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1
Water: A Fragile Resource
SUPPLY
Water Distribution
Water Cycle
Human Impact on Water Cycle
Water Use and Solutions
Why is water important?
A tree is about 50% water
A person is about 70% water
A jellyfish is about 90% water
Water is the liquid where life evolved
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Water Distribution: Residencies Samuel Taylor Coleridge said "Water, water, everywhere, nor any drop to drink"
What part of the water is available to us?
Water Cycle: Residencies and Processes
Water atmosphere Groundwater (in aquifer) Surface water Plants and animals
20% of freshwater
The amount of water in a residency is determined by inflows and outflows
An inflow for one part of the system is an outflow for another
Humans have affected residencies by changing the speed of outflow or inflow
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Water Cycle: Processes basic processes and factors that affect them
Evaporation and transpiration:
Returning moisture to atmosphere
Depends on temperature and plants
Condensation:
Vapor turns into liquid
Depends on temperature and particles
Precipitation:
Moisture of air falls onto land
Depends on season and place
Infiltration:
Entry of water into and through soil
Depends on soil, soil cover, rainfall
Runoff:
movement of water across surface
Depends on rainfall, slope, soil and soil cover
runoff
infiltration
Human impact to the water cycle: Urbanization Changing the surface cover
increase surface runoff
floods
pollutants (quality)
decrease infiltration
reduced groundwater inflow
What happened to the LA river?
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In 1960, California voters approved
financing for construction of the
initial features of the State Water
Project (SWP).
The SWP provides irrigation water
to farms in the San Joaquin Valley,
and is a major source of supply for
cities in Los Angeles, Riverside,
San Bernardino, San Diego, and
other parts of southern California.
The 1,440-mile-long Colorado River
passes through parts of seven
states, several Indian reservations
and the Republic of Mexico.
LA aqueduct completed in 1913 has
served as a major water supply
source, conveying water from the
Owens River in the eastern Sierra.
A second aqueduct, completed in
1970, added another 50 percent
capacity to the water system.
About 30 percent of California's total
annual water supply comes from
groundwater in normal years, and
up to 60 percent in drought years.
Human impact to the water cycle:
Pumping groundwater - 1 in 3 humans relies on groundwater for drinking
- 99% of the rural U.S. uses groundwater for drinking
- Extraction from aquifers is increasing,
due to industrial agriculture
Outflow is faster than inflow
Impact:
Subsidence and Salt water intrusion
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Subsidence ground may suddenly collapse in sinkholes.
Salt water intrusion Movement of salt water
into
a depleted coastal aquifer
The growth of Los Angeles County’s
population and significant events in
the history of ground-water usage.
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Diverting water from rivers can affect ecosystems
Los Angeles Aqueduct:
1913, Diverted water from Owens River
Consequence:
1926 Owens Lake was dried up
Destroyed the feeding and nesting site of migratory
Water birds
Created respiratory problems from dust blown to
Nearby towns (PM is 25 x higher than federal limits)
Pictures!
Mono Basin extension:
1941, Diverted water from Mono creeks
1977, Study highlighted the dangers caused to Mono Lake
1994, Courts ruled to allow water to flow into Mono lake
Human impact :
Surface water diversion
Mono Lake: Oldest lake
in the US formed at least 760,000 years ago
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Colorado River water diverted today
from a series of dams to:
Colorado, New Mexico
Utah, Wyoming, Arizona,
Nevada, California and Mexico.
…so much water is withdrawn
that it barely reaches the sea
Colorado Aqueduct (1941)
At Parker Dam
Human impact to the water cycle:
Surface water diversion
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Colorado River
Human impact to the water cycle: Dams We build dams blocking the flow of rivers in order to:
• Generate electricity
• Provide drinking water and irrigation
Problem:
Affect water quantity
And quality
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What do we use water for?
• 80,000 gallons of water is needed to produce the finished steel for one car
• 4 gallons of water to make 1 pound of plastic (twice as much water to
produce a plastic water bottle as the amount of water in the water bottle)
• 700 gallons of water for one new cotton shirt.
Water Use Cooling coal plants, irrigation, electricity, public supply and industrial products
Not all uses affect the water supply:
Consumptive use
water is removed from an aquifer or surface body, and not returned.
examples:
Nonconsumptive use
removal of water is only temporary.
examples:
….but we also need to consider
how it affects water quality
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Water Use: Agriculture Agriculture = 87% of world’s consumptive use of water Most irrigation practiced today is very inefficient Only 45% ends up being used by crops. Agriculture relies on water inefficient crops Subsidies for irrigation $2.2 billion a year (1/3 of in Midwest)
Case:
Central Valley Project
CVP transformed millions of acres of land
that were essentially desert into fertile
farmland
Biggest farms get most of the water
Average price paid for irrigation water from
the CVP
< 2 % of what residents of LA pay for
drinking water
Chinook salmon is endangered
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Solutions to Agriculture
Stop subsidies
We should reward water conservation,
not water use
Choose crops appropriate to climate
sod farms in desert areas
Better irrigation methods
Drip method 90% efficient
10% crop yield increase
Solutions to Agriculture: Consumer choices
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Water use: Public supply and industry
Colorado river situation:
Demand is growing
LA has grown 6 times
LV has grown 200 times
Flow is decreasing
Climate change will bring more
Severe and extended droughts
Buffer reservoirs are decreasing
Lake Mead has dropped 30 feet
Lake Powell 100 feet
Solutions to Public and Industry:
Increase supply • Desalinization:
removal of salt from seawater to create freshwater
Problems: Cost and harm to ocean ecosystems
water pollution
• Reclaimed water
waste water that has been purified and it is reused instead of being discharged
Study by UCLA of Lake Arrowhead in the 90’s demonstrated the ability to take
domestic wastewater and treat it to the point that was cleaner than their
drinking water . But because the drought ended, it was never implemented!
Problem: Public’s perception
13
Solutions to Public and Industry:
Increase supply • Increase groundwater recharge
replacing concrete with porous materials
installing bioswales
• Rain gardens and rain barrels
900 homes in LA and Culver city
Install low-flow faucets and appliances
Replace lawns with native vegetation
½ of residential water demand in CA
If you keep lawns, water them at night
Water conservation habits:
Shaving: 20 gallons vs. 1 gal
Tooth brushing: 10 gallons
Front loading washers
save 40% water (7000 gallons/year)
… and save 50% energy
Solutions to Public and Industry:
Decrease demand