Hydro Lecture 4

Lecture 4: Aquifers
Aquifer- a geologic unit capable of storing and transmitting water in sufficient quantities to supply wells

  • not about amount of water, but geologic unit
  • Keys:
  1. water must be stored
  2. water must be able to move
  3. water must be in a significant amount, but we don't know what that significant number is yet

Aquiclude (aka aquitard)- a geologic unit that resists water flow (relative to an aquifer)

  • doesn't mean no flow at all, just less
  • again, we don't have any figures for this definition, but we will in the near furture
  • aquitards are the furture aquifers

These terms are especially applicable to the petroleum industry. See "tight gas," "shale gas" and "coal gas"

Best aquifers by rock type:

  1. unconsolidated
  2. sandstone
  3. sandstone and carbonate (eg limestone)
  4. semiconsolidated
  5. carbonate-rock
  6. volcanic, if highly weathered and/or fractured
  7. other rocks

Top 3 are the best.

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Aquifuge- no flow of water, absolutely impermeable
Aquiclude- very low water flow (aka hydraulic conductivity)
Aquitard- low permeability, but can store water and transmit water slowly (aka leaky confining layers)
Perched Aquifer- smaller aquifer often mistaken for real aquifer, but occurs above the main water table due to layer of impermeable material
Unconfined aquifer- consists of an unsaturated zone seperate from saturated zone by the groundwater table
Confined Aquifer- an aquifer with a slightly impermeable layer running over and under the saturated zone, usually deeper than unconfined; however, very few aquifers are completely confined, this definition is taken in theory only

Water Table Terms
insert pic here
water table- boundary between unsaturated and saturated zonesundwater
groundwater- anything below groundwater table; soil msture is not groundwater

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