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Groundwater Movement and Storage

Learn about the movement and storage of groundwater, including the concept of porosity, the water table, aquifers, springs, wells, and potential threats to groundwater supply.

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Groundwater Movement and Storage

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  1. Lesson 6 The Movement and Storage of Groundwater

  2. Precipitation and Groundwater… Remember the water cycle? Most water in the atmosphere comes from oceans! Most precipitation that falls on land becomes groundwater. Eventually groundwater will… … return to the ocean to complete the water cycle.

  3. Groundwater Storage… 1. Porosity is… …the percentage of pore space in a material 2. The types of soil that have - a. highest porosity - well- sorted b. lowest porosity – poorly- sorted

  4. Groundwater Storage… 1. Groundwater is stored… in the pore spaces of rocks & sediments …and can be compared to a hard sponge

  5. Groundwater Storage… 3. The zone of saturation is the… … depth below surface where groundwater completely fills all the pores 4. The water table is the … … upper boundary of the zone of saturation

  6. soil Zone of aeration Water table Zone of saturation

  7. Groundwater Storage… 5. The depth of the water table varies… …in swampy areas- water table is at or almost at surface, …in arid regions -water table is far beneath surface

  8. Groundwater Storage… If the water table is high, it is more likely to flood. low, it is less likely to flood. 7. The water table fluctuates with the seasons and weather conditions because… it depends on rain to recharge it

  9. Groundwater Movement: Permeability… 1. What is permeability? ability of a material to let water pass through What subsurface materials are permeable? sand, sandstone, & gravel (good for parking lots so water can infiltrate) What subsurface materials are impermeable? clay, silt, shale, & pavement (bad for infiltration!) Why is clay used to line ponds & landfills? It is impermeable (our storm drainage pond)

  10. Groundwater Movement: Aquifers… An aquifer … underground storage area for water (permeable rock layers) An aquiclude … impermeable layer above or below an aquifer.

  11. Groundwater Movement… 6. Confined aquifer (Pic on next slide…) 7. 8. aquiclude

  12. Lesson 7 Groundwater Systems, Use, and Threats!

  13. Springs… Ground water discharges (comes out) at… Earth’s surface These natural discharges of water are called…springs Water may flow out of a rock when… an aquifer meets an aquiclude at Earth’s surface (a spring!)

  14. Perched Water Table  • Fault- blocked Road Cuts  Limestone Regions  http://www.physicalgeography.net/fundamentals/8m.html

  15. Hot Springs… 3. The temperature of ground water is… same as average annual temperature 4. Hot springs are… have temperatures higher than the human body Hot springs are so hot because… the subsurface is still hot from recent igneous activity Picture on next slide 

  16. Springs and Geysers… 4. Most hot springs in our country are found in the… western states 5. A geyser is an … explosive hot spring that erupts at regular intervals Old Faithful Geyser Yellowstone NP

  17. Wells… 1. A well is… a hole dug to reach groundwater 2. A cone of depression is produced by… over pumping wells Drawdown is… the difference b/tw the original water table level and that of a pumped well Water is drawn! Water table goes down! Draw down… Wells can run dry or pull up salt Streams can run dry Coastal aquifers - saltwater intrusion

  18. Wells… 5. Recharge is… water from rain or runoff is added to an aquifer Aquifers are recharged by rain.

  19. Wells http://pubs.usgs.gov/gip/gw_ruralhomeowner/gw_ruralhomeowner_new.html http://ga.water.usgs.gov/edu/earthgwlandsubside.html

  20. Wells… • The entire water table can be lowered due to… …overuse of wells • Ground above an overused well can… • …sink! • This is called subsidence

  21. Groundwater Use 8. In the USA, 23% of all freshwater is obtained from… … aquifers (groundwater) … Florida, Hawaii, and Nebraska depend almost entirely on groundwater.

  22. Environmental Issues: Saltwater Intrusion… 9. Saltwater intrusion… … saltwater intruding into coastal wells… … Outer Banks (on coast) … too many wells

  23. Threats to Our Groundwater Supply… Overuse Subsidence Pollution (sewage, industrial waste, landfills, agriculture) Chemicals (not filtered out by sediments; hard to remove from groundwater) Salt (esp. coastal areas) Radon (radioactive decay of uranium in rocks – esp. granite and shale)

  24. Protection of Groundwater… Identify and eliminate pollution sources. Monitor pollution. Pump groundwater to surface and treat it.

  25. Lesson 8 Groundwater Erosion

  26. Caves… What is a cave? A natural underground opening with a connection to Earth’s surface Which acid forms caves? Carbonic acid (H2O + CO2 in the soil) Which rock is eroded by this acid to form a cave? limestone

  27. Karst Topography: Sinkholes… 1. What is a sinkhole? A depression in the ground caused by the collapse of a cave http://southeastsinkhole.com/

  28. Karst Topography 2. Karst topography are limestone regions that have sinkholes, sinks, and sinking streams – named for an area in Croatia. http://www.virginiacaves.org/lok/ccvup56.htm

  29. Karst Topography…

  30. Hard Water… 4. Hard water is water that contains high concentrations of calcium, magnesiun, or iron. Common in limestone areas Causes deposits of calcium bicarbonate and can clog water pipes. (p. 247) More soap must be used

  31. Erosional Stream Load… 1. All the materials that the water in a stream carries is known as the stream’s load.

  32. Erosional Stream Load… Three ways in which a stream carries its load... Material is carried in solution after it becomes dissolved in a stream’s water. All particles small enough to be held up by the turbulence of a stream’s moving water are carried in suspension. Sediments that are too large or heavy to be held up by turbulent water are transported as a stream’s bed load.

  33. Erosional Stream Load… 2. Carrying capacity is the ability of a stream to… transport material

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