Le rapport sur l’état de l’environnement 2022 est un document technique destiné à un usage interne. Il n’est disponible qu’en anglais.

Introduction

The Northwest Territories (NWT) has an abundance of fresh water. This water is essential to ecosystem health, and to the social, cultural, and economic well-being of territorial residents. Northerners rely on water for sustenance, recreation, and transportation. Major water uses in the NWT include municipal use and industrial development, such as mining, oil and gas and hydroelectric power production. For Indigenous peoples, who make up approximately 51% of the territory’s population, water has intrinsic cultural, spiritual, and historical value. Water is considered by many Indigenous peoples in the NWT to be a heart – giving life to people, wildlife, fish, and plants.

Most of the NWT lies within the Mackenzie River Basin (MRB), where water flows through river systems that eventually flow into the Mackenzie River and drain into the Beaufort Sea (Arctic Ocean). The MRB is Canada’s largest river basin and the second largest river basin in North America, draining parts of British Columbia, Alberta, Saskatchewan, the Yukon, Nunavut, and the NWT. As a basin that spans six provinces and territories, traditional areas for many Indigenous peoples and many ecological zones, monitoring and maintaining the ecological integrity of this immense watershed requires a lot of cooperation and collaboration.

The MRB has different names in different languages. Kuukpak is the Inuvialuktun name, Nagwichoonjik is the Gwich’in name, Deho is the North Slavey name, Dehcho is the South Slavey name, and Grande Rivière is the Michif name.

Northerners have always placed importance on the state of our water quality and quantity. With increasing regional, national, and international pressures, actions are required to ensure our water resources are sustained for future generations. Transboundary agreements with neighbouring jurisdictions and environmental monitoring and research activities provide a foundation for making sound decisions about water management in the NWT.

To assess ecosystem health, indicators such as water quality and quantity are useful to track changes in the aquatic ecosystem. A few different indicators are provided that describe the current state of water quality and quantity at certain locations throughout the NWT.

 

 

11.1 Trends in Water Quality in Select NWT Rivers

This indicator measures changes in water quality in select rivers across the North. Water quality is influenced by the geology and ecology of a watershed and is affected by changes to the landscape (e.g., permafrost thaw, or human activities). Water quality conditions are influenced by water flow. Some parameters increase with flow, while others decrease with flow. The relationships between water quality and flow vary between rivers, watershed, and seasons. Substances (e.g., salts, metals) enter the river a number of ways, including through groundwater, surface runoff during a rainstorm and spring melt, and drainage from near surface soils and vegetation.

This indicator was prepared by the Government of the Northwest Territories, Department of Environment and Climate Change, using information obtained from the Water Management and Monitoring Division. 

NWT Focus

Fresh water is fundamental to life. Clean and abundant fresh water ensures healthy and productive ecosystems. These are essential to the social, cultural and economic wellbeing of people, particularly for Indigenous residents of the Northwest Territories (NWT). The quality of water, and the health of rivers, lakes and wetlands, depend on how people develop and use the surrounding and upstream land. The NWT has an abundance of fresh water which is used for drinking, fisheries, recreation and industry. Long-term water quality monitoring is important to determine whether water quality is suitable for a particular purpose. Given that our northern environment is particularly sensitive to a warming climate, analyzing long-term data is also very important for understanding whether water quality is changing and, more importantly, to understand the ecological implications of changing water chemistry.

 

Current View: status and trend

Water Quality Trend Analyses

There are many different approaches to explore water quality trends. For this indicator, we use a method that identifies 1) whether there is a trend, 2) the direction of the trend (increasing or decreasing), and 3) the level of confidence we have that the trend is real (Table 1) (Ref. 1, Ref. 3).

Table 1. Confidence Scale (adapted from Ref. 2)

Term	Range of Confidence
Highly likely	95-100%
Very likely	90-95%
Likely	66-90%
Uncertain (no trend)	50-66%

 

Site and Parameter Selection

In the NWT, there are many water quality monitoring sites operated by the Department of Environment and Climate Change, Government of the Northwest Territories (GNWT-ECC), and Environment and Climate Change Canada (ECCC).. The following trend analyses are calculated from the sites mentioned in using ECCC’s long-term data (Table 2).

Table 2. Long-term Water Quality Monitoring Sites (arranged from south to north)

Monitoring Site (abbreviation)	Years of Monitoring
Slave River at Fitzgerald (SR)	48*
Hay River near Alberta/NWT Border (HR)	32
Mackenzie River at Strong Point (MR-SP)	26
Liard River near the Mouth (LR)	46
Lockhart River at Outlet of Artillery Lake (LKR)	51
Great Bear River at Outlet of Great Bear Lake (GBR)	49
Mackenzie River at Norman Wells (MR-NW)	54
Mackenzie River above Arctic Red River (MR-ARR)	46
Peel River above Fort McPherson (PR)	39

*Although continuous monitoring has taken place since 1960, the period of record for this analysis has been shortened to 1972-2020 to investigate trends following the filling of the W.A.C. Bennett Dam.

Water quality samples are collected from the long-term water quality sites listed in Table 2. Samples are analyzed for major ions (e.g., calcium, potassium, chloride, sulphate), metals (e.g., aluminum, iron, lithium), nutrients (e.g., phosphorus, nitrogen, organic carbon), and other parameters.  

For the purposes of these analyses, 9 parameters were assessed for trends. These 9 parameters were selected because they have the longest period of record consistent with the monitoring sites listed in Table 2. The parameters were arranged into three groups:

• Major Ions and Solids: alkalinity, chloride, turbidity
• Metals: total arsenic, total aluminum, total iron
• Nutrients: dissolved organic carbon (DOC), total organic carbon (TOC), dissolved nitrogen

Major Ions and Solids - Alkalinity, Chloride and Turbidity

Alkalinity levels appear to be increasing at seven of nine sites. A decreasing trend was observed for the Hay River and no significant trend was detected for the Peel River (Figure 1).

