International Rainy-Lake of the Woods Watershed Board

Water Quality FAQ

How is water quality data collected?

Climate Change

How is climate change affecting the basin?

Algal blooms and Algal toxins

What causes algal blooms?

Are algal blooms increasing in the Rainy – Lake of the Woods basin?

Are all algal blooms harmful?

Nutrients and internal loading

What are “nutrients” and which are of concern in the Rainy – LoW Basin?

What is a phosphorous budget?

What are TMDLs and TP?

What are the sources of phosphorous for the Rainy – LoW Basin, and how does it get released from the system?

What are we still working to understand?

What contaminants threats exist in the basin?

How does mining pose a contaminants risk to the basin?

How is mercury a contaminant of concern for the basin?

What about other contaminants like PCBs, pesticides, endocrine disruptors and pharmaceuticals?

Water Levels and Erosion

What are some concerns related to controlling water levels?

Where and how is erosion a problem?

Aquatic Invasive Species

What are some aquatic invasive species of concern?

How can I help limit the spread of aquatic invasive species?

How is water quality data collected?

In the Rainy-Lake of the Woods basin, there has been widespread collection of data by the Ontario Ministries of Environment and Natural Resources (OMOE/OMNR) and by the Minnesota Pollution Control Agency (MPCA). Areas upstream of the Lower Rainy River have been monitored by Voyageurs National Park (VNP) and by MPCA and in many areas by citizen monitoring groups.

Much of this data collection has been through routine monitoring whereby samples are collected and analyzed for the same substances in the same locations either annually or on a rotating basis. Other data have been collected in connection with special studies that are limited in scope and these are often directed by universities or through non-governmental organizations to answer specific questions about local ecosystem health – for example, using satellite images to track the spread and severity of algal blooms between years. The result is that
a great deal of data exists and much of this information
is being combined to answer compelling questions that remain about water quality throughout the basin.

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Algal blooms and Algal toxins

What causes algal blooms?

Nuisance algal blooms are often caused by phytoplankton called cyanobacteria. These algae are often blue-green in appearance (hence
 the common name blue-green algae), although they can range in colour from green to red. A very high concentration of cyanobacteria is called a bloom, and when algal cells rise to the water surface it is called a surface scum. Blooms often occur in still or slow-moving water during the warm summer months. Algal blooms occur in many areas of Lake of the Woods and in some areas of the Rainy Lake sub-basin.

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Are algal blooms increasing in the Rainy – Lake of the Woods basin?

Algal blooms are recorded in historical records from the area as long as 200 years ago, but there is a perception that blooms have become worse in recent years and there may be some evidence that this may be correct. 

Recent studies have shown that warming trends in the past few decades have led to changes in the algal communities in the lakes in many areas of the basin. These changes in the climate and the environment are known to favour cyanobacteria (blue-green algae).  At the same time, the input to the lake system of phosphorous, the nutrient that is most responsible for feeding algal blooms, has actually either not increased or has been reduced, which makes the increase of algal blooms somewhat counter-intuitive. 

A lot of scientific research has been focused on this problem over the past few years, and the science has revealed a complex process at work in the Lake of the Woods.  While climate change is providing ideal conditions for algal blooms to flourish, particularly by extending the growing season (more ice-free days means more days for algae to grow), at the same time nutrients in lake sediments are remaining available to algae instead of getting flushed out of the system. 

Bloom intensity also increases during warmer, drier conditions that have been the trend into the later part of summer / early fall over recent years, too.

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Are all algal blooms harmful?

In addition to algal blooms being aesthetically unpleasant, some species of cyanobacteria naturally produce and store potentially harmful toxins that are released into the water.
 The levels that accumulate depend
 on location and severity of the bloom. Toxins produced by certain cyanobacteria can be hepatotoxins (affect the liver) which are prevalent in Canadian fresh waters or neurotoxins (interfere with the transmission of signals in neurons) which are much less common. Microcystins are prevalent hepatotoxins in Canadian water (including the LoW basin) and microcsystin-LR (MCLR) is among the most common of over 70 types of microcystin.

Elevated MCLR concentrations in LoW have been reported during the summer months by many researchers. As a general rule it is advisable to avoid drinking and body contact with water during times when algal blooms are occurring. Water samples cannot be used to assess the safety of the water for drinking since toxins can appear at any time.

