3. Distribution of Earth’s water
97.6% in oceans (saltwater)
2.4% is freshwater
most freshwater is frozen (N and S poles, glaciers)
very little freshwater is directly accessible
5. Potential fates of precipitation
evaporation: back to atmosphere
transpiration: through plants to atmosphere
infiltration: to soil and groundwater
runoff: rare in most natural ecosystems
6. Humans have increased runoff…
• Runoff takes topsoil with it!!
Rill Erosion
(most soil erosion loss) Gully Erosion
8. Groundwater
zone of aeration: soil pores filled with water and air,
zone of saturation: soil pores filled with water,
groundwater: water in zone of saturation,
water table: top of groundwater…
16. Domestic water use
about 2/3 used in the bathroom (toilet flushing and bathing)
relatively little used for drinking and cooking
17. Water Supply
• Because water is essential for most human
activities, long-term human habitation
requires a renewable water supply
=Water resources that are replenished regularly
(mainly surface water and shallow ground water)
• Often dependant on precipitation
18. Where do we get our water?
well: hole in soil/bedrock from which water is extracted
many cause a cone of depression in water table
may cause nearby shallow wells to “run dry”
19. Where do we get our water?
reservoirs: created by construction of dams
constructed for:
1) flood control
2) consistent water supply
20. The problems with dams
• Water in reservoirs
evaporates more
quicklywater loss
• They change natural,
seasonal flow regimes
• They stop the water and
allow sediment to settle
behind the dam
– Eventually the reservoir will
fill with sediment
21. The problems with dams
• They drown valleys
and destroy free-
flowing rivers
• They impede
migrations of fish and
land animals
22. Water Use
• Water can be reused if it is not contaminated
• Withdrawal- total water taken from a water body
(most could be returned to circulation)
• Consumption- water evaporated, absorbed or
contaminated (water “lost” to immediate future
use
• We must use water conscientiously to protect
and conserve it!
23. • Conservative
irrigation may save
vast amounts of
water
24. Water use and conservation
use of native plants gaining popularity in dry regions,
native plants are well-adapted to dry conditions
25. Watersheds
• Watershed = the area drained by a
particular stream
• Watershed conservation involves the idea
of monitoring and conserving the
resources within a watershed’s boundaries
to protect the water resource
26. Part 2
Water Pollution
• Any physical, biological, or chemical change in
water quality that adversely affects living
organisms can be considered pollution.
– Point Sources - Discharge pollution from specific
locations (channeled).
• Factories, Power plants
– Non-Point Sources - Scattered or diffuse, having no
specific location of discharge.
• Agricultural fields, Feedlots
• Atmospheric Deposition
29. Infectious Agents
• Main source of waterborne pathogens is
untreated and improperly treated human
waste.
– Animal wastes from feedlots and fields is also
an important source of pathogens.
30. Testing water for infectious agents
• Individual disease-causing organisms are
difficult/expensive to test for.
• Infectious agents are more common in water
with high concentrations of untreated waste.
• Coliform bacteria (E. coli) are common in the
digestive tracts of warm blooded animals.
• Fecal coliforms are used as indicators that other
more infectious agents may also be present in
water.
– If a test shows coliform bacteria are present, there is
untreated waste in the water and it is assumed to be
unsafe to drink.
31. Threats to groundwater:
illegal dumping
faulty septic systems
fertilizer & pesticide application
leaky tanks
34. Pollution by Organic Material
(untreated sewage)
decomposition of OM “uses up” dissolved oxygen in water
(high Biological Oxygen Demand = BOD)
little or none left for aquatic organisms
36. Cultural Eutrophication
• Large excesses of nutrients are often put into
rivers for “disposal”
• When these rivers empty into the sea/ocean
they can cause large “dead zones” without any
dissolved Oxygen (DO)
• The largest dead zone in the world is in the Gulf
of Mexico at the mouth of the Mississippi
– During summer months (when algae growth is
highest) the dead zone may reach 7,000 square
miles, the size of NJ.
