Water Flashcards
(89 cards)
1
Q
Nile
A
-shared by 10 countries
-most water used by Egypt, Sudan,
and Ethiopia
-Egypt gets more than 97% of
water from Nile and last in line
-must import 40% of grain to feed
growing population
-Ethiopia and Sudan plan to divert
more water from the Nile ->
decreased water availability in
Egypt
- Egypt’s options:
> go to war w/ Sudan & Ethiopia
> cut population growth
> increase irrigation efficiency
> work out water sharing agreements
2
Q
Tigris-Euphrates
A
-shared by turkey, Syria, and Iraq
- turkey:
> at headwaters -> controls flow
downstream
> building 24 dams to generate
electricity for irrigation
> will reduce flow by 35% or more
- Syria plans to build dams -> less
water for Iraq -> may lead to war
between Syria and Iraq
3
Q
Jordan
A
- most water - short region
- share by Jordan, Syria, and Israel
- population in area expected to
double by 2050 - 1994: Israel and turkey signed a
treaty which turkey will supply
Israel with water in exchange for
weapons - Syria plans to build dams -> Israel
threatened to destroy dams
4
Q
Waters Importance
A
- oceans help regulate climate
- oceans dilute and degrade wastes
- oceans provide habits for many
species - organisms are made up mostly of
water - water used in:
> agriculture
> manufacturing
> transportation
5
Q
Surface water
A
- surface runoff - rivers, lakes, reservoirs - watershed (drainage) basin - reliable runoff - 1/3 of total (2/3 lost by seasonal floods)
6
Q
Groundwater
A
- zone of saturation
- water table
- aquifers - porous, water -
saturated layer of groundwater
that can be economically used - natural recharge - replenished
from the side by nearby streams
7
Q
Aquifers
A
- if rate of withdrawal > rate of
renewal…
> salt-water intrusion may occur
in coastal areas
> depletion of aquifer may result
in decreased flow of rivers and
streams fed by aquifer - fossil aquifer
> gets very little recharge on a
human scale
> considered a non-renewable
resource
> “water mining” - withdrawal of
large amounts is water from
ancient water deposits
8
Q
Case study: freshwater resource in the USA
A
- Western USA - water poor
> too little precipitation
> groundwater
> large use: irrigation (85%)
> water problems
-> shortage of runoff
-> prolonged drought
-> decreased water table
(sinkholes)
- Eastern USA - water rich
- ample precipitation
- surface water
- largest use:
-> energy productivity
-> cooling
-> manufacturing
- water problems
-> flooding
-> occasional shortage
-> pollution
( ex. 3 million Long Island NY
residents rely on and
increasingly contaminated
aquifer)
9
Q
World Statistics
A
- 2002 UN report: > 500 million people live in water stressed/ water scarce areas -> projected to increase to 2.4 - 3.4 billion people by 2025 - china: water supply can only support 50% of it's current population - water shortages will cause: > decreased food production > decreased economic growth and development - 1 out of 6 people - no regular access to clean water and live in hydrological poverty > cannot afford safe, clean water > do not have municipal water supply and most use unsafe water or buy water
10
Q
Human activities worsen flooding
A
- urbanization > paving and building -> increase runoff - draining wetlands (that absorb floodwaters) - removal of water - absorbing vegetation on hill slopes - increased population living on floodplains
11
Q
Channelization: reducing flooding risks
A
- the straightening, widening, and
deepening of a stream
> advantages:
-> decreased upstream flooding
> disadvantages:
-> can increase bank erosion
(due to increased velocity)
-> can increase downstream
flooding
-> can increase sedimentation
downstream
-> \$\$$
12
Q
Levees
A
- increase streams capacity to hold
water
> advantages:
-> decreased flooding
> disadvantages:
-> false sense if security ->
people build too close
-> if water breeches levee ->
cannot recede -> areas stay
underwater longer
13
Q
Identify and manage flood-prone areas
A
- zoning laws:
