Statistical analysis of factors affecting the spatial variability of annual minimum flow characteristics in a cold temperate continental region (southern Québec, Canada)

We have analyzed relationships between environmental factors (physiographic, climatic, geological, geographic and land use) and extreme minimum flow characteristics. We have defined 18 hydrological variables on the annual minimum flow series according to the “natural flow regime” paradigm. Application of the principal component analysis (PCA) to these 18 variables allowed us to extract five principal components, each associated with a fundamental characteristic (magnitude–frequency, timing, inter-annual variability of magnitude and timing, shape of distribution curve) of the annual minimum flows. The analysis of indices and values of the loading of the five PC revealed a spatial difference in the annual minimum flow characteristics between stations on the north and south shores of the St. Lawrence River (Québec, Canada). South shore stations are generally characterized by lower magnitude, later timing, and sharper inter-annual variability of magnitude and timing of the annual minimum flows than those on the north shore. The analysis of correlations (simple correlation and canonical correlation) between the five hydrological PC and the seven environmental PC, also extracted by means of the PCA, revealed that the spatial difference between the annual minimum flow characteristics observed between the north and the south shore stations is mainly due to precipitation (climatic factor) based on a highly complex relationship, which mainly involves the timing of annual minimum flows.