A strange type of stream that isn’t protected from pollution by law could impact water quality across the country.
These rivers, called ephemeral streams, only flow after rainfall or snowmelt. Last year, the Supreme Court ruled that they do not fall under the protection of the Clean Water Act.
However, a new study in the journal Science has found that these ephemeral streams may contribute over 50 percent of the flow in downstream river systems.
This means that any pollution that legally enters these ephemeral streams could have widespread reach across the United States river network.
In the paper, the researchers from the University of Massachusetts Amherst describe how they modeled where the water in over 20 million rivers, lakes and reservoirs had originated. They discovered that 55 percent of the water discharged into the oceans by river systems comes from ephemeral streams.
River network map highlighting the ephemeral streams in the Colorado River Headwaters basin in the Rocky Mountains. 74 percent of mean annual river flow from the Colorado system is provided by ephemeral streams and their… River network map highlighting the ephemeral streams in the Colorado River Headwaters basin in the Rocky Mountains. 74 percent of mean annual river flow from the Colorado system is provided by ephemeral streams and their watersheds. More Craig Brinkerhoff
They also found that in the west of the U.S., ephemeral streams were even higher contributors to downstream flow, at up to 79 percent on average. The discharge of river systems in Black Rock Desert, Nevada, and Humboldt County, California, is 94 percent comprised of ephemeral stream water.
For instance, 94 percent of the water coming out of the river systems in Black Rock Desert, Nevada, and Humboldt County, California, comes from ephemeral streams.
US Rivers’ Total Water Output at Pollution Risk, Study Warns
