1. Journal #3 Describe your observations in yesterday’s lab
Why do you think you saw what you did?
What is that called?
How does pollution affect our water supply?

2. Today, we will summarize how a river develops

3. Stream Erosion
A river system begins to form when precipitation exceeds evapotranspiration in a given area.
After the soil soaks up as much water as the soil can hold, the excess water moves downslope as a runoff.
As runoff moves across the land surface, it erodes rock and soil and eventually may form a ditch called a gully.
Eventually this process will develop into a valley with a permanent stream.

4. Parts of a River System
A river system is made up of a main stream and tributaries
Tributaries are streams that flow into a lake or larger stream
The water from which water runs off into these streams is called watershed.
The ridges or elevated regions that separate water sheds are called divides.
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5. Channels
The narrow depression in which a stream follows downhill is called its channel.
The edges of a stream channel that are above water level are called the stream’s banks.
The part of the stream channel that is below the water level is called the stream’s bed.

6. Channel Erosion River systems change continuously because of erosion.
Erosion of the slopes in a watershed can also extend a rivers system and add to the area of watershed.

7. Your Assignment:
Draw a diagram of a stream/river and label the following:
Main stream
Tributaries
Watershed
Divide
Channel
Bed
River