The U.S. Bureau of Reclamation says the Rocky Mountain snowpack will raise half-empty Lake Powell by 50 feet, opening a crucial shortcut for boaters for the first time in five years.

The so-called Castle Rock cut — still a stretch of exposed rock — will let houseboats get to the most popular beaches quickly from Wahweap marina on the Utah-Arizona border, shaving a dozen miles off the trip.

Park concessionaire Aramark says it's offering a free day on houseboat rentals plus a $200 fuel credit if the Castle Rock cut doesn't open by June 15, when the peninsula is expected to disappear under 20 feet of water.

Glen Canyon National Recreation Area spokesman Kevin Schneider says a nearly decade-long drought has made impassable many of the labyrinth canyons of the 186-mile-long reservoir. The biggest obstacle for many boaters motoring upstream was Castle Rock.

Impressive Rocky Mountains snowfall will boost flows into the Colorado River, but scientists say one good winter doesn't necessarily mean the end of a long drought.