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Chapter 0 introduction to water resources.ppt

  1. 1. Chapter 0 Introduction to Water Resources Prof. Dr. Ali El-Naqa Hashemite University June 2013
  2. 2. The blue Planet – How come we lack of sufficient Water Supply?  2 ??? Source: [Accessed: 30.01.2012] Source: content/uploads/2010/04/eath-hands.jpg [Accessed: 30.01.2012]
  3. 3. What is Water Used For?  3 Agricultural •Irrigation •Livestock farming Industrial •Production of goods and energy •Transportation of goods •Process water Domestic • Drinking water • Food preparation • Sanitation • Personal hygiene • Cultural asset • Gardening, Car wash ECOSYSTEMHUMANUSE Plants Animals Photosynthesis SoilsAquatic Systems
  4. 4. Think in Cycles rather than in linear Processes  4 he Global Water Cycle • The energy of the sun constantly transforms the water from solid (ice) to liquid (water) to gaseous (vapour) • Constant transformation puts the water into motion and hence activates the global water cycle • Characteristics of the cycle:  Permanent circulation  Renewable resourceSource: OWENS (2006)
  5. 5. The blue Planet?  70% of the earth’s surface is covered by water. (PIDWIRNY 2006)  2.5% is freshwater whereas a fifth is easily accessible for human use. (INFORESOURCES FOCUS 2006)    only 0.5% of global water resources are usable  5 3. Freshwater Resources Source: WBCSD (2009)
  6. 6. Disparities Distribution of freshwater resources is characterized by  strong regional differences  annual and seasonal variation (WWAP 2003) Water Scarcity Index 6 Freshwater Distribution Source: REKACEWICZ (2009)
  7. 7. We do influence the hydrological Cycle substantially Main drivers for the increasing pressure on water resources:  Population growth  Increasing living standards  Urbanisation Influences On the Water Cycle in Cities 7 Human Influence on the Water Cycle Source: AUCKLAND CITY COUNCIL (2010)
  8. 8. Where the Water ends up being used The consumption pattern of water use is influenced by:  Living standards  Climate conditions Composition of water use in different countries 8 Source: WBCSD (2009)
  9. 9. Increasing Water Scarcity  9 Consequences of Water Use Drivers: • Population growth • Change in living standards • Uncontrolled pollution • Climate change Growing water scarcity in various regions of the world As of today, 1.2 billion of the world’s population are affected by water scarcity (INFORESOURCES FOCUS 2006) (WBCSD 2009)
  10. 10. What are drylands?  Different people define drylands in different ways.  In terms of the absolute amount of rainfall. For example, the Convention to Combat Desertification defines drylands as areas with between 0 and 600 mm of rainfall per year, depending on altitude and latitude.  In terms of the length of the wet season and the temperature. For example, areas with less that three months of enough moisture to support plant growth, and with an average temperature of at least 80° Fahrenheit (27°C).  By comparing the annual rainfall with the amount of ‘potential evapotranspiration’ (roughly, the amount of water that evaporates from a pond or a well-irrigated field in one year). One definition is those areas wherethe rainfall is less than 40% of the potential evapotranspiration.
  11. 11. What are drylands?  In terms of vegetation. Drylands are areas where conditions favour perennial grasses rather than annual cereals. Rainfed cropping therefore has an inherent risk of failure.  In terms of land use. Some farming systems are more sensitive to drought than others: for example, cattle in wetter areas may not eat dry grass during a drought.  Pastoralists may regard grazing areas as drylands, in contrast to the wetter areas, usually highlands, where crops are grown.
  12. 12. What are drylands?  The definition of dryland varies from country to country. For example, most of Uganda has relatively high rainfall. If the maize crops fail once in five years, people regard the area as dryland.  Such a definition is of little use in countries such as lowland Kenya or Ethiopia, where rainfall levels are generally much lower. Some 80% of Kenya is classified as dryland.  Some areas normally regarded as wet may in fact be dryland. For example, not all the East African highlands are wet. Certain areas on the shores of Lake Victoria lie in a rain shadow and receive only 600 mm of rain a year.  There is no firm boundary between dryland and wetter areas. One grades into the other, and the boundary changes from year to year. Prolonged drought, unseasonal rains and other climate changes may mean the area expands or contracts.
