Key Questions for Key Questions for Understanding Understanding Surface WaterSurface Water

Section 9.1Section 9.1

1) What are 3 possibilites 1) What are 3 possibilites for water that reaches the for water that reaches the

Earth’s surface?Earth’s surface?

It can evaporate into the atmosphereIt can evaporate into the atmosphere It can soak into the groundIt can soak into the ground Or, it can flow down slopes on the Or, it can flow down slopes on the

Earth’s surfaceEarth’s surface

2) What is runoff, and what 2) What is runoff, and what are the 3 possible courses it are the 3 possible courses it

can take?can take?

Runoff is water flowing downslope Runoff is water flowing downslope along Earth’s surface.along Earth’s surface.

It may reach a body of water, it may It may reach a body of water, it may evaporate, or it may accumulate in evaporate, or it may accumulate in low-lying areas and seep into the low-lying areas and seep into the ground.ground.

3) What are the 4 3) What are the 4 conditions that determine conditions that determine

whether water…whether water…

The amount of vegetation presentThe amount of vegetation present The rate of precipitationThe rate of precipitation The composition of the soilThe composition of the soil The slope of the land surfaceThe slope of the land surface

4) How does vegetation 4) How does vegetation determine whether water determine whether water

will become runoff?will become runoff?

Soils that contain grasses or other Soils that contain grasses or other vegetation allow more water to enter vegetation allow more water to enter the ground than do soils with no the ground than do soils with no vegetation.vegetation.

Vegetation lessens the force with Vegetation lessens the force with which rain hits the ground, allowing which rain hits the ground, allowing it more time to soak into the soil.it more time to soak into the soil.

5) How does the rate of 5) How does the rate of precipitation determine…precipitation determine…

Light, gentle precipitation infiltrates Light, gentle precipitation infiltrates dry ground, but heavy precipitation dry ground, but heavy precipitation falls too quickly to soak into the falls too quickly to soak into the ground and becomes runoff.ground and becomes runoff.

6) Which soil particles lead 6) Which soil particles lead to greater amounts of to greater amounts of

runoff?runoff?

Soil with a high percentage of fine Soil with a high percentage of fine particles, such as clay, clumps particles, such as clay, clumps together and has few or no pore together and has few or no pore spaces between the particles.spaces between the particles.

7) How does a steep slope 7) How does a steep slope lead to runoff?lead to runoff?

On steep slopes, precipitation runs On steep slopes, precipitation runs downslope before it has an downslope before it has an opportunity to soak into the soil.opportunity to soak into the soil.

8) Describe how a stream 8) Describe how a stream develops from runoff.develops from runoff.

As the amount of runoff increases, As the amount of runoff increases, the channels widen, deepen, and the channels widen, deepen, and become longer.become longer.

If a consistent supply of water If a consistent supply of water develops, the water flows develops, the water flows permanently in a channel and permanently in a channel and becomes a stream.becomes a stream.

9) In which direction do all 9) In which direction do all streams flow?streams flow?

All streams flow downslope, or All streams flow downslope, or downhill.downhill.

10) What is a watershed, 10) What is a watershed, and what is a divide?and what is a divide?

A watershed is all of the land area A watershed is all of the land area whose water drains into a stream whose water drains into a stream system (also called a river basin)system (also called a river basin)

A divide is the high land area that A divide is the high land area that separates one watershed from separates one watershed from another.another.

11) Describe stream load, 11) Describe stream load, including the living and including the living and nonliving components.nonliving components.

Stream load is all of the materials Stream load is all of the materials that the water in a stream carries.that the water in a stream carries.

It includes microscopic organisms, It includes microscopic organisms, as well as larger plants and animals.as well as larger plants and animals.

It also includes sediments, dissolved It also includes sediments, dissolved minerals, and gases.minerals, and gases.

12) Describe how a stream 12) Describe how a stream can carry its load in can carry its load in

solution.solution.

Material is carried in solution after it Material is carried in solution after it becomes dissolved in a stream’s becomes dissolved in a stream’s water.water.

When water runs through rocks When water runs through rocks containing soluble minerals, it containing soluble minerals, it dissolves small amounts of the dissolves small amounts of the minerals and carries them away in minerals and carries them away in solution.solution.

13) Describe how a stream 13) Describe how a stream can carry its load in can carry its load in

suspension.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 sandare carried in suspension

14) What is bed load, and 14) What is bed load, and how does a stream move its how does a stream move its

bed load?bed load?

Bed load consists of sand, pebbles, Bed load consists of sand, pebbles, and cobbles that the stream’s water and cobbles that the stream’s water pushes or rolls along the bed of the pushes or rolls along the bed of the stream.stream.

15) What is the carrying 15) What is the carrying capacity of a stream?capacity of a stream?

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

16) What is the discharge 16) What is the discharge of a stream, how is it of a stream, how is it

measured…measured…

Discharge is the measurement of the Discharge is the measurement of the volume of stream water that flows volume of stream water that flows over a particular location in a given over a particular location in a given amount of time.amount of time.

Discharge is measured in cubic Discharge is measured in cubic meters per second.meters per second.

17) What is a floodplain, 17) What is a floodplain, and how does it gain new and how does it gain new

material?material?

A floodplain is the broad, flat area A floodplain is the broad, flat area that extends out from a stream’s that extends out from a stream’s banks and is covered by excess banks and is covered by excess water during times of flooding.water during times of flooding.

As floodwaters recede, the sediment As floodwaters recede, the sediment carried by the water is dropped on carried by the water is dropped on top of the floodplain.top of the floodplain.

18) Why does a flood often 18) Why does a flood often crest days after the crest days after the precipitation ends?precipitation ends?

Because it takes time for runoff to Because it takes time for runoff to collect in streams, the water collect in streams, the water continues to rise and may reach its continues to rise and may reach its crest days after the precipitation crest days after the precipitation ends.ends.

19) How do government 19) How do government agencies protect people agencies protect people

from floods?from floods?

In areas that are prone to flooding, In areas that are prone to flooding, warning systems are the first step in warning systems are the first step in protecting people from floods.protecting people from floods.

Homeowners are also informed if Homeowners are also informed if they live in a floodplain.they live in a floodplain.