Water: Resources and Pollution

1. Water: Resources and Pollution Chapter 10

2. Outline: • Hydrologic Cycle • Water Compartments • Water Availability • Freshwater Shortages • Increasing Water Supplies • Water Management and Conservation • Water Pollution • Water Quality Today • Water Pollution Control • Water Legislation

4. WATER RESOURCES • Hydrologic Cycle • Describes the circulation of water as it: • Evaporates from land, water, and organisms. (Transpires from plants) • Enters the atmosphere. • Condenses and precipitates back to the earth’s surfaces. • Moves underground by infiltration or overland into rivers, lakes and seas.

5. Mean Annual Precipitation

6. Water Distribution

7. MAJOR WATER COMPARTMENTS • Groundwater • Second largest reservoir of fresh water. • Infiltration - Process of water percolating through the soil and into fractures and permeable rocks. • Zone of Aeration - Upper soil layers that hold both air and water. • Zone of Saturation - Lower soil layers where all spaces are filled with water. • Water Table - Top of Zone of Saturation

8. Groundwater

9. Groundwater • Aquifers - Porous layers of sand, gravel, or rock lying below the water table. • Artesian - Pressurized aquifer intersects the surface. (Water flows without pumping) • Recharge Zone - Area where water infiltrates into an aquifer. • Recharge rate is often very slow. • Presently, groundwater is being removed faster than it can be replenished in many areas.

10. MAJOR WATER COMPARTMENTS CONT’D • Rivers and Streams • Precipitation that does not evaporate or infiltrate into the ground runs off the surface, back toward the sea. • Best measure of water volume carried by a river is discharge. • The amount of water that passes a fixed point in a given amount of time. • Usually expressed as cubic feet per second.

11. MAJOR WATER COMPARTMENTS CONT’D • Wetlands • Play a vital role in hydrologic cycle. • Lush plant growth stabilizes soil and retards surface runoff, allowing more aquifer infiltration. • Disturbance reduces natural water-absorbing capacity, resulting in floods and erosion in wet periods, and less water flow the rest of the year.

12. MAJOR WATER COMPARTMENTS CONT’D • The Atmosphere • Among the smallest water reservoirs. • Contains 0.001% of total water supply. • Has most rapid turnover rate. • Provides mechanism for distributing fresh water over landmasses and replenishing terrestrial reservoirs.

13. WATER AVAILABILITY AND USE • Renewable Water Supplies • Made up of surface runoff and infiltration into accessible freshwater aquifers. • Water-Rich ad Water-Poor Countries • Water availability usually measured in terms of renewable water per capita. • Highest per capita generally found in countries with moist climates and low population densities.

14. Water Use • Withdrawal - Total amount of water taken from a source. • Consumption - Fraction of withdrawn water made unavailable for other purposes (Not returned to its source). • Degradation - Change in water quality due to contamination making it unsuitable for desired use.

15. Quantities of Water Used • Water use has been increasing twice as fast as population growth over past century. • Worldwide, agriculture claims about 70% of total water withdrawal. • In many developing countries, agricultural water use is extremely inefficient and highly consumptive. • Worldwide, industry accounts for about 25% of all water use. • Cooling water for power plants is single largest industrial use.

16. Water Withdrawal

17. FRESHWATER SHORTAGES • Estimated 1.5 billion people lack access to an adequate supply of drinking water. • 3 billion lack acceptable sanitation. • A country where consumption exceeds more than 20% of available, renewable supply is considered vulnerable to water stress. • Globally, water supplies are abundant, but, along with capital resources, are unevenly distributed.

18. A Precious Resource • Currently, 45 countries, most in Africa or Middle East, cannot meet the minimum essential water requirements of their citizens. • More than two-thirds of world’s households retrieve water from outside the home. • Availability does not automatically equate to affordability. • Sanitation levels decline when water is expensive.

19. Depleting Groundwater • Groundwater is the source of nearly 40% of fresh water in the U.S. • On a local level, withdrawing water faster than it can be replenished leads to a cone of depression in the water table, • On a broader scale, heavy pumping can deplete an aquifer. • Ogallala Aquifer • Mining non-renewable resource.

20. Depleting Groundwater

21. Depleting Groundwater Cont’d • Withdrawing large amounts of groundwater in a small area causes porous formations to collapse, resulting in subsidence. • Sinkholes form when an underground channel or cavern collapses. • Saltwater intrusion can occur along coastlines where overuse of freshwater reservoirs draws the water table low enough to allow saltwater to intrude.