Alkalinity is a measure of a water’s capacity to neutralize an acid and is expressed as a measure of calcium carbonate (CaCO3). Previous research (Ref. 4) has shown that the overall transport of alkalinity from the Mackenzie River Basin into the Arctic Ocean has increased, and it is an indicator of increased rock weathering related to increases in sulphate concentrations. Increasing trends in both alkalinity and sulphate concentrations are also observed in the Mackenzie River above Arctic Red River (Figures 2A and 2B). (Figure 2).

Figure 1. Trends for nine long-term water quality monitoring sites. Period of records used for these nine sites vary depending on the availability of the data (see Table 2 for years of monitoring and definitions of abbreviations). Values above 0 (black line) suggest increasing trends, and values below 0 suggest decreasing trends. The likelihood of an increasing or decreasing trend increases the farther a result is from 0. Source: Water Quality Data (ECCC, 2020); Water Quality Assessment (ECC, 2021)

 

Figure 2A. Alkalinity concentration (mg/L) trend in the Mackenzie River above Arctic Red River. Source: Water Quality Data (ECCC, 2020); Water Quality Assessment (ECC, 2021)

 

Figure 2B. Sulphate concentration (mg/L) trend in the Mackenzie River above Arctic Red River. Source: Water Quality Data (ECCC, 2020); Water Quality Assessment (ECC, 2021).

 

Chloride trends were not detected at two sites on the Mackenzie River (NW & ARR), decreasing in the southern NWT rivers and the Peel River, and increasing in the Lockhart River and Great Bear River. The sites with decreasing trends are in the Interior Platform geological province, whereas the Lockhart River is draining Precambrian bedrock and the Great Bear River is draining Great Bear Lake and watershed. These regional differences in trend patterns seem to reflect differing geological and ecological settings.

Turbidity is a good indicator of amounts of suspended sediment, which is a measurement of particulate matter in surface water. Turbidity is often related to runoff from precipitation (e.g., rainstorm or snowmelt) or landscape disturbance (e.g., permafrost thaw or human activities). Based on the trend analysis, turbidity is increasing in the Slave and Liard rivers, and on the Mackenzie (NW and ARR) (Figure 3) and Peel rivers. Conversely, turbidity is decreasing on the Hay, the Mackenzie (SP), Great Bear Rivers, and the Lockhart River.

Figure 3. Turbidity (NTU) in the Mackenzie River above Arctic Red River. Source: Water Quality Data (ECCC, 2020); Water Quality Assessment (ECC, 2021)

 

Total Metals – Aluminum, Arsenic and Iron

Metals tend to bind to suspended sediment in surface waters (Ref. 5), and suspended sediment is positively related to flow. Therefore, as flow increases, the concentration of metals bound to sediment usually also increases. Once the data was corrected for flow, decreasing trends were observed for total aluminum, arsenic, and iron at the majority of long-term monitoring sites. However, total iron is increasing in the Peel River (Figure 4). It is important to note that these trends were analyzed on concentrations and not loads. Concentrations provide an indication of how much of the metals are in the water, and loads are measurements of how much of the metal is being transported in a river system as a whole.

Figure 4. Total iron (µg/L) in the Peel River above Fort McPherson. Source: Water Quality Data (ECCC, 2020); Water Quality Assessment (ECC, 2021).

 

Nutrients - Dissolved Organic Carbon (DOC), Total Organic Carbon (TOC) and Dissolved Nitrogen

Increasing trends in organic carbon (DOC and TOC) were observed across all long-term monitoring sites. Previous research (Tank et al. 2016) found that organic carbon mobilization in the NWT is related to different processes occurring at regional scales. For example, in the northern NWT, where there is extensive permafrost, DOC and TOC concentrations are related to permafrost degradation on the landscape. At the outlet of Great Bear River, DOC (Figure 5) is probably related to increases in primary production within Great Bear Lake. Further south, increases in DOC and TOC are probably related to permafrost peatland degradation and wetland expansion, which leads to water being in contact with organic-rich soils longer.

 

Figure 5. Dissolved Organic Carbon (DOC) (mg/L) in the Great Bear River at the outlet of Great Bear Lake. Source: Water Quality Data (ECCC, 2020); Water Quality Assessment (ECC, 2021).

 

Although levels of dissolved nitrogen are higher in the Slave River now than they were when monitoring began (1978), it appears that dissolved nitrogen has been decreasing since around 2008. A similar decreasing trend has been observed in the Hay River. Dissolved nitrogen is the sum of different forms of nitrogen, such as organic nitrogen, nitrate, nitrite and ammonia. Conversely, when the levels of nitrate were explored, levels in both rivers appear to be increasing. As we can see, the different forms of nitrogen can trend differently. The factors driving the formation of the different kinds of nitrogen in the aquatic environment are complex, and work is ongoing to understand the processes affecting the cycling and transport of nitrogen and other nutrients in NWT watersheds.

 

Looking forward

There are numerous natural processes and anthropogenic factors that affect water quality. Continuation of monitoring at long-term sites and at more recently established sites is essential to understand how changes in flow and the landscape affect water quality. As climate continues to change in the North, water quality is expected to continue changing. Research on the ecological implications of changing water quality is ongoing.

 

References

Ref. 1. Helsel, D.R., R.M. Hirsch, K.R. Ryberg, S.A. Archfield, and E.J. Gilroy. 2020. Statistical methods in water resources: U.S. Geological Survey Techniques and methods, book 4, chapter A3, 458 p. https://doi.org/10.3133/tm4a3.

