CGRG Bibliography of Canadian Geomorphology
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Author : Ehsanzadeh, E.; and Adamowski, K.
Date : 2007.
Title : Detection of tends in timing of low flows in Canadian stream flows (RHBN).
Publication : CMOS, CGU, AMS Congress 2007. "Air, Ocean, Earth and Ice on the Rock". May 28 - June 1, 2007. St. John's Congress Centre, Newfoundland and Labrador, Canada.
Issue :
Page(s) : H01-1C4.3.
Abstract
A study of trends and variability of low flow characteristics was conducted for the Reference Hydrometric Basin Network (RHBN established in order to assess the effects of possible climate change on Canada’s water resources). Low-flow index of 7-day from 220 hydrometric stations was extracted and examined to detect trends in timing of 7-day low-flows in both summer and winter portions of the year. Also, 17 stations with the significant number of zero 7-day low flows were examined to detect trends in the number of zero events. Man-Kendall (MK) nonparametric trend test was applied to the time series to investigate the existence of any trend at a 90% confidence level. In order to account for serial correlation, the variance of the S statistic was modified if its absolute value exceeded a certain confidence interval. It was observed that in 17% of the studied sites, timing of summer 7-day low flows showed significant trends where in 66% of these sites it shifted to arrive earlier but later for the rest of the sites. No clear pattern was observed in the distribution of upward or downward trends. Significant trends were observed in 19% of stations for winter 7-day low-flow. In 72% of detected trends, the winter 7-day low-flow shifted to arrive earlier. Regardless of the direction, the trendy sites were concentrated in Pacific and Atlantic coasts while there was no evidence of trends in Central Canada (Prairies, Northern Canada, Ontario, and Eastern Quebec). At a 90% confidence level, 65% of the stations studied for trend in the number of zero events showed significant upward or downward trends; however, after modifications to account for autocorrelation, only 12% of the studied stations showed significant trends. The stations with dominant zero 7-day low flows were exclusively observed in Prairies and Northern Canada.
Bibliography of Canadian Geomorphology