Groundwater abbrev.

Groundwater abbrev. - Hydrologic Cycle Hydrologic and...

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Unformatted text preview: Hydrologic Cycle Hydrologic and Groundwater Hydrologic Hydrologic Cycle Hydrologic Cycle Hydrologic s 1. 2. 3. Water Reservoirs Hydrosphere – includes surface Hydrosphere water (lakes, oceans, glaciers, etc.) and subsurface water or ground water water Atmosphere – water vapor Biosphere – water in plant and Biosphere animal tissue animal Ground Water Ground Ground water – all water stored below the Ground surface in open spaces within rocks. surface s Represents ~22% of the world’s supply of Represents fresh water (much more than found on the surface in streams and lakes) but only ~0.6 % of the total water on earth; >97% of all the water on earth is in the oceans (saltwater) water s Primarily derived from precipitation that Primarily percolates down into the ground percolates Ground Water Water & Porosity Porosity Water Table Water s s s s When precipitation occurs over land, it either: 1. evaporates 2. is carried away in streams and rivers 3. seeps into the ground Zone of Aeration – surface layer through which Zone water seeps; pore spaces between grains are filled with air and water with Zone of Saturation – subsurface layer in which all Zone of the pore spaces are filled with water of Water Table – boundary between zone of Water aeration and zone of saturation aeration Water Table Ground Water Water & Porosity Porosity Zonation of Ground Water Zonation Porosity and Permeability Porosity s The flow of ground water is controlled by the The physical properties of the rock it is moving through. through. 1. Porosity – percentage of a rock’s total volume Porosity that is open space or pores. that s s s examples – spaces between sediment grains, cracks examples in rocks in the higher the porosity, the greater the amount of the water a rock can hold water different rocks have different levels of porosity Ground Water Water & Porosity Porosity Sandstone: 10-30% Fractured granite ~10% 0-10% Fractured basalt 5-40% Porosity and Permeability Porosity s 1. 2. Permeability – a measure of the size of the Permeability pores and how well they are connected; if individual pores are not connected, ground water can not flow through the rock water Aquifer – permeable layer of rock that Aquifer transports water transports Aquitard or Aquiclude– impermeable layer Aquitard of rock that prevents the transport of water (often shale layers) (often Ground Water Water & Perched Perched Water Changes in the Water Table Changes s Recharge – occurs when water is added Recharge to the zone of saturation; causes the water table to rise. water s Discharge – occurs when water is Discharge removed from the zone of saturation; causes the water table to drop. causes Discharge of Ground Water Discharge 1. 2. 3. Springs – ground water flows or seeps out of the Springs ground where the water table intersects the surface; usually occur on hill slopes. surface; Water Wells – drill down below the water table Water and pump water out; if water is not replenished, pumping will cause the water table to drop and the well may go dry. the Artesian Wells – ground water is under pressure Artesian and water flows out of the well without pumping. and Ground Water Water & Perched Perched Water Costa Costa Rica Rica Spring Spring Impermeable Shale Permeable Sand Artesian Wells Ground Water Water & Porosity Porosity Artesian Water Water Well Discharge of Ground Water (cont.) Discharge 4. Hot springs and geysers – ground water is heated, usually through flow ground close to a magma chamber. close – results in the discharge of hot water and steam Hot Springs & Geysers Hot Hot Springs - Rotorua, NZ Hot Old Faithful Faithful Geyser Yellowstone Park Locations of Hot Springs and Geysers Locations Human Impact on Ground Water Human s s In the United States, ~20% of the water we use is In ground water. ground Ground water systems can be altered in several Ground ways: ways: 1. lowering of the water table – discharge lowering exceeds recharge exceeds 2. saltwater incursion – pumping of fresh water saltwater in coastal areas allows saltwater to penetrate into the aquifer and contaminate the fresh water. water. Ground Water – Cone of Depression Ground Cones of Depression Cones Ground Water Water & Salt Water Intrusion Intrusion Human Impact on Ground Water (cont.) (cont.) 1. Ground Water Contamination – disposal of sewage and other waste can disposal contaminate groundwater contaminate – examples: septic tanks, landfills, toxic waste examples: and nuclear waste disposal sites and – Pinewood landfill and Barnwell low level Pinewood nuclear disposal site nuclear Artesian Ground Water Artesian Ground Water – Contamination If the removal of water from the zone of saturation exceeds the addition of water saturation A. the position of the water table will rise B. the position of the water table will drop C. there will be no change in the position of the there water table water When dealing with a disturbed sequence of sedimentary rocks, the best way to determine the relative ages of the sedimentary layers relative A. is by using the law of superposition B. is by applying the principle of uniformitarianism C. is by examining the fossil content of the layers Next Topic Next Glaciers Chapter 19 ...
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