A recent study published in Geophysical Research Letters found that reservoirs across the United States are experiencing low storage with greater regularity and more severity than several decades ago.

In geographic regions that rely on snowpack for their source water, like Denver, this is a very important issue. The National Weather Service calls the amount of water in snow the “snow ratio.” As a rule, 12 inches of snow can represent one inch of water in the Upper Midwest states.

According to a just published article by Nature World News, the ancient Mayans, who lived in Mexico, Belize and Guatemala, dealt with water shortages due to lack of rainfall.