Download Freshwater Systems

Thinking Questions
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Why is Freshwater so Rare?
What is a River?
What makes up a river?
What creates rivers?
What is a flash flood?
What is needed to have a flash flood occur?
Why is our area of NC prone to Flash floods?
Why are mountains also prone to Flash
Flooding?
Freshwater Systems
You will be able to:
Explain how Rivers shape the land
Identify conditions which cause flooding
Identify the different zones and characteristics of River
Systems
Water Cycle
• Fresh Water comes from the Water Cycle
• Water Cycle Diagram: here
Where is the Water?
• 71% of Earth is
covered by water
• 29% Terrestrial
Surface
• 3% of water is Fresh
• 97% of all water is
salt water
Where’s the FRESHWATER?
Fresh Water Distribution
23%
Polar Ice Caps
1%
Groundwater
76%
All Rivers and
lakes
Where’s the Freshwater?
• Water in Ice caps
completely frozen all year
round
• Making ground water the
largest supplier of the
world’s FRESH WATER!
The 1%: How Rivers Form
• All Rivers form from Run-off
• Run-off is water that is not absorbed by
the ground.
• Produced from precipitation and seasonal
melting of snow and glaciers
• Run-off rates may change at different
locations within a River System
What affects Run-Off Rate?
(3 things)
• Soil Type – Major factor in determining
run-off rates. Different soil types have
different abilities to containing water.
• Precipitation/Melting amounts- Amount of
water that is able to fall upon ground
• Topography of Land- Hills produce more
run-off than flat areas because gravity
pulls water down the sides of the hill and
not into the soil
Soil Types
• Soils have different Run-off traits because of 2
primary factors
• Porosity- amount of empty spaces between soil
particles
• Permeability- how well empty spaces are
aligned.
• If both values are low, high run off rates will
occur
• 3 Basic soil Types in NC, gravel based, clay
based, or sand based
Soil Types (Con’t)
• Different Soil types traits are best
described using 2 terms;
• Aquifer- Material that allows water to travel
through it easily (high porosity, high
permeability)
• Aquitard- material that DOES NOT allow
water to travel through it easily. (low
porosity, low permeability)
What River Systems Share
• 1st Zone- Headwaters
• Small Tributaries/streams formed along
sides of mountains
• Streams are narrow but deep in places
• High erosion occurs here
• Animals small in size and streamlined
What River Systems Share
• 2nd Zone- Downriver
• Tributaries merge and form larger water
system; Current here fast and strong
”White Water rafting”
• Rivers wider, straighter
• high erosion; little deposition
• Animals larger and still streamlined
What River Systems Share
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Flood Plain- 3rd zone
Rivers begin to twist and turn,
Current slows dramatically
River is at its widest but also fairly shallow
Erosion rates equal Deposition rates;
Bends in rivers called Meanders
• Organisms are largest here; not as
streamlined.
What River Systems Share
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4th Zone- Estuary/Mouth/Delta
Where River empties into Sea
Current here very slow
No Erosion, High Deposition rates
Organisms actually get smaller in size as
you approach ocean,
What River Systems Share
• Watershed- Entire area of Land that gives
run-off to a River System
• Divide- Geographical region which
separates River Systems; Usually a
mountain range