Climate change is altering the seasonal pattern of river flow globally

Climate change is altering the seasonality of river flow, particularly at high northern latitudes, according to a new study. Patterns in river flow vary with the seasons – a cycle that plays a critical role in floods and droughts, water security, and the health of biodiversity and ecosystems worldwide. Although recent studies have shown that climate change has already altered river flow seasonality (RFS), much of the evidence is limited to local regions or fails to consider the impact of climate change explicitly, independent of other human impacts to river flow. Consequently, the impact of climate warming on RFS isn’t fully understood at the global level. To address this question, Hong Wang and colleagues combined in situ observations of monthly average river flow from 10,120 gauging stations between 1965 and 2014 with model predictions. They used this data to develop a generalized global seasonality index using apportionment entropy (AE). AE is a statistical method that quantifies how evenly flow raters are distributed across months, which, according to the authors, is well suited to characterize the highly variable flow regimes of rivers globally. Wang et al. discovered that roughly 21% of long-term river gauging stations have captured significant alterations to seasonal flow worldwide, with low flow periods most affected. Moreover, the findings reveal a discernable weakening in the seasonal cycle of river flow in the northern high latitudes above 50° N that can be directly attributed to climate change.