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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-531
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Examining controls on peak annual streamflow and floods in the Fraser River Basin of British Columbia
Charles L. Curry1,2 and Francis W. Zwiers1 1Pacific Climate Impacts Consortium, University of Victoria, Victoria, V8N 5L3, Canada
2School of Earth and Ocean Sciences, University of Victoria, Victoria, V8N 5L3, Canada
Abstract. The Fraser River basin (FRB) of British Columbia is one of the largest and most important watersheds in Western North America, and is home to a rich diversity of biological species and economic assets that depend implicitly upon its extensive riverine habitats. The hydrology of the FRB is dominated by snow accumulation and melt processes, leading to a prominent annual peak streamflow invariably occurring in June–July. However, while annual peak daily streamflow (APF) during the spring freshet in the FRB is historically well correlated with basin-averaged, April 1 snow water equivalent (SWE), there are numerous occurrences of anomalously large APF in below- or near-normal SWE years, some of which have resulted in damaging floods in the region. An imperfect understanding of which other climatic factors contribute to these anomalously large APFs hinders robust projections of their magnitude and frequency.

We employ the Variable Infiltration Capacity (VIC) process-based hydrological model driven by gridded observations to investigate the key controlling factors of anomalous APF events in the FRB and four of its subbasins that contribute more than 70 % of the annual flow at Fraser-Hope. The relative influence of a set of predictors characterizing the interannual variability of rainfall, snowfall, snowpack (characterized by the annual maximum value, SWEmax), soil moisture and temperature on simulated APF at Hope (the main outlet of the FRB) and at the subbasin outlets is examined within a regression framework. The influence of large-scale climate modes of variability (the Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO)) on APF magnitude is also assessed, and placed in context with these more localized controls. The results indicate that next to SWEmax (which strongly controls the annual maximum of soil moisture), the snowmelt rate, the ENSO and PDO indices, and rate of warming subsequent to the date of SWEmax are the most influential predictors of APF magnitude in the FRB and its subbasins. The identification of these controls on annual peak flows in the region may be of use in the context of seasonal prediction or future projected streamflow behaviour.


Citation: Curry, C. L. and Zwiers, F. W.: Examining controls on peak annual streamflow and floods in the Fraser River Basin of British Columbia, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-531, in review, 2017.
Charles L. Curry and Francis W. Zwiers
Charles L. Curry and Francis W. Zwiers
Charles L. Curry and Francis W. Zwiers

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Short summary
Key predictors of annual peak daily streamflow (APF) in the Fraser River Basin are investigated. While annual maximum snow amount is a good predictor of APF, other, unknown, climatic factors are implicated in the largest historical floods. Additional predictors are selected from observations and a process-based hydrological model. Both approaches indicate that the snowmelt rate, indices of large-scale climate variability, and spring warming rate also influence APF in the Fraser Basin.
Key predictors of annual peak daily streamflow (APF) in the Fraser River Basin are investigated....
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