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Climate Change


How is climate change affecting the basin?

Changes in the climate have the potential to impact every part of
 the basin. Changes in the duration
 of ice-cover, for example, which are directly linked to climate will have compounding effects relating to other basin concerns including algal blooms, invasive species and with water levels, waves and erosion.

Recent studies have found that warming temperatures may
increase the severity of blue-
green (cyanobacteria) blooms in nutrient enriched lakes, because
some cyanobacteria may have a competitive advantage at higher
water temperatures (e.g., > 25°C). Warming also increases the stability of temperatures in lakes, thus reducing surface water mixing which is good for blue-greens. Algal assemblages in LoW may already be responding to recent increases in air temperature. Researchers from Queen’s university (ON) examined diatom algal fossils preserved in lake sediment cores from Whitefish Bay (LoW) andfound significant changes in species composition since pre-industrial times (pre-1850), with most changes occurring over the past 30 years. The timing of these changes was the same as recent increases in air temperature and increases in the length of the ice-free season.

In addition, climate change is expected to have a profound impact on habitat for coldwater fish, such as lake trout and cisco, in North American lakes. Specific effects for coldwater fish in Lake of the Woods will depend on individual sub-basin morphometry and productivity.

Land-based ecosystems are also predicted to change dramatically
in response to changes in climate. Researchers have predicted sweeping changes in forest cover from boreal to temperate species together with large changes in the major types of animals on the landscape including shifts from moose to deer. Changes in the types of worms present in the soil will in turn affect the species of vegetation present. These changes will produce novel ecosystems that may be different from anything with which we are currently familiar. It is simply impossible to predict changes to the basin which could have effects that are as consequential as these could be.

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Nutrients and internal loading

What are “nutrients” and which are of concern in the Rainy – LoW Basin?

Nutrients are the chemicals and minerals that organisms use for basic metabolic processes.  Think of them as fertilizers or vitamins in a natural ecosystem.

Concerns over nutrient inputs to surface water in the basin are almost always focused on phosphorus, the nutrient that controls the growth of algae. It is, in fact, responsible for limiting the production of the entire ecosystem. More phosphorus means more fish but it also means more algal blooms. We need phosphorus in the system but excess amounts can be harmful.

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What is a phosphorous budget?

In 2009, the U.S. portion of the basin was listed as an impaired water.  As a result, we now measure how much phosphorous comes into the system and how much flows out of it or settles into lake sediments.  If these numbers match, the system is considered to be balanced.  The amount of phosphorous that enters the balanced system is called the “phosphorous budget”.

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What are TMDLs and TP?

Total Maximum Daily Loads (TMDLs) represent how much total phosphorous (TP) can be loaded into a system and still have it function properly and maintain good health and water quality.

TMDLs and TP are important measurements of nutrients that are tracked by scientists in the basin to describe water quality and basin health.

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What are the sources of phosphorous for the Rainy – LoW Basin, and how does it get released from the system?

The Rainy River is the major inflow to LoW. In the past, the pulp and paper companies at International Falls and Fort Frances together with domestic sewage inputs were considered to be the major point sources of nutrients to the Rainy River. In recent decades the implementation of regulations for treatment of industrial and domestic waste effluent has led to significant reductions in nutrient loads to the Rainy River. These reductions occurred most substantially between the 1970s and the 1980s.

Recent modeling using bathymetry data from Environment and Climate Change Canada, measurements of internal phosphorous loading (phosphorous from sediments that can get re-released when sediments get stirred up, such as by surface winds), and loading from the Rainy River have been used to calculate the TP budget at 1,147 tonnes per year.

Kathryn Hargan, a Masters student at Trent University, created the first nutrient budget for LoW in 2010.  Her work showed that the Rainy River is the largest source of phosphorous but also shows that more than half of the phosphorous which comes into the lake stays in the lake and does not exit at the outflow to the Winnipeg River. This phosphorous is lost 
to the sediments through the settling of particles such as algae and bacteria.

Hargan’s work also showed that the contribution of phosphorous from shoreline properties is relatively small on a whole lake scale. However, in more enclosed or isolated bays the same contribution from shoreline properties may represent a relatively larger portion of the nutrient budget.

