Water Resources Chapter 13.

Water Resources Chapter 13

Core Case Study: Water Conflicts in the Middle East: A Preview of the Future
Water shortages in the Middle East: hydrological poverty Nile River Jordan Basin Tigris and Euphrates Rivers Peacefully solving the problems

Three Major River Basins in the Middle East

13-1 Will We Have Enough Usable Water?
Concept 13-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource. Concept 13-1B One of every six people does not have sufficient access to clean water, and this situation will almost certainly get worse.

Freshwater Is an Irreplaceable Resource That We Are Managing Poorly (1)
Why is water so important? Earth as a watery world: 71% Freshwater availability: 0.024% Poorly managed resource Hydrologic cycle Water pollution

Freshwater Is an Irreplaceable Resource That We Are Managing Poorly (2)
Access to water is A global health issue An economic issue A women’s and children’s issue A national and global security issue

Girl Carrying Well Water over Dried Out Earth during a Severe Drought in India

Most of the Earth’s Freshwater Is Not Available to Us
Hydrologic cycle Movement of water in the seas, land, and air Driven by solar energy and gravity People divided into Water haves Water have-nots

We Get Freshwater from Groundwater and Surface Water (1)
Zone of saturation Water table Aquifers Natural recharge Lateral recharge

We Get Freshwater from Groundwater and Surface Water (2)
Surface runoff Watershed (drainage) basin Reliable runoff 1/3 of total

Natural Capital: Groundwater System: Unconfined and Confined Aquifer

Flowing artesian well Well requiring a pump Water table
Unconfined Aquifer Recharge Area Evaporation and transpiration Evaporation Precipitation Confined Recharge Area Runoff Flowing artesian well Well requiring a pump Stream Figure 13.3 Natural capital: groundwater system. An unconfined aquifer is an aquifer with a permeable water table. A confined aquifer is bounded above and below by less permeable beds of rock, and its water is confined under pressure. Some aquifers are replenished by precipitation; others are not. Water table Infiltration Lake Infiltration Unconfined aquifer Less permeable material such as clay Confined aquifer Confining impermeable rock layer Fig. 13-3, p. 316

We Use a Large and Growing Portion of the World’s Reliable Runoff
2/3 of the surface runoff: lost by seasonal floods 1/3 runoff usable Domestic: 10% Agriculture: 70% Industrial use: 20% Fred Pearce, author of When the Rivers Run Dry

Case Study: Freshwater Resources in the United States
More than enough renewable freshwater, unevenly distributed Effect of Floods Pollution Drought 2007: U.S. Geological Survey projection Water hotspots

Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S.

Figure 13.4 Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey) Fig. 13-4a, p. 317

Average annual precipitation (centimeters)
Less than 41 81–122 41–81 More than 122 Figure 13.4 Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey) Fig. 13-4a, p. 317

Figure 13.4 Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey) Fig. 13-4b, p. 317

Metropolitan regions with population greater than 1 million
Figure 13.4 Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey) Acute shortage Shortage Adequate supply Metropolitan regions with population greater than 1 million Fig. 13-4b, p. 317

Water Hotspots in 17 Western U.S. States

Highly likely conflict potential
Washington North Dakota Montana Oregon Idaho South Dakota Wyoming Nevada Nebraska Utah Colorado Kansas California Oklahoma New Mexico Arizona Figure 13.5 Water hotspots in 17 western states that, by 2025, could face intense conflicts over scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts suggest that this is a map of places not to live during the next 25 years. Question: If you live in one of these hotspot areas, have you noticed any signs of conflict over water supplies? (Data from U.S. Department of the Interior) Texas Highly likely conflict potential Substantial conflict potential Moderate conflict potential Unmet rural water needs Fig. 13-5, p. 318

Water Shortages Will Grow (1)
Dry climate Drought Too many people using a normal supply of water

Water Shortages Will Grow (2)
Wasteful use of water China and urbanization Hydrological poverty

