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Chapter 14
Water
Core Case Study: Water Conflicts in the Middle East - A Preview
of the Future Many countries in
the Middle East, which has one of the world’s highest population growth rates, face water shortages.
Figure 14-1
Water Conflicts in the Middle East: A Preview of the Future
Most water in this dry region comes from the Nile, Jordan or Tigris rivers.
Countries upstream are building dams and drawing more water…leaving little for downstream countries
Countries are in disagreement as to who has water rights.
War could easily erupt in this volatile part of the world
Water Conflicts in the Middle East: A Preview of the Future
Currently, there are no cooperative agreements for use of 158 of the world’s 263 water basins that are shared by two or more countries.
Emerging water shortages in many parts of the world – one of the most serious environmental problems
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
Necessary for life Moderates climate, Sculpts the land, Removes and dilutes wastes and pollutants, Moves continually through the hydrologic
cycle. Only about 0.02% of the earth’s water supply
is available to us as liquid freshwater.
Water
One of our most poorly managed resource We waste & pollute it No substitute Lack of safe water & sanitation is leading
cause of illness in world Water quality is worsening
Water By The Numbers Oceans: 97%
Glaciers / polar ices caps: 1.8%
Groundwater: 0.9%
Other land surface water (rivers, lakes): 0.017%
20% of all surface freshwater is in Lake Baikal, Russia.
The Ogallala Aquifer is the largest groundwater reserve.
The Middle East has the lowest amount of naturally available freshwater and uses desalination for their water supply.
Lake Bikal is the most voluminous freshwater lake in the world.
The Ogallala Aquifer is located in the central plains of the US because of watershed properties
Fresh Water Resources
Most of the 71% of Earth’s water, more than 1.3 billion cubic kilometers, is contained in the oceans. Only 35 million cubic kilometers is fresh water.
Only a tiny amount of the water on Earth is accessible and usable to humans because the ice caps/sheets/ glaciers are the majority of freshwater and are not readily available for use.
Earth’s total water
Seawater97 %
Fresh water3%
Fresh water
Surface water 0.3%
Ice caps and glaciers77.2%
Ground water
22.46%
Atmospheric water 0.04%
Lakes87%
Swamps11%
Rivers2%
Surface water
Surface Water
Examples – streams, rivers, and lakesSource – precipitationWatershed – Ex. small streams larger
streams rivers sea
Groundwater
Aquifers–porous rock w/ water flowing through Water Table – the level of earth’s land crust to
which the aquifer is filled Renewability – the circulation rate of
groundwater is slow (300 to 4,600 years).
Water UsageAgriculture – watering crops Industry – coolant (power plant)Domestic and Municipal – drinking,
sewage, bathwater, dishwater & laundry
Humans intervene in the water cycle by utilizing the resource for their own needs.
Water is used for consumption, municipal use, in agriculture, in power generation, and for industrial manufacturing.
Industry is the greatest withdrawer of water but some of this is returned. Agriculture is the greatest water consumer.
Using water often results in its contamination. The supply of potable (drinkable) water is one of the most pressing of the world’s problems.
The Demand for Water
Hydroelectric power generation…
Irrigation…
Washing, drinking, bathing…
Potable Water Potable water (water suitable to
drink) is a rare commodity in large parts of the world.
Access to potable water is limited by:
ease of distribution, level of water treatment (e.g. sanitation), & amount of available water resources (eg rivers)
Countries must deal with problems of removing water borne diseases and dissolved toxins.
Once treated, distribution and storage of water becomes important.
In many countries, distribution of water is difficult and storage of large amounts almost impossible.
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Water in many developing nations is difficult to come by, and treatment may be nonexistent.
In developed nations, potable water is abundant and treatment is regulated.
Comparison of population sizes and shares of
the world’s freshwater among the continents.
