Big Lost River facts for kids
Quick facts for kids Big Lost River |
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Map of the lost streams of Idaho including the Big Lost River
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| Country | United States |
| State | Idaho |
| Cities | Mackay, Arco, Atomic City |
| Physical characteristics | |
| Main source | Confluence of North Fork and East Fork Big Lost River Custer County, Idaho 6,860 ft (2,090 m) 43°56′01″N 114°06′38″W / 43.93361°N 114.11056°W |
| River mouth | Big Lost River Sinks Butte County, Idaho 4,790 ft (1,460 m) 43°47′39″N 112°50′26″W / 43.79417°N 112.84056°W |
| Length | 135 mi (217 km) |
| Basin features | |
| Basin size | 1,867 sq mi (4,840 km2) |
| Tributaries |
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The Big Lost River is a long river in the state of Idaho in the United States. It stretches for about 135 mi (217 km), which is about 217 kilometers. This river is special because it seems to disappear!
Contents
What Makes the Big Lost River Special?
The Big Lost River starts high up in the Rocky Mountains. It flows generally towards the southeast into a large flat area called the Snake River Plain. Unlike most rivers that flow into a bigger river or the ocean, the Big Lost River simply vanishes into the ground.
This is why it's called "Lost." Its water sinks into the Snake River Aquifer, which is like a huge underground sponge made of rock and gravel. This happens at a place called the Big Lost River Sinks.
Where Does the River Begin?
The Big Lost River begins where two smaller streams meet: the North Fork and East Fork Big Lost River. This meeting point is deep inside the Pioneer Mountains. These mountains are part of the larger Rocky Mountains.
The river starts in Custer County, in south-central Idaho.
The River's Journey
After starting, the river flows northeast. Then it makes a sharp turn to the southeast. This turn happens where another stream, Thousand Springs Creek, joins it. From there, the river flows into Butte County.
Near the town of Mackay, the river is dammed to create Mackay Reservoir. This reservoir helps store water for people and farms. The river then continues south through a farming valley, passing by the town of Arco.
After Arco, the river changes direction again. It flows east, then northeast, and finally straight north.
Where the River Disappears
The Big Lost River ends at the Big Lost River Sinks. This area is a marshy, wet place. Here, the river's water doesn't flow any further above ground. Instead, it slowly drains into the ground, becoming part of the underground Snake River Aquifer.
Even though the river disappears above ground, its water is still connected to the Snake River. The Snake River is the largest river in Idaho. The water from the Big Lost River travels underground through the aquifer. It then reappears in various springs along the Snake River's path.
This makes the Big Lost River one of Idaho's "lost streams." These are rivers that flow into the plain and then disappear into the earth.