> examine historical records and
create flood frequency/flood
hazard maps
> ban buildings in high risk zones
> elevated buildings
> construct a flood way that
allows water to flow through a
community with minimal
damage
14
Q
Stream Pollution
A
- natural recovery processes
> can recover rapidly from
degradable, oxygen- demanding
wastes or excess heat by a
combination of dilution and
bacterial decay
15
Q
Resolving water distribution problems requires:
A
- regional cooperation
- decreased population growth
- increased efficiency in water use
- higher water prices
- increased grain imports
- improvements in irrigation
16
Q
Water’s Unique Properties
A
- liquid water exists over a wide
temperature range
- water filters out UV -> protects
aquatic organisms
- water's high specific heat ->
change temperature slowly
> helps protect organisms from
abrupt temperature changes
> moderates climate
> excellent coolant
- superior solvent - can dissolve
many compounds
> carry dissolved nutrients into
tissues in organisms
> flush wastes out if tissues
> all-purpose cleanser
> note: this property of water
causes it to become easily
polluted
- E-X-P-A-N-D-S as it freezes -> ice
floats and life can continue in
ponds and lakes during cold
winter months
17
Q
Flowing Artesian Wells
A
- ordinary well:
> needs energy to extract
> unconfined aquifer - more likely
to be polluted
- wells A & B
> flowing artesian wells: flow
under their own natural pressure
> confined aquifer - less likely to
be polluted because of small
recharge area
18
Q
World Average Water Use
A
70% - water withdrawn is used for
agricultural reasons (typically
irrigation)
20% - water withdrawn is for
industrial use
10% - water withdrawn is used for
residential use
19
Q
Case Study: Freshwater Resources in USA
A
- USA has enough water for
everyone, but much is in the
wrong place at the wrong time
20
Q
Water Hot Spots in Western States
A
- water hot spots in 17 USA western states that, by 2050, could ave intense conflicts over scarce water needed for urban growth, recreation, and wild life
21
Q
Freshwater Shortages
A
- dry climate/aridity
- drought
> a period of 21 days (or longer) in
which precipitation is at least
70% lower than normal - desiccation
> drying of exposed soil due to
deforestation, overgrazing - water stress
> low per capita availability (due
to increased population relying
on fixed supply)
22
Q
Hydrological Poverty
A
- developed countries have the
ability to bring water into needed
areas
- developing countries, the people
are forced to live where the water
is
> water quality may decline from
animals
> improper disposal of waste
> water for bathing may also be
water for drinking
23
Q
Solutions: Increasing Freshwater Supplies
A
- dams
- watershed transfer
- tapping groundwater
- desalination
- water conservation/curbing waste
24
Q
Trade-offs of Large Dams and Reserviors
A
- provides irrigation water above and below
dam - provides water for drinking
- reservoir useful for recreation and fishing
- can produce cheap electricity (hydro-
power) - reduces downstream flooding
- flooded land destroys forests or cropland
and displaces people - $$$ to build
- large losses of water through evaporation
- deprives downstream cropland and
estuaries of nutrient rich soil - risk of failure and devastating downstream
flooding - disrupts migration and spawning of some fish
25
Case Study: China's Three Gorges Dam
- "Great Wall across the Yangtze"
- will be the world's largest hydroelectric
dam and reservoir
> dam - 1.2 miles long
> reservoir - 370 miles long
- will be completed in 2013
- cost $25 billion
- will displace 1.9 million people
- will generate the electrical equivalent of 20
coal pr nuclear power plants
- will decrease downstream flooding (which
has killed 500,000 people during past 100
years)
26
TRADE OFFS
| China's Three Gorges Dam
```
-advantages
> will generate about 10% of china's
electricity
> reduces dependence on coal
> reduces air pollution
