Freshwater flows change as global climate shifts

Naomi Lubick in Environmental Science & Technology: During the past 50 years, freshwater rivers on all continents except Antarctica (and Greenland) have undergone changes in their volume, and most of these differences can be connected to climate change, according to new research published May 15 in the Journal of Climate.

…Led by Aiguo Dai of the National Center for Atmospheric Research (NCAR), the researchers collected streamflow data from 1948 to 2004 for rivers on all major land masses except Greenland and Antarctica. They logged 925 rivers using the gage farthest downstream on all the rivers where possible. Where the data were missing, either because of lapsed stream gages or other reasons, the researchers used precipitation and other climate data to model what the river flows were likely to have been.

The team determined that in the past half century, freshwater flow dropped 3–14% for some of the major rivers feeding the Pacific and Indian Oceans; however, changing precipitation patterns linked to climate shifts has increased flow for other rivers, such as the Mississippi. (Rainfall over the part of North America that feeds the Mississippi River also is up.) This change in freshwater resources could have impacts in highly populated areas that rely on depleted rivers, such as China’s Yellow River, which flows through the country’s major agricultural belt.

Streamflow in many rivers varied over the years with the El Niño–Southern Oscillation, and others matched the variability of rainfall patterns in their basins, with the exception of the Arctic. In the subtropics and tropics in particular, decreases in rainfall that are related to climate changes were reflected in reduced river flows, according to NCAR and others’ climate models…..

The Ob River in Russia, 2004