In its annual resource plan, the Southern Nevada Water Authority uses different scenarios to predict where the community will get its water for the next 50 years. They range from optimistic-but-unlikely to alarming-but-also-unlikely. All of them assume we'll keep growing and conserving. Some of them require us to find a new, permanent water source -- maybe ocean desalination, water rights on the Virgin River, groundwater from eastern Nevada or some combination of those things. Use the sliders below to see how long our current water supply will last under different scenarios and how soon we might have to dip into our savings or bring in new supplies.

Things are looking good for Las Vegas and its main source of water. The community is growing just like the experts thought it would, and Lake Mead has somehow managed to avoid a shortage, so Southern Nevada doesn't have to give up any of its Colorado River water. Great! We can live off what we get from the river and the groundwater we pump from the valley for the next 50 years at least.

So Southern Nevada is fine for the foreseeable future, right? Not so fast. If Lake Mead keeps dropping, sending the Colorado River into shortage, we're going to have to give up as much as 7 percent of our annual river allotment. If those shortage cuts keep piling up year after year, we're going to have dip into our "temporary supplies" -- basically the savings account we've racked up over the years by storing water in Arizona, California, Lake Mead and beneath the Las Vegas Valley. No big deal. We can live off our savings for a while, so long as we don't grow any faster than expected.

Uh-oh. Where did all these people come from? If we get hit with a sudden growth spurt on top of those 7 percent shortage cuts every year, we might have to dip into our temporary supplies much sooner than we thought. And the sooner we start raiding our savings account, the sooner it runs out. We'd better find some future source of water -- and fast. We might just need that new, permanent supply within the next 25 years.

Take cover, everyone. It's the perfect storm. Southern Nevada gets swamped by an unexpected population boom just as the water level in Lake Mead falls off a cliff, forcing the community to cut its river use by 14 percent a year. Water authority officials call this one the "stress test" because they don't expect it to happen. If it does, we might start needing that new, permanent water source by 2041, and we might burn through all the temporary supplies we plan to use by 2044.