> reduces CO2 emissions
> reduces chances of downstream flooding
for 16 million people
> reduces river sitting below dam by
eroded soil
> increases irrigation water for cropland
below dam
- disadvantages
> 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
```
27
Case Study: Aral Sea Disaster
- large-scale water transfers in dry central
Asia (Uzbekistan and Kazakhstan - former
Soviet Union)
- since 1960, water was diverted from Aral
sea and 2 feeder rivers for irrigation canal -
8-- miles long
- world's longest irrigation canal - 800 miles
- salinity - increase 3x
-surface area - decreased 54%
- volume - decreased by 15%
- 14.000 square miles of human-made salt
desert
- flash extinctions and loss of fishing
industry
> 60,000 people unemployed
- wetland destruction and wildlife - loss of
50% of all bird and animal species
- "salt rain"
> wind blown salt -> kills crops
> salt settling on glaciers in the
Himalayas -> accelerating melting
- climate changes
> decreased moderating effect of sea ->
hotter summers, colder winters
> less rain
> shorter growing season
- increased use of pesticides and fertilizers
by farmers -> groundwater contamination
-> increased infant mortality and cancers
- 20-50% decreased crop yeild
28
TRADE OFFS
| Withdrawing groundwater
```
- advantages
> useful 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
- disadvantages
> aquifer depletion from over-pumping
> sinking of land (subsidence) for
over-pumping
> aquifers polluted for decades or
centuries
> saltwater intrusion into drinking water
supplies near coastal areas
> reduced water flows into surface waters
> increased cost and contamination from
deeper wells
```
29
Case Study: Ogallala Aquifer
- world's largest known aquifer
- mid-western U.S. - 8 states (South
Dakota, Nebraska, Kansas, Colorado,
Wyoming Oklahoma, New Mexico, Texas)
- fossil aquifer - filled during last ice age
- being pumped 8-10x faster than natural
recharge rate
- transformed prairie land (with little rain) ->
productive farmland that produces 20% of
agricultural output ($32 billion/year)
- depletion is encouraged by government
subsidies to farmers to grow "thirsty"
crops, and not to improve efficiency of
irrigation
NOTE: of all the water from the Ogallala aquifer was on the surface, it would cover all 50 stats with 1.5 feet of water
30
Case Study: James Bay Watershed Transfer
- involved creating 600 dams to alter, and
even reverse, the flow of 19 giant rivers
- would flood areas utilized by Cree and
Inuit tribes
- phase 2 was postponed due to opposition
and the fact that phase 1 created more
electricity than could be sold
31
Benefits of Reducing Water Waste
```
- reducing waste to 15% will allow us to
meet most of the world's water demands
for the foreseeable future
- decrease burden on waste water plants
- decreased need for dams and water
transfer projects (will disrupt fewer
habitats and displace less people)
- slow groundwater depletion
- save $
- save energy
```
32
Reducing Irrigation Water Waste
| Solutions
- line canals bringing water to irrigation
ditches
- irrigate at night to reduce evaporation
- monitor soil moisture to add water only
when necessary
- grow several crops on each plot of land
(poly-culture)
- encourage organic farming
- avoid growing water-thirsty crops in dry
places
- irrigate with treated urban waste water
- import water-intensive crops and meat
33
Reducing Water Waste
| Solutions
```
- redesign manufacturing processes to use
less water
- recycle water in industry
- landscape yards with plants that require
little water
- use drip irrigation
- fix water leaks
- use water meters
- raise water prices
- use water-less composting toilets
- require water conservation in water-short
cities
- use water-saving toilets, shower-heads,
and front-loading clothes washers
- collect and reuse household water to
irrigate lawns and non-edible plants
- purify and reuse water for houses,
apartments, and office buildings
```
34
WHAT CAN YOU DO?
