recent trends and variability in river discharge...

RECENT TRENDS AND VARIABILITY IN RIVER DISCHARGE ACROSS NORTHERN CANADA

Stephen J. Déry1 , Tricia Stadnyk2, and Matthew Macdonald1,2

1Environmental Science and Engineering Program, University of Northern British Columbia, Prince George, British Columbia, Canada 2 Department of Civil Engineering, University of Manitoba, Winnipeg, Manitoba, Canada

INTRODUCTION

• More than half the Canadian landmass drains

northward, contributing important freshwater to the

global ocean.

• This freshwater affects high-latitude biogeochemical,

oceanic, cryospheric & ecological processes.

• It is unknown to what degree climate change &

anthropogenic activities individually or collectively

affect freshwater discharge in northern Canada.

OBJECTIVE:

• Establish recent trends in northern Canadian river

discharge within the context of a changing climate

and rising anthropogenic activities.

DATA & METHODS

• A total of 42 rivers are used to assess recent

characteristics & trends in river discharge across

northern Canada.

• These are selected based on gauged data availability

(see Acknowledgements), gauged area, record

length, & data quality.

• Total gauged area = 5.26 × 106 km2

• Time series of annual & seasonal discharge are

created based on daily streamflow data for 1964 to

2013, then gap-filled (Déry et al. 2005).

• Statistics of mean, standard deviation (SD) &

coefficient of variation (CV) of annual/seasonal

discharge are done for six drainage regions: Bering

Sea, Western Arctic Ocean, Western Hudson Bay,

Eastern Hudson Bay, Eastern Arctic Ocean &

Labrador Sea.

• Mann-Kendall Test (MKT) is then used to assess

trends in annual/seasonal discharge, with p < 0.05

considered statistically-significant.

CONCLUDING DISCUSSION

• Rivers of northern Canada exhibit strong interannual

& interdecadal variability.

• No trend in total discharge across the study domain

is observed for 1964-2013; however, there is a

pronounced trend toward increasing discharge since

1989 (Fig. 4).

• Significant increasing (decreasing) trends are seen in

in some basins in winter (summer), largely due to flow

regulation (Fig. 5).

ACKNOWLEDGEMENTS

Thanks to Water Survey of Canada, Manitoba Hydro, Hydro-Québec, and Centre d’Expertise Hydrique du

Québec for access to hydrometric data and the Natural Sciences and Engineering Research Council of

Canada, Manitoba Hydro, and partners through funding of the BaySys project. Thanks to Marco Hernández-

Henríquez and Bunu Sharma for assistance in poster preparation and to Eric Wood for motivating this effort.

STUDY AREA DISCHARGE STATISTICS

REFERENCES

Déry, SJ, M Stieglitz, EC McKenna & EF Wood, 2005: Journal of Climate, 18, 2540-2557.

Fig. 2: Total annual discharge for 42 rivers of northern Canada, 1964-2013.

Fig. 4: Total seasonal discharge for 42 rivers of northern Canada, 1964-2013.

RESULTS

• Table 1 provides statistics on the mean annual, standard deviation,

coefficient of variation and trend in annual discharge for six regions of

northern Canada, 1964-2013.

• There is considerable year-to-year variability in annual discharge (CV of

9% to 16% regionally), but that variability diminishes for the total study

area (CV = 7%).

• There is no trend in the 1964-2013 annual discharge to the Bering Sea,

Western Arctic Ocean, Western Hudson Bay, and Labrador Sea (Fig. 2).

• There is an increasing (decreasing) trend in river discharge to Eastern

Hudson Bay (Eastern Arctic Ocean), largely explained by the Caniapiscau

River diversion that normally drains to Ungava Bay into the La Grande

Rivière system for enhanced hydropower production (Fig. 2)

CONTACT: SDERY@UNBC.CA

Fig. 1: Map of northern Canada showing the location of gauging stations in six major drainage basins. Table 1: Statistics of gauged area, mean, standard deviation (SD), coefficient of variation (CV) of annual

discharge, and 50-year discharge trend for six drainage regions in northern Canada, 1964-2013.

• Total annual discharge in northern Canada exhibits no trend over

1964-2013, but declining values over the first half of the study

period and increasing values in the latter half of the study period

(Fig. 3).

• There is no trend in the 1964-2013 spring and fall annual river

discharge from northern Canada, with increasing values in winter

and declining values in summer due to flow regulation and

storage for enhanced hydropower production in winter (Fig. 4).

• There are strong regional variations in seasonal trends of river

discharge, with overall winter (summer) flows increasing

(decreasing) during the study period in association mainly with

flow regulation to Hudson Bay and the Eastern Arctic Ocean (Fig.

5).

Fig. 3: Total annual discharge for 6 sub-basins of northern Canada, 1964-2013.

Fig. 5: Total seasonal discharge for 6 sub-basins of northern Canada, 1964-2013.