Flows in the Las Vegas Wash have been measured by the USGS since 1957. There are four major inputs of water to the Las Vegas Wash that create the flow: Urban Runoff, Shallow Ground Water, Reclaimed Water and Stormwater. Each of the four flow components is described below. When the Southern Nevada population changes, the amount of water that is used in the Las Vegas Valley and the amount of water that is subsequently discharged into the Las Vegas Wash increases proportionally.

Urban Runoff
How does it reach the Wash? Urban runoff is a result of overwatering of landscapes and surface street runoff. This is the water that runs down the street all year long.

Potential Water Quality Issues: Bacteria, oil, grease, pesticides, herbicides and nutrients from fertilizer are the most common compounds found in urban runoff.

Shallow Ground Water
(This is the water that is less than 30 feet below land surface in the central & southeast parts of the Valley.)
How does it reach the Wash?Shallow ground water flows towards the lowest part of the valley, which is the Las Vegas Wash, and seeps into the Wash in the southeast part of the valley.

Potential Water Quality Issues: High salinity, potential for compounds to reach shallow ground water and end up in the Wash.

Reclaimed Water
How does it reach the Wash? All indoor water used in the Valley, with the exception of water that is reused, goes to one of three water reclamation facilities. The water is highly treated and released into the Wash.

Potential Water Quality Issues: The primary concern regarding reclaimed water flow is that as the valley population increases, so will the amount of reclaimed water entering the Wash. This increase in flow can result in severe erosion, increasing sediment flow into Lake Mead.

Stormwater
How does it reach the Wash? Stormwater flows are unpredictable. Any time it rains in the valley, water will flow toward the Wash.

Potential Water Quality Issues: Massive erosion events. Accelerated inputs of oil, grease, bacteria, solvents, and pesticides from streets, landscaping, and other urban features.