Water

1
Chapter 14

• Water

2
WATERS IMPORTANCE, AVAILABILITY, AND RENEWAL

• Water keeps us alive, moderates climate, sculpts
  the land, removes and dilutes wastes and
  pollutants, and moves continually through the
  hydrologic cycle.
• Only about 0.02 of the earths water supply is
  available to us as liquid freshwater.

3
WATERS IMPORTANCE, AVAILABILITY, AND RENEWAL

• Comparison of population sizes and shares of the
  worlds freshwater among the continents.

Figure 14-2
4
WATERS 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.

5

Unconfined Aquifer Recharge Area
Evaporation and transpiration
Evaporation
Precipitation
Confined Recharge Area
Runoff
Flowing artesian well
Recharge Unconfined Aquifer
Stream Well requiring a pump
Water table
Infiltration
Lake
Infiltration
Unconfined aquifer
Less permeable material such as clay
Confined aquifer
Confining impermeable rock layer
Fig. 14-3, p. 308
6
WATERS IMPORTANCE, AVAILABILITY, AND RENEWAL

• We currently use more than half of the worlds
  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).

7
Water in the United States

• Average precipitation (top) in relation to
  water-deficit regions and their proximity to
  metropolitan areas (bottom).

Figure 14-4
8
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
9
TOO LITTLE FRESHWATER

• About 41 of the worlds 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.

10
Stress on the Worlds River Basins

• Comparison of the amount of water available with
  the amount used by humans.

Figure 14-6
11
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.

12
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.

13
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.

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Trade-Offs
Withdrawing Groundwater
Advantages
Disadvantages
Useful for drinking and irrigation
Aquifer depletion from overpumping
Sinking of land (subsidence) from overpumping
Available year-round
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
Increased cost and contamination from deeper wells
Cheaper to extract than most surface waters
Fig. 14-7, p. 313
15
Groundwater Depletion A Growing Problem

• Areas of greatest aquifer depletion from
  groundwater overdraft in the continental U.S.

• The Ogallala, the worlds largest aquifer, is
  most of the red area in the center (Midwest).

Figure 14-8
16
Other Effects of Groundwater Overpumping

• Groundwater overpumping can cause land to sink,
  and contaminate freshwater aquifers near coastal
  areas with saltwater.

Figure 14-11
17
Other Effects of Groundwater Overpumping

• Sinkholes form when the roof of an underground
  cavern collapses after being drained of
  groundwater.

Figure 14-10
18
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
19

Solutions
Groundwater Depletion
Prevention
Control
Raise price of water to discourage waste
Waste less water
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
Set and enforce minimum stream flow levels
Do not grow water-intensive crops in dry areas
Fig. 14-12, p. 316
20
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.

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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. 14-13a, p. 317
22

Powerlines
Reservoir
Dam
Powerhouse
Intake
Turbine
Fig. 14-13b, p. 317
23
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.

24
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.

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Case Study The Aral Sea Disaster

• The Aral Sea was once the worlds fourth largest
  freshwater lake.

Figure 14-17
26
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 seas salinity has tripled and
  the water has dropped by 22 meters most likely
  causing 20 of the 24 native fish species to go
  extinct.

27
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.

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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.

29
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.

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INCREASING WATER SUPPLIES BY WASTING LESS WATER

• Sixty percent of the worlds 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.

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Drip irrigation
(efficiency 9095)
Gravity flow
(efficiency 60 and 80 with surge valves)
Center pivot
(efficiency 8095)
Water usually pumped from underground and sprayed
from mobile boom with sprinklers.
Above- or below-ground pipes or tubes deliver
water to individual plant roots.
Water usually comes from an aqueduct system or a
nearby river.
Fig. 14-18, p. 325
32

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
Fig. 14-19, p. 326
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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
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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
Fig. 14-21, p. 327
35
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.

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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.

37
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.

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TOO MUCH WATER

• Comparison of St. Louis, Missouri under normal
  conditions (1988) and after severe flooding
  (1993).

Figure 14-22
39
TOO MUCH WATER

• Human activities have contributed to flood deaths
  and damages.

Figure 14-23
40

Solutions
Reducing Flood Damage
Prevention
Control
Preserve forests on watersheds
Strengthen and deepen streams (channelization)
Preserve and restore wetlands in floodplains
Build levees or floodwalls along streams
Tax all development on floodplains
Use floodplains primarily for recharging
aquifers, sustainable agriculture and forestry,
and recreation
Build dams
Fig. 14-24, p. 331
41
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