  13. 13. Categories of drylands  Drylands are not homogeneous: different categories exist. Understanding this is important to identify whether opportunities exist to change or develop the dominant pastoral production system.  Two broad types of dryland can be distinguished: arid and semi-arid; and subhumid, wetter drylands. The dividing line is often put at 600 mm of rain per year
  14. 14. Arid and semi-arid drylands  In these areas rainfall is the limiting factor for the condition of the vegetation. The number of cattle grazing has no lasting negative effect on the vegetation.  Overgrazing is not a problem. Droughts, when they occur, cause the cattle to die, keeping numbers down. The vegetation is very resilient; even after a serious drought, it is able to restore itself.  The concept of ‘carrying capacity’ does not apply. In these areas, pastoralists and their livestock dominate. It is not advisable to replace the pastoral production system as it already uses all available resources to a maximum.
  15. 15. Wetter drylands  In these areas the condition of the vegetation depends on the number of cattle. Overgrazing may occur when their numbers exceed the so-called carrying capacity.  This damages the vegetation, which is not able to regrow after a serious drought. Despite the high risks, the wetter drylands are increasingly used to grow crops.  It may be possible to develop new land-use systems that combine various uses. The aim should be to develop a system that is more productive than the pastoral system it replaces.
  16. 16. Characteristics of drylands  Natural capital  Rainfall The rainfall is low, erratic and scattered, and is concentrated in a few heavy storms. The rains may be delayed, and droughts are frequent. Rains may occur at times when they do not benefit crops in the field.  Soils The soils are thin and easily eroded. They are low in organic matter (less than 2%) and dry out quickly. Some soil types occur only in dryland areas. Within the drylands there are scattered patches with better soils or a wetter climate.  Vegetation The vegetation is sparse, leaving a large proportion of the soil surface exposed. This allows rain to compact the surface, forming a crust which stops water from seeping into the soil. The water runs off instead, causing erosion and flash floods.
  17. 17. Characteristics of drylands  Physical capital  Infrastructure There are few roads, and permanent settlements are sparse. Markets, abattoirs and food storage and transport facilities are poorly developed. Irrigation from groundwater or dams has converted some otherwise dry areas to more productive cropland – while preventing pastoralists from grazing their animals on this land.  Farming systems The major dryland crops are sorghum, pearl millet, finger millet, short-season maize, cowpeas and haricot beans. In wetter areas or land with irrigation, farmers also grow cassava and pigeonpeas for local consumption, and beans and Asian vegetables for export. Livestock herders keep cattle, sheep, goats, camels and donkeys; sedentary farmers may also keep chickens. Camels, goats and donkeys are hardier than cattle and sheep.
  18. 18. Characteristics of drylands  Human capital  Indigenous knowledge Pastoralists have a rich store of indigenous knowledge about their environment and animals, how to predict drought, where to find pastures and water, and how to prevent and treat livestock diseases. Indigenous sedentary farmers have equivalent knowledge about their crops and soils. However, new settlers may not be as familiar with the problems and opportunities in the drylands.  Education Most people in the drylands are poorly educated. Illiteracy rates are high, especially among women. Children often attend boarding schools in the towns, and may be reluctant to return to their original lifestyles after graduating. Dropout rates are high.
  19. 19. Characteristics of drylands  Social capital  Lifestyles The majority of people depend directly on the land. There are two broad groups: nomadic or semi-nomadic pastoralists, and sedentary farmers who grow crops. Pastoralists and sedentary farmers may belong to different ethnic groups, each with its own culture. However, pastoralists and crop farmers are not necessarily distinct: ‘agropastoralists’ may also grow crops in addition to keeping livestock, and crop farmers also keep livestock and may move with them if required.  Mobility Pastoralists, in particular, are highly mobile. They move with their  herds in search of grazing and water. They take advantage of the scattered rainfall in a way that no other production system does. They pay little attention to government, and often cross district and international boundaries.