| Water Use and Waste
- use water-saving toilets 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
- use recycled (gray) water for watering
lawns and household plants and for
washing cars
- 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 water
- replace your lawn with native plants that
need little if any watering
- water lawns and yards in the early
morning or evening
- use drip irrigation and mulch for gardens
and flowerbeds
35
Benefits of Flooplains
- fertile soil -> productive farmland
- nearby rivers for transportation and
recreation
- flatland's for urbanization and farming
- recharge groundwater
- ample water for irrigation
- highly productive wetlands
36
Dangers of Floodplains and Floods
- deadly and destructive
- failing dams and water diversion
- Hurricane Katrina and the Gulf Coast
> removal of coastal wetlands
- in MDCs, people deliberately settle on
floodplains and then expect dams, and
levees to protect them
NOTE: in U.S. 10 million homes and businesses (valued at $1 trillion) are located on floodplains
37
Case Study: Floodplains of Bangladesh
- dense population
> one of the world's poorest and most
densely populated countries (147 million
people in area the size of Wisconsin)
- located on coastal floodplain
- moderate annual floods maintain fertile
soil
- "great" floods used to occur every 50
years
- increase frequency of large floods since
the 1970s
- changes in the Himalayan watershed ->
increased flooding:
> population growth
> deforestation (uphill)
> overgrazing
> unstable farming on hilly slopes
> destruction of coastal wetlands
-> Bangladesh's poor have cleared
mangrove forests (for fuel wood) ->
increased flooding because swamps
absorb water
-1998 flood:
> covered 2/3 of Bangladesh's land area
for 9 months
> leveled 2 million homes
> drowned approximately 2,000 people
> left 30 million people homeless
> destroyed 25% crops -> led to
thousands of deaths by starvation
- 2002 flood:
> left 5 million homeless
- dangers from cyclones and storm surges
> since 1971, 17 cyclones have hit area
> 1970 storm: 1 million people drowned
> 1991 storm surge: killed 139, 000 people
38
Reducing Flood Damage
| Solutions
```
- prevention
> preserve forests on watershed
> preserve and restore wetlands in
floodplains
> tax development on floodplains
> use floodplains primarily for recharge
aquifers, sustainable agriculture and
forestry
- control
> strengthen and deepen streams
(channelization)
> build levees or flood walls along streams
> build dams
```
39
1973: U.S. Federal Flood Disaster Protection Act
- requires all local governments to adopt
floodplain development regulations in order
to be eligible for federal flood insurance
- denies federal funding to proposed
construction projects in designated flood
hazard areas
- federal flood insurance program
underwrites $185 billion in policies
because private insurance companies are
not willing to insure people who live in
flood plains
NOTE: many environmentalists feel that it would make more sense for the government to buy back the land that floods regularly rather than making disaster payments
OR: should we adopt a "LIVE AT YOUR OWN RISK" policy with no federal flood insurance
40
Solutions: Increasing Freshwater Supplies
- dams
- watershed transfer
- tapping groundwater
- desalination
- water conservation/curbing waste
41
Trade-offs of Large Dams and Reserviors
- provides irrigation water above and below
dam
- provides water for drinking
- reservoir useful for recreation and fishing
- can produce cheap electricity (hydro-
power)
- reduces downstream flooding
- flooded land destroys forests or cropland
and displaces people
- $$$ to build
- large losses of water through evaporation
- deprives downstream cropland and
estuaries of nutrient rich soil
- risk of failure and devastating downstream
flooding
- disrupts migration and spawning of some fish
42
Case Study: China's Three Gorges Dam
- "Great Wall across the Yangtze"
- will be the world's largest hydroelectric
dam and reservoir
> dam - 1.2 miles long
> reservoir - 370 miles long
- will be completed in 2013
- cost $25 billion
- will displace 1.9 million people
- will generate the electrical equivalent of 20
coal pr nuclear power plants
- will decrease downstream flooding (which
has killed 500,000 people during past 100
years)
43
TRADE OFFS
| China's Three Gorges Dam
```
-advantages
> will generate about 10% of china's
electricity
> reduces dependence on coal
> reduces air pollution
> reduces CO2 emissions
> reduces chances of downstream flooding
for 16 million people
> reduces river sitting below dam by
eroded soil
> increases irrigation water for cropland
below dam
- disadvantages
> 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
```
44
Case Study: Aral Sea Disaster
- large-scale water transfers in dry central
Asia (Uzbekistan and Kazakhstan - former
Soviet Union)
- since 1960, water was diverted from Aral
sea and 2 feeder rivers for irrigation canal -
8-- miles long
- world's longest irrigation canal - 800 miles
- salinity - increase 3x
-surface area - decreased 54%
