Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA.


United States

Major Habitat Type

Xeric freshwaters and endorheic (closed) basins

Drainages flowing into

The Lahontan Basin is a closed drainage system that does not flow outward into any rivers or oceans.

Main rivers to other water bodies

Major watersheds include those of the Humboldt, Walker, Carson and Truckee rivers, all of which flow east and originate as high elevation, high gradient streams. Large lakes in this ecoregion include Lake Tahoe on the Nevada-California border, Mono Lake to the east of Yosemite in California, Eagle Lake to the east of Lassen National Forest in California, Pyramid Lake on the Pyramid Lake Indian Reservation in western Nevada, and Walker Lake just south of the Walker River Indian Reservation in western Nevada. Both Pyramid and Walker lakes are remnants of Lake Lahontan, a Late Pleistocene lake that at its maximum size approximated that of Lake Erie.



This ecoregion occupies almost the entire state of Nevada, portions of eastern California east of the Sierra Nevada mountains, and two small disjunct areas of southeastern Oregon.


This ecoregion is characterized by north-south trending mountains interspersed with interior playas. Elevation ranges from 1,200 to 3,000 m (McNab and Avers 1994). 

Freshwater habitats

Lake Tahoe is distinguished by being one of the largest high-mountain lakes in the world, with a surface area of 304 km2, a maximum depth of 501 m, and an altitude of 1,899 m above sea level (Moyle 1976). Within the ecoregion there are also numerous small playa lakes, as well as both warm and cold springs. The ecoregion is characterized by extreme aridity that has reduced the native freshwater fauna to a handful of species from a much greater number in pluvial times (Hubbs et al. 1974).

One endorheic basin of note is Railroad Valley, located in central Nevada and encompassing approximately 9,233 km2. Within Railroad Valley, a series of cool and thermal springs discharge relatively high volumes of water, creating in some cases large spring pools and outflow creeks (Williams et al. 1985). Mono Lake, on the border with the Death Valley ecoregion [11], represents a rare habitat type. It is too saline to support fish, but contains abundant populations of the alkali fly (Ephydra hians) and an endemic brine shrimp (Artemia monica), which in turn support a diverse migratory bird fauna (Moyle 1976).

Terrestrial habitats

Lake Tahoe and Eagle Lake are both surrounded by coniferous forests, which contrasts with the other desert lakes (Minckley et al. 1986).

Description of endemic fishes

Endemic fish include the Railroad Valley springfish (Crenichthys nevadae), cui-ui (Chasmistes cujus), desert dace (Erimichthys acros), and the Tahoe sucker (Catostomus tahoensis) (Moyle 1976; Page & Burr 1991; Sigler & Sigler 1994). The cui-ui was historically found only in Pyramid and Winnemucca lakes, but today the latter is dry (Page & Burr 1991). The desert dace, a relict species found only in thermal spring habitats of Soldier Meadow, Nevada is distinguished by its ability to inhabit much hotter water than any other minnow species. Railroad Valley supports a highly endemic fauna, with five subspecies of tui chub (Gila bicolor ssp.) and the Railroad Valley springfish. Each of the tui chub subspecies is restricted to single localities (Kate Spring, Butterfield Spring, Blue Eagle Spring, Bull Creek, Green Springs, and Duckwater Creek), with no apparent overlap. A sixth subspecies of tui chub is shared with two other nearby valleys (Williams et al. 1985).

Justification for delineation

Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995). Modifications to the boundaries of this ecoregion were based on a biogeographic assessment performed by The Nature Conservancy. The boundaries were modified to exclude the watersheds of Massacre Lake, Madeline Plains, and a small portion of Surprise Valley, now placed in the Oregon Lakes [124] ecoregion.


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