Surface Water
What You Need to Learn
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What landscape
features on Earth are formed and changed by surface water
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How surface water
moves materials and impacts humans
Surface Water Movement
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Water moves through the water cycle in a
never-ending, natural circulation
The Water Cycle
Runoff
l Water flowing downhill along the Earth’s surface
l If water doesn’t flow it will eventually soak into the
ground or evaporate
Factors that effect Runoff
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Vegetation: soils
with more vegetation allow more water to enter the ground
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Barren soils
become compacted during rain and allow less water to enter
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Rate of
Precipitation: water that falls too quickly can’t absorb into the ground
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Soil Composition:
humus allows more water to absorb; coarse particles allow more absorption
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Slope: steep
slopes increase runoff
Stream Systems
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Channeled bodies
of water that flow downhill to a lake, ocean, or larger stream
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All of the land
area whose water drains into a stream system is called a watershed
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Divide: is a high
land area that separates one watershed from another
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Stream load: all
the material that the stream carries
Three ways streams carry material
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Solutions:
dissolved in the water
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Suspensions:
small material held in the stream’s turbulence
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Bed Load: sand,
pebbles, and cobbles that roll along the bottom of the stream bed
How much material can a stream transport?
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Depends on the
velocity and amount of water (discharge)
Discharge
(m³/s) = width (m) x depth (m) x velocity (m/s)
Floodplains
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When a river or
stream can’t hold an increase in water a flood occurs
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Water spills out
over a flat area called the floodplain
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Large amounts of
sediment are deposited in the floodplain
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To provide
warning, streams are constantly monitored
Stream Development
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Moving water from
the headwaters of a stream cut a stream channel; as the channel widens it forms
a stream bank which contains the moving water. Over time this can lead to the
formation of a V shaped valley. As a stream ages the V shape gradually develops
into a U shape and the stream begins to meander (slowing down and dropping more
sediment)
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Rejuvenation can
occur if the headwaters uplift or the base level lowers
Lakes and Freshwater Wetlands
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A lake is a depression in the surface of the
land that collects water
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They receive water from streams, runoff, local
precipitation, springs, and other sources
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Usually have an outlet
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Are important for water supplies and wildlife
habitat
Origin of Lakes
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Oxbow lakes form
from meandering streams
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Blocked streams
can form lakes
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Receding
low-lying areas
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Glaciers can form
lakes
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Dissolved
limestone can form cavern lakes
The life of a lake
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Lakes are
dependent on their water supply
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As time goes on
lakes increase in organic matter and organisms will change
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Eutrophication:
the gradual filling in of a lake with organic material, eventually leading to
the “death” of the lake
Wetlands
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Include bogs,
marshes, swamps
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Rich in
specialized organisms
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Example: Sphagnum
peat moss
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Abundant in
wildlife
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Natural filtering
system for water
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Decreasing due to
human influences
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Late 1700’s to
the mid 1980’s the U.S. lost 50% of its wetlands