22. INCREASING WATER SUPPLIES • Seeding Clouds • Condensation Nuclei • Towing Icebergs • Cost • Desalination • Most common methods are distillation and reverse osmosis. • Three to four times more expensive than most other sources.

23. INCREASING WATER SUPPLIES CONT’D • Dams, Reservoirs, and Canals - Trap excess water in areas of excess and transfer it to areas of deficit. • Environmental Costs • Upsets natural balance of water systems. • Ecosystem Losses • Loss of wildlife habitat. • Reservoir Size • Water Quality

24. Dams, Reservoirs, and Canals • Displacement of People • Three Gorges Dams in China will force relocation of over a million people. • Evaporation, Leakage, Siltation • Evaporative losses from Lake Mead and Lake Powell on the Colorado River is about 1km3 per year (264 billion gallons). • Dams slow water flow, allowing silt (nutrients) to drop out. • Loss of Free-Flowing Rivers

25. Price Mechanisms and Water Policy • Throughout most of U.S. history, water policies have generally worked against conservation. • Eastern - Riparian Use Rights • Western - Prior Appropriation Rights • In most federal reclamation projects, customers have been charged only for the immediate costs of water delivery.

26. WATER MANAGEMENT AND CONSERVATION • Watershed Management • Watershed - All the land drained by a stream or river. • Retaining vegetation and ground cover helps retard rainwater and lessens downstream flooding. • Additionally, retaining crop residue on fields reduces flooding and minimizing plowing and forest cutting on steep slopes protects watersheds.

27. Domestic Conservation • Estimates suggest many societies could save as much as half of current domestic water usage without great sacrifice or serious change in lifestyle. • Largest domestic use is toilet flushing. • Small volume of waste in large volume of water. • Significant amounts of water can be reclaimed and recycled. • Purified sewage effluent

28. Discharge of untreated municipal sewage (nitrates and phosphates) Nitrogen compounds produced by cars and factories Natural runoff (nitrates and phosphates Discharge of detergents ( phosphates) Manure runoff From feedlots (nitrates and Phosphates, ammonia) Discharge of treated municipal sewage (primary and secondary treatment: nitrates and phosphates) Runoff from streets, lawns, and construction lots (nitrates and phosphates) Lake ecosystem nutrient overload and breakdown of chemical cycling Runoff and erosion (from from cultivation, mining, construction, and poor land use) Dissolving of nitrogen oxides (from internal combustion engines and furnaces) Pollution of Water Bodies • Eutrophication- the excessive growth of algae in rivers and streams and oceans due to the presence of large amounts of ammonia & phosphorous in streams/rivers • (example: brown tides on long island) • Slow turnover of water • Thermal Pollution (e.g. Con Edison) Fig. 19.5, p. 482

29. WATER POLLUTION • Any physical, biological, or chemical change in water quality that adversely affects living organisms can be considered pollution. • Point Sources - Discharge pollution from specific locations. • Factories, power plants, oil wells • Non-Point Sources - Scattered or diffuse, having no specific location of discharge. • Agricultural fields, feedlots, golf courses • Atmospheric Deposition

30. Infectious Agents • Main source of waterborne pathogens is untreated and improperly treated human waste. • Animal wastes from feedlots and fields is also an important source of pathogens. • In developed countries, sewage treatment plants and pollution-control devices have greatly reduced pathogens. • Coliform bacteria - Intestinal bacteria. • Escherichia coli (E. coli)

31. Oxygen-Demanding Wastes • Water with an oxygen content > 6 ppm will support desirable aquatic life. • Water with < 2 ppm oxygen will support mainly detritivores and decomposers. • Oxygen is added to water by diffusion from wind and waves, and by photosynthesis from green plants, algae, and cyanobacteria. • Oxygen is removed from water by respiration and oxygen-consuming processes.

32. Oxygen-Demanding Wastes Cont’d • Biochemical Oxygen Demand - Amount of dissolved oxygen consumed by aquatic microorganisms. • Dissolved Oxygen Content - Measure of dissolved oxygen in the water. • Effects of oxygen-demanding wastes on rivers depend on volume, flow, and temperature of river water. • Oxygen Sag - Oxygen levels decline downstream from a pollution source as decomposers metabolize waste materials.

33. Oxygen Sag

34. Plant Nutrients and Cultural Eutrophication • Oligotrophic - Bodies of water that have clear water and low biological productivity. • Eutrophic - Bodies of water that are rich in organisms and organic material. • Eutrophication - Process of increasing nutrient levels and biological productivity. • Cultural Eutrophication - Increase in biological productivity and ecosystem succession caused by human activities.

