Pyramid Lake sits in a basin that was formerly occupied by the pluvial Lake Lahontan. Several ancient beach lines demarking varying lake levels are visible within the basin. The lakes climate is characterized by cold winters, hot summers and 5-8 inches of average annual precipitation. The three surrounding mountain ranges (Virginia Mountains, Pah Rah Range, Lake Range) are classic Basin and Range, block fault uplift mountains. The Truckee River, the major tributary to the lake, provides approximately 500,000 acre-feet of inflow each year, depending on climate and upstream agricultural, municipal, and industrial diversions.
Plant communities surrounding the lake are dominated by desert shrub, but also include limited riparian and wetland habitats.
Two large, prominent, islands are visible in the lake. Pyramid Island is steep, arid, and relatively small. Anaho Island is larger and lower in profile, but supports extensive nesting colonies of American White Pelican (one of the largest in the West, in fact). Peregrine falcons historically nested on the island as well. The island constitutes the entire extent of the Anaho Island National Wildlife Refuge.
Anaho Island National Wildlife Refuge (NWR) is located near the eastern shoreline of Pyramid Lake, Washoe County, Nevada. The refuge was established by President Woodrow Wilson in 1913 as a sanctuary for colonial nesting birds, primarily American white pelicans. Anaho Island is a part of the Pyramid Lake Paiute Indian Reservation, but is managed by the U.S. Fish and Wildlife Service as part of the National Wildlife Refuge System under an agreement with the Pyramid Lake Paiute Tribe. (http://stillwater.fws.gov/anaho.html)
The island supports one of the largest breeding colonies of American white pelicans in the western United States. In recent years, between 8,000 and 10,000 pelicans have returned to Anaho Island during the spring from their wintering areas in Southern California and Baja, Mexico. These fish-eating birds rely on the spring spawning runs of Pyramid Lake fish as well as the numerous shallow lakes and wetlands within 70 miles of the island, primarily the Lahontan Valley and Stillwater National Wildlife Refuge. The island also provides nesting habitat for Double crested cormorants, California gulls, Great blue herons, Black-crowned night herons, and occasionally Caspian terns. (http://stillwater.fws.gov/anahopage2.html)
The lake as a whole provides migration stop-over opportunities for significant numbers of waterbirds. Large numbers of Clark's and Western Grebes, Eared Grebes, American White Pelicans, and numerous species of ducks pass through in migration.
Upstream water diversions, particularly for growing industrial and municipal needs, particularly during late summer/low flow periods. Pollution--tertiary treated water entering system alters water chemistry, can encourage eutrophication, agricultural return flows contain high levels of dissolved solids.
Research conducted by USFWS on the feeding ecology of the nesting pelicans is on-going.
7% Lowland riparian.