Key Questions for Understanding Surface Water

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Key Questions for Understanding Surface Water

• Section 9.1

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1) What are 3 possibilites for water that reaches
the Earths surface?

• It can evaporate into the atmosphere
• It can soak into the ground
• Or, it can flow down slopes on the Earths surface

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

• Runoff is water flowing downslope along Earths
  surface.
• It may reach a body of water, it may evaporate,
  or it may accumulate in low-lying areas and seep
  into the ground.

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3) What are the 4 conditions that determine
whether water

• The amount of vegetation present
• The rate of precipitation
• The composition of the soil
• The slope of the land surface

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

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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.

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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.

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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.

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8) Describe how a stream develops from runoff.

• 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.

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9) In which direction do all streams flow?

• All streams flow downslope, or downhill.

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

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

• 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 also includes sediments, dissolved minerals,
  and gases.

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

• Material is carried in solution after it becomes
  dissolved in a streams water.
• When water runs through rocks containing soluble
  minerals, it dissolves small amounts of the
  minerals and carries them away in solution.

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

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

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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.

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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 measured in cubic meters per second.

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

• A floodplain is the broad, flat area that extends
  out from a streams 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.

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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.

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