1. Key Questions for Understanding Surface Water Section 9.1

2. 1) What are 3 possibilites for water that reaches the Earth’s surface? It can evaporate into the atmosphere It can evaporate into the atmosphere It can soak into the ground It can soak into the ground Or, it can flow down slopes on the Earth’s surface Or, it can flow down slopes on the Earth’s surface

3. 2) What is runoff, and what are the 3 possible courses it can take? Runoff is water flowing downslope along Earth’s surface. Runoff is water flowing downslope along Earth’s surface. It may reach a body of water, it may evaporate, or it may accumulate in low-lying areas and seep into the ground. It may reach a body of water, it may evaporate, or it may accumulate in low-lying areas and seep into the ground.

4. 3) What are the 4 conditions that determine whether water… The amount of vegetation present The amount of vegetation present The rate of precipitation The rate of precipitation The composition of the soil The composition of the soil The slope of the land surface The slope of the land surface

5. 4) How does vegetation determine whether water will become runoff? Soils that contain grasses or other vegetation allow more water to enter the ground than do soils with no vegetation. Soils that contain grasses or other vegetation allow more water to enter the ground than do soils with no vegetation. Vegetation lessens the force with which rain hits the ground, allowing it more time to soak into the soil. Vegetation lessens the force with which rain hits the ground, allowing it more time to soak into the soil.

6. 5) How does the rate of precipitation determine… Light, gentle precipitation infiltrates dry ground, but heavy precipitation falls too quickly to soak into the ground and becomes runoff. Light, gentle precipitation infiltrates dry ground, but heavy precipitation falls too quickly to soak into the ground and becomes runoff.

7. 6) Which soil particles lead to greater amounts of runoff? Soil with a high percentage of fine particles, such as clay, clumps together and has few or no pore spaces between the particles. Soil with a high percentage of fine particles, such as clay, clumps together and has few or no pore spaces between the particles.

8. 7) How does a steep slope lead to runoff? On steep slopes, precipitation runs downslope before it has an opportunity to soak into the soil. On steep slopes, precipitation runs downslope before it has an opportunity to soak into the soil.

9. 8) Describe how a stream develops from runoff. As the amount of runoff increases, the channels widen, deepen, and become longer. As the amount of runoff increases, the channels widen, deepen, and become longer. If a consistent supply of water develops, the water flows permanently in a channel and becomes a stream. If a consistent supply of water develops, the water flows permanently in a channel and becomes a stream.

10. 9) In which direction do all streams flow? All streams flow downslope, or downhill. All streams flow downslope, or downhill.

11. 10) What is a watershed, and what is a divide? A watershed is all of the land area whose water drains into a stream system (also called a river basin) A watershed is all of the land area whose water drains into a stream system (also called a river basin) A divide is the high land area that separates one watershed from another. A divide is the high land area that separates one watershed from another.

12. 11) Describe stream load, including the living and nonliving components. Stream load is all of the materials that the water in a stream carries. Stream load is all of the materials that the water in a stream carries. It includes microscopic organisms, as well as larger plants and animals. It includes microscopic organisms, as well as larger plants and animals. It also includes sediments, dissolved minerals, and gases. It also includes sediments, dissolved minerals, and gases.

13. 12) Describe how a stream can carry its load in solution. Material is carried in solution after it becomes dissolved in a stream’s water. Material is carried in solution after it becomes dissolved in a stream’s water. When water runs through rocks containing soluble minerals, it dissolves small amounts of the minerals and carries them away in solution. When water runs through rocks containing soluble minerals, it dissolves small amounts of the minerals and carries them away in solution.

14. 13) Describe how a stream can carry its load in suspension. All particles small enough to be held up by the turbulence of a stream’s moving water are carried in suspension. Particles such as silt, clay, and sand are carried in suspension

15. 14) What is bed load, and how does a stream move its bed load? Bed load consists of sand, pebbles, and cobbles that the stream’s water pushes or rolls along the bed of the stream. Bed load consists of sand, pebbles, and cobbles that the stream’s water pushes or rolls along the bed of the stream.

16. 15) What is the carrying capacity of a stream? The ability of a stream to transport material is its carrying capacity. It depends upon the velocity and volume of water in the stream. The ability of a stream to transport material is its carrying capacity. It depends upon the velocity and volume of water in the stream.

17. 16) What is the discharge of a stream, how is it measured… Discharge is the measurement of the volume of stream water that flows over a particular location in a given amount of time. Discharge is the measurement of the volume of stream water that flows over a particular location in a given amount of time. Discharge is measured in cubic meters per second. Discharge is measured in cubic meters per second.

18. 17) What is a floodplain, and how does it gain new material? A floodplain is the broad, flat area that extends out from a stream’s banks and is covered by excess water during times of flooding. A floodplain is the broad, flat area that extends out from a stream’s banks and is covered by excess water during times of flooding. As floodwaters recede, the sediment carried by the water is dropped on top of the floodplain. As floodwaters recede, the sediment carried by the water is dropped on top of the floodplain.

19. 18) Why does a flood often crest days after the precipitation ends? Because it takes time for runoff to collect in streams, the water continues to rise and may reach its crest days after the precipitation ends. Because it takes time for runoff to collect in streams, the water continues to rise and may reach its crest days after the precipitation ends.

20. 19) How do government agencies protect people from floods? In areas that are prone to flooding, warning systems are the first step in protecting people from floods. In areas that are prone to flooding, warning systems are the first step in protecting people from floods. Homeowners are also informed if they live in a floodplain. Homeowners are also informed if they live in a floodplain.