Ref. 2. Mastrandrea, M.D., C.B. Field, T.F. Stocker, O. Edenhofer, K.L. Ebi, D.J. Frame, H. Held, E. Kriegler, K.J. Mach, P.R. Matschoss, G.-K. Plattner, G.W. Yohe, and F.W. Zwiers. 2010. Guidance note for lead authors of the IPCC fifth assessment report on consistent treatment of uncertainties. Intergovernmental Panel on Climate Change (IPCC). http://ipcc-wg2.awi.de/guidancepaper/ar5_uncertainty-guidance-note.pdf.

Ref. 3. McBride, G.B. 2019. Has water quality improved or been maintained? A quantitative assessment procedure. Journal of Environmental Quality 48:412-420.

Ref. 4. Tank, S.E., R.G. Striegl, J.W. McClelland, and S.V. Kokelj. 2016. Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic Ocean. Environmental Research Letters 11:054015.

Ref. 5. Sanderson, J., A. Czarnecki, and D. Faria. 2012. Water and Suspended Sediment Quality of the Transboundary Reach of the Slave River, Northwest Territories. Water Resources Division, Renewable Resources and Environment Directorate, NWT Region, Aboriginal Affairs and Northern Development Canada. Yellowknife, NWT.

 

11.2 Mercury Levels in Select NWT Rivers

This indicator reports on mercury measured in selected rivers of the Northwest Territories. This includes concentrations of total and dissolved mercury in water samples collected from the Hay, Liard, Mackenzie, Peel and Slave Rivers.

Figure 1. An example of bioaccumulation and biomagnification. In this example, zooplankton ingests mercury, then a seal eats the fish, and a polar bear eats the seal. The longer an animal lives, the more mercury can build up. This is called bioaccumulation. When mercury levels rise through the food chain, this is called biomagnification. Adapted from blue-growth.org.

 

Mercury, like cadmium and lead, is known as a "heavy metal" and can be toxic to living organisms. It is released into the environment from natural processes such as volcanic activity, weathering of rocks and because of human activity. Human activity is the main cause of mercury releases, particularly coal-fired power stations, residential coal burning for heating and cooking, industrial processes, and waste incineration (Ref. 1).

There are various forms of mercury (Hg) in the aquatic environment. As it changes form, it may become more or less available to aquatic organisms (Ref.2). Methylmercury is the most toxic form of mercury and it bioaccumulates and biomagnifies in the food web (Ref.3). Water samples are analyzed for both total mercury (THg), which includes particulate and dissolved inorganic and methyl mercury (MeHg)and dissolved mercury (DHg).

This indicator was prepared by the Government of the Northwest Territories, Department of Environment and Climate Change, using information obtained from the Water Management and Monitoring Division. 

 

NWT Focus

Through a variety of monitoring programs, the Department of Environment and Climate Change (ECC), in partnership with communities, collects water samples throughout the NWT. These water samples are tested for many different substances, including mercury. Included here are the mercury data for the Hay, Liard, Mackenzie, Peel and Slave Rivers.

All water samples are analyzed by the Taiga Environmental Laboratory in Yellowknife. Results for THg, MeHg and DHg are stored in ECC’s Lodestar water quality database and are available upon request.

 

Current View: status and trend

To date, results indicate that average mercury in NWT rivers are below the Canadian Council of Ministers of the Environment (CCME) freshwater aquatic life guideline for DHg and THg, suggesting that levels are safe for fish and aquatic life.

While the average levels of THg are highest in the Peel River (denoted by “+”), the maximum THg level measured to date was in the Slave River in July 2020 (100 ng/L; Table 1; Figure 1). This is likely due to slumping and higher sediment load.

Table 1. Average levels of dissolved (DHg) and total (THg) mercury in June through September in various major NWT rivers (Ref. 4). Source: Water Quality Data (ECCC, 2020; ECC, 2020)

River	Sampling Year	n	DHg (ng/L) CCME Freshwater Aquatic Life Guideline (4 ng/L)5	THg (ng/L) CCME Freshwater Aquatic Life Guideline (26 ng/L)5
Hay River (near Alberta/NWT Border)	2014-2020	21	1.8 ± 0.5	7.1 ± 6.8
Liard River (above Fort Liard)	2014-2020	27	1.0 ± 0.7	10.2 ± 8.8
Mackenzie River (upstream of Arctic Red River)	2014-2020	18	0.6 ± 0.3	10.1 ± 9.1
Peel River (above Fort McPherson)	2014-2020	31	0.7 ± 0.3	16.7 ± 12.3
Slave River (at Fort Smith)	2014-2020	39	0.9 ± 0.6	13.5 ± 17.6

In July of 2020, suspended sediments in the Slave River were very high due to the sustained high flows associated with record high levels of precipitation in the Slave River and upstream watersheds. Given the strong association between sediment load and mercury, it was not unexpected to see higher THg in 2020 on the Slave River.

Figure 2. Total mercury (ng/L) levels in selected NWT Rivers. Each dot represents the nanograms of mercury in one litre of water. Samples were collected in June through September between 2014 and 2020.

 

Looking Forward

Mercury will continue to be monitored and long-term trends will be explored. As part of regular biological monitoring on the Slave River, which is a transboundary river, mercury is also being measured in fish tissue to assess accumulation. This work will continue to ensure mercury levels are safe in transboundary rivers as well as other important sites across the NWT such mining wastewater.

