Abstract
AbstractLow river flows can negatively impact society and the riverine environment. Thus, it is useful to predict their seasonal timing and reveal their main drivers. The typical timing of low flows varies between regions, yet systematic overviews across Europe and the United States are rare. Here, we identify regional patterns of the seasonal timing of annual minimum flows, and the consistency of that timing, across 1860 European and US catchments. Catchments where low flows typically occur during late summer or winter tend to have more consistent low‐flow timings. We compare the timing of annual low flows with that of potential climatic drivers. Low flows in 89% of the European and 86% of the US catchments exhibit a statistically significant (p < 0.05) overlap in timing with at least one potential climatic driver. In most catchments, low flows tend to occur during the warm season, reflecting a period of high potential evapotranspiration exceeding precipitation. In the higher elevation European Alps, Scandinavia, the Rocky Mountains, and the Upper Midwest and Plains states, low flows mostly occur during winter as a result of freezing temperatures which inhibit snowmelt. Binomial statistics also enabled us to statistically exclude individual climatic drivers for certain regions. The regional patterns of timings and drivers of low flows across Europe and the contiguous US can inform low‐flow management, provide context for the evolution of low flows under climate change, and point to processes that require attention in future low‐flow research.
Highlights
Low river flows affect water quality and river ecology, as well as water availability for industry, agriculture, and navigation (e.g., Bradford & Heinonen, 2008; Laaha et al, 2013; Poff et al, 1997; van Vliet et al, 2012)
In most of continental Europe, annual low flows tend to occur during late summer and early autumn
Low flows in 89% of the European catchments, and 86% of the United States (US) catchments, exhibit statistically significant (p < 0.05) overlap in timing with at least one potential climatic driver (Figure 6), with strong regional
Summary
Low river flows affect water quality and river ecology, as well as water availability for industry, agriculture, and navigation (e.g., Bradford & Heinonen, 2008; Laaha et al, 2013; Poff et al, 1997; van Vliet et al, 2012). Low-flow seasonality has been used for regionalization purposes and to assess climate change impacts (e.g., Laaha & Blöschl, 2006b; Demirel et al, 2013; Vezza et al, 2010). Connections between climatic drivers and flood seasonality have been studied at the continental scale (e.g., Berghuijs et al, 2016; Blöschl et al, 2017), but assessments of the timing and drivers of low flows are only available for a limited number of catchments or regions (e.g., Cooper et al, 2018; Dierauer et al, 2018; Floriancic et al, 2020; Laaha & Blöschl, 2006a; Van Loon et al, 2015; Van Loon & Van Lanen, 2012). These analyses illuminate when low flows typically occur, and which climatic drivers most likely control their occurrence
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