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 Hoover Dam (1931-35) on Colorado River “Water: The Fate of Our Most Precious Resource”, 1999 Marq de Villiers(1940-) (Start, 11/07/2008)

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 : Ar, Ca, Co, Nv, NM, Ut – Overused • Las Vegas, Nevada, is growing rapidly, and needs more water. • The other states had to allow Las Vegas to drill for underground water, even though it threatens the area’s ecology and people Colorado River Delta • Four Civilizations & • Big Cities w/ water (O, R or L) • Nile River • Tigris-Euphrates • Indus • Yellow

4. The Hydrologic Cycle (Water Cycle):Evaporation, Precipitation, Transpiration

5. Freshwater systems • Water seems abundant, but drinkable water is rare • Freshwater: relatively pure, with few dissolved salts (~0.05 %) • Only 2.5% of Earth’s water is fresh • Most freshwater is tied up in glaciers and ice caps (very pure) 1 m3=264 gal 1 km3 =264 G gal =809815 acre-ft 1 acre-ft =1,235m3 1,400 M km335 M km3 0.35 M km3 3,500 km3 370 Egal=(700mi)39.3 Egal=(200 mi)393 Pgal =(45 mi)3920 Ggal (~0.02% mass) =(10 mi)3

6. Chemical Composition of Natural Water Conc. of Ca (in ppm) in Ground water 0 – 20: Soft(Aggressive) 20 – 40: Moderately soft 40 – 60: Slightly hard 60 – 80: Moderately hard 80 –120: Hard >120: Very Hard How to Soften Water? Add Na2CO3 Ca2+(aq), Mg2+(aq) →CaCO3(s) + Mg(OH)2(s)

7. 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

8. A river may shift course • Floodplain: areas nearest to the river’s course that are flooded periodically • Frequent deposition of silt makes floodplain soils fertile • Riparian: riverside areas that are productive and species-rich • Water of rivers and streams hosts diverse ecological communities

9. Wetlands include marshes, swamps, and bogs • Wetlands: systems that combine elements of freshwater and dry land, includes - 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. Wetlands in Botswana, Africa

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

11. Lakes and ponds are ecologically diverse - bodies of open, standing water • Littoral zone: region ringing the edge of a water body • 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 • Benthic zone: extends along the entire bottom of the water body • Home to many invertebrates

12. A typical lake Ocean Photic Pelagic Benthic

13. 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 may leads to hypoxia (ref. p179, The Gulf of Mexico’s Dead Zone)

14. 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 (gigantic ground water storage tank) • 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

15. A typical aquifer Top Layer: Soil Clay, Silt, Sand, (Gravel, Rock) Porocity: allow water to pass & contained Water Permeability Well : 10m limit ← Lower Confining Layer: Clay or Bed Rock

16. There are two categories of aquifers • Unconfined aquifer: no upper layer to confine it • Readily recharged by surface water • Confined or artesian aquifer : water-bearing, porous rocks are trapped between layers of less permeable substrate (i.e., clay) • Is under a lot of pressure • Groundwater becomes surface water through springs or human-drilled wells • Groundwater may be ancient: the average age is 1,400 years

17. The Ogallala Aquifer • The world’s largest known aquifer ~ 3 G acre-feet 1 E gal (1018 gal) 3,700 km3 (881 mi3) - Underlies the Great Plains of the U.S. • Its water has allowed farmers to create the most bountiful grain-producing region in the world * 1 acre-feet = 326,000 gal =1,235m3,

18. 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

19. Water is distributed unevenly in time, too • Monsoon seasons bring concentrated storms • Half a region’s annual rain may fall in a few hours • People erect dams to store water

20. How we use water • We have achieved impressive engineering accomplishments to harness freshwater sources • 60 % of the world’s largest 227 rivers have been strongly or moderately affected • Dams, canals, and diversions • Consumption of water in most of the world is unsustainable • We are depleting many sources of surface water and groundwater

21. 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 Pop. Den.(/km3) US: 36 India: 336 Lithuania: 54

22. Different types of water use • Consumptive use: water is removed from an aquifer or surface water body, and is not returned • Non-consumptive use: does not remove, or only temporarily removes, water from an aquifer or surface water • Electricity generation at hydroelectric dams

23. 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

24. A typical dam

25. 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

26. Drawbacks of the Three Gorges Dam • Cost $25 billion to build • Is flooding 22 cities and the homes of 1.13 million people • Submerging 10,000-year-old archaeological sites • Drowning farmland and wildlife habitat • Tidal marshes at the Yangtze’s mouth are eroding • Pollutants will be trapped • China will spend $5 billion to build sewage treatment plants

