Mackenzie Great Bear – Water Quantity

Water Quantity

Water quantity in the Mackenzie Great Bear sub-basin has undergone moderate change overall. Based on Indigenous and scientific observations, the sub-basin is subject to significant reductions in snow and ice cover, slightly earlier river ice break-up, and reduced spring river peak flows since the 1970s. These are likely linked to significant changes in climate over the past few decades, such as increased temperatures, particularly in winter. Human water use within the sub-basin has negligible impacts on water quantity due to the small population and large water yield in this sub-basin. Annual average river flows have mostly been stable, but winter and spring river flows have increased by up to 2% per year. The observed changes have potential to impact aquatic ecosystems and the ability for Indigenous communities to practice traditional land uses in the Mackenzie Great Bear sub-basin.

Information Availability

The following table summarizes the availability of information for each Water Quantity indicator.

Signs and Signals	Indigenous Knowledge Information and Data	Indigenous Knowledge Availability ¹	Science Information and Data	Science Data Availability²
Snow and Ice	Local observations and oral histories of changes in snow quality, ice thickness, presence and break up of ice jams	Some observations from few locations.	Available modeling information / stats on snow quality, ice thickness, presence and break up of ice jams	Snow data and analyses available from many weather stations. Low availability of ice data; limited ice monitoring.
Water Flows and Levels	Local observations and oral histories of changing flow / water levels in rivers / lakes and aquifers over time	Many observations from several locations.	Seasonal statistics including changes in flow / water levels in rivers / lakes and aquifers over time	Data available from many Water Survey of Canada stations; analyzed six representative sites across the basin.
Climate	Local observations and oral histories of temperature, precipitation normals and extremes over time	Limited observations from few locations.	Temperature, precipitation normals and extremes over time	Data available from many weather stations in the basin, analyses was provided.
Water Use	Not assigned to a Sign or Signal	Not assessed.	Number of water licenses, purpose, volume allocated, and volume used vs. water flow / level; Water demand from various sectors, including dams, agriculture, oil and gas, etc., trends in water use over time	Water Licences issued by Water Boards, not collected for this version.

¹ Qualifiers for the availability of local and Indigenous Knowledge observations in publicly available sources: Limited = 1-2 observations; Some = 3-4 observations; Many = 5 or more observations
² Qualifiers for the availability of science data in publicly available sources: Low = Individual studies or locations; Many = Network of monitoring stations across the basin

Snow & Ice

Reduced snowpack, shorter duration of ice cover, and earlier ice break-ups in some rivers and lakes have been observed in some locations in the Mackenzie Great Bear sub-basin.

Observations by Indigenous communities and scientific data indicate that snow cover has declined in many areas of the Mackenzie Great Bear sub-basin

Observations by the Dehcho First Nations and by scientists suggest there is less snowfall in some parts of the Mackenzie Great Bear sub-basin. Members of the Dehcho First Nations have reported there is less snowfall in the Dehcho region of the Northwest Territories than in the past.^[1] Observations by other Indigenous communities were not found. Similarly, snow data recorded by Environment Canada data show that there was reduced snowpack in Inuvik, NT from 1957 to 2012.^[2] Published snow mass estimates show that snow mass decreased west of the Mackenzie in the Mackenzie Mountains and near the west and south shores of Great Bear Lake, but remained stable or increased in the northernmost and southernmost parts of the sub-basin.^[3]

Change in Average March Snow Mass (as Snow Water Equivalent, in mm/decade) in the Mackenzie Great Bear sub-basin 1980 to 2015. Positive (yellow, light green) values indicate increases in snow mass, negative (dark green) values indicate declines in snow mass.

Snow mass trends were derived using a multi-dataset approach described in Mudryk et al. 2020, and provided by Environment and Climate Change Canada.

Observations by Indigenous communities suggest ice freeze-up occurs later in the fall, while scientific data suggests ice break-ups are significantly earlier than in the past

Indigenous communities in the Sahtu region of the Northwest Territories and scientists have witnessed a shift in the timing of ice break-up and freeze-up in the Mackenzie Great Bear sub-basin. Members of the Sahtu communities have reported the timing of freeze-up in waterbodies near Great Bear Lake has shifted from September to later in the fall. They have also observed how freeze-up takes longer than in the past, and that the ice is “not freezing as hard.”^[4] Statistical analyses of hydrometric data from Water Survey of Canada indicated that spring ice break-up on the Mackenzie River has shown a trend to occur significantly earlier between 1969 and 2006.^[5]This is supported by the spring hydrographs of the 2000s that showed earlier increases and peaks in spring flows (by about 5 days, on average) compared to the 1970s and 1980s (this study).

