Water: Chapter 5; questions
1-11, 14, 16-26
Geology 3
Hydrologic Cycle
Freshwater
2.5%
Atmosphere
0.001%
Lakes
and rivers
0.01%
Oceans
97.5%
Hydrosphere
Ice caps
and glaciers
1.8%
Groundwater
0.63%
Freshwater component
(2.5% of total hydrosphere)
Fig. 11.1, p.263
Streams: important agent of
erosion and deposition
Remove soil and bedrock
Deposit sediments
Alluvial fan, Death Valley
Penitencia Creek, San Jose
Erosion, sediment deposition,
and sediment transport
Drainage basin or water shed
• All water from rain, runoff, drain systems
empties into a river
• Drainage divide separates one drainage basin
from another
Penitencia
Creek is part of
the Coyote
Creek
Watershed
Coyote
Creek
Watershed
The Continental Divide: runs
through the Rocky Mountains
To the
Columbia
River
To the
Colorado
River
To the
Mississippi
River
Mississippi Water Basin
Drains 2/3 of the U.S. into the Gulf of Mexico
West of the
Mississippi
Columbia River
Internal
drainage
Colorado River
California’s water cycle
• Rain shadow: orographic lifting
• Precipitation (rain and snow) in the Sierra
Nevada
Klamath River drainage basin
San Joaquin River drainage basin
Sacramento River
drainage basin
Stream
formation
• Formation of a
stream
• Sheetwash of water
• Water takes the path of
least resistance
Stream formation
• Tributaries form and
feed into the main
channel
Stream Valleys: headlands
•
•
•
•
•
Point of origin
Highest elevation
Steepest gradient
Spring or narrow runoff channel
Merge into larger tributary
valleys
Minnesota
Stream valley: mouth or base
level
• The lowest level a
stream can erode
• Sea level is the
ultimate base level
• Lakes are temporary
or local base levels
Base Level: lowest level
erosion can take place
• San Francisco Bay is the base level for the San
Joaquin and Sacramento Rivers
• San Francisco Bay is an estuary (fresh water
meets salt water)
Breeding
ground to
many juvenile
species
Gradient: the slope of a stream
• Feet per mile
• If a stream descends
20 feet over a
distance of 40 miles
• 20/40 = 0.5 ft/mile
Gradient
Decreases from the headwaters to
the base level
(The Sierra Nevada to SF Bay)
Velocity: determines
the amount of
erosion, transport,
and deposition
Fastest in center of channel
Average: 3 miles/ hour
Flood: 18 miles/hour
Discharge: the amount of water
passing a point on a stream
Cubic feet or
meters per
second
High discharge in California: Rainy season and snow melt
Streams: Discharge
• Increased discharge:
–
–
–
–
Increases streams capacity-amount of sediment
Increases the size of sediment moved (competence)
Removes organic material
Increases erosion
Stream load: the amount of
sediment that is transported
Streams: transport sediment
• Saltation- bouncing along bottom, larger size
particles
• Suspended load- clay
• Dissolved ions- Explains why the sea is salty
Streams
• Natural channels
have variations of
water flow
• Where the water is
turbulent, the bedload
is moved.
• Where the water is
quiet, smaller
sediment is deposited
River Systems
• Transport sediments: move larger sizes
of sediment in the upper portions; smaller
size sediment in the lower portions
Sierra Nevada
Large size sediment:
boulders and cobbles
Central valley
Sand and
gravel
San Francisco bay mud
Streams: profile
Streams: landforms-valleys
• The upper portion of the stream generally produces
well defined V-shaped valleys.
• The Valley floor remains relatively clear of small size
sediments.
River Systems
• Create landforms: V-shaped valleys in
mountainous regions;
Streams
• Farther downstream
• Channel is wider
Stream Valleys
• Broad valleys in lowlands (Salinas Valley)
MEANDERING AND BRAIDED
STREAMS
Meandering Rivers
Williams River, Alaska
Meandering Rivers
•
•
•
•
Outer bank erosion
Inner bank: deposition
Depth variations
Velocity variations
Meandering Rivers
Streams: profile
V-shaped valleys, large grain size, high
energy
Broad valleys, small grain
size, lower energy, higher
discharge
Flood Plain
• Flat area adjacent to
river channel
Flood Stage: high rain fall in a short
amount of time or rapid snow melt
• When discharge
exceeds the
channel’s capacity
• Organic material is
deposited on adjacent
land
• Natural levees are
built up along the
channel
Egyptian Culture developed in
association with the Nile’s cycle
• Deposits organic-rich
material in the broad
valleys providing nutrients
for vegetation
• Egyptian culture
developed around the
Nile River’s cycle
• Planting, harvesting and
fishing
• Flooding: time for other
activities (art, building,
reading and writing)
Braided Streams
• Large volume of
sediment
• Base of
mountains
New Zealand
Alaska
Bed load
30 million
metric tons
Dissolved
load 120
million
metric tons
Suspended
load 300
million
metric tons
Fig. 11.4, p.266
Riparian Corridor
The land and native vegetation adjacent to the stream
channel.
