Water supply in Las Vegas

In most places, the hydrology cycle is a process that occurs on a daily basis, but in some places, like Las Vegas, water isn’t as available. Las Vegas, one of the driest cities in the United States, is located on a desert basin. According to the Las Vegas Valley Water District, The Las Vegas Valley gets about 90 percent of its water from the Colorado River, which is currently facing the worst drought on record. The water level in Lake Mead (which is in the Colorado River) has dropped about 100 feet since 2000. One cause of the current drought has to do with a decreased snowfall in the Rocky Mountains that feed water to the Colorado River and then to Lake Mead.

"Bath tub ring" of Lake Mead; water drop since 2000.

Shallow ground water through the Las Vegas Wash is one important aspect to how Las Vegas gets its water source. When it rains and snows, some water runs into lakes, rivers, and streams; some of it evaporates and some plants absorb. The other water soaks into the ground and becomes a part of the water table. The ground water beneath the entire city of Las Vegas is usually referred to as the "shallow groundwater system." This water needs to be monitored, because it can be very salty and can increase the amount of dissolved solids in Wash water, which can adversely affect the growth of wetlands and have negative impacts to habitat. This cannot be used for drinking.

Water flow of Las Vegas Wash

Since very little storms occur in Vegas, little precipitation and less of a hydrology cycle occurs. Therefore there are droughts that take place. Not every day can have precipitation like the photo below.

Storm in  Spring Mountains Las Vegas, Nevada.

Sources: http://www.flickr.com/photos/ideum/4648476744/
http://www.lvwash.org/html/what_flow_shallow.html