Water

1
Chapter 14

• Water

2
Chapter Overview Questions

• Why is water so important, how much freshwater is
  available to us, and how much of it are we using?
• What causes freshwater shortages, and what can be
  done about this problem?
• What are the advantages and disadvantages of
  withdrawing groundwater?
• What are the advantages and disadvantages of
  using dams and reservoirs to supply more water?

3
Chapter Overview Questions (contd)

• What are the advantages and disadvantages of
  transferring large amounts of water from one
  place to another?
• Can removing salt from seawater solve our water
  supply problems?
• How can we waste less water?
• How can we use the earths water more
  sustainably?
• What causes flooding, and what can we do about it?

4
Core Case Study Water Conflicts in the Middle
East - A Preview of the Future

• Many countries in the Middle East, face water
  shortages.
• Middle East has one of the worlds highest
  population growth rates

Figure 14-1
5
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 are in disagreement as to who has water
  rights.
• Currently, there are no agreements for use of 158
  of the worlds 263 water basins that are shared
  by two or more countries.

6
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
  water (hydrologic) cycle.

7
WATERS IMPORTANCE, AVAILABILITY, AND RENEWAL

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

Figure 14-2
8
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.
• watershed or drainage basin where surface water
  drains into a body of water

9

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
10
WATERS IMPORTANCE, AVAILABILITY, AND RENEWAL

• About 70 of the water we take 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).

11
Case Study Freshwater Resources in the United
States

• 17 western states by 2025 could face intense
  conflict over water needed for urban growth,
  irrigation, recreation and wildlife.

Figure 14-5
12

Wash.
N.D.
Montana
Oregon
Idaho
S.D.
Wyoming
Nevada
Neb.
Utah
Kansas
Colo.
California
Oak.
N.M.
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Fig. 14-5, p. 310
13
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 (dessication)
• Lakes and seas shrinking.

14
Case Study Who Should Own and Manage Freshwater
Resources

• There is controversy over whether water supplies
  should be owned and managed by governments or
  private corporations.
• European-based water companies aim to control 70
  of the U.S. water supply by buying water
  companies and entering into agreements with
  cities to manage water supplies.

15
TOO LITTLE FRESHWATER

• Cities are outbidding farmers for water supplies
  from rivers and aquifers.
• More crops are being used to produce biofuels.
• Our water options are
• Get more water from aquifers
• Desalinate ocean water
• Waste less water

16
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 1/4 of the farms in India are being
  irrigated from over-used aquifers.

17
Groundwater Depletion A Growing Problem

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

• The Ogallala, the worlds largest aquifer, is
  most of the red area in the center (Midwest).
• Water being used 8x faster than it can be
  recharged

Figure 14-8
18
Other Effects of Groundwater Overpumping

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

Figure 14-11
19
Other Effects of Groundwater Overpumping

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

Figure 14-10
20

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
21
USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER

• Large dams and reservoirs can
• produce cheap electricity
• reduce downstream flooding
• provide year-round water for irrigating
  cropland
• but they also displace people and disrupt
  aquatic systems.

22

Disadvantages
Provides water for year-round irrigation of
cropland
Flooded land destroys forests or cropland and
displaces people
Advantages
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
23

Powerlines
Reservoir
Dam
Powerhouse
Intake
Turbine
Fig. 14-13b, p. 317
24
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).

25
Case Study The Colorado Basin an Overtapped
Resource

• Lake Powell, is the second largest reservoir in
  the U.S (Lake Mead is largest)
• It has one of the hydroelectric plants located on
  the Colorado River.

Figure 14-15
26
The Colorado River Basin

• The area drained by this basin is equal to more
  than 1/12 of the land area of the lower 48 states.

Figure 14-14
27
Case Study Chinas Three Gorges Dam

• There is a debate over whether the advantages of
  the worlds largest dam and reservoir will
  outweigh its disadvantages.
• 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 a fault and already has small
  cracks.
• Construction started in 1994 and finished in 2008

28
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 toxins into the environment.

29
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
  where water is not naturally supplied.

30
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
31
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
• Reverse osmosis uses high pressure to force
  saltwater through a membrane filter.

32
Continued

• 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.

33
INCREASING WATER SUPPLIES BY WASTING LESS WATER

• We waste about 2/3 of the water we use, but we
  could cut this waste to 15.
• 65-70 of the water people use is lost through
  evaporation, leaks, etc.
• The lack of government incentive for improving
  the efficiency of water use contributes to water
  waste.

34
INCREASING WATER SUPPLIES BY WASTING LESS WATER

• 60 of the worlds irrigation water is currently
  wasted, but improved irrigation techniques could
  cut this waste to 5-20.
• Low pressure sprinklers spray water directly onto
  crop.
• It allows 80 of water to reach crop.
• Has reduced depletion of Ogallala aquifer in
  Texas by 30.

35

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
36

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
37
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
38

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
39
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 low flow toilets and low flow
  showerheads.

40
TOO MUCH WATER

• Heavy rainfall, rapid snowmelt, removal of
  vegetation, and destruction of wetlands cause
  flooding.
• Floodplains, (which 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.

41
TOO MUCH WATER

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

Figure 14-22
42

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
43
SOLUTIONS USING WATER MORE SUSTAINABLY

• We can use water more sustainably by
• Cutting waste
• Raising water prices
• Preserving forests and wetlands in water
  basins
• Slowing population growth.

Figure 14-25
44

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.
Fig. 14-25, p. 333