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ENV 301: Environmental Science A Study of Interrelationships

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Presentation on theme: "ENV 301: Environmental Science A Study of Interrelationships"— Presentation transcript:

1 ENV 301: Environmental Science A Study of Interrelationships
Discussion notes: Scott M. Graves Text: Enger • Smith Ninth Edition Chapter 16 Water Management Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Water Management Chapter 16

3 Chapter Outline Physical Properties Hydrologic Cycle Domestic Water Use Agricultural Water Use Industrial Water Use Kinds and Sources of Water Pollution Water Use Planning Issues Wastewater Treatment Preserving Scenic Water Areas

4 The Water Issue Physical Properties: Polar: One molecule is slightly positive, and the other is slightly negative. Molecules tend to stick together. Separate other molecules from each other (solvent). Stores Heat Industrial coolant Modifies local climates

5 The Water Issue 70% of earth’s surface is covered by water. Fresh Water = 3% Potable: Unpolluted, fresh water, suitable for drinking. Shortages can be directly attributed to human-induced water pollution. WHO estimates 25% of world population does not have access to safe drinking water.

6 Freshwater Resources

7 Hydrologic Cycle All water is locked into a constant recycling process—Hydrologic Cycle. Solar energy evaporates water. Evapotranspiration—Plants giving off water. Warm, moist air rises, cools, condenses, and falls as precipitation. Some precipitation remains on the surface and evaporates, while most sinks into the soil or returns to the oceans.

8 Hydrologic Cycle

9 Hydrologic Cycle Groundwater—Water entering the soil is either taken up by plant roots or moves downward until it reaches an impervious layer of rock, and accumulates in porous strata called an aquifer.

10 Aquifers and Groundwater

11 Aquifers Aquifer—Porous soil saturated with water. Unconfined Aquifer—Usually near land’s surface. Lower boundary is impermeable layer of clay or rock. Water at atmospheric pressure and recharged by rainfall and percolation. Water Table—Top layer. Vadose Zone (Zone of Aeration)—Area above water table unsaturated with water.

12 Aquifers Confined Aquifer—(Artesian) Bounded on top and bottom by impermeable layer. Water stored under high pressure and recharged from a geologic recharge zone. Aquiclude—Impervious confining layer. Aquitard—Permeable confining layer. Porosity—Measure of size and number of species in the substrate.

13 Human Influences On The Hydrologic Cycle
Runoff and infiltration rate are greatly influenced by human activity. Major concern in many urban areas is transportation of storm water. Water Withdrawal—Withdrawing water and returning it to its original source. Water Consumption—Withdrawing water and incorporating it into a product, or otherwise moving it to another area, so it does not make it back to original source.

14 Domestic Water Use Average person in N.A. home uses approximately 400 liters of water per day. 70% used as solvent to carry wastes. 30% used for lawn and garden. Very small fraction used for drinking. Natural processes cannot cope with highly concentrated urban wastes. Must be treated before release.


16 Domestic Water Use Public attitude has been major force working against water conservation. As long as water is a considered limitless, inexpensive resource, few conservation measures will be taken.


18 Agricultural Water Use
Four common irrigation methods: Surface / Flood Spray Trickle Sub-irrigation

19 Industrial Water Use Accounts for nearly 50% of all water withdrawal in U.S., and 23% worldwide. 90% of water used by industry is for cooling, and is returned to the source. Very little actually consumed. Most processes involve heat exchange. Water used to dissipate and transport waste. Stream and lake degradation.

20 In-Stream Uses In-stream uses make use of water in its channels and basins. Non-consumptive. Major in-stream uses are hydroelectric power, recreation, and navigation. Presently, hydroelectric power plants produce 13% of a electricity generated in U.S.

21 Dams Although hydroelectric dams control flooding and create electricity, they have drawbacks. High construction costs. Habitat destruction (above and below dam). Retard stream flow and silt deposition. Impounded water has elevated evaporation rate. Retard scouring effects of flooding. Reduced habitat regeneration.

22 Kinds and Sources of Water Pollution
Dissolved organic matter is a significant water pollution problem. Biochemical Oxygen Demand (BOD) Amount of oxygen required to decay a certain amount of organic matter. If too much organic matter is added, all available oxygen will be used up. Anaerobic bacteria begins to break-down waste.

23 Kinds and Sources of Water Pollution
Nutrients can also be a pollution problem. Eutrophication—Excessive growth of algae and aquatic plants due to added nutrients. Particulate matter can also affect quality.