Spring Hydrograph of Mackenzie River at Inuvik for 1972-1991 and 1998-2017

Indigenous communities have observed thinner ice and changes in ice quality in some parts of the Mackenzie Great Bear sub-basin

Indigenous communities throughout the sub-basin have observed changes in ice thickness and quality. The Inuvialuit have noticed that ice that forms in the Mackenzie River Delta has become thinner in some areas in the last 5 to 10 years.^[6] In a study with Déline elders, participants suggested that ice thickness on Great Bear Lake has decreased from about 8 feet (2.4 m) to 6 feet (1.8 m) in recent winters compared to the past.^[7] Members of the Dehcho First Nations have similarly noticed changes in ice thickness and quality, describing it in one study as “a different kind of ice – slushy, not thick, solid, and clear.”^[8] In the Mackenzie and Selywn Mountains, Shúhtagot’ine elders and caribou hunters have observed how perennial ice patches are melting.^[9] Measured ice thickness data are available for 1960 to 2016 for Inuvik and preliminary analysis indicates a decreasing trend over this time period (this study).

The most common change referenced throughout interviews was that the ice did not freeze as thick and melted earlier and faster than in the past,
Parlee and Maloney, 2017

Ice break-up along the shores of Great Bear Lake, Deline NT. Image source: mattcatpurple via Flickr Creative Commons (copyright-free).

Ice thickness for Mackenzie River at Inuvik 1960-2016, based on ECCC data. Black dotted line indicates linear trend.

Water Flows & Levels

Changes in seasonal flow patterns and lower water levels in some rivers and lakes have been observed in the Mackenzie Great Bear sub-basin.

Indigenous communities have observed lower water levels in some lakes and the Mackenzie River Delta, while monitoring data only provide evidence for declining water levels in the Delta

The Inuvialuit and communities in the Sahtu region have observed a decline in the water levels in the Mackenzie River Delta and Great Bear Lake.^[10] Similarly, an analysis of river flow data recorded by Water Survey of Canada indicates that peak water levels during spring break-up in the Mackenzie River Delta have declined, which can result in reduced off-channel flows and reduced replenishment of delta lakes.^[11] Measured lake levels in Great Bear Lake, however, have been stable in summer and have increased in fall and winter, possibly related to the increased winter stream flows discussed below.

Trends in February and July lake levels at Selected Water Survey of Canada Stations in the Mackenzie Great Bear sub-basin. Data labels are the Sen’s slope (annual change in mean monthly level in m) and annual percent change relative to long term mean monthly level. Data from the Water Survey of Canada

Indigenous communities have encountered more sand bars and other navigational hazards in certain rivers and lakes

An increase in the number of gravel bars, sand bars, and shallower water conditions makes it challenging or impossible for people to access some areas by boat. In one study, elders expressed concern for the eroding shorelines of Brackett and Willow Lakes due to melting permafrost. The erosion has prompted the relocation of some cabins to Loche Lake and disrupts fish passage into nearby Kelly Lake.^[12]

Bear Rock on the banks of the Mackenzie River, Tulita NT. Image source: michael_swan via Flickr Creative Commons (copyright-free).

Scientific monitoring data suggests that average annual stream flows are relatively stable across the Mackenzie Great Bear sub-basin

Average annual flows at the mouth of the Mackenzie River have been stable^[13]as were average annual flows at five Water Survey of Canada discharge stations across the sub-basin: Mackenzie River at Fort Simpson, Mackenzie River at Norman Wells, Mackenzie River at Inuvik, Redstone River, and Great Bear River (this study). Only the Camsell River, a southern tributary of Great Bear Lake, experienced a significant increase in mean annual discharge from 1964 to 2018, by 0.78% per year. Accelerated permafrost thaw was cited as a key reason for increased runoff in watersheds of the discontinuous permafrost zone, in the absence of changes in precipitation,^[14] and Camsell River is the only watershed analyzed that is located in that zone. Flows in the Mackenzie River are regulated (Bennett dam) and subject to authorized withdrawals.^[15]

“Accelerated permafrost thaw was cited as a key reason for increased runoff in watersheds of the discontinuous permafrost zone.”^[16]

Scientific monitoring data suggests that flows in rivers have increased in the winter months and early spring

All six Water Survey of Canada station datasets analyzed showed significant increases in average monthly flows from January to April from 1972 to 2018 (this study). Discharge increased from around 0.2% per year at Great Bear River, to around 1.5% per year at the Mackenzie River mainstem stations and up to 5.6% per year at the Redstone River.