35. Toxic Tides • Excessive nutrients support blooms of deadly aquatic microorganisms in polluted waters. • Increasingly common where nutrients and wastes wash down rivers. • Pfiesteria piscicida is a poisonous dinoflagellate recognized as killer of fish and shellfish in polluted rivers and estuaries.

36. Hidden along the Caribbean coast is one of the most spectacular Bioluminescent Bays in the world. The mysterious blue-green light is created by micro-organisms which thrive in an environment uniquely suited to their needs. A trip into the bay on a balmy night is a magical experience. Fish flash by in dark water

37. Inorganic Pollutants • Metals • Many metals such as mercury, lead, cadmium, and nickel are highly toxic. • Highly persistent and tend to bioaccumulate in food chains. • Mercury released from incinerators and coal-burning power plants is the most widespread toxic metal contamination in North America. • Mine drainage and leaching are serious sources of environmental contamination.

38. Inorganic Pollutants Cont’d • Nonmetallic Salts • Many salts that are non-toxic at low concentrations can be mobilized by irrigation and concentrated by evaporation, reaching levels toxic to plants and animals. • Leaching of road salts has had detrimental effect on many ecosystems. • Acids and Bases • Often released as by-products of industrial processes.

39. Organic Chemicals • Thousands of natural and synthetic organic chemicals are used to make pesticides, plastics, pharmaceuticals, pigments, etc. • Two most important sources of toxic organic chemicals in water are: • Improper disposal of industrial and household wastes. • Runoff of pesticides from high-use areas. • Fields, roadsides, private lawns

40. Sediment • Human activities have accelerated erosion rates in many areas. • Cropland erosion contributes about 25 billion metric tons of suspended solids to world surfaces each year. • Sediment can either be beneficial (nourish floodplains) or harmful (smother aquatic life).

41. Thermal Pollution • Raising or lowering water temperatures from normal levels can adversely affect water quality and aquatic life. • Oxygen solubility in water decreases as temperatures increase. • Species requiring high oxygen levels are adversely affected by warming water. • Industrial cooling often use heat-exchangers to extract excess heat, and discharge heated water back into original source. • Thermal Plume • Produce artificial environments which attract many forms of wildlife.

42. WATER QUALITY TODAY • Areas of Progress • Clean Water Act (1972) established a National Pollution Discharge Elimination System, which requires a permit for any entity dumping wastes in surface waters. • In 2003, EPA reported 91% of all monitored river miles and 88% of all accessed lake acres are suitable for their designated uses. • Most progress due to municipal sewage treatment facilities.

43. Water Quality Today

44. Watershed Approaches • In 1998, EPA switched regulatory approaches. Rather than issue standards on a site by site approach, the focus is now on watershed-level monitoring and protection. • States are required to identify waters not meeting water quality goals and develop total maximum daily loads (TMDL) for each pollutant and each listed water body.

45. Remaining Problems • Greatest impediments to achieving national goals in water quality are sediment, nutrients, and pathogens, especially from non-point discharges. • About three-quarters of water pollution in the U.S. comes from soil erosion, air pollution fallout, and agricultural and urban runoff. • Single cow produces 30 kg manure/day. • Some feedlots have 100,000 animals.

46. Problems and Progress in Other Countries • Sewage treatment in wealthier countries of Europe generally equal or surpass the U.S. • In Russia, only about half of the tap water supply is safe to drink. • In urban areas of South America, Africa, and Asia, 95% of all sewage is discharged untreated into rivers. • Two-thirds of India’s surface waters are contaminated sufficiently to be considered dangerous to human health.

47. Groundwater Pollution • About half the U.S. population, and 95% of rural residents, depend on underground aquifers for drinking water. • For decades, groundwater was assumed impervious to pollution and was considered the gold standard for water quality. • Estimated 1.5 million Americans fall ill from fecal contamination annually. • Cryptosporidium outbreaks

48. Groundwater and Drinking Water • EPA estimates 4.5 trillion liters of contaminated water seep into the ground in the U.S. every day. • MTBE - Gasoline additive, and suspected carcinogen, is present in many urban aquifers. • In agricultural areas, fertilizers and pesticides commonly contaminate aquifers and wells.

49. Groundwater Pollution

50. Ocean Pollution • Estimated 6 million metric tons of plastic bottles, packaging material, and other litter tossed from ships into the ocean annually. • Few coastlines in the world remain uncontaminated by oil or oil products.