Download Water and Water Pollution

Water and Water Pollution
Earth’s Water Budget
All water
Fresh water
Readily accessible fresh water
Groundwater
0.592%
Biota
0.0001%
Lakes
0.007%
Oceans and
saline lakes
97.4%
Fresh water
2.6%
Rivers
0.0001%
0.014%
Ice caps
and glaciers
1.984%
Soil
moisture
0.005%
Atmospheric
water vapor
0.001%
Hydrologic Cycle
Unconfined Aquifer Recharge Area
Evaporation and transpiration
Precipitation
Confined
Recharge
Area
Runoff
Flowing
artesian well
Infiltration
Recharge
Unconfined
Aquifer
Stream
Water
table
Infiltration
Less
permeable material
such as clay
Well
requiring
a pump
Lake
Evaporation
Groundwater
Use of Water Resources
 Runoff use: about 54%
 Freshwater use
 US freshwater resources
 Domestic, agricultural, and industrial use
Annual
Precipitation and
Water-deficit
Regions of the
Continental US
Water Hot Spots in Western States
Wash.
Montana
N.D.
Oregon
S.D.
Idaho
Wyoming
Neb.
Nevada
Colo.
Utah
Kansas
California
Oak.
N.M.
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Freshwater Shortages
Causes of water
scarcity: dry climate and
too many people
Stresses on world’s
major river systems
1 of 6 people have no
regular access to clean
water
Poverty hinders access
to water
Hydrological poverty
Stress on World’s River Basins
Europe
North
America
Asia
Africa
South
America
Australia
Stress
High
None
Politics and Ethics of Water
 Who should pay for the water?
 Public or private ownership
Increasing Freshwater Supplies
 Dams and reservoirs
 Extracting
groundwater
 Desalination
 Reducing water
waste
 Importing food
 Importing water
 Catching
precipitation
Tradeoffs of Large Dams and
Reservoirs
Large losses
of water through
evaporation
Flooded land destroys
forests or cropland and
displaces people
Migration and
spawning of
some fish are
disrupted
Downstream cropland and
estuaries are deprived of
nutrient-rich silt
Provides water
for year-round
irrigation of
cropland
Reservoir is useful for
recreation and fishing
Can produce
cheap electricity
(hydropower)
Downstream
flooding is
reduced
Ecological Services of Rivers
NaturalCapital
Ecological Services of Rivers
• Deliver nutrients to sea to help sustain
coastal fisheries
• Deposit silt that maintains deltas
• Purify water
• Renew and renourish wetlands
• Provide habitats for wildlife
California Water Project and
Central Arizona Project
CALIFORNIA
NEVADA
Shasta Lake
UTAH
Oroville Dam and
Reservoir
Sacramento
River
Lake Tahoe
Feather
River
North Bay
Aqueduct
Sacramento
San Francisco
South Bay
Aqueduct
Hoover Dam
and Reservoir
(Lake Mead)
Fresno
San Luis Dam
and Reservoir
Colorado
River
Los Angeles
Aqueduct
California Aqueduct
Colorado River
Aqueduct
Santa Barbara
ARIZONA
Central Arizona
Project
Los Angeles
San Diego
Salton Sea
Phoenix
Tucson
MEXICO
 Large-scale water transfers in dry
central Asia
 Salinity
Aral Sea Disaster
 Wetland destruction and wildlife
 Fish extinctions and fishing
 Wind-blown salt
 Water pollution
 Climatic changes
 Restoration efforts
Shrinking Aral Sea
Tradeoffs of Withdrawing
Groundwater
Trade-Offs
Withdrawing Groundwater
Advantages
Disadvantages
Good source of water for
drinking and irrigation
Aquifier depletion from overpumping
Available year-round
Sinking of land (subsidence)
when water removed
Exists almost everywhere
Polluted aquifiers unusable
for decades or centuries
Renewable if not overpumped or contaminated
Saltwater intrusion into
drinking water supplies near
coastal areas
No evaporation losses
Cheaper to extract than
most surface waters
Reduced water flows into
streams, lakes, estuaries,
and wetlands
Increased cost, energy use,
and contamination from
deeper wells
Aquifer Depletion
Groundwater
Overdrafts:
High
Moderate
Minor or none
Saltwater Intrusion into Coastal Water
Wells
Well contaminated
with saltwater
Major
irrigation
well
Fresh
groundwater
aquifer
Water
table
Sea Level
Interface
Saltwater
Intrusion
Interface
Normal
Interface
Groundwater Depletion
Solutions
Groundwater Depletion
Prevention
Waste less water
Control
Raise price of water to
discourage waste
Subsidize water
conservation
Ban new wells in
aquifiers near surface
waters
Buy and retire groundwater withdrawal rights in
critical areas
Do not grow waterintensive crops in dry
areas
Reduce birth rates
Tax water pumped
from Wells near
surface water
Set and enforce
minimum stream flow
levels

Desalination
Removal of salts from ocean or brackish waters to
produce useable water
 Distillation method
 Reverse osmosis method
 Used in 120 countries
 Major problems: high cost and a lot of brine wastes
 Research is needed
Reducing Water Waste
 Benefits of water conservation
 Reduce leakage and save water
 Water prices, government subsidies, and waste
 Improve irrigation
 Using less water in homes and businesses
Major Types of Irrigation Systems
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.
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.
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 droughtresistant and salt tolerant crops varieties
•Irrigating with treated urban waste water
•Importing water-intensive crops and meat
Using Water More Sustainably
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
What Can We Do?
What Can You Do?
Solutions
Water Use and Waste
Reducing Water 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.
•Redesign manufacturing processes
•Landscape yards with plants that require little
water
•Use drip irrigation
•Fix water leaks
• Wash only full loads of clothes or use the lowest
possible water-level setting for smaller loads.
•Use water meters and charge for all municipal
water use
• Wash a car from a bucket of soapy water, and use the
hose for rinsing only.
•Use waterless composting toilets
• If you use a commercial car wash, try to find one that
recycles its water.
•Require water conservation in water-short
cities
• Replace your lawn with native plants that need little if
any watering.
•Use water-saving toilets, showerheads, and
front-loading clothes washers
• Water lawns and garden in the early morning or
evening.
•Collect and reuse household water to irrigate
lawns and nonedible plants
• Use drip irrigation and mulch for gardens and
flowerbeds.
• Use recycled (gray) water for watering lawns and
houseplants and for washing cars.
•Purify and reuse water for houses, apartments,
and office buildings
Fig. 11-21, p. 251