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Unit 7 NC curriculum unit for freshwater

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  1. 1. Unit 7: Water Cycle & Climate
  2. 2. No other planet in the solar system has the unique combination of fluids which Earth does. Earth has a surface that is mostly covered with liquid water, water vapor in the atmosphere, and both frozen and liquid water on the land.
  3. 3. A. Earth’s Water • The continuous interchange of water between the atmosphere and Earth ’s surface. • Includes the phase changes of water and the movements of water above, on, and below the Earth’s surface.
  4. 4. Water (or Hydrologic) Cycle 1. Precipitation : The falling of water as liquid (rain) or solid (ice, hail, and snow). – It can: Infiltrate the Earth’s surface  Runoff from the surface into streams, lakes or ocean  Be stored in the form of ice and snow  Be evapotranspired back into the atmosphere from large bodies of water, soil, plants and animals
  5. 5. Infiltration
  6. 6. The Earth is a CLOSED system . • Water is a sustainable and renewable resource • Our water is limited and must be conserved
  7. 7. Infiltration – Seeping and absorption of water into the ground surface as the result of percolation and storage.
  8. 8. The Water Cycle 5. Ground Water – Water that is found under the Earth’s surface as the result of infiltration and storage
  10. 10. • Underground water provides drinking water for more than 50% of the US population, 40% of irrigation water and more than 25% of industry’s needs. • The amount of water underground depends on: – Steepness of slope – Nature of surface materials – Intensity of rainfall – Type and amount of vegetation
  11. 11. • How does water infiltrate the ground? – Before runoff and evapotranspiration, water will usually infiltrate the Earth’s surface and become part of the groundwater.
  12. 12. Ground Water 1. In order for water to move into the surface materials of the Earth, the materials (rocks/soil) must be permeable and unsaturated .
  13. 13. Ground Water 2. Porosity – The ratio of the volume of openings compared to the volume of the material. • Depends on:    Shape of the particles Looseness of the particles. How well sorted the material is
  14. 14. Porosity • Water will pass more easily through a cylinder full of round beads, than a cylinder full of square blocks of the same size.
  15. 15. Porosity
  16. 16. Ground Water 3. Permeability – A material is said to be permeable if it allows water to pass through the connecting pore spaces of the material. • How permeable a material is depends on the porosity
  17. 17. Ground Water • The larger the pore spaces between the particles that make up a material, the greater the permeability of that material. – – Gravel (large) = High permeability Clay (very small) = Low permeability
  18. 18. •Precipitation recharges the groundwater supply. •Wetlands and streams are present where the water table lies at the ground surface. •Streams gain water during the wet season and may lose water during the dry season.
  19. 19. Groundwater flows down the hydraulic gradient (slope) from high elevations to low elevations. The shape of the flow path varies depending upon the local geological characteristics.
  20. 20. Ground Water • Zone of Aeration – Portion of ground through which water passes until the water reaches the zone of saturation. • Zone of Saturation – Portion of saturated ground with an upper boundary called the water table. • Water Table – The top of the zone of saturation
  21. 21. Ground Water
  22. 22. Water Beneath the Surface • Aquifers : Permeable rock layers that allow groundwater to move freely. • Aquitard : Impermeable layers that do not let water pass through.
  23. 23. Water Beneath the Surface • An artesian well is any formation in which groundwater rises on its own under pressure . – Conditions: • Aquifer that is tilted and exposed to the surface • Aquitards both above and below the aquifer (which increases pressure )
  24. 24.
  25. 25. Water Beneath the Surface • Aquitards can block upward movement of water causing it to move sideways. When the water in the water table approaches the ground surface, a spring is formed. • Spring : Flow of water that emerges naturally at the surface.
  26. 26. Water Beneath the Surface • Hot springs : Groundwater is heated at great depths and then quickly flows to the surface (there are more than 1000 in the US). • Geyser : A hot spring/fountain that shoots up with great force at intervals.
  27. 27.
  28. 28. Ground Water • Ground Water can be easily contaminated • • • • • • by: Landfills Herbicides Fertilizers Underground Storage Tanks (gasoline) Oils Failed Septic Systems
  29. 29. Ground Water • Capillarity – upward movement of water against the force of gravity in a narrow space, such as a tube, plant vessel, or fine sand particles. • The smaller the particle size the better the capillarity
  30. 30. 6.3: Water Beneath the Surface • Formations associated with Groundwater: – Caverns : Naturally formed underground chambers. • Most are formed by water erosion with limestone at or below the water table in the zone of saturation. • Dripstone features (dripping water leaves behind minerals): – Stalactites : Hang from the ceiling. – Stalagmites : Build up from the floor. – May join together to form a column .