A new study reveals that climate change is changing the seasonality of river flows, especially at high northern latitudes. According to the study published on February 29 in the journal Science, river flow patterns vary depending on the seasons, a cycle that plays a crucial role in floods, droughts, water security, and the health of biodiversity and ecosystems around the world.
After analyzing historical data from river gauging stations around the world, the researchers found that 21% of North American, European and Russian rivers showed significant changes in seasonal rise and fall in water levels.
Human interventions
To show how river flow changes relate to seasons at latitudes above 50 degrees north, the research team conducted a reconstruction and simulation of river flow based on monthly data from 10,120 measuring stations spanning the period between 1965 and 2014.
According to the results reported in the study's press release , the authors ruled out that direct human interventions - such as reservoir management or water extraction operations - are responsible for the widespread decline in river flow seasonality, and attributed it to climate changes caused by human-induced emissions in the post-industrial period.
Study co-author Liu Guojun, professor of hydrology at North China University of Water Resources and Energy Sciences, said: Human influences on climate have caused a decline in the seasonality of river flows, especially at high northern latitudes.
John explained in an interview with Al Jazeera Net that the results based on observations of the average monthly river flow indicate a continuous and significant decrease in the seasonality of the river flow if air temperatures continue to rise.
The researcher pointed out that the year 2023 was the hottest since records began, as the rise in temperature approached the threshold of 1.5 degrees Celsius above pre-industrial levels set by the Paris Agreement . Therefore, the researcher points out that human-induced climate change has led to this phenomenon and the resulting changes in the seasonality of river flow in the Northern Hemisphere.
Human activities are changing the flow patterns of rivers around the world, either directly through flow regulation such as reservoirs, or indirectly through land use change and the effects of climate change on air temperature, precipitation, soil moisture and snowmelt.
Aerial view of rainforest at the Araguaia River on the border of the states of Mato Grosso and Goias in Brazil
Flow measurement
The researchers found that 40% of the 119 stations monitored in northern North America showed a significant decrease in the seasonality of river flows, and similar results were also observed in southern Siberia, where 32% of the stations showed a significant decrease. The same thing was proven by monitoring operations in Europe, where 19% of river measuring stations witnessed a significant decline, mainly in northern Europe, western Russia, and the European Alps.
In contrast, the researchers found a significant increase in the seasonality of river flow at 25% of measuring stations in southeastern Brazil (the Southern Hemisphere), which led them to believe that changes in the water cycle vary between the north and south of the planet due to rising air temperatures that, It fundamentally changes the natural patterns of river flow.
“The worrying aspect of this change is the observed weakening in the seasonality of river flow,” John said. “This is a direct result of historical human-caused emissions, and this indicates a continuing and significant decline in the seasonality of river flow if air temperatures continue to rise.”
According to the researchers, poor seasonality of river flow - for example due to low river levels in spring and early summer in areas of snowmelt - can also have an impact on riverbank vegetation and organisms living in the river itself.