Natural Capital Degradation: Stress on the World’s Major River Basins

Asia Europe North America Africa South America Australia Stress High
Figure 13.6 Natural capital degradation: stress on the world’s major river basins, based on a comparison of the amount of water available with the amount used by humans (Concept 13-1B). Questions: If you live in a water-stressed area, what signs of stress have you noticed? In what ways, if any, has it affected your life? (Data from World Commission on Water Use in the 21st Century) Stress High None Fig. 13-6, p. 319

Long-Term Severe Drought Is Increasing
Causes Extended period of below-normal rainfall Diminished groundwater Harmful environmental effects Dries out soils Reduces stream flows Decreases tree growth and biomass Lowers net primary productivity and crop yields Shift in biomes

In Water-Short Areas Farmers and Cities Compete for Water Resources
2007: National Academy of Science study Increased corn production in the U.S. to make ethanol as an alternative fuel Decreasing water supplies Aquifer depletion Increase in pollution of streams and aquifers

Who Should Own and Manage Freshwater Resources? (1)
Most water resources Owned by governments Managed as publicly owned resources Veolia and Suez: French companies Buy and manage water resources Successful outcomes in many areas

Who Should Own and Manage Freshwater Resources? (2)
Bechtel Corporation Poor water management in Bolivia A subsidiary of Bechtel Corporation Poor water management in Ecuador Potential problems with full privatization of water resources Financial incentive to sell water; not conserve it Poor will still be left out

13-2 Is Extracting Groundwater the Answer?
Concept Groundwater that is used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.

Water Tables Fall When Groundwater Is Withdrawn Faster Than It Is Replenished
India, China, and the United States Three largest grain producers Overpumping aquifers for irrigation of crops India and China Small farmers drilling tubewells Effect on water table Saudi Arabia Aquifer depletion and irrigation

Trade-Offs: Withdrawing Groundwater, Advantages and Disadvantages

TRADE-OFFS Withdrawing Groundwater Advantages Disadvantages
Useful for drinking and irrigation Aquifer depletion from overpumping Sinking of land (subsidence) from overpumping Available year-round Aquifers polluted for decades or centuries Exists almost everywhere Saltwater intrusion into drinking water supplies near coastal areas Renewable if not overpumped or contaminated Figure 13.7 Advantages and disadvantages of withdrawing groundwater. Question: Which two advantages and which two disadvantages do you think are the most important? Why? Reduced water flows into surface waters No evaporation losses Increased cost and contamination from deeper wells Cheaper to extract than most surface waters Fig. 13-7, p. 321

Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer

Case Study: Aquifer Depletion in the United States
Ogallala aquifer: largest known aquifer Irrigates the Great Plains Water table lowered more than 30m Cost of high pumping has eliminated some of the farmers Government subsidies to continue farming deplete the aquifer further Biodiversity threatened in some areas California Central Valley: serious water depletion

Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S.

Groundwater Overdrafts:
Figure 13.9 Natural capital degradation: areas of greatest aquifer depletion from groundwater overdraft in the continental United States, including the vast, central Ogallala aquifer. Aquifer depletion is also high in Hawaii and Puerto Rico (not shown on map). See an animation based on this figure at CengageNOW™. Question: If you live in the United States, how is your lifestyle affected directly or indirectly by water withdrawn from the essentially nonrenewable Ogallala aquifer? (Data from U.S. Water Resources Council and U.S. Geological Survey) High Moderate Minor or none Fig. 13-9, p. 322

Natural Capital Degradation: The Ogallala is the World’s Largest Known Aquifer

SOUTH DAKOTA WYOMING NEBRASKA COLORADO KANSAS OKLAHOMA NEW MEXICO
Figure 13.10 Natural capital degradation: The Ogallala is the world’s largest known aquifer. If the water in this aquifer were above ground, it could cover all of the lower 48 states with 0.5 meter (1.5 feet) of water. Water withdrawn from this aquifer is used to grow crops, raise cattle, and provide cities and industries with water. As a result, this aquifer, which is renewed very slowly, is being depleted, especially at its thin southern end in parts of Texas, New Mexico, Oklahoma, and Kansas. (Data from U.S. Geological Survey) Miles TEXAS 100 160 Kilometers Saturated thickness of Ogallala Aquifer Less than 61 meters (200 ft.) 61–183 meters (200–600 ft.) More than 183 meters (600 ft.) (as much as 370 meters or 1,200 ft. in places) Fig , p. 323