Figure 14-2
Global Water Reserves
Ogallala Aquifer A vast water-table aquifer located beneath the Great Plains in the US. It is extensively used for irrigation. At current usage rates it may be depleted by 2020.
Mississippi RiverDrains most of the area between the Rocky Mountains and the Appalachians. A series of locks and dams provide for barge traffic.
Amazon River Accounts for 20% of the world's total river flow and drains 40% of South America. Brazil has the largest supply of freshwater in the world.
North American Great Lakes The largest group of freshwater lakes on Earth, containing 22% of the world's fresh surface water.
Global Water ReservesVolga RiverWith its many tributaries, drains an area of about 1.35 million km2 in the most heavily populated part of Russia. High levels of chemical pollution currently give cause for environmental concern.
Yangtze RiverFlows 6300 km East China Sea. The Yangtze is subject to extensive flooding, which is only partly controlled by the Three Gorges Dam. It is also heavily polluted.
Congo RiverIs the largest river in Western Central Africa with the second-largest flow in the world. It drains an extensive area of rainforest.
Murray-Darling BasinDrains one-seventh of the Australian land mass. Over 70% of Australia's irrigation resources are concentrated there.
Ganges BasinCentral to the agricultural economy of India. A recent UN report indicates the glaciers feeding the Ganges may disappear by 2030, leaving it as a seasonal system fed by the monsoon rains.
Lake BaikalIs the second most voluminous lake in the world. Contains 20% of the world’s freshwater
Fresh Water Use Intensive agriculture uses large
amounts of water, 69% of the freshwater.
Improved irrigation techniques can reduce the amount required. Every year huge quantities of water as transported to irrigate crops.
Industrial water use increases along with the human population, using about 22% of freshwater.
The cooling of power plants and the processing of almost all commercial goods requires the use the water.
Manufacturing and production processes are usually water intensive. Some everyday items use surprisingly large amounts of water in their production.
Industrial treatment uses 22%
Irrigation accounts for 69%
An automobile: 380,000 liters of water
Municipal Water Use
Cities and residences use only 8% of the freshwater. Nearly half of the municipal water in the US is used to flush toilets or water lawns.
Another 20-35% is lost in water leaks. Large savings can be made by improving the efficiency of water use.Treatment of waste water is a major issue.
454 g of grain-fedbeef: 3,000 liters of water
The cotton in a pair of jeans: 6,800 liters of water
Municipal supply is about 8%
Industrial Water UseC
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Agricultural Water Use
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Domestic Water Use
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Water Use: America
Source: Worldwater.org
Domestic Water Use
Agricultural Water Use
Industrial Water UseC
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Water Use: Africa
Source: Worldwater.org
Industrial Water UseC
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Agricultural Water Use
Cub
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Domestic Water Use
Cub
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Water Use: Asia
Source: Worldwater.org
Domestic Water Use
Agricultural Water Use
Industrial Water UseC
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Water Use: Europe
Source: Worldwater.org
Agricultural Water Use
Industrial Water UseC
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Domestic Water Use
Source: Worldwater.org
Cub
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Water Use: Oceania
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
Some precipitation infiltrates the ground and is stored in soil and rock (groundwater).
Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water. The land from which the surface water drains into
a body of water is called its watershed or drainage basin.
Fig. 14-3, p. 308
Unconfined Aquifer Recharge Area
Precipitation Evaporation and transpiration Evaporation
Confined Recharge Area
Runoff
Flowing artesian well
Recharge Unconfined Aquifer
Stream Well requiring a pumpInfiltration Water
table LakeInfiltration
Unconfined aquifer
Confined aquiferConfining impermeable rock layer
Less permeable material such as clay
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
We currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by 2025.
About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources.
Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).
Water in the United States
Average precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom).
Figure 14-4
Fig. 14-4a, p. 309
Average annual precipitation (centimeters)
More than 122
Less than 41 81–122
41–81
Fig. 14-4b, p. 309
Acute shortage
Metropolitan regions with population greater than 1 million
Shortage
Adequate supply
Case Study: Freshwater Resources in the United States
17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.
