Water Temperatures Rising in U.S. Rivers and Streams, Study Says

Water temperatures are increasing in many U.S. rivers and streams, including the Colorado, Potomac, Delaware, and Hudson, according to a new study. Annual mean temperatures at 40 sites nationwide have increased by 0.02 to 0.14 degrees F per year in recent decades, say researchers at the University of Maryland Center for Environmental Science. Typically, that warming correlated with air temperature increases, and river and stream warming was most rapid in urban areas. The fastest rate of increase occurred in the Delaware River near Chester, Penn., and Maryland’s Patuxent River has experienced a 3-degree F temperature increase since 1939. Overall, 20 of the 40 streams studied showed statistically significant long-term warming trends, while 13 showed temperature increases that were not statistically significant. “We are seeing the largest increases in the most highly urbanized areas, which lead us to believe that the one-two punch of development and global warming could have a tremendous impact on stream and river ecosystem health,” said Sujay Kaushal, lead author of the study published in the journal Frontiers in Ecology and the Environment.