Winter storms have covered the Rocky Mountains with snow from Wyoming to northern New Mexico, leaving a bounty of runoff that should boost the levels of the Colorado River’s depleted reservoirs this spring and summer. The snow that fell during the past month has pushed the accumulated snowpack across the Upper Colorado River Basin to nearly 140 percent of average. Federal officials now estimate there could be enough snow to narrowly avert a declaration of a shortage at Lake Mead next year, which would hold off water cutbacks in the Southwest for another year.