Groundwater Overpumping Has Other Harmful Effects (1)
Limits future food production Bigger gap between the rich and the poor Land subsidence Mexico City Sinkholes

Groundwater Overpumping Has Other Harmful Effects (2)
Groundwater overdrafts near coastal regions Contamination of the groundwater with saltwater Undrinkable and unusable for irrigation

Solutions: Groundwater Depletion, Using Water More Sustainably

SOLUTIONS Groundwater Depletion Prevention Control Waste less water
Raise price of water to discourage waste Subsidize water conservation Tax water pumped from wells near surface waters Limit number of wells Figure 13.11 Ways to prevent or slow groundwater depletion by using water more sustainably. Question: Which two of these solutions do you think are the most important? Why? Set and enforce minimum stream flow levels Do not grow water-intensive crops in dry areas Divert surface water in wet years to recharge aquifers Fig , p. 324

Science Focus: Are Deep Aquifers the Answer?
Locate the deep aquifers; determine if they contain freshwater or saline water Major concerns Geological and ecological impact of pumping water from them Flow beneath more than one country Who has rights to it?

Active Figure: Threats to aquifers

13-3 Is Building More Dams the Answer?
Concept 13-3 Building dam and reservoir systems has greatly increased water supplies in some areas, but it has disrupted ecosystems and displaced people.

Large Dams and Reservoirs Have Advantages and Disadvantages (1)
Main goals of a dam and reservoir system Capture and store runoff Release runoff as needed to control: Floods Generate electricity Supply irrigation water Recreation (reservoirs)

Increase the reliable runoff available Reduce flooding Grow crops in arid regions

Displaces people Flooded regions Impaired ecological services of rivers Loss of plant and animal species Fill up with sediment within 50 years

Advantages and Disadvantages of Large Dams and Reservoirs

The Ataturk Dam Project in Eastern Turkey

Some Rivers Are Running Dry and Some Lakes Are Shrinking
Dams disrupt the hydrologic cycle Major rivers running dry part of the year Colorado and Rio Grande, U.S. Yangtze and Yellow, China Indus, India Danube, Europe Nile River-Lake Victoria, Egypt Lake Chad Africa: disappearing

Case Study: The Colorado River Basin— An Overtapped Resource (1)
2,300 km through 7 U.S. states 14 Dams and reservoirs Located in a desert area within the rain shadow of the Rocky Mountains Water supplied mostly from snowmelt of the Rocky Mountains

Supplies water and electricity for more than 25 million people Irrigation of crops Recreation

Four Major problems Colorado River basin has very dry lands Modest flow of water for its size Legal pacts allocated more water for human use than it can supply Amount of water flowing to the mouth of the river has dropped

What will happen if some of the reservoirs empty out? Economic and ecological catastrophe Political and legal battles over water

The Colorado River Basin

Aerial View of Glen Canyon Dam Across the Colorado River and Lake Powell

The Flow of the Colorado River Measured at Its Mouth Has Dropped Sharply

Hoover Dam completed (1935)
30 Hoover Dam completed (1935) 25 20 Flow (billion cubic meters) 15 Glen Canyon Dam completed (1963) 10 Figure 13.16 The flow of the Colorado River measured at its mouth has dropped sharply since 1905 as a result of multiple dams, water withdrawals for agriculture and urban areas, and prolonged drought. (Data from U.S. Geological Survey) 5 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year Fig , p. 328

Case Study: China’s Three Gorges Dam (1)
World’s largest hydroelectric dam and reservoir 2 km long across the Yangtze River Benefits Electricity-producing potential is huge Holds back the Yangtze River floodwaters Allows cargo-carrying ships

Case Study: China’s Three Gorges Dam (2)
Harmful effects Displaces about 5.4 million people Built over a seismic fault Significance? Rotting plant and animal matter producing CH4 Worse than CO2 emissions Will the Yangtze River become a sewer?

13-4 Is Transferring Water from One Place to Another the Answer?
Concept Transferring water from one place to another has greatly increased water supplies in some areas, but it has also disrupted ecosystems.

