This lecture will help you understand:

2. This lecture will help you understand: • Water and the hydrologic cycle • Water’s distribution on Earth • Freshwater ecosystems • Use and alteration of freshwater systems • Problems of water supply and solutions • Problems of water quality and solutions • How wastewater is treated

3. Plumbing the Colorado River • The 2,330 km Colorado River begins in the Rocky Mountains and trickles into the Gulf of California • Dams and irrigation provide water to millions of people in 7 states • Las Vegas, Nevada, is growing rapidly, and needs more water • The other states are allowing Las Vegas to drill for underground water, even though it threatens the area’s ecology and people

4. Freshwater systems • Water may seem abundant, but drinkable water is rare • Freshwater = relatively pure, with few dissolved salts • Only 2.5% of Earth’s water is fresh • Most freshwater is tied up in glaciers and ice caps

5. Rivers and streams wind through landscapes • Water from rain, snowmelt, or springs forms streams, creeks, or brooks • These merge into rivers, and eventually reaches the ocean • Tributary = a smaller river slowing into a larger one • Watershed = the area of land drained by a river and its tributaries

6. Wetlands include marshes, swamps, and bogs • Wetlands = systems that combine elements of freshwater and dry land • Freshwater marshes = shallow water allows plants to grow above the water’s surface • Swamps = shallow water that occurs in forested areas • Can be created by beavers • Bogs = ponds covered in thick floating mats of vegetation • A stage in aquatic succession

7. Wetlands are valuable • Wetlands are extremely valuable for wildlife • They slow runoff • Reduce flooding • Recharge aquifers • Filter pollutants • People have drained wetlands, mostly for agriculture • Southern Canada and the U.S. have lost more than half of their wetlands

8. Lakes and ponds are ecologically diverse • Lakes and ponds are bodies of open, standing water • Littoral zone = region ringing the edge of a water body • Benthic zone = extends along the entire bottom of the water body • Home to many invertebrates • Limnetic zone = open portions of the lake or pond where the sunlight penetrates the shallow waters • Profundal zone = water that sunlight does not reach • Supports fewer animals because there is less oxygen

9. A typical lake

10. Lakes vary in their nutrients and oxygen • Oligotrophic lakes and ponds = have low nutrient and high oxygen conditions • Eutrophic lakes and ponds = have high nutrient and low oxygen conditions • Eventually, water bodies fill completely in through the process of succession • Inland seas = large lakes that hold so much water, their biota is adapted to open water

11. Groundwater plays a key role • Groundwater = any precipitation that does not evaporate, flow into waterways, or get taken up by organisms • Groundwater makes up one fifth of the Earth’s freshwater supply • Aquifers = Porous sponge-like formations of rock, sand, or gravel that hold groundwater • Zone of aeration = pore spaces are partially filled with water • Zone of saturation = spaces are completely filled with water • Water table = boundary between the two zones • Aquifer recharge zone = any area where water infiltrates Earth’s surface and reaches aquifers

12. Water is unequally distributed across Earth’s surface • Different regions possess vastly different amounts of groundwater, surface water, and precipitation • Many areas with high population density are water- poor and face serious water shortages

13. Water supplies houses, agriculture, and industry • Proportions of these three types of use vary dramatically among nations • Arid countries use water for agriculture • Developed countries use water for industry

14. We have erected thousands of dams • Dam = any obstruction placed in a river or stream to block the flow of water so that water can be stored in a reservoir • To prevent floods, provide drinking water, allow irrigation, and generate electricity • 45,000 large dams have been erected in more than 140 nations • Only a few major rivers remain undammed • In remote regions of Canada, Alaska, and Russia

15. A typical dam

16. China’s Three Gorges Dam • The dam, on the Yangtze River, is the largest in the world • 186 m (610 feet) high, 2 km (1.3 mi) wide • Its reservoir stretches for 616 km (385 mi) • Provides flood control, passage for boats, and electricity

17. Benefits: Power generation Crop irrigation Drinking water Flood control Shipping New recreational opportunities Drawbacks: Habitat alteration Fisheries declines Population displacement Disruption of flooding Risk of failure Lost recreational opportunities Benefits and drawbacks of dams

18. We divert – and deplete – surface water People have long diverted water to farm fields, homes, and cities The once mighty Colorado River has been extensively dammed and diverted

19. The Colorado River is heavily diverted • What water is left after all the diversions comprises just a trickle into the Gulf of California • On some days, water does not reach the gulf • Diversion has drastically altered the river’s ecology

20. The Aral Sea Once the fourth-largest lake on Earth It has lost more than 80% of its volume in just 45 years The two rivers leading into the Aral Sea were diverted to irrigate cotton fields Consequences of a shrinking sea 60,000 fishing jobs are gone Pesticide-laden dust from the lake bed is blown into the air The cotton cannot bring back the region’s economy

21. Can the Aral Sea be saved? People may have begun saving the northern part of the Aral Sea

22. Inefficient irrigation wastes water • Today, 70% more water is withdrawn for irrigation than in 1960 • The amount of irrigated land has doubled • Crop yields can double

23. Will we see a future of water wars? • Freshwater depletion leads to shortages, which can lead to conflict • 261 major rivers cross national borders • Water is a key element in hostilities among Israel, Palestinians, and neighboring countries • Many nations have cooperated with neighbors to resolve disputes

24. Desalinization “makes” more water • Desalinization = the removal of salt from seawater or other water of marginal quality • Distilling = hastens evaporation and condenses the vapor • Reverse osmosis = forces water through membranes to filter out salts • Desalinization facilities operate mostly in the arid Middle East • It is expensive, requires fossil fuels, and produces concentrated salty water

