSSA International Annual Meeting. ASA-CSSA-SSSA, 2021; Chammi P. Attanayake, Randombage Saman Dharmakeerthi, Darshani Kumaragamage, Srimathie Priyanthika Indraratne, and Doug Goltz. “Flooding-induced inorganic phosphorus transformations in two soils, with and without gypsum amendment.” Journal of Environmental Quality, 51(1), 90-100, December 29, 2021; Emily Van, Darshani Kumaragamage, Geethani Amarawansha, and Doug Goltz. “Ferric Chloride Amendment Reduces Phosphorus Losses from Flooded Soil Monoliths to Overlying Floodwater,” Canadian Journal of Soil Science, September 3, 2022. Accessed November 30, 2022.

[xi]Darshani Kumaragamage – Mimimizing Phosphorus,” UWinnpeg, accessed November 30, 2022; “Harmful algal blooms investigated in water bodies across Canada,” UWinnipeg, September 13, 2017, accessed November 30, 2022; Reducing phosphorus runoff, University of Winnipeg. Accessed January 27, 2023.

[xii] “Lake Winnipeg Community-Based Monitoring Network,” Lake Winnipeg Foundation, accessed November 30, 2022.

[xiii] Glen Dawkins, “Feds, province, City invest over $550M into North End Sewage Treatment Plant upgrades,” Winnipeg Sun, August 16, 2022. Accessed November 30, 2022.

[xiv] Cameron MacLean, “5-year fight removes less than 1% of phosphorus from Lake Winnipeg basin”. CBC News Manitoba, September 17, 2017. Accessed November 30, 2022.