4. We Are Misusing Our Freshwater Earth’s surface is 71% saltwater Water is necessary for life, food, and shelter Global Health Issue – lack of water is single largest cause of illness Economic Issue – vital for reducing poverty and producing food and energy Environmental Issue – many environmental indicators related to water are worsening

5. Availability of Freshwater Only.024% of Earth’s water is readily available Hydrologic cycle recycles Earth’s freshwater Groundwater – collected water underground Aquifers – underground caverns of rock through which water flows Surface water – lakes, rivers, streams, etc. Reliable surface runoff – the amount of surface runoff that we can generally count on as a source of freshwater We are using a large and growing portion of the world’s reliable surface runoff

6. Water Cycle

7. Water Shortage Drought – prolonged period in which precipitation is at least 70% lower and evaporation is higher than normal Water shortages are growing By 2025, 3 billion people could lack access to safe water 30% of Earth’s land experiences severe drought Who should own and manage freshwater resources?

9. Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigation Available year-round Exists almost everywhere Renewable if not overpumped or contaminated No evaporation losses Cheaper Aquifer Depletion Sinking of land – subsidence Polluted aquifers Saltwater intrusion near coast Reduced water flows into surface waters Increased cost and contamination

10. Aquifer Depletion

12. Large Dams and Reservoirs Dam – structure built across a river to control the river’s water flow Reservoir – created behind dam Increase reliable runoff Generate electricity Areas must be flooded to build the dam Reservoirs can lose water due to evaporation

13. Dams

15. California Water Project Divert water from North to arid South Major issue in CA Analysts  improve irrigation efficiency

16. Case Study: The Shrinking of the Aral Sea 1960  Soviet Union creates large irrigation system Salt desert left behind Himalayas melting Locals becoming ill Hope for future

17. China’s Water Transfer Project Water arid North Benefits outweigh risks & costs Unfortunate ending for China?

19. Desalination Distillation Evaporate water & condense it Requires lot of energy Reverse Osmosis (Microfiltration) Pressure pushes water through filter Expensive

21. Irrigation Three types of Irrigation: Gravity Flow  60% efficiency; 80% w/ surge valve Center Pivot  80% efficiency; 90-95% w/ LEPA sprinkler Drip Irrigation  90-95% efficiency

22. Flood Irrigation Center Pivot Irrigation Drip Irrigation

23. Domestic Water Use

24. Solutions for Sustainable Water Use at Home and in Industry

26. Floodplains Flat land surrounding streams/rivers with potential for flooding Humans have major impact on frequency & damage of flooding We can reverse the current trend

27. Case Study: Flooding in Bangladesh Many people on small amount of land Flat terrain at sea level Annual monsoon flooding; 1 major every 50 yrs. Due to human hand, major flood every 4 yrs. Global warming a problem for future

29. Hoover Dam Border of Arizona and Nevada – Colorado River Opened in 1936 726 feet high Reservoir – Lake Mead – 167,800 sq miles Generates 4.2 billion KWh annually Provides power to Nevada, Arizona, and Southern California

30. Environmental Impact Decline of estuary at Colorado River Delta Eliminated natural flooding of Colorado River – causing extinctions Decreasing water levels due to evaporation