Bdale Envir Ch 14 – Water Resources and Water Pollution
Intro is a water wars story about Nile River
Nile essential to life in Egypt, but Ethiopia plans to divert water
Fig 14-1 shows the region, rivers
Quote indicates “spreading scarcity of fresh water facing the world in this new
millennium”
14-1 – Water’s importance and unique properties
This IS the water planet…..70% water.
Many organisms, including people, are 50-65% water.
There are a number of unique properties that are listed:
 Hydrogen bonds
 Exists over a wide range of temperature
 High heat capacity moderates earth’s temp fluctuations
 Water has tremendous dissolving power
 Unique property of density decrease upon freezing (ice floats)
14-2 - supply, renewal, and use
just a tiny fraction of planet’s water is available as fresh water (Fig 14-2)
97.4% is in ocean
2.59% is in ice caps & glaciers
0.01% is available for soil moisture, GW, lakes/streams
analogy – if there were100 liters (26 gallons) total of water on the planet, only
2.5 teaspoons would be usable fresh water
luckily, fresh water is continuously recycled through the hydro cycle, so fresh
water is continuously being pulled out of the ocean and returning to Earth.
But GW acts like a non-renewable resource if we pull it out of the ground faster
than it recharges
(Show an example problem…)
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discussion of various components of hydro cycle…Fig 14-3
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surface water – lakes, streams, overland flow
groundwater – subsurface flow, some water in aquifers may be thousands
of years old…..
how much of the world’s water supply are we using?
Water use has increased almost 10x since 1900….biggest use is irrigation (Fig
14-4)
70% goes to irrigated land
20% goes to industry
10% goes to cities and industries
Freshwater resources in US:
Miller makes point that US has plenty of water, but it is in the “wrong place” or it
is getting contaminated (example of Long Island aquifer, supporting 3 million
people)
Imbalance: plenty water in eastern US, not enough in western US (fig 14-7)
Western US uses lots of water for irrigation, but does NOT get much through
recharge. So there is the danger of a net loss of water…..especially since people
continue to move out west….
14-3 – too little water
what causes shortages of fresh water?
 Dry climate
 Drought
 Dessication of soil
 Water “stress”
Stress is low per capita (per person) availability of water
How can freshwater supplies be increased?
 Build dams & reservoirs to store water
 Bring in water from elsewhere
 Increase GW withdrawal
 Desalinate salt water
 Improve efficiency of use of existing water supplies
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- Worldwide, dams increase amt of runoff available for human use by 1/3
But there are problems with dams too…reduced downstream flow, and disruption
of ecology that is dependent upon periodic flooding that is stopped by dams
Dams also provide electric power, cleaner than with coal power plants
- large scale water transfer
Miller cites California water project as example –
An example of a disaster was the Aral Sea transfer, where the size of the sea
has decreased dramatically in 40 years (story on p.335)
- groundwater withdrawal
there are a number of problems with increasing GW withdrawal
scary stat – in US, GW is being withdrawn at 4 times the replacement rate !
-desalination
desalination is used but does not contribute much volume at this point in time,
and it is both expensive and environmentally harmful (due to all the salt waste)
14-4 too much water
Miller discusses problems with flooding
Flooding is very important to agriculture, because nutrient-rich silt gets deposited
on the floodplain during flooding, and this creates good crop conditions
Because floodplains are so important for agriculture many people in developing
countries insist upon settling there, and then they are subject to danger during
flooding
14-5 types, effects, sources of water pollutants
Table 14-1 lists major categories:
 Infectious agents (bacteria, etc)
 Organic waste (takes free oxygen away from fish)
 Inorganic chemicals (acids, heavy metals)
 Organic chemicals (oil, gasoline, pesticides, solvents)
 Plant nutrients (nitrate, phosphate, ammonium)
 Sediment (soil, silt)
 Radioactive materials (uranium, radon, etc)
 Heat (power plant cooling, etc)
Measuring water quality
Several methods:
 Coliform bacteria count – the lower the better
 BOD (biological oxygen demand) – essentially the amount of dissolved
oxygen (DO) in the water required by aerobic decomposers to break down
waste matter – the more DO, the less waste matter is in the water
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Life forms present – certain species require very clean water (trout), or
others such as clams or cattails can be chemically analyzed for chemicals,
metals, pesticides)
Point and non-point sources of water pollution
Point sources are specific locations such as sewer discharges. In most
developed countries, these discharges are regulated, but in most undeveloped
countries, that are uncontrolled.
Non-point sources cannot be traced to a specific discharge site. Usually coming
from large land areas or “airsheds” that pollute large areas. In US, non-pt
pollution is estimated to account for about 60% of pollutants entering lakes and
streams.
Interesting stat – 25% of people in developing countries do NOT have access to
clean drinking water. Also some frightening stats about China, Russia, Africa.
14-6 Pollution of streams, lakes, aquifers
flowing stream exhibits an oxygen sag curve (fig 14-21)
no major oxygen demand upstream of pollution source, but downstream, DO is
pulled out of water by aerobic bacteria feeding upon the water. Organisms
requiring DO can not survive, so other “trash fish” predominate in the
decomposition zone. After this comes the septic zone, which supports little life
because there is so little DO. Beyond this is a recovery zone, where trash fish
come back, and finally back to a clean zone.
