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Water Resources

Water Resources. Chapter 9. Water, water, everywhere…. Most (97%) of Earth’s water is saltwater Of the 3% that is freshwater, <1% is available for us The rest is frozen or deep underground. Groundwater.

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Water Resources

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  1. Water Resources Chapter 9

  2. Water, water, everywhere… • Most (97%) of Earth’s water is saltwater • Of the 3% that is freshwater, <1% is available for us • The rest is frozen or deep underground

  3. Groundwater • Aquifer – groundwater is located in small spaces within permeable layers of rock and sediment • Unconfinedaquifer– porous rock + soil; water can move in and out freely • Confined aquifer – surrounded by impermeable layers • Springs or artesian wells

  4. Groundwater… • Water table – the uppermost level of water saturation in the soil • Groundwater recharge – water from precipitation that percolates back into the soil

  5. Groundwater… • Pumping water out of the ground faster than it can be recharged will cause a drop in the water table • Wells near the coastline can suffer from saltwater intrusion as the freshwater is infiltrated with ocean water

  6. Surface Water • Streams, rivers, ponds, lakes, wetlands • 3 largest rivers based on volume: • Amazon in South America • Congo in Africa • Yangtze in China • Human settlement and impacts • Transportation • Irrigation • Agriculture

  7. Surface water… • Lakes – surface area versus depth and volume determine size • Classification of lakes: • Oligotrophic • Low nutrient levels = low productivity • Mesotrophic • Moderate productivity • Eutrophic • Highly productive

  8. Surface water… • Wetlands – help to offset flooding during periods of heavy rainfall • Also are very useful at absorbing pollutants

  9. Atmospheric water • Drought – lack of rainfall • Harm ecosystems and humans • Also impact soil: • Harder for nutrients to cycle • Dried soil more vulnerable to wind erosion • Flooding – too much rainfall • Also cause crop and property damage • Ground has been paved • Excess water can’t soak in

  10. Humans alter water availability • Flood control/prevention: • Levees • Mississippi River (New Orleans) • Black Warrior River (Northport) • Floodwaters move downstream • Encourages development of floodplain • Risk of collapse or breach • Dikes • Levees for ocean waters • The Netherlands

  11. Humans alter water availability… • Dams – cross rivers to produce a reservoir • Water used for consumption, generation of electricity, flood control, recreation • Environmental issues: • Disrupt ecosystems during construction • Interfere with natural flow of water • Silt behind the dam

  12. Humans alter water availability… • Aqueducts – carry water to another place • New York City & Los Angeles • Environmental issues • Disruption of ecosystem during construction • Less water available in ecosystem feeding the aqueduct • Can cause international disputes

  13. Humans alter water availability… • Desalination – making saltwater fresh • Distillation: boiled water leaves salt behind, steam is captured and cooled to condense • Requires a lot of energy • Reverse osmosis: water is forced through a membrane which blocks the salt • More efficient and less costly • Brine – super salty water waste

  14. Water use • Agriculture • Irrigation: considerations – cost, amount of evaporation • Furrow ~ 65% efficient • Flood ~ 70-80% efficient • Spray ~ 75-95% efficient • Drip > 95% • Hydroponic agriculture

  15. Water Use… • Industry • Electrical generation: • In the U.S. ~ ½ of all water used goes toward generating electricity • Hydroelectric generation returns water to source • Thermoelectric power plants use water to cool the system and it leaves as water vapor • Refining metals and making paper • Gallons used per kg made: • Copper 116, Aluminum 108, Steel 68, paper 33

  16. Water Use… • Households ~ 10% of all water used in U.S.

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