New Study Shows Rising Water Temperatures in Potomac, Other U.S. Rivers

New research by a team of scientists led by the University of Maryland shows that water temperatures are increasing in many streams and rivers throughout the United States, including two that flow to the Chesapeake Bay.

The Potomac River, one of the Bay’s largest tributaries, was one of 20 major U.S. rivers and streams showing statistically significant long-term warming. In Maryland’s Patuxent River, University of Maryland Center for Environmental Science (UMCES) researchers have noted a 3°F increase since 1939.

Other major U.S. rivers showing warming trends include the Colorado, Delaware and Hudson rivers.

Long-term temperature increases can affect the diversity of aquatic life, because animals and plants can die if water temperatures rise too high. It can also affect basic ecological processes, such as oxygen levels, because warmer water is not able to hold as much oxygen.

Long-term increases in stream water temperatures typically correlated with increases in air temperatures. Rates of warming were most rapid in urbanized areas, where “heat island” effects caused by large areas of asphalt and concrete increase the temperature of polluted stormwater runoff that flows into storm drains and streams.

“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 Dr. Sujay Kaushal of UMCES and lead author of the study.

To help reduce increased water temperatures, the authors of the study pointed to conserving streamside forest buffers, reducing impervious surfaces, adopting green infrastructure practices such as rain gardens, and reducing greenhouse gas emissions.

The research appeared in the article, “Rising stream and river temperatures in the United States,” in the journal Frontiers in Ecology and the Environment.