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• Distribution of water on earth, amount of fresh water available?

• U.S. water use, how much, what for

• Unequal Distribution: floods and scarcity

• Reasons for fresh water shortages?

• Some technological solutions to water shortages

(Pros and Cons):• https://sanjose.carpe-diem.events/calendar/7959597-plastic-water-

faire-consortium-at-the-418-project/

• Water Pollution: general definition, analysis, source, major types of water pollution

Pros and Cons of

Building Dams

Why Build a Dam?

PROS:

• Hydroelectric Power / Provide Electricity / Improve Economy decrease dependence on coal / nuclear

• Provide New Fishing Industry / Improve Economy

• Provide Water for Human Consumption

• Flood Control / Reduce Downstream Flooding

• Provide Water for Irrigation / Increased Food Production

• Provide Recreation / Swimming, Boating, Fishing

China’s “3 Gorges Dam” on Yangtze River

Longest river in Asia, 3rd longest in world#1) Nile, #2) Amazon #4) Mississippi

China’s “3 Gorges Dam” on

Yangtze River Pros• Reduced the dependence on Coal

• Generates ~10% of China’s electricity, = to ~10

Hoover Dams, or enough to power a city 10X as large

as LA!

• Help reduce CO2 emissions, fewer coal burning plants

• Reduce flooding; over 500,000 have been killed by floods

on the Yangtze River in last 100 years, 4,000 in 1998

• The cost of damage from the 1998 flood equals the

cost of the dam

• Increases irrigation for cropland below dam

• Increases rivers shipping capacity

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Why Build a Dam? CONS:

• Expensive to build, danger of collapse, seismic issues, many built long ago. Since 1949, >3,200 dams in China collapsed killing several 100,000 people

• Loss of water through evaporation

• Loss of biodiversity; sardines, mackerel, shrimp, lobster industry loss in Egypt, 17 of 47 fish species left in Nile, loss of ~30,000 jobs

• Deltas receive less sediment and coastal erosion occurs, i.e. Nile and Mississippi River Delta

China’s “3 Gorges Dam” Cons

• Cost is at least 26 billion

• Displaced over 1.24 million people, 1,350 villages and cities, many with archeological sites

• Floods large areas of croplands and forests

• Created a 600 km long reservoir that will collect waste, untreated sewage, sediment and cause crustal subsidence (SF to LA ~ 600Km)

• The large reservoir is eroding shorelines, causing slope instability / landslides along edge of reservoir

China’s “3 Gorges Dam” Cons

• It’s built on a seismically active area, ~80 small cracks already discovered, risk of dam breaking?

• Disrupts spawning and migration of some fish downstream

• Releasing lots of methane

• Farming regions below dam will not receive nutrient rich sediments from floods

• Lack of sediment in delta cause saltwater to move inland

Sierra de la Laguna, near the town of Miraflores

Other dams completely filled with sediment in Ca: San Clemente Dam on Carmel River

Gibraltar Dam on Santa Ynez RiverMatilija Dam on the Ventura River

Rindge Dam on Malibu Creek

Aswan dam displaced~125,000 people

Aswan Dam was completed in 1970. Located ~600 miles south of Cairo.

Dam enables year round irrigation which also contributes to a regional rise in water table.

Fertilizers, pesticides, soil additives needed. Costs: ~100 million/yr, uses up much of the hydroelectric energy created from the dam.

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What is a Delta?

Mississippi River discharges

~3.7 million gal/sec into the Gulf of Mexico

The sediment supply has Decreased ~50% in last 100 years

Mississippi River Delta~40% of all coastal wetlands in US, ~35 Sq miles lost per year on avg

The height of a storm surge is reduced by ~1 foot for every 3 Sq miles

of marsh that it crosses. (3 mi2 = 1,920 acres) Over 1.2 million acres or 1,875 mi2 have already been lost

Dams and artificial levees ultimately lead to erosion.

Dams & the Mississippi River Delta

• Further loss of delta and salt marsh comes from “diking, draining and filling” for agriculture, industry and residential

• compaction, subsidence, SL rise & wave erosion VS

deposition or “sedimentation”

Currently: ~11-13mm/yr……. VS ~5.9-7.5 mm/yr……

• Solutions: “Move the Mississippi” Web Link

http://www.usatoday.com/news/nation/2005-11-21-wetlands-restoration_x.htm (for over 3 billion $$) (geologist Sherwood Gagliano)

• Re-channel / redirect sediment to starved areas, Stop draining / filling, establish zoning of coastal areas, Build dams / retaining walls to prevent saltwater flooding of freshwater marshes

11-13mm/yr VS 5.9 – 7.5mm/yr

compaction, subsidence, SL rise & wave

erosion VS deposition or “sedimentation”

year 1900 1950 1980 1998

# of dams >15m high

worldwide

0 5270 36,562 47,655(China 22,000)

Dams and Development

• Developed countries

– some new dams planned; many dams being decommissioned; in

US decommissioning>construction

• Developing countries

– Many new large dams under construction for irrigation, flood

control, hydropower, water supply

– India, China, Turkey, Iran and Indonesia, Japan are currently most

active dam building countries

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Klamath River Dams• Four dams on the Klamath River (J.P.Boyle, Copco 1 & 2 &

Iron Gate) are all coming down…….. Starting in 2020.