Figure 14-5
Fig. 14-5, p. 310
Wash.
MontanaOregon
N.D.
IdahoWyoming S.D.
Nevada Neb.
UtahColo.
Kansas
California Oak.
N.M.Texas
Highly likely conflict potential
Moderate conflict potentialUnmet rural water needs
Substantial conflict potential
TOO LITTLE FRESHWATER
About 41% of the world’s population lives in river basins that do not have enough freshwater.
Many parts of the world are experiencing: Rivers running dry. Lakes and seas shrinking. Falling water tables from overpumped aquifers.
Stress on the World’s River Basins
Comparison of the amount of water available with the amount used by humans.
Figure 14-6
Case Study: Who Should Own and Manage Freshwater Resources
There is controversy over whether water supplies should be owned and managed by governments or by private corporations.
European-based water companies aim to control 70% of the U.S. water supply by buying up water companies and entering into agreements with cities to manage water supplies.
TOO LITTLE FRESHWATER
Cities are outbidding farmers for water supplies from rivers and aquifers.
Countries are importing grain as a way to reduce their water use.
More crops are being used to produce biofuels.
Our water options are: Get more water from aquifers and rivers,
desalinate ocean water, waste less water.
WITHDRAWING GROUNDWATER TO INCREASE SUPPLIES
Most aquifers are renewable resources unless water is removed faster than it is replenished or if they are contaminated.
Groundwater depletion is a growing problem mostly from irrigation. At least one-fourth of the farms in India are being
irrigated from overpumped aquifers.
Fig. 14-7, p. 313
Trade-Offs
Withdrawing Groundwater
Advantages Disadvantages
Useful for drinking and irrigation
Aquifer depletion from overpumping
Available year-round
Sinking of land (subsidence) from overpumping
Exists almost everywhere
Polluted aquifers for decades or centuries
Renewable if not overpumped or contaminated
Saltwater intrusion into drinking water supplies near coastal areas
Reduced water flows into surface waters
No evaporation losses
Cheaper to extract than most surface waters
Increased cost and contamination from deeper wells
Human Effects Most water used by humans comes
from rivers, lakes, & aquifers. Damming rivers for electricity
affects water flow downstream as seen in the James Bay project in Quebec with over 600 dams blocking 19 rivers.
Irrigation and diversions for drinking water displace vast amounts of the water for these resource stores.
Pollution from fertilizers, waste, an sewage can have paralyzing effects on rivers, lakes, and oceans.
These actions can have dramatic effects on the habitats and can cause loss of biodiversity.
Irrigation can move move millions of liters of water from rivers and aquifers, affecting land down stream.
Damming and diverting rivers lowers the availability of water downstream and stops annual floods that
replace soil nutrients.
Dams, locks and other obstacles make it very difficult for migratory fish to find their way to breeding grounds.
Rivers as Highways The major rivers of the worlds
provide water for irrigation and drinking and enable the transport of large amounts of freight especially when dammed.
Huge barges moved by tugboats are used on many rivers and lakes of developed countries.
However there are many negative environmental effects.
Some rivers such as the Yangtze are so polluted and congested with ships that little can live in them.
The Yangtze River Dolphin was last seen in 2002 and has since been declared functionally extinct. It is the first cetacean extinction directly attributable to human interference.
Mississippi River, USA
Yangtze River, China Pho
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Groundwater Depletion: A Growing Problem
The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).
Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S.
Figure 14-8
Other Effects of Groundwater Overpumping
Groundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater.
Figure 14-11
Fig. 14-11, p. 315
Major irrigation well
Well contaminated with saltwater
Water tableFresh
groundwater aquifer
Sea level
Saltwater
InterfaceSeaflo
or
Saltwater intrusion
Interface
Normal interface
Other Effects of Groundwater Overpumping
Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater.
