Although all of that water flooding into the Midwest is coming from record snowpack in the Rockies, in the long term, snow pack levels in the mountain range have been decreasing since the 1980s. The U.S. Geological Survey wanted to know how dramatic the current dip in levels is, so it looked back more than 1,000 years to gauge the long-term trend.
Researchers examined hundreds of thousands of tree rings, which reflect winter snow accumulation. The result: snowpack levels are in the worst dip on record. There were two other periods of decline, one in 1300s, the other in the 1500s, but neither matched the severity of this one.
It's not only ski bunnies who should worry about this trend. The Rockies are where the West gets its water from.
1,000-Year Record Shows Unusual Snowpack Decline, Greenwire.