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) Ground water Zone of saturation Water table Aquifers Natural recharge Lateral recharge
We Get Freshwater from Groundwater and Surface Water (2) Surface Water Surface runoff Watershed (drainage) basin Reliable runoff 1/3 of total
Natural Capital: Groundwater System: Unconfined and Confined Aquifer
Precipitation Confined Recharge Area Runoff Unconfined Aquifer Recharge Area Evaporation and transpiration Evaporation Less permeable material such as clay Flowing artesian well Infiltration Water table Well requiring a pump Infiltration Stream Unconfined aquifer Confined aquifer Lake 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.
Fig. 13-4a, p. 317
Average annual precipitation (centimeters) Less than 41 81 122 41 81 More than 122 Fig. 13-4a, p. 317
Fig. 13-4b, p. 317
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
Washington Oregon Idaho Montana Wyoming North Dakota South Dakota Nevada Utah Colorado Nebraska Kansas California Arizona New Mexico Oklahoma 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
Europe Asia North America Africa South America Australia 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 13-2 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 Useful for drinking and irrigation Available year-round Exists almost everywhere Renewable if not overpumped or contaminated No evaporation losses Cheaper to extract than most surface waters Disadvantages Aquifer depletion from overpumping Sinking of land (subsidence) from overpumping Aquifers polluted for decades or centuries Saltwater intrusion into drinking water supplies near coastal areas Reduced water flows into surface waters Increased cost and contamination from deeper wells 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: High Moderate Minor or none Fig. 13-9, p. 322
Natural Capital Degradation: The Ogallala is the World s Largest Known Aquifer
WYOMING SOUTH DAKOTA NEBRASKA COLORADO KANSAS NEW MEXICO OKLAHOMA TEXAS Miles 0 100 Saturated thickness of Ogallala Aquifer 0 160 Kilometers 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. 13-10, 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 Waste less water Control Raise price of water to discourage waste Subsidize water conservation Limit number of wells Do not grow waterintensive crops in dry areas Tax water pumped from wells near surface waters Set and enforce minimum stream flow levels Divert surface water in wet years to recharge aquifers Fig. 13-11, 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)
Large Dams and Reservoirs Have Advantages and Disadvantages (2) Advantages Increase the reliable runoff available Reduce flooding Grow crops in arid regions
Large Dams and Reservoirs Have Advantages and Disadvantages (3) Disadvantages 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
Case Study: The Colorado River Basin An Overtapped Resource (2) Supplies water and electricity for more than 25 million people Irrigation of crops Recreation
Case Study: The Colorado River Basin An Overtapped Resource (3) 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
Case Study: The Colorado River Basin An Overtapped Resource (4) 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
35 Flow (billion cubic meters) 30 Hoover Dam completed (1935) 25 20 15 10 5 Glen Canyon Dam completed (1963) 0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year Fig. 13-16, 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 CH 4 Worse than CO 2 emissions Will the Yangtze River become a sewer?
13-4 Is Transferring Water from One Place to Another the Answer? Concept 13-4 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
Sacramento River North Bay Aqueduct San Francisco South Bay Aqueduct San Luis Dam and Reservoir California Aqueduct CALIFORNIA Shasta Lake Feather River Santa Barbara Oroville Dam and Reservoir Sacramento Los Angeles NEVADA Lake Tahoe Fresno Hoover Dam and Reservoir (Lake Mead) Los Angeles Aqueduct Colorado River Aqueduct UTAH Colorado River ARIZONA Central Arizona Project San Diego Salton Sea Phoenix Tucson MEXICO Fig. 13-17, 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 Stepped Art Fig. 13-18a, 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 13-5 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 13-6 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
Gravity flow (efficiency 60% and 80% with surge valves) Water usually comes from an aqueduct system or a nearby river. Drip irrigation (efficiency 90 95%) Above- or below-ground pipes or tubes deliver water to individual plant roots. 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. Fig. 13-20, p. 335
Gravity flow (efficiency 60% and 80% with surge valves) Water usually comes from an aqueduct system or a nearby river. Drip irrigation (efficiency 90 95%) Above- or below-ground pipes or tubes deliver water to individual plant roots. 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. Stepped Art Fig. 13-20, 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 Get agreements among regions and countries sharing surface water resources Raise water prices Slow population growth Fig. 13-23, p. 337
What Can You Do? Water Use and Waste
13-7 How Can We Reduce the Threat of Flooding? Concept 13-7 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
Oxygen released by vegetation Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Tree roots stabilize soil Forested Hillside Vegetation releases water slowly and reduces flooding Fig. 13-25a, p. 339
Tree plantation Gullies and landslides Roads destabilize hillsides Evapotranspiration decreases Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Heavy rain erodes topsoil Silt from erosion fills rivers and reservoirs After Deforestation Rapid runoff causes flooding Fig. 13-25b, p. 339
Oxygen released by vegetation Diverse ecological habitat Tree roots stabilize soil Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Tree plantation Gullies and landslides Roads destabilize hillsides Heavy rain erodes topsoil Evapotranspiration decreases Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Vegetation releases water slowly and reduces flooding Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding Forested Hillside After Deforestation Stepped Art Fig. 13-25a, 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 Preserve forests on watersheds Control Straighten and deepen streams (channelization) Preserve and restore wetlands in floodplains Tax development on floodplains Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry Build levees or floodwalls along streams Build dams Fig. 13-26, p. 340
Active Figure: Effects of deforestation