Recent trends and variability in river discharge across northern Canada

Stephen J. Déry, Tricia A. Stadnyk, Matthew K. MacDonald, Bunu Gauli-Sharma
2016 Hydrology and Earth System Sciences  
<p><strong>Abstract.</strong> 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<span class="thinspace"></span> × <span class="thinspace"></span>10<sup>6</sup><span class="thinspace"></span>km<sup>2</sup> and are selected based on data availability and quality, gauged area and record length. Inter-annual variability in
more » ... l variability in river discharge is greatest for the eastern Arctic Ocean (coefficient of variation, CV<span class="thinspace"></span> = <span class="thinspace"></span>16<span class="thinspace"></span>%) 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<span class="thinspace"></span> = <span class="thinspace"></span>7<span class="thinspace"></span>%). Based on the Mann–Kendall test (MKT), no significant (<i>p</i><span class="thinspace"></span>&amp;gt;<span class="thinspace"></span>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 (<i>p</i><span class="thinspace"></span>&amp;lt;<span class="thinspace"></span>0.05) decline of 102.8<span class="thinspace"></span>km<sup>3</sup> 25<span class="thinspace"></span>yr<sup>−1</sup> in discharge occurs over the first half of the study period followed by a statistically significant (<i>p</i><span class="thinspace"></span>&amp;lt;<span class="thinspace"></span>0.05) increase of 208.8<span class="thinspace"></span>km<sup>3</sup> 25<span class="thinspace"></span>yr<sup>−1</sup> 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.</p>
doi:10.5194/hess-20-4801-2016 fatcat:bdr4h6dsnrhrxpgly5zrhcnuky