- volume - decreased by 15%
- 14.000 square miles of human-made salt
desert
- flash extinctions and loss of fishing
industry
> 60,000 people unemployed
- wetland destruction and wildlife - loss of
50% of all bird and animal species
- "salt rain"
> wind blown salt -> kills crops
> salt settling on glaciers in the
Himalayas -> accelerating melting
- climate changes
> decreased moderating effect of sea ->
hotter summers, colder winters
> less rain
> shorter growing season
- increased use of pesticides and fertilizers
by farmers -> groundwater contamination
-> increased infant mortality and cancers
- 20-50% decreased crop yeild
45
TRADE OFFS
| Withdrawing groundwater
```
- advantages
> useful 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
- disadvantages
> aquifer depletion from over-pumping
> sinking of land (subsidence) for
over-pumping
> aquifers polluted for decades or
centuries
> saltwater intrusion into drinking water
supplies near coastal areas
> reduced water flows into surface waters
> increased cost and contamination from
deeper wells
```
46
Case Study: Ogallala Aquifer
- world's largest known aquifer
- mid-western U.S. - 8 states (South
Dakota, Nebraska, Kansas, Colorado,
Wyoming Oklahoma, New Mexico, Texas)
- fossil aquifer - filled during last ice age
- being pumped 8-10x faster than natural
recharge rate
- transformed prairie land (with little rain) ->
productive farmland that produces 20% of
agricultural output ($32 billion/year)
- depletion is encouraged by government
subsidies to farmers to grow "thirsty"
crops, and not to improve efficiency of
irrigation
NOTE: of all the water from the Ogallala aquifer was on the surface, it would cover all 50 stats with 1.5 feet of water
47
Case Study: James Bay Watershed Transfer
- involved creating 600 dams to alter, and
even reverse, the flow of 19 giant rivers
- would flood areas utilized by Cree and
Inuit tribes
- phase 2 was postponed due to opposition
and the fact that phase 1 created more
electricity than could be sold
48
Benefits of Reducing Water Waste
```
- reducing waste to 15% will allow us to
meet most of the world's water demands
for the foreseeable future
- decrease burden on waste water plants
- decreased need for dams and water
transfer projects (will disrupt fewer
habitats and displace less people)
- slow groundwater depletion
- save $
- save energy
```
49
Reducing Irrigation Water Waste
| Solutions
- line canals bringing water to irrigation
ditches
- irrigate at night to reduce evaporation
- monitor soil moisture to add water only
when necessary
- grow several crops on each plot of land
(poly-culture)
- encourage organic farming
- avoid growing water-thirsty crops in dry
places
- irrigate with treated urban waste water
- import water-intensive crops and meat
50
Reducing Water Waste
| Solutions
```
- redesign manufacturing processes to use
less water
- recycle water in industry
- landscape yards with plants that require
little water
- use drip irrigation
- fix water leaks
- use water meters
- raise water prices
- use water-less composting toilets
- require water conservation in water-short
cities
- use water-saving toilets, shower-heads,
and front-loading clothes washers
- collect and reuse household water to
irrigate lawns and non-edible plants
- purify and reuse water for houses,
apartments, and office buildings
```
51
WHAT CAN YOU DO?
| Water Use and Waste
- use water-saving toilets 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
- use recycled (gray) water for watering
lawns and household plants and for
washing cars
- 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 water
- replace your lawn with native plants that
need little if any watering
- water lawns and yards in the early
morning or evening
- use drip irrigation and mulch for gardens
and flowerbeds
52
Benefits of Flooplains
- fertile soil -> productive farmland
- nearby rivers for transportation and
recreation
- flatland's for urbanization and farming
- recharge groundwater
- ample water for irrigation
- highly productive wetlands
53
Dangers of Floodplains and Floods
- deadly and destructive
- failing dams and water diversion
- Hurricane Katrina and the Gulf Coast
> removal of coastal wetlands
- in MDCs, people deliberately settle on
floodplains and then expect dams, and
levees to protect them
NOTE: in U.S. 10 million homes and businesses (valued at $1 trillion) are located on floodplains
54
Case Study: Floodplains of Bangladesh
- dense population
> one of the world's poorest and most
densely populated countries (147 million
people in area the size of Wisconsin)
- located on coastal floodplain
- moderate annual floods maintain fertile
soil
- "great" floods used to occur every 50
years
- increase frequency of large floods since
the 1970s
- changes in the Himalayan watershed ->
increased flooding:
> population growth
> deforestation (uphill)
> overgrazing
> unstable farming on hilly slopes
> destruction of coastal wetlands
-> Bangladesh's poor have cleared
mangrove forests (for fuel wood) ->
increased flooding because swamps