 

Find out more

Mercury data for rivers throughout the NWT are available online through Mackenzie DataStream at https://mackenziedatastream.ca/ and in Environment and Climate Change Canada’s National Long-term Water Quality Monitoring database at: http://data.ec.gc.ca.

 

References

Ref.1. United States Environmental Protection Agency (USEPA). 2020. Basic Information about Mercury. (https://www.epa.gov/mercury/basic-information-about-mercury)

Ref.2. United States Environmental Protection Agency (USEPA). 2020. Basic Information about Mercury. (https://www.epa.gov/mercury/basic-information-about-mercury)

Ref.3. Environment and Climate Change Canada (ECCC). 2013. Mercury in the Food Chain. (https://www.canada.ca/en/environment-climate-change/services/pollutants/mercury-environment/health-concerns/food-chain.html)

Ref.4. Government of the Northwest Territories (GNWT), Environment and Climate Change (ECC), Water Management and Monitoring Division (WMMD). Lodestar Database, 2020.

Ref.5. Canadian Council of Ministers of the Environment (CCME). Water Quality Guidelines for the Protection of Aquatic Life (total mercury and methylmercury). (https://ccme.ca/en/summary-table)

 

11.3 What’s Happening in Jackfish Lake?

Jackfish Lake, located near Yellowknife, has been undergoing dramatic changes over the last decade from re-occurring algal blooms. Research into these changes suggest that Jackfish Lake may provide some insight on how some freshwater lakes may change in the future with a climate warming.

Algal blooms occur when naturally occurring phytoplankton (photosynthetic organisms including single-celled plants and cyanobacteria) multiply very quickly (Ref 2). Over-enrichment of lakes with nutrients such as phosphorus and nitrogen – a condition known as eutrophication – can lead to excessive phytoplankton growth and declining water quality. Additional factors such as water temperature, sunlight, and wind mixing play important roles in the onset, duration and severity of algal blooms (Ref 3).

This indicator was prepared by the Government of the Northwest Territories, Department of Environment and Climate Change, using information obtained from the Water Management and Monitoring Division.

 

NWT Focus

Not long ago, Jackfish Lake was a welcoming feature of the City of Yellowknife (Photo 1). The lake can be accessed from town and was well known for large Northern Pike. Today, the lake is often discoloured and matted with blooms (Photo 2).

 

Current View: status and trend

Analysis of a sediment core collected from the lake bottom suggests increases in nutrient levels and chlorophyll-a (Figure 1), and water monitoring has confirmed that cyanobacterial algal blooms have been occurring since 2013. These blooms are likely a cumulative response to nutrient enrichment and warming water temperatures. Research and monitoring efforts are underway to better understand what is happening in Jackfish Lake.

 

Staff with the NWT Power Corporation (NTPC), City of Yellowknife and Department of Environment and Climate Change (ECC) are working with researchers at Queen’s University, Wilfrid Laurier University, University of Saskatchewan and the Aurora Research Institute to better understand the causes of the changes to the lake. This includes the processes driving the current algal blooms.

Figure 1. Results from a sediment core collected from Jackfish Lake in 2015 (Ref.1). Results show relatively constant levels Chl-a from 1900 to 2013 when a large jump in Chl-a occurred.

 

Photo 1. Jackfish Lake (west bay) in 2010 (© Ron Erwin)

 

Photo 2. Jackfish Lake (east bay) in 2017 (A.Czarnecki)

 

Looking Around and Looking Forward

Some local and applicable research is trying to address how changing lake ice conditions influence the cycling of nutrients and metals in Taiga Shield lakes. The research team is using Jackfish Lake as an analogy for how lakes in the region may be impacted by climate change, since warm water discharged to the lake from the Jackfish power plant results in warmer water temperatures and a longer ice-free season, which are both expected climate change impacts. Water and sediment conditions at Jackfish Lake are being compared with several other lakes in the region to assess how changes to lake ice and water temperature influence metal and nutrient dynamics in the region. This information will help us to better understand future trajectories of change in Taiga Shield lakes, including how lakes recover from legacy mining pollution and how climate change may influence the productivity of lakes.

 

Find out more

In 2019, the NWT Chief Health Officer stated that Jackfish Lake should be avoided for swimming and fishing due to the annual algal blooms and legacy arsenic contamination. More information about Jackfish Lake and other lakes around Yellowknife is available from Health and Social Services at: www.hss.gov.nt.ca.

 

References

Ref. 1. Sivarajah, B., Simmatis, B. and J. Smol, Biology Dept., Queen’s University, 2015 (with permission).

Ref. 2. Environment and Climate Change Canada (ECCC). 2020. EOLakeWatch: Remote Sensing of Algal Blooms. (https://www.canada.ca/en/environment-climate-change/services/water-overview/satellite-earth-observations-lake-monitoring/remote-sensing-algal-blooms.html)

Ref. 3. United States Environmental Protection Agency (USEPA). 2019. Climate Impacts that Might Affect Algal Blooms: Warming water temperature. (https://www.epa.gov/nutrientpollution/climate-change-and-harmful-algal-blooms)

 

 

11.4 Trends in Water Flow

This indicator reports on trends in both total annual flow in small, medium and large streams and rivers in the NWT, as well as trends in seasonal flow.

Water flow and level data from a select group (total n=21) of sites were obtained from monitoring gauges that are part of the larger NWT Hydrometric Network, a partnership between Environment and Climate Change Canada (ECCC) and the Government of the Northwest Territories (GNWT). Historic and real-time data are available online at Water Survey of Canada’s website: https://wateroffice.ec.gc.ca/. Only finalized data from stations that have been operating for more than 15 years and that had a sufficient annual record (i.e., very few days of data missing) were included. Data from the sites selected were grouped by watershed size (Table 1):

• Small watersheds (< 10,000 km2): n = 11
• Medium watersheds (10,000 – 100,000 km2): n = 7
• Large watersheds (> 100,000 km2): n = 3

This indicator was prepared by the Government of the Northwest Territories, Department of Environment and Climate Change, using information obtained from the Water Management and Monitoring Division.  

