Two scientists at the US Geological Survey developed a mathematical model of the water movements—snowfall, rainfall, run-off, evaporation—in the upper Colorado River basin for the period from 1913 to 2017.
They observed that global warming had led each year to a reduction in the snow pack, or the amount of snow that accumulates. So if there is less and less snow, it melts earlier and earlier each spring.
The study shows that during the 1913-2017 period, the flow decreased by roughly 20 percent.
"More than half of this decrease was associated with warming. The rest was related to variations in precipitation," Milly said.