absorb water
-1998 flood:
> covered 2/3 of Bangladesh's land area
for 9 months
> leveled 2 million homes
> drowned approximately 2,000 people
> left 30 million people homeless
> destroyed 25% crops -> led to
thousands of deaths by starvation
- 2002 flood:
> left 5 million homeless
- dangers from cyclones and storm surges
> since 1971, 17 cyclones have hit area
> 1970 storm: 1 million people drowned
> 1991 storm surge: killed 139, 000 people
55
Reducing Flood Damage
| Solutions
```
- prevention
> preserve forests on watershed
> preserve and restore wetlands in
floodplains
> tax development on floodplains
> use floodplains primarily for recharge
aquifers, sustainable agriculture and
forestry
- control
> strengthen and deepen streams
(channelization)
> build levees or flood walls along streams
> build dams
```
56
1973: U.S. Federal Flood Disaster Protection Act
- requires all local governments to adopt
floodplain development regulations in order
to be eligible for federal flood insurance
- denies federal funding to proposed
construction projects in designated flood
hazard areas
- federal flood insurance program
underwrites $185 billion in policies
because private insurance companies are
not willing to insure people who live in
flood plains
NOTE: many environmentalists feel that it would make more sense for the government to buy back the land that floods regularly rather than making disaster payments
OR: should we adopt a "LIVE AT YOUR OWN RISK" policy with no federal flood insurance
57
Stream Pollution
```
- oxygen sag curve
> curve in the oxygen
concentration line when
degradable wastes or heat are
introduced into a stream/river
> O2 levels decrease at the point
of discharge -> reach their
lowest point in the sceptic zone
-> and then begin to increase in
the recovery zone
> the depth and width of the curve
(and therefore the time and
distance needed for the stream
to recover) depend on:
-> stream volume
-> stream flow rate
-> stream temperature
-> pH
-> volume of incoming
degradable wastes
```
58
Pollution Prevention in Streams
```
- require cities to withdraw their
water downstream (rather than
upstream) -> force cities to clean
up their own waste
- good news
> water pollution control laws
(1970s)
-> increased the number and
improved the quality if waste
water treatment plants
-> required industries to
decrease/eliminate point
source discharge into surface
waters
--> ex. Ohio's cuyahoga river -
caught fire in 1969
- bad news
> increased pollution in LDCs
> USA has too few monitoring
stations (64% unknown)
```
59
Lake Pollution
```
- dilution less effective than with
streams
> stratification
-> little mixing and less dilution
> low flow
-> flushing and changing water
in lakes takes a long time (1-
100 years) compared to
streams
- lakes are more vulnerable than
streams
- eutrophication - natural aging
process
> oligotrophic
( Best recovery -> least recovery )
( River -> lake -> groundwater )
```
60
Lake Pollution - Cultural Eutrophication
```
- causes
> over nourishment of lakes with
plant nutrients as a result of
human activities (agriculture,
urbanization, sewage plants,
etc.)
- prevention
> advanced waste treatment
> ban/limit phosphates
(detergents, cleansers)
> soil conservation - prevents
nutrient-rich soil from entering
lakes
- cleanup
> dredge bottom of lakes (remove
nutrient buildup)
> pump oxygen into lakes (to
increase DO)
> remove weeds and undesirable
plant growth
```
61
Stream Pollution
```
- oxygen sag curve
> curve in the oxygen
concentration line when
degradable wastes or heat are
introduced into a stream/river
> O2 levels decrease at the point
of discharge -> reach their
lowest point in the sceptic zone
-> and then begin to increase in
the recovery zone
> the depth and width of the curve
(and therefore the time and
distance needed for the stream
to recover) depend on:
-> stream volume
-> stream flow rate
-> stream temperature
-> pH
-> volume of incoming
degradable wastes
```
62
Pollution Prevention in Streams
```
- require cities to withdraw their
water downstream (rather than
upstream) -> force cities to clean
up their own waste
- good news
> water pollution control laws
(1970s)
-> increased the number and
improved the quality if waste
water treatment plants
-> required industries to
decrease/eliminate point
source discharge into surface
waters
--> ex. Ohio's cuyahoga river -
caught fire in 1969
- bad news
> increased pollution in LDCs
> USA has too few monitoring
stations (64% unknown)
```
63
Lake Pollution
```
- dilution less effective than with
streams
> stratification
-> little mixing and less dilution
> low flow
-> flushing and changing water
in lakes takes a long time (1-
100 years) compared to
streams
- lakes are more vulnerable than
streams
- eutrophication - natural aging
process
> oligotrophic
( Best recovery -> least recovery )
( River -> lake -> groundwater )
```
64
Lake Pollution - Cultural Eutrophication
```
- causes
> over nourishment of lakes with
plant nutrients as a result of
human activities (agriculture,
urbanization, sewage plants,
etc.)