  20. 20. Characteristics of drylands  Financial capital  Poverty The vast majority of both pastoralists and sedentary farmers are poor. They have limited cash. Pastoralists tend to have more capital (in the form of animals) than do sedentary farmers. A few people are wealthier: they own larger herds or more (or more fertile) land.  Income sources Pastoralists are commercially oriented: they sell animals in order to buy food (grains, sugar, tea) and things they cannot make themselves (cooking utensils, clothes), to pay school, veterinary and medical fees, and to buyfood in an emergency. However, pastoralists often lack a market for their animals. Crop farmers are more subsistence-oriented: they grow most of their own food. Many men seek employment in the cities for at least part of the year.
  21. 21. Characteristics of drylands  Changes in the drylands  Population The human population is rising, both by natural increase and by immigration from more densely populated high-potential areas. This puts extra pressure on the limited resources. Intensive cultivation degrades the soils, and overgrazing depletes the ground cover.  Climate In recent years, the climate has been in a state of flux. Droughts have become more frequent, and rains fall at unusual times of the year. These changes may be caused by global warming.  Land use and ownership Settlers erect fences and encroach on traditional grazing lands. Irrigation schemes are built in areas with better soils, which are often the same areas used by pastoralists as dry-season grazing. Common land is increasingly claimed as private property, encouraging a change from pastoralism to crop farming, and removing the best land from the pastoralists. Powerful, city based individuals have grabbed large tracts of land
  22. 22. Water  Water is the principal limiting factor. The low, unreliable rainfall means that often very little moisture is available for plant growth. The rains may start on time but then stop again, killing seedlings.  Or the rains may be late, making the season too short for sustainable growth during the crucial phase of flowering. Recurrent droughts cause frequent crop failures. Farmers respond by using various ways to conserve rainfall and store it in the root zone.
  23. 23. Soil and water conservation  A significant percentage of rainwater in dryland areas is lost as surface runoff. Much of the rest evaporates or percolates deep into the ground where plant roots cannot reach it. Plants quickly absorb the little moisture still in the soil, and soon the ground becomes dry, incapable of supporting crops.  Erosion is a related problem.Dryland soils are often thin, have poor soil structure, are low in organic matter and are bare of vegetation. Crusts form on the surface of many soils, reducing the amount of water that can seep into the soil. The water runs off easily, forming gullies and carrying valuable topsoil with it.
  24. 24. Soil and water conservation
  25. 25. Soil and water conservation  Crop farmers cannot afford to lose the little moisture and soil there is, so they have for centuries used indigenous conservation techniques. These range from stone terraces in mountainous areas to tillage practices in flat areas. They focus on conserving moisture to improve crop yields. However, the main priority (from the farmers’ viewpoint) is higher production, with soil conservation coming second.  Only crop farmers are willing to invest in conservation measures; pastoralists are not very interested because they are mobile. Degradation of grazing lands is a problem in wetter areas with many people and livestock, and around communal watering points. Degradation is caused by continuous grazing and tracking, shifting cultivation, indiscriminate cutting of trees and uncontrolled burning.
  26. 26. Soil and water problems, and some ways to address them
  27. 27. Irrigation  Rainfall in the drylands is usually not enough to guarantee reliable, steady production of crops. So some kind of irrigation is helpful, either to provide extra water to a rainfed crop, or to water a second crop during the dry season.  If water is available, the dryland climate favours irrigated crops. High temperatures stimulate plant growth. Pests are few due to the low humidity. The extended dry season and the lack of a winter enables growers to produce crops when demand is high in the export market.
  28. 28. Soil and water conservation  For small-scale crop farmers, irrigation may mean the difference between a secure harvest and no yield at all.  There is a wide range of traditional small-scale irrigation practices, mostly along small rivers in mountainous terrain, along riverbeds, using residual moisture in valley bottoms, or tapping shallow groundwater.  Farmers using these practices use very few external inputs and often show a remarkable talent for improvisation when confronted with new situations.  New techniques, such as drip irrigation (page 104) and manually operated treadle pumps, have shown promise on small farms ranging from small gardens (15–30 m2) to over 1.5 ha.  Irrigated areas are generally small, from under 1 ha to 20–40 ha. Most farmers own less than 1 ha of irrigated land. The fields are located as close as possible to the source of water.
