River Basin and Estuary Review

Which describes an estuary?

• A large body of fresh water.

• A large body of salt water.

• The wide, lower course of a river where fresh and salt water mix.

Which best describes the water found in estuaries?

• brackish

• salt water

• freshwater

When would you expect the concentration of salt in the estuary water to be LOWEST near the mouth of the river?

• when the river flow is low and the tide is low

• when the river flow is high and the tide is low

• when the river flow is low and the tide is high

• when the river flow is high and the tide is high

Which best explains how estuaries support plant and animal life?

• The dry land removes pollutants.

• The water provides energy for growth.

• The habitat areas provide nutrients and shelter.

• The cold temperatures decrease dissolved oxygen

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How does the water in an estuary compare to the water in the open ocean?

• Estuaries have less concentrated nutrients and salt.

• Estuaries have more concentrated nutrients and salt.

• Estuaries have less concentrated nutrients and more concentrated salt.

• Estuaries have more concentrated nutrients and less concentrated salt.

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Which would be the impact on the environment if there were no estuaries?

• There would be a drought.

• There would be more pollutants in the oceans.

• There would be a decreased concentration of salt in the oceans.

• There would be less boating, fishing, and swimming in local rivers.

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Estuaries are called “the nurseries of the sea” because many species lay eggs and develop their young in estuaries. Which two features of estuaries support this role most?

• concentrated nutrients and a steep salt gradient

• abundant shelter and concentrated nutrients

• a steep salt gradient and shallow water

• shallow water and abundant shelter

Which part of a river provides the best evidence that water weathers and erodes the land it flows over?

• Headwaters

• Mouth

• Delta

• Tributaries

Answer explanation

Sediment deposited at the delta comes from erosion.

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What is the primary job of a river basin?

• To soak into the ground and become groundwater

• To collect all the water in a large area that runs off into a specific river

• To divide land between watersheds

• To hold water in one area permanently

Answer explanation

This is the definition of a river basin

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Which is the best explanation for why estuaries form?

• Estuaries are filled in with river and ocean water.

• Estuaries are created when rivers meet the ocean.

• Estuaries are specific pieces of land where freshwater meets salt water.

• Estuaries contain brackish water and are found at the end of a river.

Answer explanation

Estuaries need the mixing of salt and fresh water to form brackish water. D, however, is just the description of estuary conditions and location, not an explanation for its formation. The land where the waters meet is not the estuary either (C), nor are estuaries like swimming pools or bathtubs waiting to be filled in (A) because if a river is diverted to a different part of the ocean, the place (land) it used to be located is not still called an estuary.