10/14/2015. Why Build a Dam? PROS: How can we increase freshwater supplies for a growing human population?

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1 How can we increase freshwater supplies for a growing human population? 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): 6 Technological Solutions to Water Scarcity: 1. Extract Groundwater 2. Build Dams and Reservoirs to store runoff Water Pollution: general definition, analysis, source, major types of water pollution Why Build a Dam? PROS: Hydroelectric Power / Provide Electricity / Improve Economy decrease dependence on coal / nuclear China s 3 Gorges Dam on Yangtze River Longest river in Asia, 3 rd longest in world #1) Nile, #2) Amazon #4) Mississippi 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 1

2 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 CO 2 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 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 Genetic Pollution; less sediment downstream, water > clear, trout and eagles appear in Colorado River 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 2

3 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 River Matilija Dam on the Ventura River Rindge Dam on Malibu Creek Aswan dam displaced ~125,000 people Aswan Dam was completed in 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. What is a Delta? 3

4 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 mi 2 = 1,920 acres) Over 1.2 million acres or 1,875 mi 2 have already been lost Mississippi River discharges ~3.7 million gal/sec into the Gulf of Mexico The sediment supply has Decreased ~50% in last 100 years 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 ~ mm/yr Solutions: Move the Mississippi Web Link wetlandsrestoration_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 mm/yr compaction, subsidence, SL rise & wave erosion VS deposition or sedimentation 4

5 year # of dams >15m high worldwide Dams and Development ,562 47,655 (China 22,000) 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 Klamath River Dams Four dams on the Klamath River (J.P.Boyle, Copco 1& 2 and Iron Gate) are all coming down.. Starting in 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 Down help salmon 4 Klamath damscoming down php Web Link Tearing Down The Elwah River Dam (ended 3/12) Web Link Dams in California, some # s about SAND Read this after class 16,000 mi 2 of states coastal watersheds are effected by dams. Flow of sand to beaches has been reduced by ~25% or 3.6 million Yds 3/yr or 360,000 dump trucks/yr Total sand trapped behind Ca s coastal dams is ~ 200 million Yds 3, 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 (2.7 million Yds 3/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, 5

6 Pont Du Gard Aqueduct, France Roman Empire, ~2,000 years old, ~51 kilometers long, bridge carried 44 mill/gal/day Eventually Roman Empire had 12 Aqueducts, >577Km, most underground, some still used today Begins in 1909 Completed in 1913 Completed in 1941 LA Aqueduct: designed by William Mulholland & begins in 1909, cost 24 million, opens November 13 th, 1913, pop of LA doubles in 10 yrs, provides 200mill gal/day to LA. Stress in Owens Valley. (Collapse of St Francis Dam ( / 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. 108 meters (608ft) long ~600 killed; worst civil eng disaster in history of Ca. 2 nd only to 1906 E-Quake for loss of life St. Francis Dam meters (195ft) tall 6

7 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, CO 2 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 4 th 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 million that live within the areas watershed. 7

8 The Aral Sea (ecological, economical and health) Disaster 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 March 2011 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 4. Desalination: converting salt water to fresh water 8

9 Desalination by the Numbers 17,000+ The total number of desalination plants worldwide (as of 2013) More than 80 million cubic meters per day The global capacity of commissioned desalination plants (as of 2013) 21.1 billion US gallons The equivalent of 66.5 million cubic meters per day 150 The number of countries where desalination is practiced More than 300 million The number of people around the world who rely on desalinated water for some or all their daily needs Most Common Techniques: Reverse Osmosis, over 17,000 plants worldwide Meets less than 1% of world s water needs. Would have to increase ~33 fold just to supply 10% of current water use. Major Challenges: Expensive; it takes large amounts of energy, CO 2 output Produces lots of waste water with high level of salt and other minerals. Large structures, unsightly, noise Could harm marine environment Existing facilities and facilities under construction Algeria Aruba Australia Bahrain Chile China Cyprus Egypt Gibraltar Grand Cayman Hong Kong India Iran Israel Malta Maldives Oman Saudi Arabia South Africa Spain United Arab Emirates United Kingdom United States Carlsbad Ca Desalination Project: Construction began in 2009, may be operational in late 2015 at a cost of ~ $530 million. Will produce 50 million gal/day: supply region with ~7% of drinking water, will be the largest desal plant in the western hemisphere. web link: WATCH THIS VIDEO Other Desal techniques, Unconventional html 9