Lake Mead

Where Lake Mead's water comes from

The reservoir behind Hoover Dam, at the end of the Grand Canyon, the Virgin River and Las Vegas Wash.

Map of the Lake MeadLake MeadVirgin MountainsBlack MountainsMuddy MountainsColorado RiverPearce FerryRiversideOvertonEcho BayTemple BarCallville BayHoover DamDetrital WashVirgin RiverGrand WashMuddy RiverHualapai WashCallville Wash10 miles
Lake Mead. River lines from the USGS National Hydrography Dataset.
Boulder City, built for the dam's workers, from the air in the 1930s.
Boulder City, built for the dam's workers, from the air in the 1930s.Bureau of Reclamation. U.S. National Archives, public domain · source

Headwaters

The Colorado through the Grand Canyon

Most of Lake Mead's water is the Colorado River, released from Lake Powell at Glen Canyon Dam and carried through the Grand Canyon. It enters the lake near Pearce Ferry, at the east end.1,2

The Virgin and the Muddy

The Virgin River, from the plateaus above Zion, and the spring-fed Muddy River from the Moapa Valley enter the Overton Arm at the lake's north end.3,1

Las Vegas Wash

Las Vegas Wash carries treated wastewater and runoff from the Las Vegas Valley into Las Vegas Bay. It is a small share of the lake's water, but it flows every day, and it carries the valley's storm floods.4

The river, top to bottom

Columnar basalt at the mouth of Grand Wash on the Colorado, 1871, where the river now meets Lake Mead.
Columnar basalt at the mouth of Grand Wash on the Colorado, 1871, where the river now meets Lake Mead.Timothy O'Sullivan, Wheeler Survey. Library of Congress, public domain · source
  1. Pearce Ferry & Gregg BasinThe Colorado enters from the Grand Canyon.
  2. Grand, Hualapai & Detrital washesLong desert washes from Arizona.
  3. Overton ArmThe Virgin and Muddy rivers join.
  4. Callville BayCallville Wash comes in from the north.
  5. Las Vegas BayLas Vegas Wash brings the valley's water.
  6. Hoover DamThe lake ends at Black Canyon; the river continues to Lake Mohave.

Main tributaries

StreamJoinsNotes
Colorado RiverEast endReleases from Lake Powell plus Grand Canyon side rivers.
Virgin RiverOverton ArmSnowmelt and flash floods from southern Utah.
Muddy RiverOverton ArmSpring-fed; floods with Meadow Valley Wash.
Las Vegas WashLas Vegas BayTreated wastewater and urban runoff.
Detrital & Hualapai washesArizona sideDry except after storms.

Why it matters for floods

Hoover Dam holds the Colorado's floods. The lake's fast floods come from storms over the desert: the Virgin and Muddy rivers, Las Vegas Wash and the big Arizona washes can all run hard after heavy rain, while the lake itself rises only a little.5,6 The live map watches the gauges along the way.

Lake Mead and its Tributaries

Map of Lake Mead and its tributaries in southern Nevada and northwestern Arizona, with Virgin Mountains, Black Mountains, Muddy Mountains: rivers, side canyons, contour lines and summit elevations, in a classic survey style.
A classic map of the river and the mountains around it. Full size · Vector (SVG) · © 2026 Southwest River Watch
Sources
  1. Lake Mead (Wikipedia)
  2. NPS: Grand Canyon, the Colorado River
  3. Virgin River (Wikipedia)
  4. Las Vegas Wash (Wikipedia)
  5. Bureau of Reclamation: Hoover Dam
  6. NPS: Lake Mead National Recreation Area

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