The Truckee-Carson Irrigation District (TCID) is a political subdivision of the State of Nevada

Nevada

Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

, which operates dams at Lake Tahoe

Lake Tahoe

Lake Tahoe is a large freshwater lake in the Sierra Nevada of the United States. At a surface elevation of , it is located along the border between California and Nevada, west of Carson City. Lake Tahoe is the largest alpine lake in North America. Its depth is , making it the USA's second-deepest...

, on the Truckee River

Truckee River

The Truckee River is a stream in the U.S. states of California and Nevada. The river is about long. Its endorheic drainage basin is about , of which about are in Nevada. The Truckee is the sole outlet of Lake Tahoe and drains part of the high Sierra Nevada, emptying into Pyramid Lake in the Great...

 and Lake Lahontan

Lake Lahontan (reservoir)

Modern Lake Lahontan is a reservoir on the Carson River in northwest Nevada in the United States. It is formed by the Lahontan Dam and is located between Fallon, Nevada and Carson City, Nevada. The flows from the Carson River is augmented by diversions from the Truckee River...

 as well as 380 miles (611.5 km) of canal

Canal

Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

s and 340 miles (547.2 km) of drains in support of agriculture in Lyon County

Lyon County, Nevada

Lyon County is a county located in the U.S. state of Nevada. As of the 2010 census, the population was 51,980. Its county seat is Yerington.-History:...

 and Churchill County

Churchill County, Nevada

Churchill County is a county located in the western U.S. state of Nevada. As of the 2000 census, the population was 23,982. As of July 1, 2007, the population of Churchill County was estimated at 27,190. The county, named after Mexican-American War hero brevet Brigadier General Sylvester Churchill,...

.

Diversion of water by the TCID from the Truckee River has caused a reduction in the level of Pyramid Lake, and endangered

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 the endemic

Endemic (ecology)

Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...

 species of fish that live in it. In the mid 1980s the United States Environmental Protection Agency‎ initiated development of the DSSAM Model

DSSAM Model

The DSSAM Model is a computer simulation developed for the Truckee River to analyze water quality impacts from land use and wastewater management decisions in the Truckee River Basin. This area includes the cities of Reno and Sparks, Nevada as well as the Lake Tahoe Basin...

 to analyze effects of variable Truckee River

Truckee River

The Truckee River is a stream in the U.S. states of California and Nevada. The river is about long. Its endorheic drainage basin is about , of which about are in Nevada. The Truckee is the sole outlet of Lake Tahoe and drains part of the high Sierra Nevada, emptying into Pyramid Lake in the Great...

flow rates and water quality upon these endangered fish species.