Rivers and Streams

I. Part of a River System A. Tributary – a smaller stream or river that flows into a larger body of water

B. Drainage Basin (also called a watershed) – B. Drainage Basin (also called a watershed) – the area of land that is drained by the river system

a. Major U. S. Drainage Basins – a. Major U.S. Drainage Basins – Mississippi, Columbia, Rio Grande, Colorado

C. Divide – an area of higher ground that separates the drainage basins

II. How a River is formed Erosion – moving water cuts through rock and soil creating a channel Factors affecting the speed of the stream Gradient – the change in elevation over the distance a. Higher gradient = More erosive river

2. Discharge – the amount of water a river carries in a given amount of time Higher Discharge = More erosive river Storms and melting increase discharge

3. Load – the material carried in a river Bed Load – larger rocks which drag with the water current on the river bed Suspension Load – small pebbles, soil, and grains which travel in the water without dragging on the bottom Dissolved Load – the minerals and particles dissolved in the river

4. Channel Shape/ Size The wider the channel the slower the flow of water and the less energy in the stream. When large volumes are constricted into narrower channels the energy of the stream increases causing increased erosion.

Narrow channel Wide channel