25 Kinds and Sources of Water Pollution
Pollution Sources: Point—Source of pollution readily located and identified. Municipal and industrial waste discharge pipes. Non-Point—Diffuse pollutants. Agricultural runoff

26 Kinds and Sources of Water Pollution
Municipal Water Pollution Wastes from homes consists primarily of organic matter from garbage, food production, and human waste. Fecal Coliform Bacteria—Generic term for bacteria found in warm-blooded animal intestines. Numbers and types of bacteria present are directly related to amount of fecal matter entering system.

27 Municipal Water Pollution
At one time, many detergents contained phosphates which contributed to eutrophication. Eliminated from most major detergents since 1994. Pharmaceuticals, hormones, insecticides, caffeine, cholesterol, and coprostanol, among other chemicals, also found in municipal water discharge.

28 Agricultural Water Pollution
Excessive fertilizer use may lead to eutrophication in many aquatic habitats. Runoff from animal feedlots carries nutrients, organic matter, and bacteria. Agricultural runoff from large, open expanses is major source of water pollution. Leave conservation buffer. Keep soil covered with crop. Control amount and timing of fertilizer application.

29 Industrial Water Pollution
Factories and industrial complexes frequently dispose of waste in municipal sewage systems. May require special wastewater treatment. Often point sources. Mining Chemical run-off. Acid mine drainage.

30 Thermal Pollution Thermal Pollution—Occurs when water is withdrawn, used for cooling purposes, and heated water then returned to original source. Steam from steam turbines must be condensed into water after leaving turbine for maximum efficiency. An increase in temperature, even a few degrees, may significantly alter some aquatic ecosystems.

31 Marine Oil Pollution Tanker accidents are spectacular, but more oil is released as a result of small, regular releases from other sources. 2/3 of all human-caused marine oil from: Street run-off. Improper disposal of lubricating oil. Intentional oil discharges during tanker loading and unloading. 1992—New oil tankers must be double-hulled. Currently 15% of all tankers double-hulled.

32 Groundwater Pollution
Major Sources: Agricultural Products Underground Storage Tanks Landfills Septic Tanks Surface Impoundments

33 Groundwater Contamination

34 Water Use Planning Issues
Metropolitan areas must deal with and provide three basic services: Water supply for industrial needs. Wastewater collection and treatment. Storm-water collection and management. Must also deal with great volumes of excess water during storms (Storm-Water Runoff). Urban areas are paved, thus little water can be absorbed into the ground.

35 Water Use Planning Issues
Water Purity Act (1987) requires municipalities obtain permits for discharges of storm-water runoff so that non-point pollution sources are controlled. Many cities have separated storm sewers from sanitary sewers to avoid contamination under time of flooding and heavy storm-water runoff.

36 Water Diversion Water diversion is seen as a necessity in many parts of the world. One major consequence of diverting water for irrigation and other purposes is water bodies downstream are deprived of their source of water. Ecological Effects Lake Levels Decline Fish Population Issues

37 Wastewater Treatment Primary Treatment Removes large particles via filtration and then pumps remaining water into settling ponds and lakes. After settling, water is drawn off the top, and although devoid of large particulate matter, it still has a heavy load of organic matter, dissolved salts, bacteria, and microorganisms.

38 Secondary Treatment Facilities designed to degrade organic matter by promoting bacterial and other microorganism growth. Wastewater mixed with large quantities of highly oxygenated water. Trickling Filtering System—Provides anchor substrate for bacteria.

39 Secondary Treatment Organic waste concentrated into particles large enough to settle out. Sewage Sludge Activated-sludge sewage treatment plants hold wastewater in settling tanks with air continuously bubbled through it, and water and sludge separate.

40 Tertiary Treatment and Runoff
Some plants now utilize an additional stage to remove even more dissolved pollutants i.e. phosphorous and nitrogen. Extremely costly Some municipalities using natural or constructed wetlands. Some areas use effluent as fertilizer.

41 Salinization As plants extract water from the ground, salt content of the ground increases. Irrigation of arid farmland can make salinization more acute due to increased evaporation rates.

42 Groundwater Mining Removing water from an aquifer faster than it can be replenished. Extended periods of mining can lead to: Land subsidence. Lowering of the water table. Salt-water intrusion of wells near coastal areas.

43 Saltwater Intrusion

44 Preserving Scenic Water Areas
United States Federal Wild and Scenic Rivers Act (1968). Established system to protect wild and scenic rivers from development. All federal agencies must take these areas into consideration when planning and implementing procedures. Only recently has natural and economic importance of wetlands been recognized.

45 Wetlands Conservation

46 Chapter Summary Physical Properties Hydrologic Cycle Domestic Water Use Agricultural Water Use Industrial Water Use Kinds and Sources of Water Pollution Water Use Planning Issues Wastewater Treatment Preserving Scenic Water Areas


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