“World’s biggest dam removal project…”

Dams supply enough electricity for 70,000 homes

• Future challenges: ecosystem disruption, salmon restoration

•

• To Help Salmon, 4 Klamath Dams Coming Downhttp://archive.kuow.org/post/4-dams-klamath-river-are-one-step-closer-coming-

downWeb Link

• Tearing Down The Elwah River Dam (ended 3/12) Web Link

http://www.popularmechanics.com/science/environment/a472/2294301/

http://projects.seattletimes.com/2016/elwha/ (2016)

Dams in California, some #’s about SANDRead this after class

• 16,000 mi2 of states coastal watersheds are effected by dams.

• Flow of sand to beaches has been reduced by ~25% or

3.6 million Yds3/yr or 360,000 dump trucks/yr

• Total sand trapped behind Ca’s coastal dams is ~ 200 million Yds3,

which = to a line of dump trucks bumper to bumper around the

word 4 times. Varies with location: ~5% in northern Ca, 31% in

central Ca and 50% in southern Ca.

• Effects of beach widths??? Not that much in So Ca. Coastal

engineering structures (dredging new marinas, construction on

dunes) has led to 170 million cubic yards of new sand between

1930 - 1993 (2.7 million Yds3/yr) between Santa Monica and San

Diego.

• Engineering + wave climate (El Nino / La Nina) partially

overshadows reduction of sand from dam construction.

source: Gary Griggs

How can we increase freshwater supplies for a

growing human population?

6 Technological Solutions to Water Scarcity:

1. Extract Groundwater

2. Build Dams and Reservoirs to store runoff

3. Bring in surface water from other areas:

Watershed Transfer

Long history: Asia, Middle East, Roman Empire (38mill gal/day),

CA, politics, power, greed, pop growth, ecosystem disruption

PROS: development, (humans living in cities) can help control

flooding, provide water for industry, agriculture, domestic use,

Pont Du Gard Aqueduct, FranceRoman Empire, ~2,000 years old,

~51 kilometers long, bridge carried >38 mill/gal/dayEventually Roman Empire had 12 Aqueducts,

>577Km, most underground, some still used today

Begins in 1909Completed in 1913

Completed in 1941

• LA Aqueduct: designed by William Mulholland & begins in 1909,

cost 24 million, opens November 13th, 1913, pop of LA doubles in

10 yrs, provides 200mill gal/day to LA. Stress in Owens Valley.

(Collapse of St Francis Dam (1926 – 1928 / Mulholland project)

20 bill gal water, 100 ft high, ~600 killed)

• California Aqueduct: completed in 1941, longest in world at

~440 miles, brings 500 mill gal/day to LA region. Population of LA

county ~10 million, without aqueducts, LA has enough water to

support ~250,000. Water pump over Tehachapi Mnts (up 600m) is

largest in world: >2mill gal water/minute!

• Hetch Hetchy Aqueduct: completed in 1934, took 20 years to

build, 176 miles of dams, reservoirs, tunnels, pump stations

provides ~240 mill gal/day to SF Bay region

• New York City: three aqueducts bring 1.3 billion gal/day from

Catskills, one completed in 1967, the other two in 1936 and 1917,

much repair work needed.

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St. Francis Dam

1926 - 1928

59 meters (195ft) tall

108 meters (608ft) long

~600 killed; worst civil eng disaster in history of Ca. 2nd only to 1906 E-Quake

for loss of life

California Water Project

Transferring water from one place to another

LA relies on aqueducts for ~85% of its water. Water flows by pumps and gravity to heavily populated areas and arid agricultural regions in southern California.

~20% of the En in Ca is used for pumping water, CO2 output

Reduces flushing capacity, lowers groundwater table, lowers lake levels, threatens aquatic organisms

The Aral Sea Disaster

Soviet Government started diverting rivers with irrigation canals in the early 1960’s to grow rice, melons, cotton. The Aral Sea (ecological, economical and health) Disaster

• The Aral Sea was once the world’s 4th largest fresh water lake.

• World’s largest irrigation canal (~1,300Km) transfers water

• Since 1961 the salinity has tripled, 58% less surface area, water level dropped 72 feet, ~83% of water is lost, >14,000 sq mi!!

• ~85% of regions wetlands lost, and ~1/2 bird and mammal species disappeared, >80% of native fish species.

• Exposed salt and dust blows over 300Km: pollutes water, kills wildlife, harms crops, causes health problems.

• Dust is accumulating on Himalayan glaciers possibly causing them to melt faster than normal.

• Farmers have increased insecticides and fertilizers: chemicals are leaching into the groundwater, the source of drinking water for many of the regions 45 - 58 million that live within the areas watershed.

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• Greatly increased health problems from a combination of

toxic dust, salt and contaminated water for a growing

number of the 58 million people living in the Aral Sea's

watershed.

Such problems include abnormally high rates of:

• infant mortality, tuberculosis

• Anemia, respiratory illness (one of the world's highest)

• eye diseases (from salt dust), throat cancer

• kidney and liver diseases (especially cancers)

• arthritic diseases, typhoid fever, hepatitis

The Aral Sea (ecological, economical and health) Disaster