"We used to believe that when new precipitation entered the soil, it mixed well with other water and eventually moved to streams. We just found out that isn't true," said researcher Jeff McDonnell of Oregon State University, Corvallis.
Studies in the Pacific Northwest showed soil clings so tenaciously to the first rain after a dry spell that the precipitation almost never mixes with other water, McDonnell and his team wrote in a recent issue of the journal Nature Geoscience.
The findings will force scientists to rethink how pollutants move through soils and how nutrients are transported from soils to streams. The findings also will promote new understanding of how streams function and how vegetation might respond to climate change, McDonnell said.
"This could have enormous implications for our understanding of watershed function," McDonnell said. "It challenges about 100 years of conventional thinking."