TP budget modeling has shown that phosphorous comes from the following sources: tributary inflow (principally the Rainy River) 42%, internal load 36%, precipitation 13%, shoreline erosion 6%, non-point inflow 2%, and point sources, 1%. The model estimates that 55% of the phosphorus is retained within the lake.

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What are we still working to understand?

  • Seasonal variability in nutrient loading
  • Nutrient loading variability across different parts of the basin (e.g. shallow and relatively homogenous Big Traverse Bay versus deeper, more isolated northern bays)
  • Climate impacts on algal blooms
  • The role of dissolved phosphorous relative to total phosphorous in driving algal blooms

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Surface and Ground Water Contamination

What contaminants threats exist in the basin?

Generally, the Rainy – LoW basin has fewer contaminants threats than many other major basins in North America, such as the Great Lakes.  Reducing the inputs of contaminants through the Rainy River has also significantly reduced the impacts of contaminants.

There are historical contaminants sources, as well as potential future threats, plus some ongoing point sources of contaminants.  Contaminants concerns exist related to:

  • Areas listed as Federal Contaminated Sites (in Canada)
  • Areas that may have legacy contamination from historic mining activity
  • Areas that demonstrate atmospheric contamination of lakes and fish by mercury
  • Areas that receive point-source discharges from industry and municipalities
  • Areas that are affected by emerging potential for industrial activities, especially mining, to increase once again in the basin.

Contaminants may enter surface water (and ground water) from many sources including point sources such as industrial outfalls, wastewater treatment plants, storm water 
drains, etc. and diffuse sources such as from agriculture, private septic systems, precipitation, etc. Generally the point sources are controlled through regulation that stipulates the concentrations of contaminants that are allowed in the discharge.

Diffuse sources tend to be poorly quantified and are either not controllable directly (e.g., contaminants in precipitation) or must be controlled by more widespread efforts and best management practices such as those required to reduce agricultural inputs or inputs from sources such as road salt.

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How does mining pose a contaminants risk to the basin?

Historically, mines have released dredged and stored suspended sediments into nearby waterways.  For example, the Steep Rock Mine near Atikokan operated from 1944-1979, and was at the time one of the largest iron ore mines, involving many water diversions and disturbances to the natural drainage.  In 1951, a particularly high volume spring freshet resulted in the mine releasing its stored sediments into the nearby Seine River. 

Historically in the Lake
 of the Woods watershed there were many gold mining sites and processing operations. Environment Canada (2013) noted that several of its sediment monitoring sites (where sediment concentrations of arsenic and barium were higher than expected) were adjacent to historic gold mines.

In Minnesota, there are effects
from leaching metals from sulfide waste rock stockpiles at the historic Dunka taconite mine near Babbitt, and contaminants enter Birch Lake which is near to the Boundary Waters Canoe Area Wilderness.

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How is mercury a contaminant of concern for the basin?

Mercury is a naturally occurring element that is present in rocks and soil, but the contribution of mercury to lakes from these sources is negligible compared to atmospheric sources with origins relating to human activity. Mercury in the aquatic environment will bioaccumulate in biota and biomagnify in aquatic food webs. Larger fish,
 and especially older fish, have higher concentrations of mercury due to their higher position in the food web and a longer time spent accumulating mercury. Mercury concentrations in fish have resulted in fish consumption restrictions in both Ontario and Minnesota.

In Canada, the major contribution of atmospheric mercury until the 1980s was the chloralkali industry but all chloralkali plants are now closed in Ontario. The resulting decline in emissions combined with reductions from mining and smelting industries throughout the 1990s has resulted in an overall decline in the amount of mercury emitted to the atmosphere from human sources.

In 2011, Canada emitted under 3.7 tonnes of mercury, 27% of which was attributed to electricity generation and 26% to incineration. Ontario was responsible for 27% of the total Canadian emissions.  U.S. mercury emissions are also declining (from approximately 250 tons/yr in 1990 to 100 tons/yr in 2005).