 

NWT Focus

The hydrology of a watershed (Fig. 1a) and the resultant water flow and level of streams, rivers and lakes depends on many factors including climate, geology, vegetation, landscape and permafrost, which vary substantially across the NWT. In northern environments, cold region hydrological processes create streamflow characteristics that differ from more temperate environments. For example, northern streamflow is highly dependent on snowfall amounts, ice content in the ground, and freeze/thaw events. Cold, northern basins typically see an accumulation of a snowpack over winter (typically six to eight months), followed by a rapid release of snowmelt water. This rapid snowmelt event generally results in the highest water levels of the year and is typically the dominant feature on hydrographs of NWT rivers (Fig. 1b).

NWT rivers have distinct snowmelt (or nival) hydrological regimes which are characterized by one major spring snowmelt streamflow period (freshet) and a transition to lower flows as the watershed snow source is depleted during the spring and early summer months (Fig. 1b). Secondary peaks in the summer and fall can result from rainfall events. Low flow (or baseflow) over winter is highly dependent on the distribution and thickness of permafrost which strongly controls the flow and storage of subsurface water.

Figure 1. Watershed definition and a conceptual graph of typical annual NWT hydrology.

 

Current View: status and trend

 

Trends in Annual Flow:

In general, the total amount of water flowing through the outlet of small, medium, and large watersheds studied has increased since monitoring began, but this amount varies across the NWT and depends on watershed size and characteristics.

Changes to the total annual flow of rivers may be caused by anthropogenic influences and/or by climate change. Specifically, changes may be due to:

1. the timing, amount, and form of precipitation;
2. the amount of open water evaporation and transpiration from vegetation;
3. changes in the amount of water stored in the watershed (surface and subsurface); and
4. anthropogenic influences (flow regulation, extraction of water, land use changes).

Although we cannot identify a single cause for the observed trends in flow from watersheds with varying size, it is likely a combination of changes to all these variables that are leading to observed changes in water yields across the NWT.

 

What is annual yield?

Annual water yield is defined as the average amount of water that runs off in a watershed in a year. Yield is calculated by dividing the mean annual volume of flow that is in a watershed by the area of the watershed.

 

Annual Flow vs Annual Yield:

To compare changes in rivers and streams of various sizes, the annual flow value for each river is converted to a value called ‘annual yield’. Yield is calculated by dividing a river’s total annual flow by the area of its watershed. As a result, a river such as the La Martre River (13,900 km2) can be compared on similar terms to the Peel River (70,900 km2). This annual flow trend analysis relies on yield for its comparison.

 

Small Rivers:

Most small rivers in the NWT display stable or increasing basin yields over their period of record. If all the small rivers that were analyzed in this report are combined, there is an increasing trend of approximately 1.2 mm per year in yield (Figure 2a). Mean annual yield in small watersheds in the southern Taiga Shield in the NWT has not changed (Ref. 1), while yield of small watersheds in the southern Taiga Plains region near Fort Simpson has been increasing since the mid-1990s (Ref. 2). Annual yields in small watersheds in the northern Taiga Plains and southern Arctic have also been increasing, but at a slower rate than those in the southern Taiga Plains (Ref. 3). In small watersheds, these changes are generally a result of changes to how water moves and is stored in a watershed which has been linked to thawing permafrost.

 

Medium Rivers:

Medium-sized rivers in the NWT have also displayed increasing basin yields that have increased at a rate similar to small watersheds at approximately 1.0 mm per year (Figure. 2b). The rate of increase in these basins is variable and more difficult to detect than in smaller basins because these medium-sized river basins straddle multiple ecozones and their flows are the net result of differing hydrological regimes. They are not solely representative of the ecozone through which their main stems flow. Like small rivers, it has been suggested that increasing basin yields could be related to permafrost thaw allowing for groundwater to be better connected with surface water (Ref. 3), while further increases in yields are anticipated from increasing precipitation (Ref. 4).

 

Large Rivers:

The 1,738 km long main channel of the Mackenzie River flows north-northwest from Great Slave Lake to the Beaufort Sea, via the Mackenzie River Delta. The Slave River is a major tributary to Great Slave Lake, which feeds the Mackenzie River. The largest tributaries to the main stem of the Mackenzie River (i.e., the length of the river downstream of Great Slave Lake) include the Liard, Great Bear, Arctic Red and Peel rivers. Streamflow patterns on the Mackenzie River are the combined signal of changes occurring across all watersheds that flow into it (located in NWT, Alberta, Yukon, British Columbia, Saskatchewan, and Nunavut). Although annual river yields in major tributaries such as the Liard (Figure 3b) and Peel rivers (Figure 2b) are decreasing (0.1 mm and <0.1 mm, respectively), annual river yields on the Mackenzie River are increasing (Figure 3c), but the amount of change (<0.1 mm per year) is much smaller compared to other rivers in the NWT.

The Slave River drains a very large area (> 600,000 km2) of northern British Columbia, Alberta and Saskatchewan, and contributes over 75% of the inflow to Great Slave Lake. One of the primary tributaries to the Slave River is the Peace River, on which construction of the W.A.C Bennett Dam was completed in 1967, and filled by 1971, creating the Williston Reservoir. Excluding non-typical reservoir operations from the data (filling [1968-1971] and large release [1996-1997]), annual yields have significantly decreased (0.4 mm per year) on the Slave River over the period of record (1960-2017) (Figure 3a), with significant decreases in yields on both the Peace and Athabasca rivers observed during the same time.

