A study of more than 2,000 streams and rivers around North America has uncovered that those altered by human activity are at greater risk of flooding.
They discovered that human-managed streams, which are those that are impacted by man-made developments such as dams, canals, or heavy urbanisation, have had significantly different flow patterns compared to streams in natural watersheds.
Severe flooding risk increase
A greater flow increase in managed watersheds indicates more severe flooding could occur— possibly as a result of the increased paved surfaces in urban regions. Flow dampening, on the other hand, can lead to water shortages and a loss in biodiversity in managed streams.
The study utilised natural watersheds untouched by human activity to measure the impact of climate change on streamflow. Using them as a baseline, the researchers then compared flow in managed streams within a radius of 115 kilometres to measure the impact of human developments.
“Compared to their natural neighbours, about 48% of the human-altered streams had significant increases in seasonal flow trends, while 44% showed a significant decrease in the seasonal flow tends,” explained Nitin Singh, a postdoctoral fellow in Waterloo’s Department of Earth and Environmental Sciences, and lead author of this study.
“We used machine learning to show conclusively that these changes are caused by human activity.”
Seasonal effects on stream flows
While previous studies have analysed stream flows at the annual scale, this study considers seasonal effects such as spring flooding and summer droughts, which are critical for water management.
“It is important to recognise that human modifications of the landscape often amplify the effects of climate change on streamflow,” concluded Nandita Basu, Professor of Earth and Environmental Sciences and Civil and Environmental Engineering.
“We need to take responsibility to manage our landscape sustainably, because it’s not just climate that is changing it.”
The study ‘The human factor in seasonal streamflow’s across natural and managed watersheds of North America,’ was recently published in the journal Nature Sustainability.