The Impact of Snow Storage on Summer Low Water Flow in Southern Quebec

Abstract:

The duration of snow cover and the amount of snow accumulated in winter in the basins of the cold regions is changing in response to climate change, directly affecting the spring floods in the rivers (magnitude and time of occurrence). Spring floods will be earlier and less widespread under a warmer climate. However, the impact of the snow cycle on low flow during summer remains unclear especially in Quebec. To address this knowledge gap, the dominant predictors (climate) on summer flow from 12 natural basins in southern Quebec were first identified through correlation analysis. The sensitivity of the summer low flow response variables to each of the dominant predictor variables and basins descriptors was then quantified by hierarchical regression analysis.

The results show that in these low elevation basins, interannual variability of summer low flow magnitude (Q7min) is sensitive to both winter and summer climate conditions. In summer Q7min is more sensitive to Rainfall (r=0.57). As for the winter climate factors maximum SWE (r=0.18) is the dominant control over the magnitude of low flow, particularly at the end of the summer. Winters with a large amount of snow water equivalent correspond to a much higher level of low flow late in summer. The date of occurrence of low flow is not significantly influenced by snow cover in winter, but rather affected by a combined effect of liquid precipitation and evapotranspiration during summer (p<0.05). Therefore, when rainfall is important in spring and summer, the lowest flow during the same year will also occur later, and vice versa. Besides meteorological conditions, basin characteristics were also found to influence low flow. The hierarchical regression models (R² = 0.84) highlights the importance of forest cover area on low summer flow (α= 0.42) compared to agricultural basins. The results indicated that Q7min level is higher in forest basins. Consequently, the interannual magnitude variability is highly dependent on terrestrial hydrological processes. With climate warming and subsequent shifts in precipitation patterns, our outcomes may provide another perspective on the potential effects of climate change on cold-climate hydrology.