Water

All ecosystems and humans depend on water; therefore, there is a direct connection between ecosystem health and the state of water resources. It is important to NWT residents that the quantity and quality of water resources within the Territory are maintained.

Water resources are not limitless. There are increasing pressures on these resources through climate change and human actions.  Aquatic ecosystems are made up of water, sediments, living organisms and their interactions. If one of these components is impaired, the overall health of the aquatic ecosystem is compromised.

To track the integrity of the ecosystem, it is useful to establish indicators for each of the components including water quality and quantity. 

Water in the Taiga Plains:  Falls along the Hay River c. M. Oldham/ENR

Indicators are reported within each NWT ecozone and the Beaufort Sea.  The vast majority of the NWT lies withing the Mackenzie River Basin.  Lands drained by river systems eventually drain into the Mackenzie River and into the Beaufort Sea.  It is Canada's largest river basin and the second largest river basin in North America with river systems draining part of British Columbia, Alberta, Saskatchewan, Yukon, Nunavut and NWT.

Ultimately, if aquatic ecosystem health is compromised, it is reflected in the biological community.  Biomonitoring enhances water quality and quantity monitoring assessments by measuring the health of the biological community, reflecting the combined effects of water chemistry, sediment chemistry, physical habitat characteristics, hydrology, nutrient levels and food availability.

11.1 Trends in winter flow in NWT Rivers

This indicator tracks the trends in winter flows in selected rivers of the NWT.

Winter flows are reported for 13 rivers in the NWT, organized by ecozone and catchment area.  Winter flows are calculated by averaging the November to April monthly data, expressed in cubic meters per second.  Trends in winter flows are estimated using decade averages.  Catchment area is total drainage area of a river above the gauge site.

Some of the larger rivers include tributary sub-catchments for several ecozones.  All the selected rivers have natural flow regimes without any artificial controls and generally have data records of 30 to 40 years.  For more information on a regulated river, the Slave, see Indicator 11.2.   

Data are obtained from the Water Survey of Canada Hydat website²² and graphs and analysis are by Bob Reid, Water Resources Division, AANDC¹⁸. 

Cameron Falls in winter, Taiga Shield c. S. Carriere.

NWT Focus

In the NWT, as in most northern regions, the lowest stream flows occurs during winter⁴.  Summer flows can be many times higher than winter flows (see hydrograph for Peel River below).  Adequate winter flows are important for overwintering fish, providing habitat with water temperatures and dissolved oxygen levels sufficient for fish survival³.

Daily mean flow (cubic metre per second) obtained from the Peel River for year 1969-2009.  Multi-year average of daily flow is shown as MEAN (black line).

Current view - status and trend

In general, using decade averages, winter flow show increasing trends across all ecozones, and for large and small basins alike.  The Cordillera and Taiga Plains rivers show small increases between the 1970s and 1980s and larger increases in the 1990s and 2000s over a range of catchment sizes.  The two Taiga Shield rivers (Cameron River and Baker Creek) are relatively small and have a shorter period of record but show large increases in the decade average in the 2000s.  The Southern Arctic (Tundra Shield) rivers are relatively stable through the 1970s to the 1990s with an increase in winter flows apparent in the 2000s.  The larger rivers, such as the Mackenzie River with tributary inflows from more than one ecozone, also show increasing winter flows based on decade averages by also possibly show some cyclical patterns.

Peel River, Taiga Cordillera, Catchment Area:  70,600 km²

Arctic Red River, Taiga Cordillera, Catchment Area:  18,750 km²

South Nahanni River, Taiga Cordillera, Catchment Area:  14,500 km²

LaMartre River below Lac LaMartre, Taiga Plains, Catchment Area:  13,900 km²

Trout River at Highway #1, Taiga Plains, Catchment Area:  9,270 km ²

Jean Marie River at Highway #1, Taiga Plains, Catchment Area:  1310 km²

Lockhart River at outlet of Artillery Lake, Southern Arctic (Tundra Shield), Catchment Area:   26,660 km²

Coppermine River at Point Lake, Southern Arctic (Tundra Shield), Catchment Area:  19,300 km²

Cameron River below Reid Lake, Taiga Shield, Catchment Area:  3,600 km²

Baker Creek at Lower Martin Lake, Taiga Shield, Catchment Area:  140 km²

Hay River at Hay River, Taiga Plains, Catchment Area:  51,700 km²

Liard River at Fort Liard, Cordillera and Taiga Plains, Catchment Area:  222,000 km²