Despite these reductions in North American emissions the deposition
of mercury may continue to increase due to increases in global emissions which may delay recovery in mercury contamination in the biota. Studies in Minnesota and elsewhere in the Great Lakes basin have shown decreasing trends in mercury in fish between the 1980s and the mid-1990s after which the trend of mercury in fish tissue begins to rise once again. One explanation for this is that although regional emissions of mercury have declined considerably over the past 30 years, these have been offset by recent increases in the global emissions of mercury.

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What about other contaminants like PCBs, pesticides, endocrine disruptors and pharmaceuticals?

Luckily, in the Rainy – LoW basin, at present there are no immediate contamination threats to food webs by persistent pollutants such as PCBs.  Nevertheless, it is important
 to note that contaminants which include industrial chemicals are released as by-products of many industrial and domestic processes.

Pesticides, particularly those which are suspected endocrine disruptors, were identified as a possible health risk factor in LoW by the IJC Health Task Force. Environment Canada sampled herbicides and pesticides at several of its LoW monitoring stations in 2009 and 2010 and the maximum concentrations detected were below Canadian Water Quality Guideline concentrations for the protection of aquatic life by several orders of magnitude suggesting that the concentrations present in LoW do not pose a threat to biota.

There does not seem to be 
any indication that the basin is impacted by contaminants other than mercury but very little is known about the prevalence of emerging contaminants of concern (such as those associated with pharmaceuticals or microbeads – those tiny plastic beads found in many facial cleansers, toothpastes and other cosmetic and cleaning products in waste water) within the basin.  Monitoring work and community advocacy to ensure public awareness of contaminants risks will need to continue to ensure our basin is not impaired by these emerging contaminants.

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Water Levels and Erosion

What are some concerns related to controlling water levels?

The effects of water level control are currently being studied in the Rainy Lake and Namakan Reservoir system to assess whether the 2000 Rule Curves should be modified.

On Lake of the Woods, there were many potential ecological effects that followed the installation of outlet control structures at Kenora in the 1890s. These structures raised the water level in LoW by approximately 1 meter (3.3 ft) and this has had many effects on ecological function, some of which have been noted in research studies that have examined long-term changes in LoW algal communities.

The equalization of the water levels in LoW and Shoal Lake makes it possible for water to flow in both directions between the two lakes and potential effects of this are an ongoing concern.

In addition to ecological impacts, changes in water level regulation, specifically related to flooding damage and loss, also are the basis of ongoing concerns for First Nations around the basin.  Cultural and economic losses have been tied to damage done to wild rice beds and fisheries as a result of higher water levels.

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Where and how is erosion a problem?

In the southern areas of LoW the shoreline experiences significant erosion. Analysis of aerial photos from 1940 to 2003 showed rapid erosion of several undeveloped wetland areas of the shoreline and relatively slow erosion of developed areas along Sandy Shores and Birch Beach. Analysis of Pine and Sable Islands showed a combination of erosion, rebuilding, and shifting. Historical accounts document erosion in the southern portion of Lake of the Woods for hundreds of years.  This erosion threatens habitat providing refuge for a number of federally threatened and endangered species.

These eroding sediments are a source of nutrients to the lake. Results show an estimated average total phosphorus load of 82 tons/yr but it is unclear what the net load to the water itself would be, after particulate phosphorus settles out.

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Aquatic Invasive Species

What are some aquatic invasive species of concern?

The basin has been invaded by many non-native species which have disrupted the biological communities. Invasions have occurred in all trophic levels of the aquatic ecosystem from algae up to fish. The hybrid cattail, spiny water flea, rusty crayfish, papershell crayfish, clearwater crayfish and rainbow smelt are confirmed invaders in parts of the R-LoW basin. Zebra mussels have been reported by MDNR in headwater lakes of the Big Fork River near Bemidji, MN (May 2013). There is potential for further invasions that will require ambitious focused effort to avoid/slow the spread of these species and to better understand their impacts to natural systems.

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How can I help limit the spread of aquatic invasive species?

Practice good hygiene when you move between waterways:

  • scrub your boat and motor before moving them from one waterway to another
  • purge your bilge, float plane floats, minnow buckets and other water-holding containers far from a waterway which you could potentially contaminate with AIS
  • make sure life jackets, floatation devices and water toys have a chance to thoroughly dry out or get cleaned before moving them among waterways
  • observe all regional prohibitions on the use of invasive bait species when fishing

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