CA, U.S., Transfers Water from Water-Rich Areas to Water-Poor Areas
Water transferred by Tunnels Aqueducts Underground pipes May cause environmental problems California Water Project

The California Water Project and the Central Arizona Project

Oroville Dam and Reservoir
CALIFORNIA Shasta Lake NEVADA UTAH Sacramento River Oroville Dam and Reservoir Feather River North Bay Aqueduct Lake Tahoe Sacramento San Francisco Hoover Dam and Reservoir (Lake Mead) South Bay Aqueduct Fresno San Luis Dam and Reservoir San Joaquin Valley Colorado River Los Angeles Aqueduct California Aqueduct ARIZONA Colorado River Aqueduct Santa Barbara Figure 13.17 The California Water Project and the Central Arizona Project. These projects involve large-scale water transfers from one watershed to another. Arrows show the general direction of water flow. Central Arizona Project Los Angeles Phoenix Salton Sea San Diego Tucson MEXICO Fig , p. 330

Case Study: The Aral Sea Disaster (1)
Large-scale water transfers in dry central Asia Salinity Wetland destruction and wildlife Fish extinctions and fishing

Case Study: The Aral Sea Disaster (2)
Wind-blown salt Water pollution Climatic changes Restoration efforts

Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake

1976 2006 Figure 13.18 Natural capital degradation: the Aral Sea was once the world’s fourth largest freshwater lake. Since 1960, it has been shrinking and getting saltier because most of the water from the rivers that replenish it has been diverted to grow cotton and food crops (Concept 13-4). These satellite photos show the sea in 1976 and in It has split into two major parts, little Aral on the left and big Aral on the right. As the lake shrank, it left behind a salty desert, economic ruin, increasing health problems, and severe ecological disruption. Question: What do you think should be done to help prevent further shrinkage of the Aral Sea? Stepped Art Fig a, p. 331

Ship Stranded in Desert Formed by Shrinkage of the Aral Sea

China Plans a Massive Transfer of Water
South-North Water Transfer Project Water from three rivers to supply 0.5 billion people Completion in about 2050 Impact Economic Health Environmental

13-5 Is Converting Salty Seawater to Freshwater the Answer?
Concept We can convert salty ocean water to freshwater, but the cost is high, and the resulting salty brine must be disposed of without harming aquatic or terrestrial ecosystems.

Removing Salt from Seawater Seems Promising but Is Costly (1)
Desalination Distillation Reverse osmosis, microfiltration 15,000 plants in 125 countries Saudi Arabia: highest number

Removing Salt from Seawater Seems Promising but Is Costly (2)
Problems High cost and energy footprint Keeps down algal growth and kills many marine organisms Large quantity of brine wastes Future economics

Science Focus: The Search for Improved Desalination Technology
Desalination on offshore ships Solar or wind energy Better membranes Better disposal options for the brine waste Reduce water needs, conserve water

13-6 How Can We Use Water More Sustainably?
Concept We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.

Reducing Water Waste Has Many Benefits (1)
Water conservation Improves irrigation efficiency Improves collection efficiency Uses less in homes and businesses

Reducing Water Waste Has Many Benefits (2)
Worldwide: 65–70% loss Evaporation, leaks, etc. Water prices: low cost to user Government subsidies: more needed?

We Can Cut Water Waste in Irrigation
Flood irrigation Wasteful Center pivot, low pressure sprinkler Low-energy, precision application sprinklers Drip or trickle irrigation, microirrigation Costly; less water waste

Major Irrigation Systems

(efficiency 60% and 80% with surge valves)
Figure 13.20 Major irrigation systems. Because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new, low-cost, drip-irrigation systems may change this situation. Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Drip irrigation (efficiency 90–95%) Gravity flow (efficiency 60% and 80% with surge valves) Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually pumped from underground and sprayed from mobile boom with sprinklers. Water usually comes from an aqueduct system or a nearby river. Fig , p. 335