Figure 14-10
Groundwater Pumping in Saudi Arabia (1986 – 2004)
Irrigation systems from the nonrenewable aquifer appear as green dots. Brown dots are wells that have gone dry.
Figure 14-9
Fig. 14-12, p. 316
Solutions
Groundwater Depletion
Prevention Control
Waste less water Raise price of water to discourage waste
Subsidize water conservation
Ban new wells in aquifers near surface waters
Tax water pumped from wells near surface waters
Buy and retire groundwater withdrawal rights in critical areas
Do not grow water-intensive crops in dry areas
Set and enforce minimum stream flow levels
USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER
Large dams and reservoirs can produce cheap electricity, reduce downstream flooding, and provide year-round water for irrigating cropland, but they also displace people and disrupt aquatic systems.
Dams and Reservoirs
•Benefits: Hydroelectric power; provides water to towns; recreation; controls floods downstream
• Problems: Reduces downstream flow; prevents water from reaching the sea (Colorado River) devastates fish life; reduces biodiversity.
Figure 14-13
Fig. 14-13a, p. 317
Provides water for year-round irrigation of cropland
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation
Provides water for drinking Downstream
cropland and estuaries are deprived of nutrient-rich silt
Reservoir is useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Downstream flooding is reduced
Migration and spawning of some fish are disrupted
Fig. 14-13b, p. 317
Powerlines
Reservoir
Dam
PowerhouseIntake
Turbine
Case Study: The Colorado Basin – an Overtapped Resource
The Colorado River has so many dams and withdrawals that it often does not reach the ocean. 14 major dams and reservoirs, and canals. Water is mostly used in desert area of the U.S. Provides electricity from hydroelectric plants for
30 million people (1/10th of the U.S. population).
Case Study: The Colorado Basin – an Overtapped Resource
Lake Powell, is the second largest reservoir in the U.S.
It hosts one of the hydroelectric plants located on the Colorado River.
Figure 14-15
The Colorado River Basin
The area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states.
Figure 14-14
Case Study: China’s Three Gorges Dam
There is a debate over whether the advantages of the world’s largest dam and reservoir will outweigh its disadvantages. The dam will be 2 kilometers long. The electric output will be that of 18 large coal-
burning or nuclear power plants. It will facilitate ship travel reducing transportation
costs. Dam will displace 1.2 million people. Dam is built over seismatic fault and already has
small cracks.
Three Gorges Dam
The Three Gorges Dam spans the Yangtze River at Sandouping, China, and is the largest hydroelectric dam in the world, capable of producing 22,500MW of electricity.
Major construction began in 1994 and is expected to be fully completed by 2011.
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Filling the Dam The reservoir behind the Three Gorges Dam extends
600km upstream. The dam itself is over 2km wide and 186m high.
Satellite image of Three Gorges Dam 1987, before construction.
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Filling the Dam
Satellite image of Three Gorges Dam 2000 Image: NASA
Filling the Dam
Satellite image of Three Gorges Dam 2004 Image: NASA
Satellite image of Three Gorges Dam 2006
Filling the Dam
Image: NASA
Dam Removal
Some dams are being removed for ecological reasons and because they have outlived their usefulness. In 1998 the U.S. Army Corps of Engineers
announced that it would no longer build large dams and diversion projects in the U.S.
The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams.
Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.
TRANSFERRING WATER FROM ONE PLACE TO ANOTHER
Transferring water can make unproductive areas more productive but can cause environmental harm. Promotes investment, jobs and strong economy. It encourages unsustainable use of water in
areas water is not naturally supplied.
Case Study: The California Experience
A massive transfer of water from water-rich northern California to water-poor southern California is controversial.
Figure 14-16
Case Study: The Aral Sea Disaster
The Aral Sea was once the world’s fourth largest freshwater lake.
