Pyramid Lake (Nevada)

Pyramid Lake is a large, unique body of water located in southeastern Washoe County, Nevada. It sits within an elongated intermontane basin, which is a valley located between mountain ranges. The Lake Range borders the east, while the Virginia Mountains lie to the west. The Pah Rah Range is situated to the southwest. This lake is the largest remaining part of ancient Lake Lahontan. Lake Lahontan was a massive inland sea that covered much of western Nevada during the last major global glaciation.

The lake functions as an endorheic lake. This means it is a closed system where water does not flow out to an ocean. Instead, water only leaves the lake through evaporation or sub-surface seepage. The primary source of water is the Truckee River. This river carries water from the headwaters of Lake Tahoe into the southern end of the lake. While Lake Tahoe is clear, the Truckee River delivers turbid water to Pyramid Lake. This turbidity is caused by the river collecting silt-loaded surface runoff as it moves through steep Sierra terrain.

Pyramid Lake is defined by its specific chemistry and physical scale. It holds about 25% more volume than the Great Salt Lake, even though its surface area is only 10% as large. The water is saline, meaning it contains salt. However, the salinity of Pyramid Lake is approximately 1/6 that of sea water. The lake's environment is shaped by its surrounding geography and climate. Temperatures can range from near freezing at 32°F to over 100°F. The water has a pH level of about 9.

Human history at the lake spans thousands of years. Archaeological evidence shows people lived in this area between 9500 B.C.E. and 1400 A.D. The Pyramid Lake Paiute Tribe has deep ancestral ties to the water. In the Northern Paiute language, the lake is called Kooyooe Panunadu, named after the cui-ui fish. A major band of the Northern Paiute, the Kooyooe Tukadu, calls themselves "cui-ui eaters." The Washo people also have a name for the lake, which means "trout lake." The explorer John C. Frémont was the first non-indigenous person to map the area. He gave the lake its English name after seeing a rock formation that resembled a bent pyramid.

The lake is famous for its spectacular tufa formations. Tufa is a type of calcium carbonate rock. These formations appear as towers or domes along the shores and in the water. One notable formation is Anaho Island, which is the largest tufa island. Anaho Island is a protected area that hosts a large colony of American white pelicans. Another site is called The Needles, located at the northern end of the lake.

In the 20th century, the lake faced a major ecological crisis. In 1905, the Derby Dam was completed to divert water from the Truckee River. This water was sent through the Truckee Canal to irrigate croplands in Fallon. This diversion caused lake levels to drop significantly. By the mid-1970s, the lake had lost a large portion of its depth. This change threatened the survival of native fish. The Lahontan cutthroat trout, a very large inland trout species, became extinct in the lake by 1939.

Efforts to restore the ecosystem have seen remarkable success. In 1979, Dr. Robert Behnke discovered a remnant population of the original Pyramid Lake cutthroat trout in a small brook on Pilot Peak. This discovery allowed for a reintroduction program. Today, fish populations are sustained by tribally-run hatcheries and state and federal agencies. By 2017, fishermen were catching 24-pound trout in the lake again. The Cui-ui lakesucker, an endangered fish endemic to this lake, also relies on these restoration efforts. These fish require sufficient river inflow to travel up the Truckee River to spawn.