Lakes are even more vulnerable to contamination, mostly because they don’t
flow, so clean water doesn’t come in quickly to dilute pollutants
Nutrient enrichment causes eutrophication of lakes, a loss of oxygen. Nutrients
cause algae to grow. Algae use up oxygen during respiration at night, and they
also are decomposed by aerobic bacteria when they die, which also uses up DO.
Once the DO is depleted, anaerobic bacteria will take over the job of
decomposing the algae, but with byproducts including H2S, and CH4, both
dangerous gases.
Groundwater pollution is also a serious problem
GW is not cleaned up as readily as surface water, because flow rates are very
slow (1 foot per day is FAST) and there are less bacteria to decompose waste.
Some stats suggest that 25% of usable GW in US is contaminated (Miller claims
that every major aquifer in NJ is contaminated)
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14-7 Ocean water pollution
“oceans are the ultimate sink for much of our waste”
oceans dilute a lot of pollution, and some forms of marine life may be “more
resilient” to pollution than previously thought
coastal areas “bear the brunt” of ocean pollution (Fig 14-26)
why?
 40% of world’s population lives within 100 km (60 miles) of a coast, so
there are a lot of people in this area
 world’s 15 largest metro areas (each > 10,000,000) are on coasts
 coastal areas growing fast
what are some of the sources ?
 Municipal sewage & waste, sometimes untreated
 Runoff of fertilizer, etc
 Deposition from atmosphere
These all bring in nutrients that promote “explosive” algae growth that is
ultimately harmful to fish, seafood, birds.
Good example of this is Fig 14-28, depleted oxygen zone that forms every year
off the mouth of Mississippi R., fed by a huge drainage basin in middle of U.S.
Miller cites big problems in Chesapeake Bay Fig 14-29, where there is much
pollution due to large population, but only 1% of waste entering the Bay actually
gets “flushed” into the ocean.
However, an integrated coastal mgmt program has started to achieve
“impressive” results, reducing nitrogen and phosphate
What pollutants do we dump into the ocean?
US has stopped dumping industrial waste offshore, but many countries still do it.
But we still dump “dredge spoils” …these are sediments dredged from bottoms of
rivers and harbors to maintain shipping channels….Maintenance of shipping
channels is a major task of the US Army Corps of Engineers
Other countries also dump sewage sludge (waste material that is removed from
wastewater at sewage treatment plants), but US stopped doing this in 1992.
Effects of oil upon the ocean
The most dramatic incidents (tanker spills and well blowouts) are not necessarily
the most damaging…..Miller cites releases during normal oil well operations,
pipeline leaks, and washing of oil tankers as more important.
Other sources are natural, such as seeps.
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Oil hurts organisms several diff ways….
 Larvae get killed
 Bird feathers and marine mammal fur gets coated, destroying insulation
and buoyancy
 Heavy oil can sink to ocean floor, smother bottom-dwelling organisms
Crude, unrefined oil appears to be less damaging to environment; many forms of
life can recover within 3 years.
Refined oil causes longer recovery time, perhaps 10 years…also, spill effects in
confined areas tend to last longer
Oil-polluted beaches washed by waves can get clean in about a year, whereas
those in sheltered areas may remain contaminated for several years.
14-8 solutions: preventing and reducing surface water pollution
nonpoint sources:
 reduce fertilizer input from land
 create vegetation buffer zones between crops and surface water
 reduce pesticide runoff
 reduce manure runoff
 reduce soil erosion
point sources:
big diff between developing and developed countries – point source pollution is
regulated in developed countries, so some cleanup occurs prior to discharge
Clean Water Act of 1972 resulted in many improvements in US by 1998:
 fishable/swimmable rivers & lakes incr from 36% to 62%
 topsoil loss reduced by 1 billion tons
 % US population served by sewage treatment incr from 32% to 74%
 annual wetland loss decr 83%
Sewage treatment – complex issue
In many older US cities, it’s too expensive to create separate systems to handle
both sewage and stormwater runoff, so when heavy rains occur and cause
potential overflow of waste treatment facilities, the entire system dumps
untreated waste into rivers, lakes, etc
Sewage treatment process:
Primary – mechanical filtering process, allows solids to settle out
Secondary – biological process, where aerobic bacteria remove up to 90% of
“oxygen-demanding” organic wastes
14- 9 achieving a more sustainable water future
the Incas said “the frog does not drink up the pond in which it lives”
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Miller cites 3 important steps in sustainable water management:
 irrigate crops more efficiently
 use water-saving technology
 improve watershed mgmt
and several steps in reducing water pollution:
 reduce toxicity and volume of pollutants
 reuse wastewater, rather than simple discharge
 recycle pollutants (like solvents) rather than simply discharging them
Miller closes by indicating we must understand that all aspects of the
environment – air, water, soil, and life, is an “interconnected whole”. This means
we need an integrated, holistic approach to environmental management, in order
to not move environmental problems from one part of the environment to
another.
A good place to end….good advice.
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