Figure 2. Summary of the general trend in annual river yield (mm) for small (<10,000 km2) and medium watersheds studied (10,000-100,000 km2) across the NWT. Data source: ECCC NWT Hydrometric Network available at: https://wateroffice.ec.gc.ca/ Data interpreted by ECC-WMMD.

 

Figure 3. Summary of the general trend in annual river yield (mm) for the (a) Slave River, (b) Liard River and (c) Mackenzie River. Note that non-typical reservoir operations were excluded from the data analyses for the Slave River (filling [1968-1971] and large release [1996-1997]). Data source: ECCC NWT Hydrometric Network available at: https://wateroffice.ec.gc.ca/ Data interpreted by ECC-WMMD.

 

Seasonality:

The seasonality of NWT hydrology varies with latitude and is closely linked to regional weather, and in particular, to regional air temperature. As a result, the timing of spring flow and the length of the open water period varies across the territory. For example, rivers in the South Slave and Dehcho regions usually experience peak flows in May, while peak flows in southward-flowing rivers in the North Slave region do not usually occur until late June. Rivers further north and west in the Sahtu, Gwich’in and Inuvialuit settlement regions may not experience peak flows until June or July, given the colder, sub-Arctic and Arctic climates. Despite this variability, rivers studied across the NWT show similar changes in the seasonality of flows since monitoring began in the 1970s (Figure 4).

 

Spring (Apr – Jun):

Of the rivers studied across the NWT, spring flow is generally occurring earlier in the year by approximately 1 week for all watershed sizes; except for the Hay River, which shows little to no change in the onset of spring flow (Figure 4). Changes to the timing of spring snowmelt across the Arctic and sub-Arctic have largely been attributed to increasing air temperatures because of climate change (Ref. 5).

 

Summer (Jul – Aug):

There has not been a consistent change in summer flows in rivers in the NWT. In response to an earlier snowmelt, the onset of summer conditions has become earlier, and the growing season has become longer. Increasing air temperatures provide more energy for evapotranspiration in the summer, but also results in an increase in convective rain events (e.g., localized thunderstorms) that return moisture to the ground (Ref. 6).

 

Fall (Sep – Oct):

The most pronounced change in all rivers is the increase in the proportion of flow occurring later in the summer and fall due to increases in the magnitude and frequency of rainfall (Ref. 7) (Figure 4). The Dehcho First Nations (2011; Ref. 8) have reported that the region is getting warmer and wetter overall, with more rainfall in August and September and even into October. More rainfall in the late summer/fall saturates the ground and provides more water availability for fall and winter subsurface flow. Wet soil also takes longer to freeze in the winter compared to drier soil, meaning that even without warmer air temperatures, freezing of the subsurface will take longer in years with increased late season rainfall.

 

Winter (Nov – Mar):

Winter yields have increased significantly (0.08-0.14 mm per year) and in some small watersheds (< 10,000 km2), surface water flow is beginning to occur year-round in some rivers that would previously freeze to the bed in the winter (e.g., Caribou Creek, Rengleng River).

 

Winter baseflow is the amount of water in a stream or river that flows in the winter, typically underneath ice cover. In northern rivers, winter baseflow is usually sourced primarily from groundwater inputs as precipitation is usually stored as snow for the duration of winter. Observed changes in winter flows have been attributed to:

1. increasing air temperatures (Ref. 9);
2. changing precipitation patterns (Ref. 10);
3. more water stored in the ground prior to winter freeze-up (Ref. 11);
4. decrease in glacier coverage (Ref. 12);
5. changes to how water moves through the ground (i.e., subsurface flowpaths; Ref. 13); and
6. permafrost thaw (Ref. 14).

Increased baseflow in winter can lead to other significant changes in the hydrology of a watershed. For example, subsurface water ejected to the ground surface in winter may immediately freeze to create icings (Ref. 15) (or aufeis), potentially damaging infrastructure and impacting aquatic ecosystems.

Figure 4. Mean river flow for 10-year periods in watersheds of differing size across the NWT. (a) Rengleng River; (b) Hay River; (c) Peel River; and (d) Mackenzie River. (*) shows periods with less than 10 years of data. Data source: ECCC NWT Hydrometric Network available at: https://wateroffice.ec.gc.ca/ Data interpreted by ECC-WMMD.

 

Looking around

This assessment looks at watersheds across the NWT that transect multiple ecozones and climates. Conditions in other jurisdictions in Canada can have an impact on the quantity and flow of water within the territory as the NWT is predominately a downstream jurisdiction. The Mackenzie River has many tributaries that originate from five other Canadian provinces and territories. The main tributaries to the Mackenzie basin with headwaters in other jurisdictions include the Slave River (the Peace and Athabasca rivers), Liard River and the Peel River. Because of the nature of the Mackenzie River Basin, the GNWT has signed transboundary agreements with the Yukon, British Columbia and Alberta to ensure the ecological integrity of our water is maintained. Implementation of these agreements ensures that water flow is maintained for ecological, social and cultural reasons.

 

Looking forward

Projections for the future of water quantity in the NWT are difficult to make due to uncertainty of future climate, sparse data networks (hydrology, climate, permafrost) and poor representation of cold region processes in hydrological models. Changes to streamflow are the result of changes to every other component of the hydrological cycle which means that accurate streamflow prediction is dependent on correctly modelling future precipitation, evapotranspiration and changes in basin storage which is highly dependent on permafrost extent. Due to this variability, valid predictions on how water levels and flows will change in the future are not possible.

