PORTLAND, Ore. (AP) – Scientists in Oregon and California have found that snowpack has declined dramatically across the American West over the past six decades. The study published Friday in NPJ Climate and Atmospheric Science found drops in snow measurements at more than 90 percent of regional snow monitoring sites since 1955. The average snowpack in the region also dropped up to 30 percent in the past century. That’s the loss of the same volume of water it would take to fill Lake Mead, the West’s largest man-made reservoir. The study was authored by scientists at Oregon State University and the University of California, Los Angeles. It found California had the most gains in snowpack since 1955, but recent drought erased those gains. Eastern Oregon and northern Nevada saw the worst decrease in snowpack.