Mackenzie River at Tsiigehtchic, Cordillera, Taiga Shield and Taiga Plains, Catchment Area: 1,680,000 km²

Although the decade averages indicate an increasing trend in winter flow, rigorous statistical analyses were not done with the data for this indicator.  Statistical analyses of flow gauge data are available and confirm the trends shown above.  Strong increasing trends of winter flow are noted in the Mackenzie Basin¹ and the Peel Watershed (figure 3 in ref 9).  There is evidence the rate of increase in winter low flows may have been higher two decades ago (period prior to 1983) than recently⁹.

The timing of winter low flows has changed during the past 50 years.  Ehsanzadeh and Adamowski (2010)⁸ found that the seven-day window of low flows is occurring later in winter in recent years for most areas north of 60 between the Yukon and the Hudson Bay^{8, 10,15}.

Possible reasons for increasing winter flows could be increased autumn rainfall and/or warmer autumn and winter temperatures that delay ground freezing.  Changes in groundwater contribution (from hot or warm springs may also affect winter flows in rivers in the Cordillera⁵.

Looking Around

Monk and Baird (2010)¹⁵ have compiled trend information from a number of sources for the "Canadian Biodiversity:  Ecosystem Status and Trends Report"¹⁰ and have identified similar trends in winter flows in tributaries of the Mackenzie River.  Note that the minimum river flows in northern Canada occur in winter but in southern Canada they occur at the end of summer.  Both significant increases in winter low flows in the north and significant decreases in summer low flow in the south are consistent with what is expected in a warmer climate.

Trends in minimal river flow in natural rivers (1970-2005) reproduced from the "Canadian Biodiversity:  Ecosystem Status and Trends Report"¹⁰, based on Monk and Baird (2010)¹⁵.

Looking Forward

Further investigation of the cause(s) is warranted, including possible links between these trends and decadal fluctuations^2,6,21 and climate change⁴.  Climate change forecasts for the Mackenzie River Basin predict further increases in temperature and increases in precipitation (see THE BIG PICTURE: A CHANGING PLANET Focal Point).  As this occurs, it is expect the increasing trend in winter streamflows will continue. 

Find More

For more data on river flow, go to the Water Survey of Canada, HYDAT webpage at:  www.wateroffice.ec.gc.ca
For more information on lakes and river trends in Canada, go to the "Canadian Biodiversity: Ecosystem Status and Trends Report" at:  www.biodivcanada.ca

Technical Notes

All results and analyses reported in this indicator are limited to areas south of the 70^o N, as long-term gauge data are not available for rivers north of that latitude. 

For more information on how stream flows are monitored by the Water Survey of Canada NWT/NU Hydrometric Network, go to http://wateroffice.ec.ca

Locations of gauges as of 2010-11 season are shown on the map below. 

A summary of how trend analyses on river flows are performed in provided in Ehsanzadeh et al. (2011)⁹, and references therein.

Updated July 2011

11.2  Trends in Slave River Flows

This indicator tracks the trends in river follow of the Slave River.

River flow trends are examined using (a) total annual flow calculated from daily mean data in cubic metres per second, (b) daily mean flows averaged over the years or record and, (c) extreme and mean flows (highest and lowest daily means and annual mean) in cubic metres per second for each year.

Slave River with white pelican c M. Bradley

Data are from the Water Survey of Canada NWT/NU Hydrometric Network²² gauging station at Fort Fitzgerald.

NWT Focus

Monitoring the Slave River flow is important to inform on potential transboundary issues and to provide information for river traffic, flood monitoring and aquatic ecosystem change.  The Slave River is the largest tributary of Great Slave Lake and contributes more than 75% of the flow into Great Slave Lake.

Current view - status and trend

Total annual flows are reported for the period of record, 1960 to 2010, and show a large inter-annual variability and a slightly decreasing trend.  From 1968 to 1971, total annual flow was reduced while the Williston Reservoir on the Peace River in British Columbia (BC) was filled.  Other than during the reservoir filling period, the total annual volume of flow in the Slave River has not been changed significantly by the operations of the Williston Reservoir.  Since hydro operations began in 1972, the lowest total annual flow was experience in 2010 after several years of extremely dry conditions in the northern regions of BC, Alberta and Saskatchewan.  Comparable extreme lows occurred previously in 1980, 1981 and 1995.



