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52 Cards in this Set
- Front
- Back
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Groundwater |
subsurface water that occurs beneath the water table in the soils and geologic formations that are fully saturated |
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Hydrogeology |
study of groundwater (relationships of geological materials and water related processes) |
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Hydrology |
study of water through surface and near surface water |
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Vadose Zone |
unsaturated zone above water table: soil water, intermediate vadose water, capillary zone |
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Soil Water |
Upper soil zone with fluctuations in water volumes, part of vadose zone, available to plants, may become saturated after heavy precipitation, temporary storage |
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Intermediate Vadose Zone |
below soil water zone, stable zone with small changes in water volume, remains unsaturated through heavy precipitation, variable thickness, gravitational water drainage |
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Capillary Water |
Vadose zone, water rises due to capillarity, near saturation, under suction |
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Capillarity |
balance of forces due to gravity, surface, tension, surface wetting |
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Water Table |
Beginning of saturated/phreatic zone, water pressure is exactly atmosphereric |
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Phreatic Water |
Zone considered groundwater |
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Q |
Flow rate (m3/s or L/s) |
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dh/dl |
hydraulic gradient |
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K |
Hydraulic Conductivity (m/s) |
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q |
specific discharge/darcy flux, darcy velocity (m/s) - FLUX NOT VELOCITY |
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v |
linear velocity, representative velocity) (m/s) |
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n |
porosity |
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Conditions where Darcy's Law can be applied: |
- saturated/unsaturated - steady state & transient flow - all permeabilities - rocks and granular material - homogenous and heterogenous formations - isotropic and anisotropic formations - LAMINAR FLOW |
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Representative Elementary Volume (REV) |
volume of sample at which darcy's law works best |
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What conditions does Darcy's Law not apply? |
Lower limit: low permeability sediments (low dh/dl) Upper limit: very high permeability sediments, turbulent (high dh/dl), can be determined by Reynolds Number |
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Darcy's law is valid for what range of Reynolds Number? |
≤ 1-10 (see graph) |
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Potential: |
physical quantity, flow can be measured at every point in flow system, flow properties occur from regions of higher values to lower values regardless of direction in space |
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Types of work for fluid potential: |
- gravitational potential energy - kinetic energy - elastic energy see equation sheet |
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Piezometer |
device used to measure hydraulic head -tube open at both ends, sealed along most of length - point of measurement of head is at base of tube using screens |
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Manometer |
comparable lab device to piezometer and used in Darcy experiment |
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2 Types of porosity: |
1. primary - due to matrx (solids + voids) 2. secondary - due to solution or fracturing |
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effective porosity: |
porosity available for fluid flow, function of size of molecules relative to pore throat effective n < total n |
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Factors of sediment porosity : |
- packing - sorting - grain shape and fabric |
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Methods to change porosity of Sedimentary Rocks: |
Reduce: campaction, cementation Increase: Dissolution, fracturing, bedding planes |
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Porosity of Metamorphic and Igneous Rocks: |
Metamorphic & Plutonic: low primary porosity, increase if weathering and fracturing Volcanic: unconnected vesicles, increase with fractures |
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Uniformity Coefficient: |
Cu = d60/d10 Cu < 4: well sorted Cu > 6: poorly sorted |
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effective grain size |
d10 |
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Hydraulic Conductivity |
(K) function of porous medium and fluid (m/s) EQUATION |
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C depends on: |
- packing - sphericity of grains - distribution of grain sizes |
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permeability |
m2 |
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Saturated K value for soil can be estimated: |
1. constant head permeameter (darcy experiment) 2. falling head permeameter 3. grain size analysis |
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Heterogeneous vs. Homogeneous |
Heterogeneous - K varies from one point to another in geologic formation Homogeneous - K is independent of position in geologic formation |
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Isotropic vs. Anisotropic |
Isotropic - K is independent of flow direction at point in geologic formation Anisotropic - K depends on flow direction at point in geologic formation |
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Aquifer |
- saturated permeable geologic unit - can transmit significant quantities of water under ordinary hydraulic gradients |
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aquiclude |
- saturated geologic unit - incapable of transmitting significant quantities of water under ordinary hydraulic gradients |
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aquitards |
less permeable unit in stratigraphic sequence |
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Confined aquifer |
bounded above and below by aquitards - under high pressure |
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Artesian |
water levels of confined aquifer rise above aquifer |
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Flowing artesian |
if water levels of confined aquifer rise above ground surface |
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Potentiometric Surface |
Level to which water rises in confined aquifer |
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perched aquifer |
saturated lens of material in unsaturated zone |
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Hydrostatigraphic Unit |
mappable units on basis of hydraulic properties with lateral extent |
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Lithology |
physical characteristics (mineral comp, grain size, grain packing) - affects n and k |
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Stratigraphy |
geometrical and age relationships between sediment beds/formations - info on depositional environment |
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Structure |
features produced by deformation after deposition or crystallization |
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Unfonformities |
surface on non-deposition or erosion where weathering surface may be fractured, oxidized --> poor water quality |
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Unconsolidated Aquifers |
- surficial aquifer - blanket bedrock and infill valleys - very productive - at risk of contamination (near surface) - no cementing or alteration |
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What assumptions are made for the 3 point problem? |
planar horizontal flow in uniform medium (homogenous) |
