Pyramid Lake is the geographic sink of the Truckee River Basin, 40 mi (64 km) northeast of Reno. Pyramid Lake is fed by the Truckee River, which is mostly the outflow from Lake Tahoe. The Truckee River enters Pyramid Lake at its southern end. Pyramid Lake has no outlet, with water leaving only by evaporation, or sub-surface seepage (an endorheic lake). The lake has about 10% of the area of the Great Salt Lake, but it has about 25% more volume. The salinity is approximately 1/6 that of sea water. Although clear Lake Tahoe forms the headwaters that drain to Pyramid Lake, the Truckee River delivers more turbid waters to Pyramid Lake after traversing the steep Sierra terrain and collecting moderately high silt-loaded surface runoff.

A remnant of the Pleistocene Lake Lahontan (~890 feet deep), the lake area was inhabited by the 19th-century Paiute, who used the Tui chub and Lahontan cutthroat trout from the lake(the former is now endangered and the latter is threatened). The lake was first mapped in 1844 by John C. Frémont, the American discoverer of the lake who also gave it its English title.

In the 19th century two battles were fought near the lake, major actions in the Paiute War. In the 1960s a marker was placed commemorating these battles.

Because of water diversion beginning in 1905 by Derby Dam, the lake's existence was threatened, and the Paiute sued the Department of the Interior. By the mid-1970s, the lake had lost 80 feet of depth, and according to Paiute fisheries officials, the life of the lake was seriously under threat.

Pyramid Lake is located in southeastern Washoe County in western Nevada. It is in an elongated intermontane basin between the Lake Range on the east, the Virginia Mountains on the west and the Pah Rah Range on the southwest. The Fox Range and the Smoke Creek Desert lie to the north.

In a parallel basin to the east of the Lake Range is Winnemucca Lake now a dry lake bed. Prior to the construction of the Derby Dam in 1905 both lake levels stood at near 3,880 ft (1,180 m).[8] Following the dam completion the water levels dropped to 3,867 ft (1,179 m) and 3,853 ft (1,174 m) for Pyramid and Winnemucca respectively. In 1957 Pyramid Lake level was at 3,802 ft (1,159 m) and the dry Winnemucca Lake bed at 3,780 ft (1,150 m) had been dry since the 1930s.

The lake is the largest remnant of ancient Lake Lahontan that covered much of northwestern Nevada at the end of the last ice age. Pyramid Lake was the deepest point in Lake Lahontan, reaching an estimated 890 feet (270 m) due to its low level relative to the surrounding basins.

The name of the lake comes from the impressive cone or pyramid shaped tufa formations found in the lake and along the shores. The largest such formation, Anaho Island, is home to a large colony of American White Pelicans and is restricted for ecological reasons. Access to the Needles, another spectacular tufa formation at the northern end of the lake has also been restricted due to recent vandalism.

Major fish species include the cui-ui lakesucker, which is endemic to Pyramid Lake, the Tui chub and Lahontan cutthroat trout (the world record cutthroat trout was caught in Pyramid Lake). The former is endangered, and the latter is threatened. Both species were of critical importance to the Paiute people in pre-contact times.

en.wikipedia.org/wiki/Pyramid_Lake_(Nevada)