  29. 29. Water sources  Irrigated farming is very different from rainfed farming. In rainfed farming, the farmer prepares the field and waits for the rain to come and make the crop flourish. With irrigation, the farmer must obtain and manage the water. This can take a lot of time and money.  The cropping pattern is closely related to the amount of water and how it is obtained. The size of the irrigated area depends on how much water is available.  Small perennial or seasonal rivers are the main sources of irrigation water. Water can be lifted directly from the river, or diverted into irrigation canals or pipes using dams or weirs. Wells can be dug to tap groundwater, which can be lifted up by hand or with pumps. In some places, it is possible to tap water beneath dry stream beds. Rain and runoff water can collected and stored in small reservoirs or tanks
  30. 30. Global Water Resources Only this portion is renewable saline (salt) water: 10 to 100g/L (34g/L) brackish water: 1 to 10g/L (treatable) Fresh water: <1g/L (drinkable)
  31. 31. Global Water Cycle Principal sources of fresh water for human activities (44,800 km3/yr)
  32. 32. Global Water Availability
  33. 33. The Importance of Water  Human / Environmental Health  Dignity / Gender Equity  Economic Growth / Poverty Reduction  Environment and Ecosystem Services  Food Security / Crops and Fisheries  Energy Generation / Flood Control  Conflict Prevention and Mitigation Summary of the World Water Crisis and USG Investments in the Water Sector, USAID, 2010
  34. 34. Global Water Resources Only this portion is renewable saline (salt) water: 10 to 100g/L (34g/L) brackish water: 1 to 10g/L (treatable) Fresh water: <1g/L (drinkable)
  35. 35. Global Water Cycle Principal sources of fresh water for human activities (44,800 km3/yr)
  36. 36. Global Water Availability
  37. 37. The Importance of Water  Human / Environmental Health  Dignity / Gender Equity  Economic Growth / Poverty Reduction  Environment and Ecosystem Services  Food Security / Crops and Fisheries  Energy Generation / Flood Control  Conflict Prevention and Mitigation Summary of the World Water Crisis and USG Investments in the Water Sector, USAID, 2010
  38. 38. Population and Water Use 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 1950 1960 1970 1980 1990 2000 2010 2020 W ithdrawal (km 3/yr) Population (m illion) global freshwater use is ~4000 km3/year ~10% of the renewable supply (44,800km3/year)
  39. 39. Water Cycle Diagram Global Water Security – an engineering perspective The Royal Academy of Engineering, 2010
  40. 40. Global Water Withdrawal
  41. 41. Global Water Withdrawals World Water Assessment Programme. 2009. The United Nations World Water Development Report 3: Water in a Changing World. Paris: UNESCO, and London: Earthscan
  42. 42. Global Water Use
  43. 43. Water Use by Sector World Water Assessment Programme. 2009. The United Nations World Water Development Report 3: Water in a Changing World. Paris: UNESCO, and London: Earthscan
  44. 44. Water Supply and Sanitation  Supply (2002)  1.1 billion people lacked access to improved water sources (17% of global population)  Nearly two thirds live in Asia (733 million people)  42% of Sub-Saharan Africa is without improved water  Sanitation (2002)  2.6 billion people lacked access to improved sanitation (42% of global population)  Over half of those live in China + India (~ 1.5 billion people)  64% of Sub-Saharan Africa without sanitation coverage  69% of rural dwellers in developing countries without access to improved sanitation (27% for urban dwellers)
  45. 45. Access to Safe Water2009: 800 million people lacked access to an “improved” water sources. Summary of the World Water Crisis and USG Investments in the Water Sector, USAID, 2010
  46. 46. Access to Sanitation Summary of the World Water Crisis and USG Investments in the Water Sector, USAID, 2010 2009: more than 2 billion people lacked access to basic sanitation facilities
