11.6 Trends in water quality from three rivers on the Taiga Shield and Taiga Plains of the NWT

Last Updated: 
December 17, 2015

This indicator tracks major ions and nutrient levels in the waters of the Yellowknife, Cameron and Marian Rivers in the Northwest Territories (NWT). Major ions refer to certain elements dissolved in the water that appear commonly in many rivers worldwide. These elements can come from the surrounding landscape and the material the rivers flow upon. The major ions measured in this indicator are naturally occurring and include calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), chloride (Cl-), silicon (Si) and sulphate (SO42-). Alkalinity, the ability to neutralize an acide, and silicon are also measured. Nutrients refer to dissolved molecules that play an important role for biological processes, and can help sustain life within waters.

Precambrian granite

Precambrian granites along the Cameron River above the falls. Photo: L. Schofield.

The three rivers included in this indicator differ in underlying geology, ecology and surface area of their catchments but all are situated in an area containing discontinuous permafrost. The Yellowknife (19,353 km2) and Cameron River catchments drain the Taiga Shield. The Marian River drains an area of 23,608 km2 and straddles the Taiga Plains and Taiga Shield. Precambrian granites characterize much of the Taiga Shield, whereas the Taiga Plains are characterized by a lower density of lakes, abundance of peatlands and glacial deposits, such as tills)1,14. These rivers have been sampled monthly over a 30-year period and provide an excellent long-term dataset to evaluate changes to water chemistry over time in medium-sized nothern rivers. Data collected from these rivers was statistically analysed to determine significant monotonic trends with time. This dataset can provide a look at the current and historical geochemical trends for rivers draining the northern basins of Great Slave Lake.

Authors of this indicator are Pieter Aukes and Sherry Schiff, Unversity of Waterloo, Mike Palmer and Robin Staples, Government of the Northwest Territories (GNWT), and Michael English, Wilfrid Laurier University. Data are from Water Resources Division, Environment and Natural Resources, GNWT.

NWT Focus

The NWT represents an area of Canada highly sensitive to a warming climate. Monitoring river water chemistry provides an indication to how NWT catchments are responding2. Specifically, changes to the dissolved constituents within a river can influence both aquatic health and drinking water quality. Surface waters act as a source of drinking water for many northern communities in the NWT. Furthermore, with increased industrial development and the continual need for sustainable drinking water resources, understanding baseline conditions allows for the determination of the current status of water quality in the NWT as well as potential future impacts from industry and a changing environment.

Long-term water quality monitoring information is critical for assessing the current and continued status of freshwater ecosystems. Northern environments are particularly sensitive to a warming climate3, but changes may occur on the decadal scale or longer. Therefore, long-term data from northern rivers are required to understand the influences of inter-annual and seasonal fluctuation in water quality4. Changes to water chemistry over time can be used as an indicator for environmental changes, either natural or anthropogenic, with watersheds2,5. Monitoring water chemistry over time can help create a better understanding of how aquatic systems respond to changes occuring on the landscape.

Current View: Status and Trends

Major Ions

Major ions

Major ions

Major ions in Yellowknife and Cameron Rivers (Taiga Shield catchments), and in the Marian River (part Taiga Plains and Taiga Shield catchment), NWT. Note the scale difference between the Marian and the other rivers.

Overall, concentrations of most major ions in the Marian River are much higher than either the Yellowknife or Cameron River. The Marian River catchment (containing peatlands and till) may be easier to erode and creates higher concentrations than the more resistant Precambrian bedrock found in the Taiga Shield. Marian River exhibits the greatest annual range in parameters (resulting from seasonal effects like river discharge) than the Yellowknife or Cameron Rivers. Concentrations of major ions in the Yellowknife and Cameron Rivers have increased significantly since 1995, with statistically significant increases found in calcium (Ca2+), magnesiu, (Mg2+), sodium (Na+), potassium (K+), chloride (Cl-), sulphate (SO42-) and alkalinity (ability to neutralize an acid). These results indicate that these Shield Rivers have been increasing in major ions for at least 15 years.


Nutrients in Yellowknife and Cameron Rivers, and in the Marian River, NWT.

Nutrients in Yellowknife and Cameron Rivers (Taiga Shield catchments), and in the Marian River (part Taiga Plains and Taiga Shield catchment), NWT.

Concentrations of dissolved organic carbon (DOC) are relatively similar among all three rivers, where the Yellowknife and Marian Rivers contain significant increases over time. Annual concentration fluctuations can be observed, likely influenced by differences in seasonality and water discharge. Inorganic nitrogen concentrations are quite low for all three rivers. Marian River shows the only statistically significant increase in inorganic nitrogen (nitrate (NO3+) and nitrite (NO2-)) around 2007. Highest concentrations of inorganic nitrogen within the rivers have occurred within the last five years.

Looking Around

Geochemical changes have been observed in rivers across the Arctic and sub-Arctic, yet numerous factors are responsible for such changes (such as flow pathways or water residence time). Degradation of permafrost has been found to impact water quality through changes in organic matter6,7,8, increased nutrients such as increased nitrogen remineralisation9 and build-up of inorganic nitrogen in lakes10 or changes in major ions11. Although DOC increased in some rivers, major ion data from the NWT suggests similar trends to rivers found in other northern environments6,12, depicting changes to the current geochemical regime. It is possible that permafrost degradation contributes to the observed change in river chemistry, yet seasonality, changes to precipitation and contributing sources likely all contribute to a complex interaction of factors that impact water quality.

Looking Forward

Under continued changing conditions,  changes to sources and contributing areas within catchments are expected. For instance, a study of Arctic systems6 suggests a potential transition from surface water dominated systems to more groundwater dominated systems. Continued changes to seasonal soil thaws are believed to increase inorganic nitrogen exports into streams13, illustrating the potential for continued nutrient increases. The future also includes changing precipitation regimes, which will also affect river chemistry. A long-term study on the Baker Creek in the Taiga Shield10 observed a shift in stream flow regime within watershed from spring to fall months to occur around 1997, which is during the same period as the increase in major ions within all three rivers reported in this indicator.

Environmental watershed changes in the NWT include a number of complex interactions between terrestrial and aquatic environments, with a wide range of outcomes. However, long-term monitoring of these rivers allows for determination to how sub-Arctic rivers in the NWT are responding to such changes.


Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.


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