Figure 14-17
Case Study: The Aral Sea Disaster
Diverting water from the Aral Sea and its two feeder rivers mostly for irrigation has created a major ecological, economic, and health disaster. About 85% of the wetlands have been
eliminated and roughly 50% of the local bird and mammal species have disappeared.
Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.
Aswan High Dam Two dams straddle the Nile River at Aswan, Egypt. The
Aswan High Dam was completed in 1970 and formed Lake Nasser. which is 550 km long and capable of holding two years of the Nile's annual flow.
The main objectives of the project were:energy generation in a renewable form.
flood control in downstream locations.
provision of water for agriculture and domestic use.
A serious detrimental effect is the loss of the annual floods downstream. These used to replenish the nutrients of the flood plain and flush out accumulated salts.
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‣Without flooding, fertilizers must be applied to the land and salts build up in the soils, causing crops to fail.
‣Without annual deposition of river sediments because of build-up behind the dam, the land is eroding, allowing the sea to encroach up the river delta.
‣Damming has also caused 64% of commercially fished species in the Nile to disappear.
‣Time will tell if better management will help to reverse the problems currently being experienced in the Nile Delta region.
DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS
AND GIANT BAGGIES
Removing salt from seawater by current methods is expensive and produces large amounts of salty wastewater that must be disposed of safely. Distillation: heating saltwater until it evaporates,
leaves behind water in solid form. Reverse osmosis: uses high pressure to force
saltwater through a membrane filter.
DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS
AND GIANT BAGGIES
Seeding clouds with tiny particles of chemicals to increase rainfall towing icebergs or huge bags filled with freshwater to dry coastal areas have all been proposed but are unlikely to provide significant amounts of freshwater.
INCREASING WATER SUPPLIES BY WASTING LESS WATER
We waste about two-thirds of the water we use, but we could cut this waste to 15%. 65-70% of the water people use throughout the
world is lost through evaporation, leaks, and other losses.
Water is underpriced through government subsidies.
The lack of government subsidies for improving the efficiency of water use contributes to water waste.
Water Conservation Strategies Irrigation techniques:
Employ micro/drip irrigation
Irrigate at times of less low evaporation (eg. Night)
Choose crops that do not require irrigation in certain climates
Agricultural & other methods:
Incorporate shelterbelts or windbreaks
Reduce runoff by contour planting, strip cropping, and terracing
Cover surface with mulch to prevent evaporation
Eat less meat
Center pivot (above) and gravity flow (below) are not as efficient as drip irrigation that
allows water to trickle to the roots.
INCREASING WATER SUPPLIES BY WASTING LESS WATER
Sixty percent of the world’s irrigation water is currently wasted, but improved irrigation techniques could cut this waste to 5-20%.
Center-pivot, low pressure sprinklers sprays water directly onto crop. It allows 80% of water to reach crop. Has reduced depletion of Ogallala aquifer in
Texas High Plains by 30%. Drip Irrigation is the most efficient method
Fig. 14-18, p. 325
Center pivot
Drip irrigation
Gravity flow(efficiency 60% and
80% with surge valves)
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Water usually comes from an aqueduct system or a nearby river.
(efficiency 90–95%)
(efficiency 80%–95%)
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
Fig. 14-19, p. 326
Solutions
Reducing Irrigation Water Waste
• Line canals bringing water to irrigation ditches
• Level fields with lasers
• Irrigate at night to reduce evaporation
• Monitor soil moisture to add water only when necessary
• Polyculture
• Organic farming
• Don't grow water-thirsty crops in dry areas
• Grow water-efficient crops using drought resistant and salt-tolerant crop varieties
• Irrigate with treated urban waste water
• Import water-intensive crops and meat
Solutions: Getting More Water for Irrigation in Developing Countries –
The Low-Tech Approach
Many poor farmers in developing countries use low-tech methods to pump groundwater and make more efficient use of rainfall.
