Montana Earth Science Picture of the Week

Watershed of the Yellowstone River

Runoff into the River . . .
This image shows all the area that sends runoff into the Yellowstone River. This land is referred to as the Yellowstone River's "watershed", "drainage basin", or just "basin". Any rain or snow within the watershed that does not evaporate or soak into the ground will eventually end up in the Yellowstone River. Unfortunately, chemicals (fertilizers, herbicides, etc.) can also be carried into the river with the runoff. The primary source of water for the Yellowstone River is winter snow that falls in mountains within the basin during the winter. The flow of water (a.k.a. "discharge") in the Yellowstone is usually greatest in June when the snow in the mountains is melting rapidly.

Getting started . . .
As you might expect, the "headwaters" (starting point) of the Yellowstone River are in Yellowstone Park. The river flows northward out of the Park to Livingston. There it turns to the east, flowing toward North Dakota. The Yellowstone's larger tributaries are also shown on the map, and each of these has its own watershed. A large portion of the Bighorn and Powder River watersheds are located in north-central Wyoming.

Montana's Big Three . . .
The western third of the Montana drains into the Clark Fork River, and most of northern Montana empties into the Missouri River. Since the Yellowstone joins the larger Missouri River in North Dakota, the Yellowstone's watershed is considered to be part of the Missouri's watershed. Since the Missouri joins the Mississippi near St. Louis, its watershed is part of the Mississippi's. Unless it evaporates or is removed for use by cities or farmers, runoff from the Yellowstone River's watershed will end up in the Gulf of Mexico.

Terms: runoff, tributary


The Nature Conservancy works to protect the Yellowstone
*More about the Yellowstone Basin (watershed)
*Map of the Mississippi Basin (watershed)
*Map of the Missouri River Basin
Next picture
The Cark Fork River (Montana)
Montana Earth Science Pictures of the Week
Dead Zone at mouth of Mississippi
Colorado River
Columbia River
Rio Grande
Kissimmee River
Connecticut River
Potomac River
Susquehanna River
Delaware River
Red River of the North
Sacramento River
Catskill River
Montana Watershed Groups
American Rivers site (you do a search for a river)
Powder River (Montana/Wyoming)
Milk River (Montana/Canada)
Musselshell River (Montana)
TEACHERS: Check out this watershed activity

By Rod Benson
Earth Science Teacher at Helena High School

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