How Landscapes Determine the Paths of River Systems

Name How Landscapes Determine the Paths of River Systems

Tributaries are the smaller streams that feed into a main river. A river and all its tributaries together make up a river system. The tributaries flow toward the main river in a downhill path due to the pull of gravity.

Watersheds or Drainage Basins Just as all the water in a bathtub flows toward the drain, all the water in a river system drains into the main river. The land area that supplies water to a river system is called a watershed or drainage basin. You can identify a river’s watershed on a map by drawing an imaginary line around the region drained by all its tributaries.

Divides One watershed is separated from another by a ridge of land called a divide. Ridges are geologic features of higher elevations. Ridges can be hills or mountains. Water does not go UP a hill consequently, streams on each side of the divide flow in different directions. (Imagine a bathtub is a drainage basin/watershed and the sides of the bath tub are the divides – any drop of water that falls within the bathtub goes down the drain)

A C B D

E 1. Notice the area drained by the Mississippi River (Labeled A - yellow). This is the largest watershed or drainage basin in North America. Estimate the percentage of total surface area of the United States that is drained by the Mississippi?

2. Notice Area C drainage basin or watershed. What body of water do all the rivers in this drainage basin ultimately drain into?

3. Look at the Mississippi watershed labeled A and the watersheds labeled B and E. What ocean does all the rivers in those basins ultimately drained into?

4. The Continental Divide, the longest divide in North America, follows the line of the Rocky Mountains. West of the Continental Divide, water either flows toward the Pacific Ocean or into the dry Great Basin, where the water usually evaporates. Between the Rocky Mountains and the Appalachian Mountains, water flows toward the Mississippi River or directly into the Gulf of Mexico.

On map 1, use a pencil to trace the Continental Divide that separates all the drainage that ends up in the Pacific Ocean from all the drainage that ends up in the Atlantic Ocean.

5. Look on the map below, which landscape feature corresponds with the divide you just labeled on Map 1?

6. On the map below, which landscape feature seems to correspond with the divide between the Mississippi drainage basin and the smaller river systems that flow east across the Atlantic Coastal Plain?

7. Explain how/why a mountain range can create a drainage divide? 8. Examine the rivers on Map 1 in the basin that is shaded in blue and labeled D. What is a noticeable difference between those rivers and the others on the map?

9. Those rivers appear to “just end”, they don’t flow ultimately to the oceans. Look at the map below and locate the Great Basin. Many of these rivers dry up in the summer due to evaporation. One of those rivers in the basin flows into the Great Salt Lake which has no outlet. (Look on the right side of the basin) The river water flowing into the Great Salt Lake largely comes from Rocky Mountain snow melt which is not salty but because there is no outlet and a great deal of evaporation – the Great Salt Lake becomes very salty.

Part B There are 4 different drainage patterns that develop within the watershed or drainage basin depending on the topography: dendritic, radial, rectangular and trellis. Dendritic Pattern: Most Common type – gentle elevation Example: Mississippi Drainage Basin/watershed

Radial Pattern: occurs around highest central point – examples volcanoes or mountains

Rectangular Pattern: found in regions where there is faulting or fractures and tend to make right angles.

Trellis Pattern: common in the Appalachian Mountains where folding has occurred. 1. In the map below, find the Adirondack Mountains. Describe the pattern that the streams draining the Adirondacks make. Put an X near the highest spot.

Find the Hudson River. What direction does it flow?

2. The map below shows the stream drainage patterns for a region on Earth’s surface. Points A, B, C and D are locations in the region.

The highest elevation most likely exists at point A B C D 3. The diagram below represents an eroded dome

Which of the following maps represent the stream drainage pattern that would develop on this eroded dome?

4 3. The diagram below represents an eroded dome