A multi-scale hydroclimatic analysis of runoff generation in the Athabasca River, western Canada.

A multi-scale hydroclimatic study of runoff generation in the Athabasca River watershed located in western Canada is presented. Mann-Kendall trend detection tests performed on hydrometric data for the lower Athabasca River (LAR) revealed predominantly significant ( p < 0.05) declines in annual and open-water season median/mean runoff indices over 1958-2009, with the ice-influenced season experiencing significant declines in the median and not the mean. The presence or absence of significant declines in the 25^th and 75^th runoff percentiles helped explain these results. The only noteworthy result from the mid-point of the watershed was a probable ( p < 0.10) decline in median open-water runoff, which was not seen over the 1913-2009 period. Divergent seasonal runoff trends from the headwater zone were seen since 1958 and back to 1913, increasing ice-influenced and declining open-water season runoff trends. Although precipitation was observed to decline over 1958-2009, only the LAR watershed scale annual index emerged as a probable decline. Multiple non-linear regression analysis indicated that variation in precipitation explained >67% of the annual median/mean LAR runoff variability since 1958. A first-order precipitation driven hindcasting model suggested that LAR watershed scale runoff may have increased since 1913, warranting further study. A correlation analysis of climatic teleconnections with median/mean runoff indices revealed that the winter North Pacific American index showed a strong, positive association with open-water runoff. The results from our study demonstrated that potentially inconsistent and/or divergent trend results can be obtained when using different time periods and/or regions of the watershed, emphasizing that extreme caution should be exercised when extrapolating sub-watershed results to the watershed scale, or to adjacent watersheds. Our multi-scale study approach also identified the drainage area between Athabasca and Fort McMurray as a zone that influenced runoff declines observed at the LAR watershed scale since 1958, which warrants further investigation with competent hydrological models. Copyright © 2013 John Wiley & Sons Ltd and Her Majesty the Queen in Right of Canada Reproduced with the permission of the Ministry of the Environment. [ABSTRACT FROM AUTHOR]