  47. 47. Water Supply and Sanitation  Diarrhea (2004)  1.8 million people die every year from diarrheal diseases (including cholera)  90% are children under 5 in developing countries  88% of diarrheal disease is attributed to unsafe water supply, inadequate sanitation and hygiene  Improved access to water supply and sanitation can reduce diarrhea morbidity  Water supply: 6% – 25% (108,000 – 450,000 people)  Sanitation: 32% (576,000 people)  Total: 1.026 million
  48. 48. Diarrhea is the Second Leading Cause of Death in Children Worldwide 2008: Nearly 1.8 million children under the age of 5 died from diarrhea. This can be reduced by 30-40%. Summary of the World Water Crisis and USG Investments in the Water Sector, USAID, 2010
  49. 49. Poverty and Development  Two thirds of the 884 million people (2009) without access to safe drinking water live on less than $2 per day.  The urban poor population is large and growing rapidly. Half of urban residents live in slums where the no formal access to water or sanitation is typical.  > 1 billion people live in extreme poverty (< $1 a day)
  50. 50. Poverty in Sub-Saharan Africa World Water Assessment Programme. 2009. The United Nations World Water Development Report 3: Water in a Changing World. Paris: UNESCO, and London: Earthscan
  51. 51. Water, Sanitation & Poverty World Water Assessment Programme. 2009. The United Nations World Water Development Report 3: Water in a Changing World. Paris: UNESCO, and London: Earthscan
  52. 52. Domestic Water Use Survival = 5 L/day  Drinking, cooking, bathing, and sanitation = 50 L  United States = 250 to 300 L  Netherlands = 104 L  Somalia = 9 L * L/c/d = liters per person per day
  53. 53. Water Stress Index Based on human consumption  linked to population growth  Domestic requirement:  About 100 L/c/d = 40 m3/c/yr  Associated agricultural, industrial & energy need:  About 20 x 40 m3/c/yr = 800 m3/c/yr  Total need:  840 m3/c/yr  About 1000 m3/c/yr
  54. 54. Water Stress Index  Water availability below 1,000 m3/c/yr  chronic water related problems impeding development and harming human health  Water sufficiency: >1700 m3/c/yr  Water stress: <1700 m3/c/yr  Water scarcity: <1000 m3/c/yr
  55. 55. Water stress indicator
  56. 56. Water Scarcity (2008) Summary of the World Water Crisis and USG Investments in the Water Sector, USAID, 2010 In 2008, over 1.54 billion people suffered from water stress
  57. 57. Water Scarcity (2030) Summary of the World Water Crisis and USG Investments in the Water Sector, USAID, 2010 By 2030, 3.3 billion people will live “water stress” conditions
  58. 58. Units 1 ft = 0.3048 m  1 m3 = 28.3168x10 -3 ft3  1 m3 = 35.3147 ft3  1 ha = 10,000 m2  1 acre = 43,560 ft2 = 0.4047 ha = 4047 m2  1 gal = 3.785x10 -3 m3 = 3.785 L  1 m3 = 8.11x10-4 af 109 m3 = 8.11x105 af 1 km3 = 0.811 maf  1 m3 = 264 gal 109 m3 = 264x109 gal 1 km3 = 264 bg 1 km3/yr = 0.7234 bgd
  59. 59. Water Availability - USA  USA  Area 9.36 mln km2  Population 304 mln, 2008 Water Resources (bln m3/yr) Water Availability (1000 m3/yr) Trans- boundary Local Total per km2 per capita Minimum 107 2058 2165 231 7 Average 148 2930 3078 329 10 Maximum 178 3864 4042 432 13 From: Shiklomanov]
  60. 60. Water Availability - USA
  61. 61. Water Use - USA
  62. 62. Trends
  63. 63. Trends
  64. 64. 13-1 Will We Have Enough Usable Water?  Concept 13-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.  Concept 13-1B One of every six people does not have sufficient access to clean water, and this situation will almost certainly get worse.
  65. 65. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL  Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle.  Only about 0.02% of the earth’s water supply is available to us as liquid freshwater.
  66. 66. Girl Carrying Well Water over Dried Out Earth during a Severe Drought in India
  67. 67. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL  Comparison of population sizes and shares of the world’s freshwater among the continents.
  68. 68. IMPORTANCE, AVAILABILITY, AND RENEWAL  Some precipitation infiltrates the ground and is stored in soil and rock (groundwater).  Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water.  The land from which the surface water drains into a body of water is called its watershed or drainage basin.