27. Benefits: Power generation Emission reduction Crop irrigation Drinking water Flood control Shipping New recreational opportunities Drawbacks: Habitat alteration Fisheries declines Population displacement Sediment capture Risk of failure Lost recreational opportunities Benefits and drawbacks of dams

28. Dikes and levees are meant to control floods • Flooding is a normal, natural process • Floodwaters spread nutrient-rich sediments over large areas • Floods also do tremendous damage to property • Dikes and levees (long, raised mounds of earth) along the banks of rivers hold rising waters in channels • The U.S. Army Corps of Engineers has constructed thousands of miles of levees • Levees can make floods worse by forcing water to stay in channels and overflow

29. 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 ~12 tributaries ~15 Reservoirs ~10 Diversions

30. 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

31. 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

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

33. 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

34. Areas where water use exceeds supply

35. We are depleting groundwater • Groundwater is easily depleted • Aquifers recharge slowly • 1/3 of world population relies on groundwater • As aquifers become depleted • Water tables drop • Salt water intrudes in coastal areas • Sinkholes: areas where ground gives way unexpectedly • Some cities (Venice, Mexico City) are slowly sinking • Wetlands dry up

36. How to solve Freshwater Depletion Solutions can address supply or demand • We can either increase supply or reduce demand • Lowering demand - Causes less ecological and social damage • Politically difficult in the short term • Offers better economic returns • Increasing supply • Water can be transported through pipes and aqueducts

37. Solutions to Freshwater Shortage: Increase SupplyHow to make fresh or drinking water from sea 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 semi-permeable membranes to filter out salts • Freezing: Icebergs • Desalinization facilities operate mostly in the arid Middle East • It is expensive, requires fossil fuels, and produces concentrated salty water (End, 11/07/2008; Start, 11/11/2008)

38. The world’s largest reverse osmosis plant • Opened in 1992 Near Yuma, Arizona in order to reduce the salinity of irrigation runoff Too expensive to operate and closed after 8 months • In 2007, Being revaluated

39. How to cut down Fresh water demand 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, (ref. Fig.10.20, p283) • Xeriscaping: landscaping using plants adapted to arid conditions Boulder City, Nevada

40. Industrial demand can be reduced • Shift to processes that use less water • Wastewater recycling • Recharging aquifers with excess surface water runoff • Patching leaky pipes • Auditing industries • Promoting conservation/education

41. 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”

42. 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 - Reduce fertilizer application • Phosphate-free detergents • Planting vegetation to increase nutrient uptake • Treat wastewater

43. Detergents (Laundry) • Surfactants: Soap molecules • Builders: Na3PO4 (to soften water) → Zeolites • Others:Bleaching agents, Enzymes, Perfumes, etc.

44. Eutrophication is a natural process, but… • Human activities dramatically increase the rate at which it occurs • Excess nutrient content • → algal bloom • Low nutrient content

45. Enters water supply via inadequately treated human waste and animal waste via feedlots Causes more human health problems than any other type of water pollution Fecal coliform bacteria indicate fecal contamination of water The water can hold other pathogens, such as, typhoid, hepatitis A, giardiasis *Giardiasis — popularly known as beaver fever or backpacker's diarrhea — is a disease caused by the flagellate protozoan Giardia lamblia Pathogens and waterborne diseases

46. Pathogens cause massive human health problems • Currently, 1.1 billion people are without safe drinking water - 5 million people die per year • 2.4 billion have no sewer or sanitary facilities • Mostly rural Africans and Asians • Solutions: • Treat sewage • Disinfect drinking water (Chlorination) late 1800s and early 1900s, Cl2, NaOCl eliminated typhoid, cholera • Public education to encourage personal hygiene • Government enforcement of regulations

47. Toxic chemicals • From natural and synthetic sources • Pesticides, petroleum products, synthetic chemicals • Arsenic, lead, mercury, acid rain, acid drainage from mines • Effects include: poisoning animals and plants, altering aquatic ecosystems, and affecting human health • Solutions: • Legislating and enforcing more stringent regulations of industry • Modify industrial processes for improvement • Modify our purchasing decisions

48. Thermal pollution • Warmer water holds less oxygen • Dissolved oxygen decreases as temperature increases → Hypoxia • Industrial cooling heats water • Water that is too cold causes problems • Water at the bottom of reservoirs is colder • When water is released, downstream water temperatures drop suddenly and may kill aquatic organisms Cf. Fished in a small pond in hot summer day

49. 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

50. Freshwater pollution sources