From Las Vegas Now:
Right now, the lake level is at 1,100 feet and the water [Southern Nevada Water Authority] has managed to store, lease, or buy enough water to keep things running smoothly even if Lake Mead was to drop below 1,025 feet. But if the lake drops below that point, there will be shortages. Right now, forecasts could have the lake below 1,025 feet in less than two years. “There is a 20-percent probability that we would hit an elevation that would take us below 1,025 (feet), which would result in a shortage. There is a 13-percent probability that we would be in surplus and a 67-percent probability that it would be normal,” said Lorri Gray-Lee, Lower Colorado Regional Director with the Bureau of Reclamation.
More Colorado River Basin coverage here.