  69. 69. Fig. 13-3, p. 316 Unconfined Aquifer Recharge Area Precipitation Evaporation and transpiration Evaporation Confined Recharge Area Runoff Flowing artesian well Well requiring a pump Stream Infiltration Water table Lake Infiltration Less permeable material such as clay
  70. 70. IMPORTANCE, AVAILABILITY, AND RENEWAL  We currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by 2025.  About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources.  Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).
  71. 71. Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S. Fig 13-4
  72. 72. Fig. 13-5, p. 318 Substantial conflict potential Highly likely conflict potential Unmet rural water needs Moderate conflict potential Washington Oregon Montana North Dakota Idaho South Dakota Wyoming Nevada Nebraska Utah Colorado Kansas California Oklahoma New Mexico Texas Arizona Water Hot Spots
  73. 73. Fig. 13-6, p. 319 Europe Asia North America Africa South America Australia Stress High None
  74. 74. Long-Term Severe Drought Is Increasing  Causes  Extended period of below-normal rainfall  Diminished groundwater  Harmful environmental effects  Dries out soils  Reduces stream flows  Decreases tree growth and biomass  Lowers net primary productivity and crop yields  Shift in biomes
  75. 75. Case Study: Who Should Own and Manage Freshwater Resources  There is controversy over whether water supplies should be owned and managed by governments or by private corporations.  European-based water companies aim to control 70% of the U.S. water supply by buying up water companies and entering into agreements with cities to manage water supplies.
  76. 76. 13-2 Is Extracting Groundwater the Answer?  Concept 13-2 Groundwater that is used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.
  77. 77. Other Effects of Groundwater Overpumping  Groundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater.
  78. 78. Fig. 13-7, p. 321 TRADE-OFFS Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Available year-round Sinking of land (subsidence) from overpumping Exists almost everywhere Aquifers polluted for decades or centuries Renewable if not overpumped or contaminated Saltwater intrusion into drinking water supplies near coastal areas No evaporation losses Reduced water flows into surface waters Cheaper to extract than most surface waters Increased cost and contamination from deeper wells
  79. 79. Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer
  80. 80. Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S. Fig 13-9
  81. 81. Fig. 13-11, p. 324 SOLUTIONS Groundwater Depletion Prevention Control Waste less water Raise price of water to discourage waste Subsidize water conservation Tax water pumped from wells near surface waters Limit number of wells Set and enforce minimum stream flow levels Do not grow water- intensive crops in dry areas Divert surface water in wet years to recharge aquifers
  82. 82. 13-3 Is Building More Dams the Answer?  Concept 13-3 Building dam and reservoir systems has greatly increased water supplies in some areas, but it has disrupted ecosystems and displaced people.
  83. 83. Large Dams and Reservoirs Have Advantages and Disadvantages (1)  Main goals of a dam and reservoir system  Capture and store runoff  Release runoff as needed to control:  Floods  Generate electricity  Supply irrigation water  Recreation (reservoirs)
  84. 84. Large Dams and Reservoirs Have Advantages and Disadvantages (2)  Advantages  Increase the reliable runoff available  Reduce flooding  Grow crops in arid regions
  85. 85. Large Dams and Reservoirs Have Advantages and Disadvantages (3)  Disadvantages  Displaces people  Flooded regions  Impaired ecological services of rivers  Loss of plant and animal species  Fill up with sediment within 50 years
  86. 86. Advantages and Disadvantages of Large Dams and Reservoirs Fig 13-12
  87. 87. Matilija Dam Removal Project Click for report
  88. 88. The Colorado River Basin Fig 13-14
  89. 89. Case Study: The Colorado River Basin— An Overtapped Resource (3)  Four Major problems  Colorado River basin has very dry lands  Modest flow of water for its size  Legal pacts allocated more water for human use than it can supply  Amount of water flowing to the mouth of the river has dropped
  90. 90. Aerial View of Glen Canyon Dam Across the Colorado River and Lake Powell
  91. 91. The Flow of the Colorado River Measured at Its Mouth Has Dropped Sharply
  92. 92. Case Study: China’s Three Gorges Dam (1)  World’s largest hydroelectric dam and reservoir  2 km long across the Yangtze River  Benefits  Electricity-producing potential is huge (18 large power plants)  Holds back the Yangtze River floodwaters  Allows cargo-carrying ships
  93. 93. Case Study: China’s Three Gorges Dam (2)  Harmful effects  Displaces about 5.4 million people  Built over a seismic fault  Significance?  Rotting plant and animal matter producing CH4  Worse than CO2 emissions  Will the Yangtze River become a sewer?
