Water Resources and Water Pollution

1. Water Resources and Water Pollution Chapter 11

2. Section 11-1 WILL WE HAVE ENOUGH USABLE WATER?

3. Freshwater is an irreplaceable resource that we are managing poorly • Freshwater is relatively pure and contains few dissolved salts. • Earth has a precious layer of water—most of it saltwater—covering about 71% of the earth’s surface. • Water is an irreplaceable chemical with unique properties that keep us and other forms of life alive. A person could survive for several weeks without food, but for only a few days without water.

4. The world’s major river basins differ in their degree of freshwater-scarcity stress

5. Section 11-2 HOW CAN WE INCREASE WATER SUPPLIES?

6. Withdrawing groundwater has advantages and disadvantages

7. Irrigation in Saudi Arabia between 1986 (left) and 2004 (right)

8. Groundwater overdrafts in the United States

9. Solutions for groundwater depletion

10. Large dams and reservoirs have advantages and disadvantages

11. Provides irrigation water above and below dam Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Deprives downstream cropland and estuaries of nutrient-rich silt Reservoir useful for recreation and fishing Risk of failure and devastating downstream flooding Can produce cheap electricity (hydropower) Reduces down-stream flooding of cities and farms Disrupts migration and spawning of some fish Fig. 11-12a, p. 247

12. Since 1905, the amount of water flowing to the mouth of the Colorado River has dropped dramatically

13. Section 11-3 HOW CAN WE USE FRESHWATER WATER MORE SUSTAINABLY?

14. Reducing freshwater waste has many benefits • An estimated 66% of the freshwater used in the world is unnecessarily wasted. • In the United States—the world’s largest user of water—about half of the water drawn from surface and groundwater supplies is wasted. • It is economically and technically feasible to reduce such water losses to 15%, thereby meeting most of the world’s water needs for the foreseeable future.

15. Ways to reduce freshwater waste in irrigation

16. We can cut freshwater waste in industry and homes

17. We need to use water more sustainably • Each of us can help bring about such a “blue revolution”by using and wasting less water to reduce our water footprints.

18. We need to use water more sustainably

19. Section 11-4 HOW CAN WE REDUCE THE THREAT OF FLOODING?

20. A hillside before and after deforestation

21. Tree plantation Diverse ecological habitat Evapotranspiration decreases Evapotranspiration Roads destabilize hillsides Trees reduce soil erosion from heavy rain and wind Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land Agricultural land is flooded and silted up Gullies and landslides Tree roots stabilize soil Heavy rain erodes topsoil Vegetation releases water slowly and reduces flooding Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding Forested Hillside After Deforestation Stepped Art Fig. 11-20, p. 254

22. Ways to reduce flood risk

23. Section 11-5 HOW CAN WE DEAL WITH WATER POLLUTION?

24. Water pollution comes from point and nonpoint sources • Water pollution is any change in water quality that harms humans or other living organisms or makes water unsuitable for human uses such as drinking, irrigation, and recreation. • Point sources discharge pollutants at specific locations through drain pipes, ditches, or sewer lines into bodies of surface water. • Because point sources are located at specific places, they are fairly easy to identify, monitor, and regulate.

25. Water pollution comes from point and nonpoint sources • Nonpoint sourcesare broad, diffuse areas, rather than points, from which pollutants enter bodies of surface water or air. • Difficult and expensive to identify and control discharges from many diffuse sources. • Agricultural activities are the leading cause of water pollution, including sediment from erosion, fertilizers and pesticides, bacteria from livestock and food-processing wastes, and excess salts from soils of irrigated cropland.

26. Major Water Pollutants and Their Sources

27. The oxygen sag curve (blue) and demand curve (red)

28. Point source Normal clean water organisms (Trout, perch, bass, mayfly, stonefly) Pollution- tolerant fishes (carp, gar) Fish absent, fungi, sludge worms, bacteria (anaerobic) Pollution- tolerant fishes (carp, gar) Normal clean water organisms (Trout, perch, bass, mayfly, stonefly) 8 ppm Types of organisms 8 ppm Dissolved oxygen (ppm) Biochemical oxygen demand Clean Zone Recovery Zone Septic Zone Decomposition Zone Clean Zone Fig. 11-23, p. 258

29. Too little mixing and low water flow make lakes vulnerable to water pollution • Lakes and reservoirs are generally less effective at diluting pollutants than streams. • Deep lakes and reservoirs often contain stratified layers that undergo little vertical mixing. • Little or no flow. • Lakes and reservoirs are more vulnerable than streams to contamination by runoff or discharge of plant nutrients, oil, pesticides, and nondegradable toxic substances such as lead, mercury, and arsenic.

30. Severe cultural eutrophication has covered this lake in China with algae

31. Groundwater cannot cleanse itself very well • Groundwater pollution is a serious threat to human health. • Common pollutants such as fertilizers, pesticides, gasoline, and organic solvents can seep into groundwater from numerous sources. • When groundwater becomes contaminated, it cannot cleanse itself of degradable wastes as quickly as flowing surface water does.

32. Groundwater cannot cleanse itself very well • Flows so slowly that contaminants are not diluted and dispersed effectively. • Low concentrations of dissolved oxygen and smaller populations of decomposing bacteria. • Usually colder so chemical reactions are slower. • It can take decades to thousands of years for contaminated groundwater to cleanse itself of slowly degradable wastes. • On a human time scale, nondegradable wastes remain in the water permanently.