Figure 14-20
Fig. 14-21, p. 327
Solutions
Reducing Water Waste
• Redesign manufacturing processes
• Repair leaking underground pipes
• Landscape yards with plants that require little water
• Use drip irrigation
• Fix water leaks
• Use water meters
• Raise water prices
• Use waterless composting toilets
• Require water conservation in water-short cities
• Use water-saving toilets, showerheads, and front loading clothes washers
• Collect and reuse household water to irrigate lawns and nonedible plants
• Purify and reuse water for houses, apartments, and office buildings
• Don't waste energy
Raising the Price of Water: A Key to Water Conservation
We can reduce water use and waste by raising the price of water while providing low lifeline rates for the poor. When Boulder, Colorado introduced water
meters, water use per person dropped by 40%. A 10% increase in water prices cuts domestic
water use by 3-7%.
Solutions: Using Less Water to Remove Industrial and Household Wastes
We can mimic the way nature deals with wastes instead of using large amounts of high-quality water to wash away and dilute industrial and animal wastes. Use nutrients in wastewater before treatment as
soil fertilizer. Use waterless and odorless composting toilets
that convert human fecal matter into a small amount of soil material.
TOO MUCH WATER Heavy rainfall, rapid snowmelt, removal of
vegetation, and destruction of wetlands cause flooding.
Floodplains, which usually include highly productive wetlands, help provide natural flood and erosion control, maintain high water quality, and recharge groundwater.
To minimize floods, rivers have been narrowed with levees and walls, and dammed to store water.
TOO MUCH WATER
Comparison of St. Louis, Missouri under normal conditions (1988) and after severe flooding (1993).
Figure 14-22
TOO MUCH WATER
Human activities have contributed to flood deaths and damages.
Figure 14-23
Fig. 14-23a, p. 330
Oxygen released by vegetation
Diverse ecological habitat
Evapotranspiration
Trees reduce soil erosion from heavy rain and wind
Agricultural landSteady
river flow
Leaf litter improves soil fertility
Tree roots stabilize soil and aid water flow
Vegetation releases water slowly and reduces flooding
Forested Hillside
Fig. 14-23b, p. 330
Tree plantation
Roads destabilize hillsides
Evapotranspiration decreases
Ranching accelerates soil erosion by water and wind
Winds remove fragile topsoil
Agricultural land is flooded and silted up
Gullies and landslides
Heavy rain leaches nutrients from soil and erodes topsoil
Silt from erosion blocks rivers and reservoirs and causes flooding downstream
Rapid runoff causes flooding
After Deforestation
Fig. 14-24, p. 331
Solutions
Reducing Flood Damage
Prevention Control
Preserve forests on watersheds
Strengthen and deepen streams (channelization)
Preserve and restore wetlands in floodplains
Tax all development on floodplains
Build levees or floodwalls along streams
Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreation
Build dams
SOLUTIONS: USING WATER MORE SUSTAINABLY
We can use water more sustainably by cutting waste, raising water prices, preserving forests and wetlands in water basins, and slowing population growth.
Figure 14-25
Fig. 14-25, p. 333
What Can You Do?Water Use and Waste
• Use water-saving toilets, showerheads, and faucet aerators.
• Shower instead of taking baths, and take short showers.
• Stop water leaks.
• Turn off sink faucets while brushing teeth, shaving, or washing.
• Flush toilets only when necessary.
• Wash only full loads of clothes or use the lowest water-level for smaller loads.
• Use recycled (gray) water for lawn, gardens, house plants, car washing.
• Wash a car from a bucket of soapy water, and use the hose for rinsing only.
• If you use a commercial car wash, try to find one that recycles its water.
• Replace your lawn with native plants that need little if any watering and decorative gravel or rocks.
• Water lawns and gardens in the early morning or evening.
• Sweep or blow off driveways instead of hosing off with water.
• Use drip irrigation and mulch for gardens and flowerbeds.
