BIOLOGY 403:
PRINCIPLES OF ECOLOGY
(Water: Cycle, Use, Treatment, Purification)
WATER…THE MOST
PRECIOUS RESOURCE ???
• If the earth had a perfectly smooth surface,
the whole world would be covered by water
3 km (1.9 mi) deep!
• Very little of the water on earth is readily
available to us.
• Water has many interesting properties. We
will look at three.
SOME PROPERTIES OF WATER (I)
• High Specific Heat ( and Latent Heat)
water can absorb or lose a great amount of energy
without changing temp. greatly
this makes it a great weather modifier
areas with few bodies of water in the vicinity and/or
low relative humidity usually show great and
sudden seasonal temperature oscillations and
greater day/night temp. changes during a day
areas with much water in the vicinity and/or high
relative humidity usually show smaller and more
gradual seasonal temperature oscillations and
smaller day/night temp. changes during a day
SOME PROPERTIES OF WATER (II)
• Good Solvent
• Water can dissolve, to some extent, more
substances than any other solvent.
• This makes it a great solvent for living systems
because all life processes involve dissolved
materials.
SOME PROPERTIES OF WATER (III)
• Density changes in water
most substances tend to contract when cooled; the molecules
get closer together and the material becomes more dense per
unit of volume
most substances tend to expand as they warm; the molecules
move farther apart and the material becomes less dense per
unit of volume
water behaves this way BUT only to a certain extent
water has its greatest density (defined as 1.0) at 4 degrees C.
As it warms the molecules move apart and water becomes less
dense; water also becomes less dense as it cools below 4
degree C.
Thus 2 degree C water is less dense than 4 degree water and it
floats on top. 0 degree C water (ice) is even less dense (0.92) -- ice floats --- this has great importance in ecosystems
SOME ADDITIONAL THINGS
CONCERNING WATER (I)
• Drought
• when precipitation is 70% below average for 21 days
or longer
• Types of water
* surface vs. ground
* fresh vs. brackish vs. Salt
• THE HYDROGEOLOGIC (WATER) CYCLE
THE WATER CYCLE
SOME ADDITIONAL THINGS
CONCERNING WATER (II)
• Fresh water ---- very little
* (less than 3%)
• Salt / Brackish water ---- the great majority
* (more than 97%)
• Sources of Fresh Water
Precipitation Directly
Precipitation Indirectly
Streams
Lakes
Ground water
WATER AVAILABILITY
PROBLEMS ASSOCIATED WITH
OBTAINING AND USING WATER
Irrigation
Diversion, Dams and Reservoirs
• Desalination
• Ground Water Use
• Disposal (to treat or not to treat)
DRYING OF THE ARAL SEA
1989 (l) ----------2003 (r)
PROBLEMS ASSOCIATED WITH
OBTAINING AND USING WATER
• Irrigation
• Diversion, Dams and Reservoirs
Desalination
• Ground Water Use
• Disposal (to treat or not to treat)
OSMOSIS
REVERSE OSMOSIS
PROBLEMS ASSOCIATED WITH
OBTAINING AND USING WATER
• Irrigation
• Diversion, Dams and Reservoirs
• Desalination
Ground Water Use
• Disposal (to treat or not to treat)
THE GROUNDWATER SYSTEM
WATER TABLE DRAWDOWN
THE OGALLALA AQUIFER
GROUND SUBSIDENCE
GOING DOWN
Withdrawal of groundwater in
California’s San Joaquin
valley has caused the ground
to subside by more than 9m.
Signs in this 1977 photo, taken
near Mendota, show where the
ground surface was in 1925
and 1955.
Science News, July 20, 2002
Vol. 162, pp. 42-43
PROBLEMS ASSOCIATED WITH
OBTAINING AND USING WATER
• Irrigation
• Diversion, Dams and Reservoirs
• Desalination
• Ground Water Use
Disposal (to treat or not to treat)
WASTEWATER TREATMENT
• Primary --- Settling and Skimming
• Secondary --- activated sludge digestion
• Tertiary (= Advanced)
various treatments with chemicals to precipitate out
certain chemicals (also may use reverse osmosis)
• Chlorination (or UV light or Ozonation) is normally
used at the end of the wastewater treatment process to
destroy bacteria and viruses
• Point vs. non-point water pollution sources and their
control
SEWAGE TREATMENT
0
(1
&
0
2)
DRINKING WATER PURIFICATION
• Do Nothing ???
• Settling / Skimming
• Filter
*sand --- remove suspended material
*charcoal --- remove certain dissolved
chemicals and certain gases
• Add chemicals to precipitate out various
substances
• Chlorinate
WATER USE AND CONSERVATION
• WORLDWIDE
* could use 25% of precipitation
* currently using about 20%
• U.S. Water Use
*
*
*
*
residential --- 10%
Irrigation --- 41%
Industry --- 11%
Power Generation --- 38%
ASSOCIATED WATER TOPICS (I)
Wetlands and their Value
• water storage and release to streams / lakes
• groundwater recharge
• temporary resting / feeding areas
• major breeding / rearing areas
• water purification / filtration
• aesthetics
• coastal wetlands provide a physical buffer for
inland regions
ASSOCIATED WATER TOPICS (II)
Conservation / Preservation
Stream ‘Management’
•
•
•
•
straightening streams (Kissimmee River, FL)
dredging streams
dams
levees
Eutrophication
• Anthropogenic (= cultural)
• Non-anthropogenic (= non-cultural)