"Reduced runoff is increasing the pressure on freshwater resources in much of the world, especially with more demand for water as population increases," says NCAR scientist Aiguo Dai, the lead author of the study. "Freshwater being a vital resource, the downward trends are a great concern."

Many factors may affect river discharge, including dams and the diversion of water for agriculture and industry.

Climate change's influence on river flow comes through its effects on precipitation and evaporation. The authors compared the river discharge changes to previous studies that looked at changes in precipitation and found that areas of decreased discharge matched closely with areas of decreased precipitation (likewise, areas of increased discharge matched those of increased precipitation).

"As climate change inevitably continues in coming decades, we are likely to see greater impacts on many rivers and water resources that society has come to rely on," said study co-author Kevin Trenberth, also of NCAR.

-- Click for more news in Tech Max >>

Editor:Yang Jie