The objective of this study is to compare the spatiotemporal variability of seasonal daily mean flows measured in 17 watersheds, grouped into three homogeneous hydroclimatic regions, during the period 1930–2023 in southern Quebec. With regard to spatial variability, unlike extreme daily flows, seasonal daily mean flows are very poorly correlated with physiographic factors and land use and land cover. In fall, they are not correlated with any physiographic or climatic factor. In winter, they are positively correlated with the rainfall and winter daily mean maximum temperatures. In spring, they are strongly correlated positively with the snowfall but negatively with the spring daily mean maximum temperatures. However, in summer, they are better correlated with forest area and, to a lesser extent, with the rainfall. As for their temporal variability, the application of six different statistical tests revealed a general increase in daily mean flows in winter due to early snowmelt and increased rainfall in fall. In summer, flows decreased significantly in the snowiest hydroclimatic region on the south shore due to the decrease in the snowfall. In spring, no significant change in flows was globally observed in the three hydroclimatic regions despite the decrease in the snowfall due to the increase in the rainfall. In fall, flows increased significantly south of 47°N on both shores due to the increase in the rainfall. This study demonstrates that, unlike extreme flows, the temporal variability of seasonal daily average flows is exclusively influenced by climatic variables in southern Quebec. Due to this influence, seasonal daily mean flows thus appear to be the best indicator for monitoring the impacts of changes in precipitation regimes and seasonal temperatures on river flows in southern Quebec.

本研究的目的是比较 1930 年至 2023 年期间魁北克南部 17 个流域（分为三个同质水文气候区域）测量的季节性日平均流量的时空变化。关于空间变异性，与极端日流量不同，季节性日平均流量与自然地理因素以及土地利用和土地覆盖的相关性非常差。在秋季，它们与任何自然地理或气候因素无关。冬季，它们与降雨量和冬季日平均最高气温呈正相关。在春季，它们与降雪量呈强正相关，但与春季日平均最高气温呈负相关。然而，在夏季，它们与森林面积的相关性更好，与降雨量的相关性较小。至于其时间变化，六种不同统计测试的应用表明，由于融雪提前和秋季降雨量增加，冬季日平均流量普遍增加。夏季，由于降雪量减少，南岸降雪最多的水文气候区的流量显着减少。春季，尽管降雨量增加导致降雪量减少，但全球三个水文气候区的流量并未出现显着变化。秋季，由于降雨量增加，北纬 47°以南两岸流量显着增加。这项研究表明，与极端流量不同，季节性日平均流量的时间变化完全受到魁北克南部气候变量的影响。由于这种影响，季节性日平均流量似乎是监测降水状况和季节性气温变化对魁北克南部河流流量影响的最佳指标。