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Groundwater

Discover the fascinating world of groundwater, from precipitation and infiltration to aquifers and karst topography. Learn about the movement of water beneath the surface and its interaction with rock properties. Explore how wells, springs, and chemical weathering shape the underground landscape.

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Groundwater

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  1. Groundwater

  2. BIG Idea: • Precipitation and infiltration contribute to groundwater, which is stored in underground reservoirs until it surfaces as a spring or is drawn from a well.

  3. Infiltration: • process of water moving into the soil/ground • to penetrate, enter or gain access

  4. I. Water Beneath the Surface Groundwater:underground water that fills almost all of the pores in rock and sediment

  5. Aquifer: a body ofrockthat can store water and also let water flow through

  6. Think of an AQUIFER as a… large, horizontal sponge that absorbs and transports water along its length

  7. A. Rock Properties that Affect Groundwater • Porosity • Permeability

  8. 1.Porosity:percentage of open spaces in a rock or sediment

  9. FACTORS THAT INFLUENCE POROSITY: (a) SORTING: amount of uniformity in particle size HIGH pore space LOW pore space

  10. (b) SHAPE: rounder particles = more porous (c) PACKING: loosely packed = more porous

  11. 2. Permeability: how freely water flows through open spaces in a rock (the pores must be connected) Impermeable – water can NOT flow through

  12. Can something be porous but impermeable? The cork end is red because the grape juice went into it. Does this mean it is porous? If you turn the bottle upside down will it leak? Is the cork permeable?

  13. B. Zones of Groundwater 1. Zone of Saturation: the layer of ground where all the pores are filled with water.

  14. 2. Water Table: upper surface of the zone of saturation

  15. 3. Zone of Aeration: upper region, where water is both in the soil and seeping down to the water table.

  16. Zone ofAeration►

  17. Capillary Action: ability of water to rise UP the soil. Smallerparticle size = greater capillarity

  18. Capillary Fringe:middle layer, between the water table and the zone of aeration.

  19. C. MOVEMENT OF GROUNDWATER • Depends on: • Permeability of the aquifer • ↑ permeability = ↑ velocity • Gradient of the water table • Gradient = steepness of the slope • ↑ gradient = ↑ velocity

  20. II. Wells and Springs • Water Table:upper layer of rocks with all pores filled with water.

  21. A. Ordinary Well:A hole dug below the water table which fills up with water.

  22. Cone of Depression: lowered area of the water table due to pumping

  23. B. Artesian Wells:water flows freely with no pumping • Underground water under pressure (between two impermeable rock layers) rises to the surface • Water is naturally filtered as it passes through porous rock and seeps to surface

  24. III. Groundwater and Chemical Weathering • Caverns: rocks rich in calcite (limestone) slowly dissolved by carbonic acid. • Hard water = many dissolved minerals (Ca, Mg, Fe) • Soft water = few dissolved minerals

  25. Luray Caverns, VA

  26. Formation of a Cave

  27. 1. Stalactites:water with dissolved calcite runs from a cave’s ceiling and solidifies downward.

  28. 2. Stalagmites: calcite rich water drips on the cave’s floor and builds upward.

  29. If the two connect, then it forms a column.

  30. 3. Natural Bridge:when the roof of a cavern collapses in several places leaving an arch- shaped rock.

  31. B. KARST TOPOGRAPHY • regions where chemical weathering by groundwater is now visible at the surface • regions where it is humid and there are limestone formations near the surface • Virginia, Kentucky, Tennessee, Indiana, and Florida have Karst Topography

  32. 1. Sinkholes (the main feature of Karst Topography)

  33. How do sinkholes form? • Rain seeps through soil and absorbs carbon dioxide and reacts with decaying vegetation • Acidic water is created • Water moves through spaces and cracks underground • Limestone is slowly dissolved, creating network of cavities and voids • Pores and cracks enlarge • Land surface above collapses or sinks

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