Anatomy of Rivers

Watershed

• Any area of land where all precipitation collects and drains off into a common outlet, such as into a river or bay.

Columbia River Watershed

Major Watersheds of North America

Mississippi River Watershed

Continental Divide• The line that separates water that flows to the Pacific

Ocean and the Atlantic Ocean.

Only One Place Goes Both Directions-Two Ocean Pass

• Near Yellowstone National Park

V-shaped Valleys

• When rivers carve into mountains, they form steep V-shaped valleys.

Headwaters

• Source of a river (usually a spring or glacier/snow field)

Lake Itasca, MN, the headwaters of the Mississippi River

Main Stem (or Trunk)

• Main section of the river heading toward the ocean

Mississippi River on the Iowa/Wisconsin Border

Mississippi River at St. Louis, MO

Braided Streams

• When the plain is very flat, the river will begin to spread out looking for the quickest way through the sediment.

• Each little stream will begin to meander back and forth, sometimes spreading away from each other, sometimes rejoining later on.

• These braided streams often have thousands of little “islands”.

Flat Plains = Meandering River

Oxbow Lake

Oxbow Lakes

How a Meandering River can Form an Oxbow Lake

Flood Plain• A flood plain is the area of deposition

along a river. Often these areas flood over and over again, continually depositing more sediment.

• Often people build along flood plains because it is good farmland, only to see their cities destroyed by floods.

Tributary and Confluence

• Tributary: a stream or river that flows into a larger river

• Confluence: The meeting of two rivers

Mouth – where the river empties into the ocean or lake

River Deltas

• River deltas are where rivers enter the ocean or lakes. These deltas are the final place of deposition where silt and sand accumulate.

Mouth of the Columbia River

Estuary- zone where freshwater and saltwater mixes

Deltas at the Mouths of River Usually Provide Sand for Beaches

• Long Beach Peninsula formed due to sediment from the Columbia River being moved north from the mouth.