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 water3 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 WaterPrecipitation DirectlyPrecipitation Indirectly

StreamsLakesGround 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 SEA1989 (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 (10 & 20)

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)