Regents Earth Science
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US Drainage
Period ______
Copyright 2004 S. Kluge and L. Wood
IMPORTANT CONCEPTS:
The water flowing in a stream has come from the surrounding land that is "uphill" from the stream. The area of land
that is drained by the stream or system of streams (or that sheds its water into the stream) is called the stream's
DRAINAGE BASIN or WATERSHED. There may be many smaller streams within a single drainage basin that
contribute water to the main stream in the system. These smaller contributing streams are called TRIBUTARIES.
The height of land that divides one drainage basin from another is called a DIVIDE. In the United States there is a
major divide running along many of the high peaks of the Rocky Mountains that separates the water that ultimately
flows into the Atlantic Ocean from water that flows into the Pacific. This is called the CONTINENTAL DIVIDE. Look at
the attached map of the US, and notice the position of the Continental Divide on that map. With your finger, trace the
flow of water on either side of the continental divide to the stream systems’ end at the ocean.
GOALS
At the end of this lab, you should be able to locate the divides between major river systems and determine the extent
of a river system's drainage basin.
MATERIALS:
US Drainage Map
Four (4) colored pencils (2 warm colors, like red, orange, yellow, and 2 cool colors, like blue, purple, green).
PROCEDURE:
Ø Find the mouth of the Mississippi River (it flows into the Gulf of Mexico through the state of Louisiana.) and label
the Mississippi River.
Ø Use one of the warm colored pencils to trace the Mississippi and all of its tributaries.
Ø Use a pen or pencil to draw the divides that separate the Mississippi and all of .its tributaries from the other rivers
of the country (notice that the part of the continental divide forms the western divide of the Mississippi system).
Ø Lightly shade the Mississippi drainage basin with the warm color you are using.
Ø Use another warm color to trace all the other rivers in the U.S. that drain into the Gulf of Mexico or the Atlantic.
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Now use a cool color to trace all the river systrems that flow into the Pacific ocean.
Draw the divides of each of the rivers you just traced, and lightly shade the basins. Notice that the continental
divide forms the eastern divide of some of those rivers.
There are a few rivers in Nevada and Utah which do not seem to flow into any ocean, find them and trace them
with the other cool color.
Answer the following questions:
1. Approximately what percentage of the land area of the United States is drained by the Mississippi River system?
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2. The "dead end" rivers in Utah and Nevada are located to the east of the Sierra Nevada mountains. Think of the
type of climate that probably exists there, and suggest what is probably happening to the water form those rivers
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3. What landform(s) might exist where those rivers end? Describe their formation. (Hint: use one of the geology texts,
the internet, and/or an encyclopedia to look up playa lakes and salt flats)
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4. Approximately what percentage of the land area of the United States drains into the Pacific Ocean?
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5. Is there ANY land anywhere on earth that is not part of some drainage basin or another? EXPLAIN!
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The answer to question 5 is NO! So go back and look at your maps, and if any area on the map is NOT within a
basin, decide which river water that falls there must drain into, and adjust the position of your divide.!
6. Explain why fertilizer and pesticides use by farmers in western NY might be of some concern to people living in the
Mississippi River delta at the Gulf of Mexico.
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