1. Water
Chapter 15

2. Water Wars Water shortage Growing population
Poor irrigation efficiency
Economic competition- importing more grain to reduce need for irrigation water or work out water-sharing agreements with other countries

3. Unique Properties of Water
Strong hydrogen bonds
Liquid over wide temperature range
High heat capacity – changes temperature slowly (moderates climate, used as coolant for car engine & power plants)
Large amount of energy needed to evaporate – heat is then released during condensation (helps distribute heat & determine climate zones; evaporation/sweating = cooling process)

4. Dissolves many substances- dissolves nutrients in living tissue, flush waste out of tissues, all-purpose cleanser, helps remove/dilute water-soluble waste
Filters out UV radiation that would harm aquatic organisms
Bonds – allow capillary action – water can move upward through plants
Expands when frozen= ice floats; prevents lakes & streams from freezing solid

5. Available Freshwater
Only 0.014% is available for useh

6. Water Cycle
Surface runoff- water flowing off the land into bodies of surface water
Reliable runoff- amount of run-off that we can generally count on as a stable source of water
Watershed (drainage basin)- region from which surface water drains into a river, lake, wetland, or other body of water

7. Groundwater- water stored in spaces in soil & rock
Zone of aeration- close to surface; pore space contains mixture of air & water
Zone of saturation- lower layers of soil where pore space is filled with water
Water table- top of zone of saturation
Aquifer- (deep) porous, water-saturated layers of sand, gravel, or bedrock through which groundwater flows

8. Natural recharge- natural replenishment of an aquifer by precipitation, which percolates downward through soil & rock
Shortages result from:
Removing groundwater faster than it is replenished
Some aquifers receive little, if any recharge

9. Water Use
Withdrawal- total amount of water removed from lake, river, or aquifer for any purpose
Consumptive water use- withdrawn water is not available for reuse in basin due to losses like evaporation, seepage into ground, transportation to another area, or contamination

10. Water Use Population- up 3x Global water withdrawal- up 7x
Per capita withdrawal- up 4x
Reliable surface runoff used- 34%
Used by % (90% if per capita rises too)

11. Irrigation- 70%
Industry- 20%
Residences & cities- 10%

12. Eastern U.S.
Major water use- energy production, cooling, & manufacturing
Problems- flooding, occasional urban shortages, pollution

13. Western U.S. Major water use- irrigation
Problems- shortage of runoff, low precipitation / high evaporation, recurring prolonged drought

14. Causes of Water Scarcity
Dry climate
Drought- prolonged period with 70% less precipitation & higher than normal evaporation
Dessication- drying of exposed soil due to deforestation or overgrazing
Water stress- low per capita availability due to high population relying on limited runoff

15. Increase Freshwater Supply
Build dams & reservoirs to store runoff
Bring in surface water from another area
Desalinization
Reduce water waste
Import food to reduce water use in crops & cattle
Withdraw groundwater

16. Government Ownership - Poor management & efficiency
+ Strict government oversight
+ Equal access & fair rates

17. Private Ownership + Funds & management expertise
+ Improved efficiency, good job
- No rate control
- Profitable
- Sold as a luxary, not basic need

18. Figure 15-9 Page 313 Downstream cropland and estuaries are deprived of
nutrient-rich silt
Flooded land
destroys forests
or cropland and
displaces people
Large losses
of water through
evaporation
Downstream
flooding is
reduced
Provides water
for year-round
irrigation of
cropland
Reservoir is
useful for
recreation
and fishing
Can produce
cheap electricity
(hydropower)
Figure 15-9 Page 313
Migration and
spawning of
some fish are
disrupted

19. Colorado River Dams
+ Provides electricity from numerous hydroelectric plants
+ Provides water for 7 states
+ Multibillion dollar recreational industry (whitewater rafting, boating, fishing, camping, hiking)
- Arid area
- Legal pacts allocating water supply for US & Mexico
- River water rarely makes it to Guld of California

20. - Threatens aquatic spawning
- Destroys estuaries
- Increases saltwater contaminated coastal aquifers

21. China’s Three Gorges Dam
Trade-Offs
China’s Three Gorges Dam
Advantages
Disadvantages
Will generate about 10%
of China’s electricity
Reduces dependence
on coal
Reduces air pollution
Reduces CO2 emissions
Reduces chances of
downstream flooding
for 15 million people
Reduces river sitting
below dam by eroded
soil
Increases irrigation water
for cropland below
dam
Floods large areas of
cropland and forests
Displaces 1.9 million people
Increases water pollution
because of reduced water
flow
Reduces deposits of nutrient-
rich sediments below dam
Increases saltwater
Introduced into drinking water
near mouth of river because
of decreased water flow
Disrupts spawning and
migration of some fish
below dam
High cost
Figure Page 315

22. Aral Sea Water Transfer Project
Shrinking of Aral Sea
Regional ecological, economic, health disaster
Salinity 3x higher
Surface area down 58%
83% water loss
Feeder rivers reduced to trickles
Eliminates wetlands
Birds & mammal species disappeared

23. Extinction of 20 (of 24) native fish species
Salt dust settles on wildlife, crops, & other vegetation

24. California Water Transfer Project
NORTH
Degrade Sacramento River
Threatens fisheries
Reduces flushing of San Francisco Bay pollutants
Water sent South is wasted
SOUTH
Need more water to grow crops
Lakes shrink = reduced populations of ducks, gulls, & wading birds