 

Find out more

For more information go to: https://wateroffice.ec.gc.ca/

 

Technical Notes

Table 1: List of the hydrometric stations used to identify trends in water quantity from small, medium, and large watersheds across the NWT. Ecozone is not defined for medium and large river basins as their watershed boundaries straddle multiple ecozone

Station	ID	Watershed Area	Ecozone
Small watersheds (< 10,000 km2)
Trail Valley Creek near Inuvik	10ND002	68 km2	Southern Arctic
Baker Creek at Lower Martin Lake	07SB013	121 km2	Taiga Shield
Scotty Creek at Highway No. 7	10ED009	202 km2	Taiga Plains
Birch River at Highway No. 7	10ED003	542 km2	Taiga Plains
Caribou Creek above Highway No. 8	10LC007	590 km2	Taiga Plains
Rengleng River below Highway No. 8	10LC003	1300 km2	Taiga Plains
Jean-Marie River at Highway No. 1	10FB005	1310 km2	Taiga Plains
Indin River above Chalco Lake	07SA004	1520 km2	Taiga Shield
Martin River at Highway No. 1	10GC003	2050 km2	Taiga Plains
Cameron River below Reid Lake	07SB010	3630 km2	Taiga Shield
Hanbury River above Hoare Lake	06JB001	5770 km2	Taiga Shield
Medium watersheds (10,000 – 100,000 km2)
La Martre River below outlet of Lac La Martre	07TA001	13,900 km2	multiple
Arctic Red River near the mouth	10LA002	18,750 km2	multiple
Coppermine River at outlet of Point Lake	10PB001	19,200 km2	multiple
Lockhart River at outlet of Artillery Lake	07RD001	26,600 km2	multiple
Camsell River at outlet of Clut Lake	10JA002	32,100 km2	multiple
Hay River near Hay River	07OB001	51,700 km2	multiple
Peel River above Fort McPherson	10MC002	70,600 km2	multiple
Large watersheds (> 100,000 km2)
Liard River near the mouth	10ED002	275,000 km2	multiple
Slave River at Fitzgerald (Alberta)	07NB001	606,000 km2	multiple
Mackenzie River at Arctic Red River	10LC014	1,679,100 km2	multiple

 

References

Ref. 1.  Spence, C. & Hedstrom, N. 2018. Hydrometeorological data from Baker Creek Research Watershed, Northwest Territories, Canada, Earth System Science Data, 10(4), 1753-1767.

Ref. 2.  Connon, R.F., Quinton, W.L., Craig, J.R., & Hayashi, M. 2014. Changing hydrologic connectivity due to permafrost thaw in the lower Liard River valley, NWT, Canada. Hydrological Processes, 28(14), 4163-4178.

Ref. 3.  St Jacques, J.M., & Sauchyn, D.J. 2009. Increasing winter baseflow and mean annual streamflow from possible permafrost thawing in the Northwest Territories, Canada, Geophysical Research Letters, 36(1), 1-6.

Ref. 4.  Box, J.E., Colgan, W.T., Christensen, T.R., Schmidt, N.M., Lund, M., Parmentier, F-J.W., Brown, R., Bhatt, U.S., Euskirchen, E.S., Romanovsky, V.E., Walsh, J.E., Overland, J.E., Wang, M., Corell, R.W., Meier, W.N., Wouters, B., Mernild, S., Mard, J., Pawlak, J. & Olsen, M.S. 2019. Key indicators of Arctic climate change: 1971-2017. Environmental Research Letters. 14, 045010.

Ref. 5.  Stone, R.S., Dutton, E.G., Harris, J.M., & Longenecker, D. 2002. Earlier spring snowmelt in northern Alaska as an indicator of climate change, Journal of Geophysical Research: Atmospheres,ACL 10-1_ACL 10-13.

Ref. 6.  Kochtubajda, B., Flannigan, M.D., Gyakum, J.R., Stewart, R.E., Logan, K.A., & Nguyen, T.V. 2005. Lightning and fires in the Northwest Territories and responses to future climate change, Arctic, 59(2), 211-221.

Ref. 7.  Beel, C.R., Heslop, J.K., et al. 2020. Emerging dominance of summer rainfall driving High Arctic terrestrial-aquatic connectivity. Nature Communications. 12: 1448.

Ref. 8.  Dehcho First Nations. 2011. Traditional Knowledge Assessment of Boreal Caribou (Mbedzih) in the Dehcho Region. Report prepared for the Canadian Wildlife Services (CWS).

Ref. 9.  Duan, L., Man, X., Kurylyk, B.L, & Cai, T. 2017. Increasing winter baseflow in response to permafrost thaw and precipitation regime shifts in northeastern China, Water 9(1), 15 pp.

Ref. 10. Spence, C., Kokelj, S.A., Kokelj, S.V. & Hedstrom, N. 2014. The process of winter streamflow generation in a subarctic Precambrian Shield catchment, Hydrological Processes, 28, 4179-4190.

Ref. 11. Connon, R., Devoie, É., Hayashi, M., Veness, T., & Quinton, W. 2018. The influence of shallow taliks on permafrost thaw and active layer dynamics in subarctic Canada. Journal of Geophysical Research: Earth Surface, 123, 1-17.

Ref. 12. Liljedahl, A. K., Gaedeke, A., Baraer, M., Chesnokova, A., Lebedeva, L. … & O’Neel, S. 2016 Decrease in glacier coverage contributes to increased winter baseflow of Arctic rivers, American Geophysical Union Fall Meeting 2016.

Ref. 13. St Jacques, J.M., & Sauchyn, D.J. 2009. Increasing winter baseflow and mean annual streamflow from possible permafrost thawing in the Northwest Territories, Canada, Geophysical Research Letters, 36(1), 1-6.