  94. 94. 13-4 Is Transferring Water from One Place to Another the Answer?  Concept 13-4 Transferring water from one place to another has greatly increased water supplies in some areas, but it has also disrupted ecosystems.
  95. 95. Fig. 13-17, p. 330 CALIFORNIA Shasta Lake NEVADA Sacramento River UTAH North Bay Aqueduct Feather River Lake Tahoe San Francisco Sacramento South Bay Aqueduct Hoover Dam and Reservoir (Lake Mead) Los Angeles Aqueduct Colorado River California Aqueduct Colorado River Aqueduct Central Arizona Project ARIZONA Fresno Santa Barbara Los Angeles San Diego Salton Sea Phoenix Tucson MEXICO San Luis Dam and Reservoir Oroville Dam and Reservoir
  96. 96. Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake 1976 2006
  97. 97. Oxnard water suppliers United Water Calleguas Municipal City of Oxnard
  98. 98. 13-5 Is Converting Salty Seawater to Freshwater the Answer?  Concept 13-5 We can convert salty ocean water to freshwater, but the cost is high, and the resulting salty brine must be disposed of without harming aquatic or terrestrial ecosystems.
  99. 99. Removing Salt from Seawater Seems Promising but Is Costly (1)  Desalination  Distillation  Reverse osmosis, microfiltration  15,000 plants in 125 countries  Saudi Arabia: highest number Click for link to Desal Response Group
  100. 100. Removing Salt from Seawater Seems Promising but Is Costly (2)  Problems  High cost and energy footprint  Keeps down algal growth and kills many marine organisms  Large quantity of brine wastes Click for Oxnard’s GREAT RO plant info
  101. 101. 13-6 How Can We Use Water More Sustainably?  Concept 13-6 We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.
  102. 102. Reducing Water Waste Has Many Benefits (1)  Water conservation  Improves irrigation efficiency  Improves collection efficiency  Uses less in homes and businesses
  103. 103. Fig. 13-20, p. 335 Stepped Art Gravity flow (efficiency 60% and 80% with surge valves) Water usually comes from an aqueduct system or a nearby river. Drip irrigation (efficiency 90–95%) Above- or below-ground pipes or tubes deliver water to individual plant roots. Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Water usually pumped from underground and sprayed from mobile boom with sprinklers.
  104. 104. Solutions: Reducing Irrigation Water Waste Fig 13-21
  105. 105. Solutions: Reducing Water Waste Fig 13-22
  106. 106. Fig. 13-23, p. 337 SOLUTIONS Sustainable Water Use Waste less water and subsidize water conservation Preserve water quality Protect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release water Get agreements among regions and countries sharing surface water resources Raise water prices Do not deplete aquifers Slow population growth
  107. 107. How can you save water at home? Click for Family Water Audit
  108. 108. What Can You Do? Water Use and Waste Fig 13-24
  109. 109. 13-7 How Can We Reduce the Threat of Flooding?  Concept 13-7 We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds and by not building in areas subject to frequent flooding.
  110. 110. Some Areas Get Too Much Water from Flooding (1)  Flood plains  Highly productive wetlands  Provide natural flood and erosion control  Maintain high water quality  Recharge groundwater  Benefits of floodplains  Fertile soils  Nearby rivers for use and recreation  Flatlands for urbanization and farming
  111. 111. Some Areas Get Too Much Water from Flooding (2)  Dangers of floodplains and floods  Deadly and destructive  Human activities worsen floods  Failing dams and water diversion  Hurricane Katrina and the Gulf Coast  Removal of coastal wetlands
  112. 112. Natural Capital Degradation: Hillside Before and After Deforestation Fig 13-25
  113. 113. Fig. 13-26, p. 340 SOLUTIONS Reducing Flood Damage Prevention Control Preserve forests on watersheds Straighten and deepen streams (channelization) Preserve and restore wetlands in floodplains Tax development on floodplains Build levees or floodwalls along streams Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry Build dams