Big Lost River
Encyclopedia
The Big Lost River is a major river in the U.S. state
of Idaho
, about 135 miles (217.3 km) long. It starts in the Rocky Mountains
and flows in a generally southeast direction into the Snake River Plain
. True to its name, the Big Lost River's surface flow does not reach any larger river, but vanishes into the Snake River Aquifer
at the Big Lost River Sinks, giving the river its name. The river is one of the Lost streams of Idaho, several streams that flow into the plain and disappear into the ground.
It rises at the confluence of the North Fork and East Fork Big Lost River deep in the Pioneer Mountains
, a subrange of the Rockies, in Custer County
, south-central Idaho. It flows northeast then turns sharply southeast at the confluence with Thousand Springs Creek which comes in from the left and into Butte County
. The river is dammed to form Mackay Reservoir near the town of MacKay
, then continues south through an agricultural valley, passing Arco
. After Arco the river begins flowing east, then northeast, and finally due north. The river terminates at the Big Lost River Sinks, a patch of marshland where its water drains into the ground.
Despite the fact that its surface flow is lost (hence its name) a short distance out of the mountains, the river is hydrologically connected to the Snake River
, the largest river of Idaho by discharge, via the Snake River Aquifer and various springs along the course of the Snake in its journey through the plain.
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....
, about 135 miles (217.3 km) long. It starts in the Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
and flows in a generally southeast direction into the Snake River Plain
Snake River Plain
The Snake River Plain is a geologic feature located primarily within the state of Idaho in the United States of America. It stretches about westward from northwest of the state of Wyoming to the Idaho-Oregon border. The plain is a wide flat bow-shaped depression, and covers about a quarter of Idaho...
. True to its name, the Big Lost River's surface flow does not reach any larger river, but vanishes into the Snake River Aquifer
Snake River Aquifer
The Snake River Aquifer is a large reservoir of groundwater underlying the Snake River Plain in the southern part of the U.S. state of Idaho. Most of the water in the aquifer comes from rain and melting snow that flows onto the plain from the Snake River, Big Lost River, Bruneau River, and other...
at the Big Lost River Sinks, giving the river its name. The river is one of the Lost streams of Idaho, several streams that flow into the plain and disappear into the ground.
It rises at the confluence of the North Fork and East Fork Big Lost River deep in the Pioneer Mountains
Pioneer Mountains (Idaho)
The Pioneer Mountains is a mountain range in the U.S. state of Idaho, spanning Blaine, Butte and Custer counties. The range is bounded on the west by the Big Wood River, Trail Creek and Summit Creek, and the North Fork Big Lost River, on the north and east by the East Fork Big Lost River, Left Fork...
, a subrange of the Rockies, in Custer County
Custer County, Idaho
Custer County is a rural mountain county located in the center of the U.S. state of Idaho. Established in 1881, it was named for the General Custer Mine, where gold was discovered five years earlier . The population was 4,342 at the 2000 census; it is estimated to have fallen to 4,166 by 2007...
, south-central Idaho. It flows northeast then turns sharply southeast at the confluence with Thousand Springs Creek which comes in from the left and into Butte County
Butte County, Idaho
Butte County is a rural county located in the U.S. state of Idaho. It was established in 1917, and its county seat and largest city is Arco. As of the 2010 census, the county had a population of 2,891...
. The river is dammed to form Mackay Reservoir near the town of MacKay
Mackay, Idaho
Mackay is a city in Custer County, Idaho, United States. The population was 566 at the 2000 census.-Geography:Mackay is located at , at an elevation of 5,905 feet ....
, then continues south through an agricultural valley, passing Arco
Arco, Idaho
Arco is a city in Butte County, Idaho, United States. The population was 995 at the 2010 census. The city is the county seat of Butte County.Craters of the Moon National Monument is located along U.S. Route 20, southwest of the city. The Idaho National Laboratory is located east of Arco...
. After Arco the river begins flowing east, then northeast, and finally due north. The river terminates at the Big Lost River Sinks, a patch of marshland where its water drains into the ground.
Despite the fact that its surface flow is lost (hence its name) a short distance out of the mountains, the river is hydrologically connected to the Snake River
Snake River
The Snake is a major river of the greater Pacific Northwest in the United States. At long, it is the largest tributary of the Columbia River, the largest North American river that empties into the Pacific Ocean...
, the largest river of Idaho by discharge, via the Snake River Aquifer and various springs along the course of the Snake in its journey through the plain.