- prevention
> advanced waste treatment
> ban/limit phosphates
(detergents, cleansers)
> soil conservation - prevents
nutrient-rich soil from entering
lakes
- cleanup
> dredge bottom of lakes (remove
nutrient buildup)
> pump oxygen into lakes (to
increase DO)
> remove weeds and undesirable
plant growth
```
65
Groundwater Pollution
```
- most susceptible to pollution -> cannot
cleanse itself
> slow flow, dilution, dispersion
> fewer bacteria
> cooler temperatures (slow down
decomposition rates)
```
66
Sources of Groundwater Pollution
```
- underground storage tanks
> slow leak - 1 gallon/ day - can
contaminate aquifer
> chevron storage tank in California leaked
18x more oil than the Exxon Valdez
- landfills
- hazardous waste dumps
- deep well injection - disposal of liquid
hazardous waste
- industrial waste storage lagoons
```
67
Oceans: the "Ultimate Sink":
- have the ability to dilute, disperse and
degrade large quantities of waste
- 2 views of ocean dumping:
> safer than incineration or land burial
> too little known about deep ocean,
would delay pollution prevention and
promote degradation
68
Ocean Pollution
- coastal areas - highly productive
ecosystems
> bear brunt of our inputs of pollution
> occupied by 40% of population
> twice that population by 2050
> about 80% marine pollution originates
on land
> 80-90% of municipal sewage from
coastal LDCs is dumped into oceans
without treatment
> according to one study in the U.S. 25%
of all people using coastal beaches
develop ear infections, sore throats, eye
irritation, respiratory disease, or
gastrointestinal disease after swimming
(due to vast colonies of viruses found in
U.S. coastal waters)
- deep ocean waters
> some capacity to dilute, disperse,
degrade pollutants
69
What Pollutants are Dumped into the Ocean?
```
- dredge spoils
> scraped from bottoms of harbors and
rivers to maintain shipping channels
> filled with toxic metals
- sewage sludge
>gooey mixture of toxic chemicals,
infectious agents, and settled solids
removed fro waste water at sewage
treatment plants
- 1992 - U.S. banned dumping sewage
sludge into the ocean
```
70
Oil Pollution in Oceans
- crude and refined petroleum
- sources of oil pollution:
> tanker accidents (10% - but get much
publicity) (Exxon Valdez)
> urban runoff (45%)
> normal shipping practices (35%)
-> ballast and washing tankers
> atmosphere
> oil slick spreads from sunken rig
71
Effects of Oil Pollution on Ocean Ecosystems
- kill aquatic organisms
- volatile organic hydrocarbons
> kill larvae
> destroys natural insulation and
buoyancy
- heavy oil
> sinks and kills bottom organisms
> coral reefs die
72
Effects Depend On
```
- type of oil
> crude recovery quicker than refined
- amount of oil released
- distance from shore
- time of year and weather conditions
- water temperature
> cold water is worse
- ocean curents
```
73
Oil Cleanup Methods
```
- current methods recover no more than
15%
- prevention is most effective method
> control runoff
> double hull tanker
```
74
Case Study: Exxon Valdez Oil Spill
- march 24, 1989
- tanker went off course, hit submerged
rocks at Alaska's Prince William sound
- oil slick coated 1,000 miles of shoreline
- killed
> 300,000-645,000 birds
> 5,500 sea otters
> 300 harbor seals etc.
- response: "too little too late"
- lesson: don't drink and drive an oil tanker
75
Preventing Non-point Source Pollution
- mostly agricultural waste
- decrease fertilizer runoff by:
> using slow-release fertilizer
> not using fertilizer on steep slopes
> planting buffer zones of vegetation
between fields and nearby waterways
- decrease pesticide runoff by
> applying pesticides only when needed
> relying on biological pest controls
- decrease runoff by
> planting buffers
> not locating feedlots on steep slopes
76
Discharge Trading Policy
- proposed by EPA in 1995
- in experimental stages
- allows for permit holders to buy and sell
pollution "credits"
- opponents:
> no better than the ca set for total
pollution levels in any given area
> could allow pollutants to build up to
dangerous levels in areas where credits
are bought
77
Should CWA be Strengthened or Weakened?