Ref. 14. Wang, P., Huang, Q., Pozdniakov, S.P., Liu, S., Ma, N. … & Fu, G. 2021 Potential role of permafrost thaw on increasing Siberian river discharge, Environmental Research Letters, 16, 034046.

Ref. 15. Crites, H., Kokelj, S.V., & Lacelle, D. (2020) Icings and groundwater conditions in permafrost catchments of northwestern Canada, Scientific Reports, 10: 3288.

 

 

11.5 Trends in Water Levels of Big Lakes

This indicator is to assess the presence of trends in the water levels of Great Slave Lake and Great Bear Lake, the two largest lakes in the Northwest Territories (NWT).

Historic and real-time water level data are available online at Water Survey of Canada’s website: https://wateroffice.ec.gc.ca/. Each point on the graph in Figure 1 represents the average annual water level in metres for that year. While the Great Slave Lake data represent metres above sea level, values for Great Bear Lake are water level relative to a local benchmark.

This indicator was prepared by the Government of the Northwest Territories, Department of Environment and Climate Change, using data generated by gauges located on Great Slave Lake at Yellowknife Bay (07SB001) and on Great Bear Lake at Hornby Bay (10JE002). The gauges are part of the larger NWT Hydrometric Network, a partnership between Environment and Climate Change Canada and the Government of the Northwest Territories.

 

NWT Focus

Monitoring water levels on NWT’s great lakes is important because:

• They are large, deep water bodies which store a very large quantity of water;
• Both lakes drain into the Mackenzie River. The outlet of Great Slave Lake is the primary source of the river, while Great Bear Lake drains into Great Bear River which subsequently flows into the Mackenzie River. Water levels on Great Slave Lake have a strong influence on water levels on the Mackenzie River;
• It allows us to track potential very broad-scale impacts on water resources in the NWT;
• They have relatively long periods of record to examine long-term trends; and
• They are a foundation for traditional economies and ways of life.

 

Current View: status and trend

 

Great Slave Lake (GSL):

GSL is the deepest lake in North America (614 m), the second largest lake in the NWT, and the 10th largest lake in the world (27,200 km2). Due to its large size, changes in water levels are generally small throughout the year and from one year to another (< 30 - 50 cm). A change in water level of 40 cm on GSL is equivalent to a volume of 11 km3 (or 11,000,000,000 m3), which is more than double the total annual flow of the Hay River.

Water levels in large lakes are an integrated response of the sum of all inflows and precipitation, minus outflows, and evaporation. This means that changes to lake levels over time could be the result of changes to any (or all) component of the hydrological cycle.

Although water levels vary year to year, there is no significant increasing or decreasing trend in water levels on GSL over the period of record (1941-2019, excluding the non-typical reservoir operation periods of the Williston Reservoir) (Figure 1).

Figure 1. Mean annual water levels on Great Slave Lake at Yellowknife Bay (07SB001). There is no statistically significant increasing or decreasing trend in water level. Data during the Williston Reservoir filling period (1968-1971) and during a required release (1996-1997) were not included in the analysis but are depicted by the blue shading/dots. Source: Data were data generated by a gauge located on Great Slave Lake at Yellowknife Bay (07SB001) - Water Survey of Canada’s website: https://wateroffice.ec.gc.ca/.

 

Great Bear Lake:

Great Bear Lake is the largest freshwater lake entirely within Canada, and the eighth largest in the world (31,153 km2). The massive size of the lake provides steady flow of water throughout the year to the Mackenzie River, via the Great Bear River. Similar to GSL, a water level change of 40 cm on Great Bear Lake is approximately equivalent to a volume of 12.5 km3 (or 12,500,000,000 m3), which is slightly less than the total annual flow of the Great Bear River. Lake water levels generally decrease over the winter due to reduced input (e.g., no large river flowing into the lake) and a continuous loss of water through Great Bear River.

Although water levels vary year to year, there is no significant increasing or decreasing trend in water levels on Great Bear Lake over the period of record (1984-2018) (Figure 2).

Figure 2. Mean annual water levels on Great Bear Lake at Hornby Bar (10JE002). There is no increasing or decreasing trend in water level. Source: Data were data generated by a gauge located on Great Bear Lake at Hornby Bay (10JE002) - Water Survey of Canada’s website: https://wateroffice.ec.gc.ca/.

 

Looking around

Given the size and its geographic location, there are no comparable lakes to Great Bear Lake in Canada. Even Great Slave Lake, which is located relatively close geographically, is considerably different due to its upstream basins and the significant input it receives each year via the Slave River.

 

Looking forward

Projections for the future of water quantity in the NWT are difficult to make due to uncertainty of future climate, sparse data networks (hydrology, climate, permafrost) and poor representation of cold region processes in hydrological models. Changes to lake levels are the result of changes in other components of the hydrological cycle. This means that accurate water level and flow prediction are dependent on correctly modelling future precipitation, evapotranspiration and changes in basin storage. Changes in basin storage are highly dependent on permafrost integrity and extent. Due to this variability, valid predictions on how water levels and flows will change in the future are not possible.

 

Find out more

For more information go to: https://wateroffice.ec.gc.ca/

 

Technical Notes

Water level and flow data for Great Slave and Great Bear Lakes was obtained from monitoring gauges that are part of the larger NWT Hydrometric Network, a partnership between ECCC and the GNWT. Historic and real time data are available online at Water Survey of Canada’s website: https://wateroffice.ec.gc.ca/. Only finalized data from stations that have been operating for > 15 years and that have a sufficient annual record (e.g., very few days of data missing) were included.