25. James Bay in Canada
- 600 dams & dikes that will reverse or alter flow of 19 giant rivers
- Will flood boreal forests & tundra
- Displace of indigenous Cree & Inuits
+ Hydroelectric power

26. Withdrawing Groundwater
Trade-Offs
Withdrawing Groundwater
Advantages
Disadvantages
Good source of water for
drinking and irrigation
Available year-round
Exists almost everywhere
Renewable if not over-
pumped or contaminated
No evaporation losses
Cheaper to extract than
most surface waters
Aquifier depletion from over-
pumping
Sinking of land (subsidence)
when water removed
Polluted aquifiers unusable
for decades or centuries
Saltwater intrusion into
drinking water supplies near
coastal areas
Reduced water flows into
streams, lakes, estuaries,
and wetlands
Increased cost, energy use,
and contamination from
deeper wells
Figure Page 319

27. Excessive Withdrawal Unsustainable water mining
Limits future food production
Increases gap between rich & poor areas
Must drill deeper wells, buy larger pumps, & use more electricity
Causes sinkholes

28. Saltwater Intrusion
Movement of salt water into freshwater aquifers in coastal & inland areas as groundwater is withdrawn faster than it is recharged by precipitation
Groundwater becomes unusable

29. Ogallala Aquifer
+ Transformed vast areas of arid prairie into productive agricultural land
- Slows recharge rate
- Aquifer is thinner for southern region
- Government subsidies increased crop production & increases depletion of aquifer

30. Groundwater Depletion
Solutions
Groundwater Depletion
Prevention
Control
Waste less water
Subsidize water
conservation
Ban new wells in
aquifiers near surface
waters
Buy and retire ground-
water withdrawal rights in
critical areas
Do not grow water-
intensive crops in dry
areas
Reduce birth rates
Raise price of water to
discourage waste
Tax water pumped
from Wells near
surface water
Set and enforce
minimum stream flow
levels
Figure Page 320

31. Deep Aquifer Concerns:
Little known about geological & ecological impacts of using these aquifers
No international water treaties govern the rights to & ownership of water that underlies several countries

32. Desalinization - High cost - Large energy requirements
- Large amounts of briny waste water
- Dumping of waste increases salinity of ocean water (food resources & aquatic life threatened)
+ Make ocean water or brackish water usable

33. Seeding Clouds Does not work well in very dry areas
No scientific evidence of success
Introduces large amounts of chemicals into soil & water systems (harms people, wildlife, & agricultural productivity)
Ownership of cloud water

34. Iceberg Towing Unsure methods Cost
Probably neither (iceberg towing or cloud seeding) would provide significant amounts of freshwater

35. Wasted Water 65-70% of world water is wasted Could be reduced to 15%
Causes:
Underpricing- government subsidies for irrigation water, electricity, & diesel fuel for farmers to pump water at below-market price
Lack of government subsidies for improving efficiency of water use

36. Irrigation Systems Center pivot- uses pump to spray water on crops
80% efficient
Uses 25% less water
Drip irrigation- microirrigation- above or below ground pipes or tubes deliver water to individual plant roots
90-95% efficient
Gravity flow- water flow into ditches from aqueduct or nearby river
60-80% efficient

37. Figure 15-20 Page 324 Center Pivot Drip Irrigation Gravity Flow
(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.

38. Reducing Irrigation Water Waste
Solutions
Reducing Irrigation Water Waste
Lining canals bring water to irrigation ditches
Leveling fields with lasers
Irrigating at night to reduce evaporation
Using soil and satellite sensorsand computer systems to monitor soil moisture and add water only when necessary
Polyculture
Organic Farming
Growing water-efficient crops using drought-resistant and salt tolerant crops varieties
Irrigating with treated urban waste water
Importing water-intensive crops and meat
Figure Page 324

39. Figure 15-22 Page 325 Solutions Reducing Water Waste
Redesign manufacturing processes
Landscape yards with plants that require little water
Use drip irrigation
Fix water leaks
Use water meters and charge for all municipal water use
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
Figure Page 325

40. Reducing Water Used to Remove Waste
Use pollution prevention & waste reduction to decrease waste production
Ban toxic wastes in municipal sewer system
Waterless composting toilet
Nutrient-rich sludge returned to soil as fertilizer
New sewage treatment methods that recycle nutrients in organic waste material

41. Floods + Fertile soils + Ample water for irrigation
+ Rivers for transportation & recreation
+ Flat land suitable for crops, buildings, highways, & railroads
- Removal of water-absorbing vegetation

42. Increasing Flood Damage
Removal of water-absorbing vegetation
Draining wetlands
Living on floodplains
Pavement & buildings

43. Bangladesh Straighten & deep streams Build levees or floodwalls
Build dams
Preserve existing wetlands & restore degraded wetlands
Identify & manage flood-prone areas
Think carefully about where we live

44. Figure 15-26 Page 329 Solutions Sustainable Water Use
Not depleting aquifers
Preserving ecological health of aquatic systems
Preserving water quality
Integrated watershed management
Agreements among regions and countries sharing surface water resources
Outside party mediation of water disputes between nations
Marketing of water rights
Raising water prices
Wasting less water
Decreasing government subsides for supplying water
Increasing government subsides for reducing water waste
Slowing population growth

45. Figure 15-27 Page 330 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.
Repair water leaks.
Turn off sink faucets while brushing teeth, shaving, or washing.
Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads.
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.
Water lawns and garden in the early morning or evening.
Use drip irrigation and mulch for gardens and flowerbeds.
Use recycled (gray) water for watering lawns and houseplants and for washing cars.
Figure Page 330