- strengthening - environmentalists
> increase funding and authority:
-> to control non-point source pollution
-> for watershed planning
>improving programs to prevent and
control toxic discharges
>expanding ability of citizens to bring
lawsuits to ensure water pollution laws
are enforced
- weakening - industry, farmers, state and
local officials
> too $$$
> too restrictive
> unnecessary to test for all water pollution
78
Sewage Treatment Systems
```
- rural and suburban areas - septic tank
(25% of all US homes have septic tanks)
- urban areas - waste water treatment
plants
> primary treatment - physical process
> secondary treatment - biological
process
> chlorination - bleaching and disinfection
```
79
Treating Waste Water in Urban Areas
```
- water -> sewer pipes -> sewage treatment
center
- best scenario: separate lines for sewage
and for runoff ($$$)
- to save $, many cities have combined
systems
- problem: heavy rains can cause sewer
systems to overflow -> discharge
untreated sewage into surface waters
```
80
Sewage Treatment Plants
- 3 levels of purification:
1. primary sewage treatment
2. secondary sewage treatment
3. tertiary/advanced sewage treatment
81
Primary Sewage Treatment
- mechanical/physical process
- uses screens to filter out debris (large
particles - stick, rags)
- suspended particles settle in settling tank
(sludge)
- water is removed from top of settling
tank/lagoon and released
- after primary treatment, water
> has no sand, grit
> has organic matter, dissolved salts,
bacteria, and other microorganisms
NOTE: as long as there is high DO,
bacteria will degrade organic matter
82
Secondary Sewage Treatent
- biological process
- aerobic bacteria remove up to 90% of
biodegradable, oxygen demanding wastes
- most US cities gave secondary treatment
- two types:
> trickling filters - waste water is sprayed
over crushed stones that are covered
with bacteria (spraying aerates the
water and increases the DO)
> activated sludge process - sewage is
pumped into large tank and mixed for
several hours with bacteria rich sludge
and air bubbles to increase degradation
by microorganisms
83
What do they do with the sludge?
- incinerate
- dump into ocean
- put in landfill
- used as fertalizer
84
What Wastes Remain After Primary and Secondary Treatments?
- 3-5% oxygen demanding wastes
- 3% suspended material
- 50% nitrates
- 70% phosphates
- 30% toxic metal compounds
NOTE: 34 east coast cities screen out
large floating pesticides and discharge
85
Tertiary/Advance Sewage Treatment
- specialized chemical and physical
process that removes specific pollutant
that remain after primary and secondary
treatments
- vary according to specific contaminant to
be removed
- usually remove nitrogen and phosphorus
- very $$$ (cost 2x as much to build, 4x as
much to operate)
- can be used by industry to remove
specific pollutants
86
Chlorination
- final step in all levels of sewage treatment
- water is bleached to disinfect and remove
coloration
- problem: chlorine can react with organic
matter in water to form CHC (chlorinated
hydrocarbons) which are possible
carcinogens and may damage the
nervous, immune and endocrine systems
- alternatives: disinfect with UV light or
Ozone ($$$)
87
Drinking Water Quality - MDCs
- purification of urban drinking water
- water is stored in reservoir for several days
-> improves clarity and taste, allowing
suspended matter to settle
- water is pumped to a purification plant and
treated to meet government drinking water
standards
88
Drinking Water Quality - MDCs
- poor quality drinking water -> diseases
- WHO: purify drinking water by exposing
clear plastic bottle filled with contaminated
water to intense sunlight
> heat and UV rays kill infectious
microbes in 3 hours
> paint one side of the bottle black can
improve heat absorption
> has reduced dangerous childhood
diarrhea by 30-40%
- 2007 - danish company developed a $3
life-straw that purifies and filters
contaminated water
89
Ecological Waste-water Treatment
- working with nature to treat sewage
- living machines
- tanks with increasingly complex
organisms
- artificially created wetlands