38. Wastewater treatment--Septic system
wastewater must percolate--
1. fast enough to handle daily load,
2. slow enough to allow “purification”,
potential drainfield sites are subject to “perc” test
39. Septic systems
solids settle in septic tank where they are decomposed by bacteria,
if bacteria are killed (chemicals), system starts to fail (YUCK!)
if too many “cloggers” go down the drain, system starts to fail (YUCK!)
40. Wastewater treatment plants
the idea: centralize treatment to ensure proper treatment
problem: expensive to build and maintain
up to three treatment levels
41. Inorganic Pollutants
• Some inorganic materials are released by
natural processes
• Humans accelerate production of many
chemicals by mining, processing, and discarding
of materials
• Metals- many are toxic at high concentrations, and may
bioaccumulate
• Salts- some are toxic (selenium, arsenic). Some accumulate and
poison soils and local waters
• Acids and bases- can disrupt the fragile balance of life in surface
waters. Acids may also dissolve other toxic substances like metals.
42. Organic Chemicals
• Thousands of natural and synthetic
organic chemicals are used to make
pesticides, plastics, pharmaceuticals,
pigments, etc.
• Two most important sources of toxic
organic chemicals in water are:
– Improper disposal of industrial and household
wastes.
– Runoff of pesticides from high-use areas.
• Fields, roadsides, golf courses
43. Sediment
• Although natural, sediment can cause major
environmental problems.
– Fill lakes/reservoirs, navigation channels in Rivers
– Make it hard to treat water for drinking
– Smother stream bottom (benthic) habitatkill bugs
and fish eggs. May choke out fish (clogged gills)
– Blocks sunlightreduces primary production in
aquatic systemsmay reduce overall biomass of any
system linked to the affected aquatic ecosystem
• Anthropogenic erosion is the largest water
pollution problem in the USA.
USA
45. Thermal Pollution
• Increases/decreases in water temperature
can affect water quality and aquatic life.
• Water in nature changes temp slowly.
Organisms are not adapted to change
temp quickly.
• Vegetation and runoff patterns can affect
water temps.
46. WATER QUALITY TODAY
• Areas of Progress
– Clean Water Act (1972) established a
National Pollution Discharge Elimination
System (NPDES) which requires a permit for
any entity dumping wastes in surface waters.
• In 1999, EPA reported 91.4% of all monitored river
miles and 87.5% of all accessed lake acres are
suitable for their designated uses.*
– Most progress due to municipal sewage treatment
facilities.
– Safe Drinking Water Act (1974) requires
minimum safety standards for every
community water supply
• Also has provisions to protect groundwater
47. WATER QUALITY TODAY
• Watershed approaches are involving local
people and getting them informed about
what goes on in their watersheds
awareness about their effects on the local
water quality
• Since 1998, EPA uses a TMDL system to
regulate input of pollutants
49. Remaining Problems
• Greatest impediments to achieving
national goals in water quality are
sediment, nutrients, and pathogens,
especially from non-point discharges.
– About three-quarters of water pollution in the
US comes from soil erosion, air pollution
fallout, and agricultural and urban runoff.
• Single cow produces 30 kg manure/day.
– Some feedlots have 100,000 animals.
50. Problems and Progress in Other
Countries
• Sewage treatment in wealthier countries of
Europe generally equal or surpass the US.
• In Russia, only about half of the tap water
supply is safe to drink.
• In urban areas of South America, Africa,
and Asia, 95% of all sewage is discharged
untreated into rivers.
• Two-thirds of India’s surface waters are
contaminated sufficiently to be considered
dangerous to human health.
51. Ocean Pollution
• Estimated 6 million metric tons of plastic
bottles, packaging material, and other litter
tossed from ships into the ocean annually.
– Few coastlines in the world remain
uncontaminated by oil or oil products.
• London Dumping Convention (1990)
– International convention
– Calls for end to ocean dumping
– U.S. is a signatory to this