The flow regime of the Slave river has changed since the Bennett Dam was constructed on the Peace River and the Williston Reservoir began operations began operations for hydro-electricity generation.  Runoff from the Rocky Mountains in BC is held in the Williston Reservoir during the spring freshnet and summer for release back into the system during the autumn and winter when hydro-electricity demand is the greatest.  By the end of winter, the reservoir is generally drawn down to its lowest level and the refilling cycle continues.  Natural flows entering the Peace and Slave River system downstream of the Bennett Dam will dampen the effects of the Williston Reservoir operations.  The pre-dam and post-dam hydrographs show the effect on the Slave River from the Williston Reservoir operations on the Peace River.

The annual hydrograph shows large decreases in daily flows during spring and summer and shows winter flows have nearly doubled.

The annual and extreme flow graph shows a large reduction in maximum flows (usually a spring event) and an increase in minimum flows (usually a winter event) since the Bennett Dam was constructed and the Williston Reservoir has been operated for generating hydro-electricity.

The flow regime of the Peace River was changed with filling and operation of the Williston Reservoir for hydro-electricity generation.  Downstream of the reservoir controls, natural flows start to mask the effects of regulation but the effects are seen all along the main stem of the Peace River and on the Slave River at Fitzgerald, where the Slave River crossed the boundary into the Northwest Territories.

Looking around

"Other major rivers flowing across the NWT bordered are also measured to determine the effects of upstream developments.  Transboundary rivers with gauging stations include the Peel, Liard, Hay, Coppermine, Thelon and Back rivers." - Quote from Water Today:  Water Quality and Quantity in the NWT¹⁹.

Looking forward

The flow regime changed with the filling and operation of the Williston Reservoir.  Another hydro-electric dam and generating station are being proposed for "Site C" on the Peace River.  The river flow regulated by the Williston Reservoir at the Bennett Dam will be re-used for operation of the proposed "Site C" thus, there will be very little additional flow regime change.

Find more

Water Survey of Canada, Hydat webpage:  www.wateroffice.ec.gc.ca

BC Hydro webpage:  www.bchydro.com/sitec

Graphs prepared by Bob Reid, Water Resources Division , AANDC.

"Water Today:  Water Quality and Quantity in the NWT" available at:  www.ainc-inac.gc.ca/ai/scr/nt/pdf/wt10-eng.pdf

Updated July 2011

11.3 Trends in Great Slave Lake levels

This indicator tracks the trends in water level of Great Slave Lake in the NWT.

The data were downloaded from the Water Survey of Canada Hydat website ²² and analysis was done by Bob Reid, Water Resources Division, AANDC¹⁸.

Yellowknife Bay, Great Slave Lake c. B. Fournier

NWT Focus

Monitoring water levels on Great Slave Lake is important to inform the public and boaters of changing water levels, to provide information on water levels downstream along the Mackenzie River for ferry and barge operations and for assessing overall ecosystem changes¹⁹.

Current view - status and trend

Water levels in Great Slave lake are influenced by the Slave River as it contributes about 77% of the inflows¹⁹.  With regulation of the Peace River flow (Bennett Dame and Williston Reservoir operations) since 1968 and its effects on the Slave River, the resultant changes on Great Slave Lake are investigated.  Although the total volume of the Slave River has not been changed by the operations of the Williston Reservoir, the flow regime change has reduced the average high level of Great Slave Lake by 9 cm.  The average annual water level and the average annual low water level have both increased by 1 cm since slow regulations began on the Peace/Slave Rivers.

Annual maximum, minimum and mean water levels for Great Slave Lake were plotted for 1941 to 2010.
The 2010 water levels were the lowest on record.

Looking around

 Although Great Slave Lake water levels were affected slightly by operations of the Bennett Dam and Williston Reservoir, the annual variations in levels are due to winter snowpack/spring melt and summer rainfall throughout the watershed.  More than 65% of the Great Slave Lake watershed is outside the NWT, in the northern areas of BC, Alberta and Saskatchewan.  Precipitation amounts in these areas greatly affect the levels of Great Slave Lake.