(efficiency 60% and 80% with surge valves)
Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Drip irrigation (efficiency 90–95%) Above- or below-ground pipes or tubes deliver water to individual plant roots. Gravity flow (efficiency 60% and 80% with surge valves) Water usually comes from an aqueduct system or a nearby river. Figure 13.20 Major irrigation systems. Because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new, low-cost, drip-irrigation systems may change this situation. Stepped Art Fig , p. 335

Solutions: Reducing Irrigation Water Waste

Developing Countries Use Low-Tech Methods for Irrigation
Human-powered treadle pumps Harvest and store rainwater Create a canopy over crops: reduces evaporation Fog-catcher nets

We Can Cut Water Waste in Industry and Homes
Recycle water in industry Fix leaks in the plumbing systems Use water-thrifty landscaping: xeriscaping Use gray water Pay-as-you-go water use

Solutions: Reducing Water Waste

We Can Use Less Water to Remove Wastes
Can we mimic how nature deals with waste? Waterless composting toilets

We Need to Use Water More Sustainably
“The frog does not drink up the pond in which it lives” Blue revolution

Solutions: Sustainable Water Use

SOLUTIONS Sustainable Water Use
Waste less water and subsidize water conservation Do not deplete aquifers Preserve water quality Protect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release water Figure 13.23 Methods for achieving more sustainable use of the earth’s water resources (Concept 13-6). Question: Which two of these solutions do you think are the most important? Why? Get agreements among regions and countries sharing surface water resources Raise water prices Slow population growth Fig , p. 337

What Can You Do? Water Use and Waste

13-7 How Can We Reduce the Threat of Flooding?
Concept We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds and by not building in areas subject to frequent flooding.

Some Areas Get Too Much Water from Flooding (1)
Flood plains Highly productive wetlands Provide natural flood and erosion control Maintain high water quality Recharge groundwater Benefits of floodplains Fertile soils Nearby rivers for use and recreation Flatlands for urbanization and farming

Some Areas Get Too Much Water from Flooding (2)
Dangers of floodplains and floods Deadly and destructive Human activities worsen floods Failing dams and water diversion Hurricane Katrina and the Gulf Coast Removal of coastal wetlands

Natural Capital Degradation: Hillside Before and After Deforestation

Forested Hillside Oxygen released by vegetation
Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Figure 13.25 Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber, fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding and pollution in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.” See an animation based on this figure at CengageNOW. Question: How might a drought in this area make these effects even worse? Tree roots stabilize soil Vegetation releases water slowly and reduces flooding Forested Hillside Fig a, p. 339

After Deforestation Tree plantation Evapotranspiration decreases
Roads destabilize hillsides Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Gullies and landslides Figure 13.25 Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber, fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding and pollution in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.” See an animation based on this figure at CengageNOW. Question: How might a drought in this area make these effects even worse? Heavy rain erodes topsoil Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding After Deforestation Fig b, p. 339

Forested Hillside After Deforestation Oxygen released by vegetation
Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Tree roots stabilize soil Vegetation releases water slowly and reduces flooding Forested Hillside Agricultural land Stepped Art Tree plantation Roads destabilize hillsides Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Gullies and landslides Heavy rain erodes topsoil Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding After Deforestation Evapotranspiration decreases Figure 13.25 Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber, fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding and pollution in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.” See an animation based on this figure at CengageNOW. Question: How might a drought in this area make these effects even worse? Fig a, p. 339

Case Study: Living Dangerously on Floodplains in Bangladesh
Dense population Located on coastal floodplain Moderate floods maintain fertile soil Increased frequency of large floods Effects of development in the Himalayan foothills Destruction of coastal wetlands

We Can Reduce Flood Risks
Rely more on nature’s systems Wetlands Natural vegetation in watersheds Rely less on engineering devices Dams Levees

Solutions: Reducing Flood Damage

SOLUTIONS Reducing Flood Damage Prevention Control
Preserve forests on watersheds Straighten and deepen streams (channelization) Preserve and restore wetlands in floodplains Build levees or floodwalls along streams Tax development on floodplains Figure 13.26 Methods for reducing the harmful effects of flooding (Concept 13-7). Question: Which two of these solutions do you think are the most important? Why? Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry Build dams Fig , p. 340

Active Figure: Effects of deforestation

Water Resources Chapter 13.

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