Trends in March streamflows at Selected Water Survey of Canada Stations in the Mackenzie Great Bear sub-basin. Data labels are the Sen’s slope (annual change in mean monthly flow in m³/s) and annual percent change relative to long term mean monthly flow. Data from the Water Survey of Canada

Scientific monitoring data suggests the maximum daily flows have decreased in the spring months

Water Survey of Canada data from the Mackenzie River at Arctic Red River show a decrease in maximum daily spring flows by about 3000 m³/s (about 10%) over the past four decades (1973-2011), which was attributed to regional climate warming and its implications for snowmelt processes. The timing and amount of peak flow are linked to the timing of snowmelt. There is a need to further understand how climate change is influencing snowmelt and runoff generation processes in northern watersheds that vary in streamflow characteristics and snow cover.

Climate

Warmer air temperatures and more variability in precipitation have been recorded in the Mackenzie Great Bear sub-basin.

A rise in air temperatures has been recorded in scientific studies and observed by Indigenous communities in the Mackenzie Great Bear sub-basin

Climate records have shown that air temperature has increased significantly across the Mackenzie Great Bear sub-basin. Particularly large increases were observed in winter, with an increase of over 5.5°C from 1948 to 2016.^[18] Unusually high air temperatures have been observed in recent summers by the Tulı́t’a Got’ı̨ne and the Inuvialuit, and the Gwich’in report that recent winters are much milder than in the past, as extreme cold temperatures in wintertime are no longer reached.^[19] Some of the most pronounced warming trends have been observed in Deline, where the annual average temperature has increased 1.5°C between 1950 and 2005.^[20]

Temperature trends in the Mackenzie Great Bear Sub-basin (1948 – 2016). From: Bonsal et al. 2020^[19]

Sub-basin (as defined in Bonsal et al 2020)	Season	Temperature Change (°C)
Mackenzie	Spring	2.9
	Summer	1.6
	Fall	2.1
	Winter	5.7
	Annual	3.2
Great Bear	Spring	2.7
	Summer	1.7
	Fall	1.7
	Winter	5.4
	Annual	2.9

Note: Spring: Mar-Apr-May, Summer: Jun-Jul-Aug, Fall: Sep-Oct-Nov, Winter: Dec-Jan-Feb

The authors of this analysis divided the Mackenzie Great Bear sub-basin into two parts; combined results for the entire sub-basin were not available.

Precipitation trends are more variable across the sub-basin, according to some scientific analyses and observations by Indigenous communities

Trends in past annual precipitation in the Mackenzie Great Bear sub-basin vary between datasets and regions.^[21] However, significant precipitation increases have been detected in the recent analysis of climate data provided by Environment and Climate Change Canada (ECCC), with increases of over 30% in annual precipitation from 1948 to 2012 in the Great Bear Lake watershed and of about 13% for the areas of the Lower Mackenzie River. In fact, this was the greatest average annual precipitation increase among the six Mackenzie sub-basins.^[22] Local observations of changes in precipitation differ across the sub-basin. The Inuvialuit have observed more variability in precipitation than in the past and a rise in extreme precipitation events during the summer months.^[23] In one study with Gwich’in elders, some participants indicated that precipitation has remained consistent in recent years, while others noted there is less rainfall than in the past.^[24]

Precipitation trends in the Mackenzie Great Bear Sub-basin (1948 – 2012). From: Bonsal et al. 2020^[19]

Sub-basin	Season	Precipitation Change (%)
Mackenzie	Spring	-3.6
	Summer	-1.3
	Fall	5.7
	Winter	31.4
	Annual	13
Great Bear	Spring	19.3
	Summer	13.9
	Fall	28.9
	Winter	48.2
	Annual	30.7

Water Use

The Mackenzie Great Bear sub-basin has a small population and minimal industrial activity, and thus minimal water demand on the large water supply.

Water use likely has insignificant consequence for water quantity in the Mackenzie Great Bear sub-basin:

Information on water licencing, including volumes, is readily available for the entire region from the public registries of the Water Boards. These data have not been amalgamated or analyzed. Water use likely has insignificant consequence for water quantity in the Mackenzie Great Bear sub-basin due to the small population and localized industrial activities.

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