33. Principal sources of groundwater contamination in the U.S.

34. Polluted air Hazardous waste injection well Pesticides and fertilizers Coal strip mine runoff Deicing road salt Buried gasoline and solvent tanks Cesspool, septic tank Pumping well Gasoline station Water pumping well Waste lagoon Sewer Landfill Leakage from faulty casing Accidental spills Discharge Freshwater aquifer Freshwater aquifer Freshwater aquifer Groundwater flow Fig. 11-26, p. 261

35. Ways to prevent and clean up contamination of groundwater

36. There are many ways to purify drinking water • Most of the more-developed countries have laws establishing drinking water standards. But most of the less-developed countries do not have such laws or, if they do have them, they do not enforce them. • More-developed countries usually store surface water in a reservoir to increasing dissolved oxygen content and allow suspended matter to settle, then pumped water to a purification plant and treat it to meet government drinking water standards.

37. There are many ways to purify drinking water • Very pure groundwater or surface water sources need little treatment. • Protecting a water supply is usually a lot cheaper than building water purification plants. • We have the technology to convert sewer water into pure drinking water. But reclaiming wastewater is expensiveand it faces opposition from citizens and from some health officials who are unaware of the advances in this technology.

38. There are many ways to purify drinking water • Simple measures can be used to purify drinking water: • Exposing a clear plastic bottle filled with contaminated water to intense sunlight can kill infectious microbes in as little as three hours. • The Life Straw is an inexpensive portable water filter that eliminates many viruses and parasites from water drawn into it.

39. Residential areas, factories, and farms all contribute to the pollution of coastal waters

40. Industry Nitrogen oxides from autos and smokestacks, toxic chemicals, and heavy metals in effluents flow into bays and estuaries. Cities Toxic metals and oil from streets and parking lots pollute waters; sewage adds nitrogen and phosphorus. Urban sprawl Bacteria and viruses from sewers and septic tanks contaminate shellfish beds and close beaches; runoff of fertilizer from lawns adds nitrogen and phosphorus. Construction sites Sediments are washed into waterways, choking fish and plants, clouding waters, and blocking sunlight. Farms Runoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus. Red tides Excess nitrogen causes explosive growth of toxic microscopic algae, poisoning fish and marine mammals. Closed shellfish beds Closed beach Oxygen-depleted zone Toxic sediments Chemicals and toxic metals contaminate shellfish beds, kill spawning fish, and accumulate in the tissues of bottom feeders. Oxygen-depleted zone Sedimentation and algae overgrowth reduce sunlight, kill beneficial sea grasses, use up oxygen, cause fish kills, and degrade habitat. Healthy zone Clear, oxygen-rich waters promote growth of plankton and sea grasses, and support fish. Fig. 11-29, p. 264

41. Ocean Pollution from Oil • Crude and refined petroleum reach the ocean from a number of sources and become highly disruptive pollutants. • Visible sources are tanker accidents and blowouts at offshore oil drilling rigs. • The largest source of ocean oil pollution is urban and industrial runoff from land, much of it from leaks in pipelines and oil-handling facilities. At least 37% of the oil reaching the oceans is waste oil, dumped, spilled, or leaked onto the land or into sewers by cities and industries, as well as by people changing their own motor oil.

42. Ocean Pollution from Oil • Scientists estimate that current cleanup methods can recover no more than 15% of the oil from a major spill. • Preventing oil pollution: • Use oil tankers with double hulls. • More stringent safety standards and inspectionscould help to reduce oil well blowouts at sea. • Businesses, institutions, and citizens in coastal areas should prevent leaks and spillage of even the smallest amounts of oil.

43. Primary and secondary sewage treatment systems help to reduce water pollution

44. Primary Secondary Chlorine disinfection tank Bar screen Grit chamber Settling tank Aeration tank Settling tank To river, lake, or ocean Sludge (kills bacteria) Raw sewage from sewers Activated sludge Air pump Sludge digester Disposed of in landfill or ocean or applied to cropland, pasture, or rangeland Sludge drying bed Stepped Art Fig. 11-32, p. 269

45. Ways to help reduce or prevent water pollution

46. Three big ideas • One of the major global environmental problems is the growing shortage of freshwater in many parts of the world. • We can use water more sustainably by cutting water waste, raising water prices, and protecting aquifers, forests and other ecosystems that store and release water. • Reducing water pollution requires preventing it, working with nature to treat sewage, cutting resource use and waste, reducing poverty, and slowing population growth.

47. End of “Short Version” • The slides that follow are those taken out of the “long version” of this same lecture. You should still read the following slides for better understanding, but I will not go over them in class unless you have specific questions.

48. Freshwater is an irreplaceable resource that we are managing poorly • Concerns regarding water include: • Access to freshwater is a global health issue. Every day an average of 3,900 children younger than age 5 die from waterborne infectious diseases. • An economic issue – vital for reducing poverty and producing food and energy. • A women’s and children’s issue in developing countries because poor women and girls often are responsible for finding and carrying daily supplies of water.

49. Freshwater is an irreplaceable resource that we are managing poorly • A national and global security issue because of increasing tensions within and between nations over access to limited water resources that they share. • An environmental issue because excessive withdrawal of water from rivers and aquifers results in dropping water tables, lower river flows, shrinking lakes, and losses of wetlands.

50. Most of the earth’s freshwater is not available to us • About 0.024% is readily available to us as liquid freshwater in accessible groundwater deposits and in lakes, rivers, and streams. • The rest is in the salty oceans, in frozen polar ice caps and glaciers, or in deep underground and inaccessible locations.