Find More

Water Survey of Canada, Hydat webpage at:  www.wateroffice.ec.gc.ca

Graphs prepared by Bob Reid, Water Resources, Division, AANDC.

Reference List

Ref 1 - Abdul Aziz O. I., Burn D. H.2006. Trends and variability in the hydrological regime of the Mackenzie River Basin. Journal of Hydrology 316:282-294

Ref 22 - Water Survey of Canada,.2011. Water Survey of Canada Hydat website.

11.4  Trends in turbidity and arsenic in the Hay River

There are literally dozens of water quality parametres that can be measured as part of a monitoring program and many of these may be suitable as indicators. 
Two of these parameters are presented here.  It is important to note that as long as monitoring programs continue and water samples are collected and analyzed, other or additional parameters may be selected as indicators in the future.

Turbidity

This indicator tracks the changes in turbidity in the Hay River from 1988 through 2010 inclusive.

"Turbidity is a visual property of water and implies a reduction or lack of clarity that results form the presence of suspended particles or suspendoids"⁴.

Turbidity is often described as the "cloudiness" of water.  The concentration of suspended particles in the water affects how light travels through, and is reflected by, water.  The higher the concentration of suspended particles, the higher the turbidity of the water.  In rivers, turbidity can be influenced by the flow rate:  the higher the flow, the higher the flow; the higher the potential for bank erosion; and, the more particles tend to be stirred up and suspended in the water.  There is a seasonal component, in that the highest rate of influx of particulate matter tends to happen in spring as snowmelts and flows into the rivers. 

Turbidity can also be influenced locally by natural events such as thunderstorms where rainfall is so heavy it flows overland rather than soaking into the ground.  Construction in or near water can also cause local increases in turbidity.

Turbidity is measured using a meter or probe designed to quantify how the light travels through the water.  These data were collected from a sampling station on the Hay River nears the Alberta-Northwest Territories border and provided by Environment Canada (Yellowknife).

Arsenic

This indicator tracks the changes in arsenci concentrations in the Hay River from 1988 through 2010, where data is available.

Arsenci is classified as a "metalloid", meaning it can exhibit chemical properties of both metals and non-metals.  It occurs naturally in the rocks and soils of the NWT.  It most commonly enter the aquatic ecosystem through weathering of rocks and soils and through the groundwater.

Water samples were collected from a sampling station on the Hay River near the Alberta-Northwest Territories border by Environment Canada personnel.  Data were also provided by Environment Canada.

NWT Focus

Water quality parameters are naturally variable, influenced by season, water flow, ice cover and rainfall, to name a few.  A fairly robust data set from past years is needed to assess whether data patterns are indicative of a trend or whether they are within the naturally variability inherent in water quality measurements.  In the case of turbidity, the data set spans over 20 years.

It is useful to measure turbidity as an indicator of climate change.  In the NWT, there is already evidence of changes in ice-free dates for rivers and lakes, warming permafrost and increasing average annual temperatures³.  As climate modeling predicts the Hay River basin will become warmer and wetter in future, an increase in turbidity of the Hay River would be anticipated.

Water quality parameters are naturally variable and influenced by seasons, water flow, ice cover and rainfall, to name a few.  A fairly robust data set from past years is needed to assess whether data patterns are indicative of a trend or whether they are within the natural variability inherent in water quality measurements.  The date set for disvolved arsenic includes data from 1988 through 2010, with a four-year gap from 2002 - 2005.  The data set for total arsenic is shorter, with  data from 2002 through 2010, inclusive.

Arsenic is monitored as a "chemical of concern".  When present in high concentration, it can be toxic to aquatic biota.  Activities where the rock is broken down, such as mining, can cause increased weathering as fresh surfaces are exposed to the elements.  This is why there can be problems with high arsenic concentrations in water bodies near mines, even if arsenic was not used in the milling process.

Current view - status and trend

Turbidity

The graph below shows turbidity values measured in the Hay River 1988 through 2010, inclusive.  A simple linear regression was used to fit a trend line through the data.  The slope of the line is positive indicating a potential increase in turbidity over time.

In this graph, the R² represents the "coefficient of determination", which provides a measure of how well future outcomes are likely to be predicted by the model.  R² values can range from 0 to 1, where 0 indicates that no variability is explained by the model and 1 indicates that all variability is explained by the model.  In other words, how likely is it that turbidity is increasing in the Hay River (as shown by the positive slope of the regression line)?  Since the R² value is so low, it is unlikely turbidity is increasing over the period of record.

