Plant Trees and Chill

Software helps a conservation group see where shade trees will best cool a river. Then the hard work starts.

In 2011, the city of Medford in Oregon had a problem. The treated water being released into the Rogue River from its sewage treatment plant was too warm, threatening the river’s fish.

The historically cool Rogue River was already warming, and Medford’s discharge could raise the temperature by another 0.18 degrees Celsius. Warmer rivers have less oxygen, and cause fish to hatch earlier and die younger. To stay on the right side of Environmental Protection Agency regulations, Medford had to find a way to cool down its wastewater.

“We looked at agricultural re-use, chillers, cooling towers and lagoons, but all the options were really expensive – more than $15 million,” said Tom Suttle, construction manager for the city’s water reclamation division. Read more in Inside Science.