Ranching Practices
• Farming and ranching practices impact river
systems
• Adds sediment
• Destroys natural vegetation or the riparian
corridor
Dams disrupt the natural flow of a
stream
Trinity River, California
Adult Chinook salmon die in the
lower Klamath River
Alter stream flow and water temperature
• Spawning gravels removed during high
run-off, not replenished
• Decreased flows
• decrease velocity and capacity of system,
riparian vegetation increases, decreasing
locations for juvenile salmon
Dams
Benefits from dams
Irrigation
Reservoir
storage
Recreation
Flood control
Deltas
• Sediment
deposited at the
base level
• Velocity of stream
decreases
• Sediment is
deposited
Mississippi River Delta
Velocity of river decreases, sediment is deposited
Alluvial Fan
• Velocity decreases when water leaves a confined area
• Sediment is deposited
The Delta: where fresh water
meets salt water
• Altered because of water use
• Man-made levees
Levee failure in June,
20??
Artificial Levees
• Land subsides behind
levees
• If break occurs water
will flood the lower
area
• After a flood, when
discharge decreases,
water is trapped
behind the levee and
cannot empty back
into the stream
Yolo Bypass
•Flood control
•Between Davis and
Sacramento
Areas left to flood as a natural
process in the system
•Environmentalists,
farmers, and state agencies
working together
Groundwater: water collects
between sediment grains or
fractures in rocks
Ground water
• In 2000 165,000 acre feet was used
– 1 acre foot = 1 football field with 1 foot of
water
– 2 families of 5 for one year
– 326,000 gallons
Ground water
Upper limit of ground water
Saturated zone:
sediment
completely filled
with water
Porosity:
space
between
sediment
grains
Permeability:
pores are
connected
allowing fluid to
flow
Ground water movement: is a
response to gravity and areas of
reduced pressure
San Francisco Bay
• River Valley during
Ice Age
• Collecting gravels
(aquifer)
Coastline was 22 miles west at
the Farollon Islands
• Estuary during
warmer periods due
to rise in sea level
• Collecting muds
(aquitard)
Santa Clara Aquifer
Cone of depression: where the
water table lowers around a
pumping well
Artesian well: confined aquifer
places water under pressure
Subsidence
• When too much water
is extracted from the
aquifer
• Sediment compacts
• Surface sinks
Santa Clara Valley
• About 4 meters (16
feet) of subsidence
from 1900-1970
from extraction of
groundwater
Ground water contamination
Salt Water Intrusion
• Balance between
recharge and discharge
• The pressure of fresh
water keeps the
saltwater offshore
• Extensive pumping
lowers the pressure
• Cone of depression
• Inverted cone of
depression- salt water
will move to the well
San Jose Waste Water Plant
• 167,000 gallons of
waste water/day
• From homes,
businesses and
schools
• Highest amount of
fresh water in the
southern San
Francisco Bay
San Jose Waste Water Plant
• Santa Clara County’s sink, toilette water
travels through underground pipes
• May take ten hours to arrive
• Eight hours later 99% of the impurities are
gone
Bottled Water
• National Resources
Defense Counsel
• 4 year study
• One-third of the bottled
water tested contained
levels of contamination
• City tap water is
subjected to more
rigorous testing and purity
standards
Bottled Water
• Plastic from17 million
barrels of oil
• Bottling the water
produced more than
2.5 million tons of
carbon dioxide
• It took 3 liters of water
to produce 1 liter of
bottled water
Domestic Water Use
• 10% in the U.S.
• 800 liters of water/day
Domestic Water Use: less
developed regions
• World Health Organization: 20 liters/day
• 1/6th of the global population lack this
much water