25. The world’s largest reverse osmosis plant • Near Yuma, Arizona • Intended to reduce the salinity of irrigation runoff • Too expensive to operate and closed after 8 months

26. Agricultural demand can be reduced • Look first for ways to decrease agricultural demand • Lining irrigation canals • Low-pressure spray irrigation that spray water downward • Drip irrigation systems that target individual plants • Match crops to land and climate • Selective breeding and genetic modification to raise crops that require less water

27. Residential demand can be reduced • Install low-flow faucets, showerheads, washing machines, and toilets • Water lawns at night, when evaporation is minimal • Eat less meat • Xeriscaping = landscaping using plants adapted to arid conditions

28. Industrial demand can be reduced • Shift to processes that use less water • Wastewater recycling • Excess surface water runoff used for recharging aquifers • Patching leaky pipes • Auditing industries • Promoting conservation/education

29. Freshwater pollution and its control • Water for human consumption and other organisms needs to be… • Disease-free • Nontoxic • Half of the world’s major rivers are seriously depleted and polluted • They poison surrounding ecosystems • Threaten the health and livelihood of people • The invisible pollution of groundwater has been called a “covert crisis”

30. Nutrient pollution • Pollution = the release of matter or energy into the environment that causes undesirable impacts on the health and well-being of humans or other organisms • Nutrient pollution from fertilizers, farms, sewage, lawns, golf courses • Leads to eutrophication • Solutions • Phosphate-free detergents • Planting vegetation to increase nutrient uptake • Treat wastewater • Reduce fertilizer application

31. Eutrophication is a natural process, but… • Human activities dramatically increase the rate at which it occurs

32. Point and nonpoint source water pollution • Point source water pollution = discrete locations of pollution • Factory or sewer pipes • Nonpoint source water pollution = pollution from multiple cumulative inputs over a large area • Farms, cities, streets, neighborhoods • The U.S. Clean Water Act • Addressed point sources • Targeted industrial discharge • In the U.S., nonpoint sources have a greater impact on quality • Limit development on watershed land surrounding reservoirs

33. Freshwater pollution sources

34. Indicators of water quality • Scientists measure properties of water to characterize its quality • Biological indicators: presence of fecal coliform bacteria and other disease-causing organisms • Chemical indicators: pH, nutrient concentration, taste, odor, hardness, dissolved oxygen • Physical indicators: turbidity, color, temperature

35. Legislative efforts reduce pollution • Federal Water Pollution Control Act (1972) • Renamed the Clean Water Act in 1977 • Illegal to discharge pollution without a permit • Standards for industrial wastewater • Funded sewage treatment plants • Because of legislation, the situation is much better than it was • Other nations have also reduced pollution

36. We treat our drinking water • Technology has improved our pollution control • The EPA sets standards for more than 80 drinking water contaminants • Local governments and private water suppliers must meet • Before water reaches the user • It is chemically treated, filtered, and disinfected

37. Treating wastewater • Wastewater = water that has been used by people in some way • Sewage, showers, sinks, manufacturing, storm water runoff • Septic systems = the most popular method of wastewater disposal in rural areas • Underground septic tanks separate solids and oils from wastewater • The water drains into a drain field, where microbes decompose the water • Solid waste needs to be periodically pumped and landfilled

38. Municipal sewer systems • In populated areas, sewer systems carry wastewater • Physical, chemical, and biological water treatment • Primary treatment = the physical removal of contaminants in settling tanks (clarifiers) • Secondary treatment = water is stirred and aerated so aerobic bacteria degrade organic pollutants • Water treated with chlorine is piped into rivers or the ocean • Some reclaimed water is used for irrigation, lawns, or industry

39. A typical wastewater treatment facility

40. Conclusion • Obtaining future supplies of freshwater will be an environmental challenge • With expanding population and increasing water usage, we are approaching conditions of widespread scarcity • Water pollution is already harming freshwater around the world • New approaches can help this situation

41. QUESTION: Review The picture shows a(n) … ? a) Estuary b) Wetland c) Oxbow lake d) River delta

42. QUESTION: Review The area of a lake that contains open water that does not receive sunlight is called the _______zone. a) Littoral b) Benthic c) Limnetic d) Profundal

43. QUESTION: Review A confined aquifer is defined as…? • An aquifer that traps porous rocks between layers of less permeable substrate • An aquifer that traps porous rocks under one layer of less permeable substrate • An aquifer with porous rocks resting on bedrock • An aquifer with no upper layer

44. QUESTION: Review Arid countries tend to use their water mostly for…? • Developing industries • Agriculture • Households • Export to rich countries

45. QUESTION: Review Which of the following statements is not a benefit of dams? • Habitat alteration • Power generation • Crop irrigation • Shipping

46. QUESTION: Review Pollution is defined as “the release of matter or energy into the environment that causes ______”? • Undesirable impacts on human health • Undesirable impacts on other organisms • Undesirable impacts on human well-being • All of the above are included in the definition

47. QUESTION: Review Which of the following is a nonpoint source of water pollution? • A factory • Sewer pipes • Agricultural fields • All are nonpoint sources

48. QUESTION: Review Primary treatment of wastewater includes…? • Treating water with chemicals • Stirring and aerating water • Degradation of wastes by bacteria • Physical removal of contaminants

49. QUESTION: Interpreting Graphs and Data • Irrigation has grown more slowly than demand • Irrigation and demand have both increased • Growth of demand and irrigation will slow • The U.S. does not follow this graph What is the relationship between water consumption and the amount of land that is irrigated?

50. QUESTION: Interpreting Graphs and Data a) It is more water efficient to produce vegetables b) It is more water efficient to produce meat c) Vegetable and meat production are relatively alike in water consumption d) There is little correlation between water consumption and our diet Which conclusion can you draw from this graph? From The Science behind the Stories