Short running title
Spring freshet generation in southern Quebec
Abstract
Seasonal
forecasting of spring floods in snow-covered basins is challenging due
to the ambiguity in the driving processes, uncertain estimations of
antecedent catchment conditions and the choice of predictor variables.
In this study we attempt to improve the prediction of spring flow peaks
in southern Quebec, Canada, by studying the preconditioning mechanisms
of runoff generation and their impact on inter-annual variations in the
timing and magnitude of spring peak flow. Historical observations and
simulated data from a hydrological and snowmelt model were used to study
the antecedent conditions that control flood characteristics in twelve
snow-dominated catchments. Maximum snow accumulation (peak SWE),
snowmelt and rainfall volume, snowmelt and rainfall intensity, and soil
moisture were estimated during the pre-flood period. Stepwise
multivariate linear regression analysis was used to identify the most
relevant predictors and assess their relative contribution to the
interannual variability of flood characteristics. Results show that
interannual variations in spring peak flow are controlled differently
between basins. Overall, interannual variations in peak flow were mainly
governed, in order of importance, by snowmelt intensity, rainfall
intensity, snowmelt volume, rainfall volume, peak SWE, and soil
moisture. Variations in the timing of peak flow were controlled in most
basins by rainfall volume and rainfall and snowmelt intensity. In the
northernmost, snow-dominated basins, pre-flood rainfall amount and
intensity mostly controlled peak flow variability, whereas in the
southern, rainier basins snowpack conditions and melt dynamics
controlled this variability. Snowpack interannual variations were found
to be less important than variations in rainfall in forested basins,
where snowmelt is more gradual. Conversely, peak flow was more sensitive
to snowpack conditions in agricultural basins where snowmelt occurs
faster. These results highlight the impact of land cover and use on
spring flood generation mechanism, and the limited predictability
potential of spring floods using simple methods and antecedent
hydrological factors.