CE451Darcy_s_Law

CE451Darcy_s_Law - 1.72, Groundwater Hydrology Prof....

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1.72, Groundwater Hydrology Prof. Charles Harvey Lecture Packet #2: Aquifers, Porosity, and Darcy’s Law Lake River zone Saturated Infiltration (Exposed Water Table) Precipitation Unsaturated Water table zone - Aquifer Unsaturated Zone, Vadose Zone, Soil Moisture Zone, Zone of Aeration – rock, water and air Capillary Fringe – region above water table where water rises due to capillary forces in the porous medium. Saturated Zone, Phreatic Zone – rock and water Water Table ! Top of saturated zone ! Depressed version of topography ! Surface waters are manifestations of the water table – exposed water table Aquifer - a geologic unit that stores and transmits water Recharge Area Unconfined Aquifer Confined or Artesian Aquifer Water Table 1.72, Groundwater Hydrology Lecture 2 Prof. Charles Harvey Page 1 of 10
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Unconfined Aquifer – water is in contact with atmospheric pressure – drill and well hit the water table Confined Aquifer – recharge upgradient forces water to flow down and get trapped under an aquiclude. Water is under pressure due to the weight of the upgradient water and the confinement of the water between “impermeable” layers. Water flows to surface under artesian pressure in an Artesian Well. Aquifer contamination Contaminant Source Unconfined Aquifer Confined or Artesian Aquifer Water Table In confined vs. unconfined aquifers ! Although unconfined aquifers are used for water supply, they are often contaminated by wastes and chemicals at the surface. ! Confined aquifers are less likely to be contaminated and thereby provide supplies of good quality. ! Mechanisms of transport are advection and dispersion. ! There can be chemical interactions in aqueous phase or between the water and solid media ! Covered in Contaminant Hydrology course (1.72 is a prerequisite) 1.72, Groundwater Hydrology Lecture 2 Prof. Charles Harvey Page 2 of 10
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In A.D. 1126, in the province of Artois: Unconfined Aquifer Unconfined Aquifer Water Table Confined or Artesian Aquifer Water Table Confined or Artesian Aquifer Key Aquifer Properties Porosity – Percentage volume occupied by voids. Porosity is independent of scale. For example, a pile of marbles and a pile of beach balls have spherical shape and differing sizes; the porosities are identical due to the similar shaping. Permeability
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CE451Darcy_s_Law - 1.72, Groundwater Hydrology Prof....

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