Question of the Day - 07 April 2023

Actually, no. Most of it, yes, but not all. 

Approximately 90% of Las Vegas water comes from Lake Mead. The rest comes from a major aquifer (water-bearing rock that readily supplies water to wells and springs) that underlies Las Vegas Valley. While all the rain in the valley and snow in the mountains this winter won't have much, if any, impact on the water level of Lake Mead, it will do yeoman's service for the aquifer. 

This aquifer is the reason Las Vegas exists at all and was named "The Meadows" by Spanish explorers in the late 1700s. It bubbled up at Big Springs, present-day site of the Springs Preserve (on Valley View a few blocks north of W. Charleston) and flowed into what was called Las Vegas Creek, watering a lush meadow that attracted the desert-parched Spanish trailblazers. Indeed, water pumped from the aquifer supplied Las Vegas with all of its needs until the 1930s, when two things happened: The aquifer started to become depleted and Lake Mead began providing the growing city with its H2 and O. Still, the aquifer continued to be a major source of Las Vegas water all the way up until the '60s. 

Today, most of the runoff from all the snow that dumped on the Spring Mountains (to the south and west) and Sheep Range (to the north) will trickle down into the aquifer and raise the level of that groundwater. Some does make its way to Lake Mead via the drainage and wash system, but not enough to be noticeable -- except for this year, actually. As of this writing, the lake level sits at 1,046 feet, nearly three feet higher than projections from last month. The Bureau of Reclamations attributed the positive sign to the rainy winter. But that's an anomaly, at least over the past couple of decades. 

Nevada doesn't use its entire allotment of water from Lake Mead for commercial and residential needs. In addition, southern Nevada returns almost all of the water that's drained into sewers back to the lake, after being treated, in exchange for return-flow credits, from which its total allotment of lake water is subtracted. So even though Nevada is entitled to 300,000 acre feet of Mead and used around 475,000 over the past few years, the net use, minus the credits, was only 223,000 acre feet, right around 75% of its allotment. 

Thus, it can take the excess and "inject" it into the aquifer for storage purposes. According to a hydrologist for the Southern Nevada Water Authority, the aquifer stores about 18 months worth of water in a kind of liquid savings account. In addition, the quality of the water is excellent; it requires very little treatment.