Arsenic

The graph below shows arsenic concentrations measured in the Hay River from 1988 through 2010, where data were available. Simple linear regression was used to fit trend lines through the data. The slopes of both regression lines are positive, indicating a possible increasing trend in both total and dissolved arsenic concentrations.

In this graph, the R² represents the "coefficient of determination.", which provides a measure of how well future outcomes are likely to be predicted by the model.  R² values can range from 0 to 1, where 0 indicates that no variability is explained by the model and 1 indicates that all variability is explained by the model.  In other words, how likely is it that total and dissolved arsenic concentrations are increasing in the Hay River (as shown by the positive slope of the regression lines)?  The R² values are both low, indicating there is not a strong linear relationship.

The Canadian Environmental Quality Guidelines¹ cite a threshold of 5 μg/L for total arsenic in fresh water.  Concentrations below 5 μg/L are considered safe for aquatic life.

In the graph above, all but one value fall below the 5 μg/L threshold.

Looking forward

The trend line calculated for turbidity is a simple linear regression, which does not take seasonality or any type of cycle into account.  Work on the Hay River report is currently underway.  This will involve a more exhaustive examination of the data including separation by season and use of statistical tests more suited to this type of data.  For example, variability in turbidity during spring melt could mask trends in turbidity at other times of the year.

If current climate change trends continue, increased precipitation would lead to higher flow rates, as well as increased influx of particulate matter from the surrounding land.  Increasing influx and higher flow rates would both contribute to increasing turbidity.

The trend lines calculated for arsenic are simple linear regressions and do not take seasonality or any type of cycling into account.  Wok on the Hay River report is currently underway.  This will involve a more exhaustive examination of the data including separation by season and the use of statistical tests more suited to this type of data.  For example, arsenic can be associated with particulate matter.  Cycles in turbidity could influence arsenic concentrations on a seasonal basis.

If the current trends were to continue with dissolved arsenic concentrations increasing by about 0.15 μg/L per decade, values would still be well below the 5 μg/L threshold in 10 years.

In the future, factors which affect turbidity could also result in changing arsenic concentrations.  Increasing industrial activities many result in more sources of arsenic to the aquatic ecosystem.

Looking around

The NWT Environmental Audit and Status of the Environment Report(²) utilized turbidity and metals (aluminum, iron, copper, arsenic and zinc) as surface water indicators.  In each case, the trends were assessed as "uncertain" due to lack of general monitoring and lack of long-term monitoring.

Find more

Aboriginal Affairs and Northern Development Canada Slave River Environmental Quality Monitoring Program at:  http://www.ainc-inac.gc.ca/ai/scr/nt/n/pubs/SRE-eng.asp

Aboriginal Affairs and Northern Development Canada Water Resources Division monitoring at:  http://www.ainc-inac.com/ai/scr/nt/env/wr/mn/index-eng.asp#local

Environment Canada at:  www.ec.gc.ca

The State of the Aquatic Ecosystem Report 2003 by the Mackenzie River Basin Board, available on the MRBB website at: www.mrbb.ca/information/34/index.html

NWT Environmental Audit and Status of the Environment Report 2011  This report is produced by AANDC/CIMP every five years as mandated by the Mackenzie Valley Resource Management Act.  Reports produced by CIMP are available on their website at: www.nwtcimp.ca

Technical Notes

The information and analysis in this section was put together for the purposes of this report by Laurie J. McEachern, Water Resources Division, AANDC.  The graphs were created using data provided by Environment Canada.

Updated July 2011

References

Ref 1 - CCME 2007.  Canadian Environmental Quality Guidelines.  Canadian Council of Ministers of the Environment, Environment Canada, Ottawa, Ontario.                

Ref 2 - Mackenzie River Basin Board 2003.  Mackenzie River Basin – State of the Aquatic Ecosystem Report, 218pp.

Ref 3 - SENES Consultants Limited 2011.  NWT Environmental Audit and Status of the Environment Report. Produced for Aboriginal Affairs and Northern Development Canada, Cumulative Impact Monitoring Program, Northwest Territories.

Ref 4 - Wetzel, R.G. 2001.  Limnology: Lake and River Ecosystems.  Third Edition.  Academic Press, San Diego, California.