Water Quantity
Summary
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.
The following table summarizes the availability of information for each Water Quantity indicator.
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.
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.
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,
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.
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
Bear Rock on the banks of the Mackenzie River, Tulita NT. Image source: michael_swan via Flickr Creative Commons (copyright-free).
“Accelerated permafrost thaw was cited as a key reason for increased runoff in watersheds of the discontinuous permafrost zone.”[16]
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
Climate
Warmer air temperatures and more variability in precipitation have been recorded in the Mackenzie Great Bear sub-basin.
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 in the Mackenzie Great Bear Sub-basin (1948 – 2012). From: Bonsal et al. 2020[19]
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 Quality