They looked at the rings of thousands of ancient trees in the mountains above the most important rivers in the West.
What they found may influence how water gets used from Arizona to Canada -- and particularly in the Columbia River basin.
Despite odd years like this one, researchers have long reported declines in the mountain snows that power Western rivers. But a group of scientists recently said they now also know this: Those declines are virtually unprecedented throughout most of the last millennium.
Scientists from the U.S. Geological Survey (USGS) and University of Washington measured tree-ring growth from forests that included 800-year-old trees. They learned that snowpack reductions in the late 20th and early 21st centuries were unlike any other period dating to at least the year 1200, according to new research published in the journal Science.