Articles | Volume 20, issue 12
Research article
08 Dec 2016
Research article |  | 08 Dec 2016

Recent trends and variability in river discharge across northern Canada

Stephen J. Déry, Tricia A. Stadnyk, Matthew K. MacDonald, and Bunu Gauli-Sharma

Abstract. This study presents an analysis of the observed inter-annual variability and inter-decadal trends in river discharge across northern Canada for 1964–2013. The 42 rivers chosen for this study span a combined gauged area of 5.26  ×  106 km2 and are selected based on data availability and quality, gauged area and record length. Inter-annual variability in river discharge is greatest for the eastern Arctic Ocean (coefficient of variation, CV  =  16 %) due to the Caniapiscau River diversion into the La Grande Rivière system for enhanced hydropower production. Variability is lowest for the study area as a whole (CV  =  7 %). Based on the Mann–Kendall test (MKT), no significant (p > 0.05) trend in annual discharge from 1964 to 2013 is observed in the Bering Sea, western Arctic Ocean, western Hudson and James Bay, and Labrador Sea; for northern Canada as a whole, however, a statistically significant (p < 0.05) decline of 102.8 km3 25 yr−1 in discharge occurs over the first half of the study period followed by a statistically significant (p < 0.05) increase of 208.8 km3 25 yr−1 in the latter half. Increasing (decreasing) trends in river discharge to the eastern Hudson and James Bay (eastern Arctic Ocean) are largely explained by the Caniapiscau diversion to the La Grande Rivière system. Strong regional variations in seasonal trends of river discharge are observed, with overall winter (summer) flows increasing (decreasing, with the exception of the most recent decade) partly due to flow regulation and storage for enhanced hydropower production along the Hudson and James Bay, the eastern Arctic Ocean and Labrador Sea. Flow regulation also suppresses the natural variability of river discharge, particularly during cold seasons.

Short summary
This manuscript focuses on observed changes to the hydrology of 42 rivers in northern Canada draining one-half of its land mass over the period 1964–2013. Statistical and trend analyses are presented for the 42 individual rivers, 6 regional drainage basins, and collectively for all of northern Canada. A main finding is the reversal of a statistically significant decline in the first half of the study period to a statistically significant 18.1 % incline in river discharge across northern Canada.