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Unit 5 Chapter 15
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River Systems
Section 1 The Water Cycle
Remember from the beginning of the year we talked about the
water cycle. Again, we are talking about it. It is a never ending
process that repeats itself over and over again, from
precipitation, to evaporation and back to precip.
Movement of Water on Earth
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Where is our water kept
____%of water is in oceans - salt water
____% of water is frozen - glaciers
____%of water is fresh drinking
__________________________________
__________________________________
__________________________________
__________________________________
What this really means is that 75% of the fresh water is in the
form of Glaciers.
_______% of the fresh water that we use for drinking and things
is found UNDERGROUND, hence the word GROUND WATER
__________________________
Evaporation - water vapor going into the atmosphere
- usually by the sun, directly or indirectly
- moisture source for local water budget.
Transpiration - process by which green plants lose water through
their leaves
_________________- evaporation & transpiration combined
- the way most water enters the air
Condensation
Condensation - _______________________________________
- must have condensation nuclei (dust) to form clouds
Precipitation
Precipitation - ________________________________________
Water Budget
Water Budget –
It is the balance sheet for rain (precipitation) and water usage.
Terms:
________- more water than you need - storage is full
______- less water than you need – using water from storage
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_______ - precipitation less than needed, storage is becoming
empty
_________- rain greater than needed, adding water back into
storage
Factors that affect our Water Budget
Land use:
1. _____________- removing the trees there is nothing to hold
water in ground or prevent run off on surface.
2. Slope of the land – if it is too steep, water will run off unless it
is covered by vegetation or plants.
3. Urbanization – ______________________________________
4. Plant life – when covering the soil, can hold water, removed,
allows water to run off.
5. Saltwater encroachment (infusion)- due to over pumping in
areas by salt water, it will creep into the fresh water supply.
6. Permafrost – areas where the ground stays frozen up to 100
meters deep.
Water Use
Over use is a very big problem. When all of the water is
removed from underground the ground may become compacted
and the ground level drops. This is called subsidence.
Foundation failure and structure damage may result.
Pollution:
Chemicals – brought into the water table by pesticides, fertilizers,
and other household items.
Sewage – from urbanization
Industrial wastes – toxic wastes,
Radon – a natural radioactive gas that comes from the decay of
uranium.
Ground water areas close to this will become contaminated.
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Conservation of Water
Laws have been put into place so that we can keep our water
clean and abundant enough to use. There are also ways that we
are trying to add to our fresh water supply. Desalination is one
such process. Scientists are trying to remove the salt from ocean
water and turning it into fresh water. It is too expensive at this
time to do as a real solution.
Section 2 Stream Erosion
River Systems –
________________________________________________________
_________________________________________________________
Parts of a River System
______________________
A stream that runs into another stream
_____________________________
It is all of the land that drains into a river including all of the waters
from the tributaries.
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Canyon (gorge, chasm)
A river cuts directly down in resistant rock - vertical sides
The highland that separates one drainage basin from another is called a
divide.
____________________________________________________
East – ____________________________________________
West – __________________________________________
Mississippi River System - ___________________________________
_________________________________________________________
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Channel Erosion
Head ward erosion
___________________________________________________
_____________________________
– formed by young streams and rivers; they flow fast
- Erosion is quick - widens whole valley
Gully ________________________________________________
Stream Piracy –
When head ward erosion eats through a divide and captures another river.
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Stream Load
How Streams Transport Materials
25% solution - material dissolved into water
Ex. Ca, Mg, Fe, Na, CO2, O2
50% suspension- carrying rock materials
Ex. clay, silt, fine sand
25% bed load - moving material along the bottom
Ex. sand, pebbles, cobbles, boulders
Carrying load - total amount of sediment a stream can carry and the size
of the particles and on the velocity and volume of water
Stream Discharge
Discharge –
Is the volume of water flowing past a point in a certain period of time. Faster
moving water carries more sediment.
Velocity – ________________________________________________
Stream Gradient
Gradient – the steepness of the slope of the stream. The gradient will
Change during the length of the river or stream. It will be great when
going down a steep hill or small when approaching sea level.
Base Level - lowest level a stream or river gets to
- depends on where stream is flowing
- Height above sea level or over what types of rocks
Sea Level is the ultimate base level because all rivers eventually empty
there.
Rapids – ___________________________________________________
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Water Falls – water falling over a cliff
____________________ – water falling from the falls wears away at the
bottom of the cliff leaving an overhang. The overhang eventually falls and
the waterfall moves upstream (recedes).
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Development of River Channels
When a stream load, discharge and gradient decreases, they become
broader and slower moving, they now are called a river.
Meandering Channels
Rivers always shift to the outside of a bend - because the outside has the
fastest moving water - most erosion.
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Meanders - _______________________________________
Oxbow Lake -
a cut off meander of a river
Rivers decrease in speed and deposit sediment
All sediment is deposited when a river enters a lake or ocean
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Braided Streams
This occurs when multiple channels are divided and then again rejoined.
Section 3 Stream Deposition
As a river turns a corner, it will decrease in speed and will
deposit its sediment. Swifter moving water will carry the
sediment much further.
Deltas and Alluvial Fans
Delta __________________________________________________
Sediments drop as water slows
The river channels are choked by its own sediment
______________ land locked delta - formed as rain water flows down
a steep cliff on to flat land
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Floodplains
Flood plains are areas where rivers can over flow.
Natural Levees
Levee elevated land along rivers - either natural or man made
Back swamp low area behind levee, moist full of river deposits
Finer Flood Sediments
Finer sediments are carried into the flood plains. It is associated
with the swampy area that is along the rivers where the
sediments are deposited.
Human Impacts on Flooding
We contribute to flooding by the use of the land. Removing
vegetation and trees allows for more free flowing water which
creates flooding.
Flood Control
Prevention
1. ____________________________________________________
2. Use Dams like the Tennessee River System approx. 50 dams built to
help control flooding
3. ____________________________________________________
4. Create spillways, channels running along the river to trap water and move
it away from where it would cause damage.
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The Life Cycle of Lakes