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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

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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

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