Geol 343 Revised

Front 1

Define Aquifer:

Back 1

An underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials from which groundwater can be extracted to make a well

Alternatively: Geologic unit that can transmit water at rates fast enough to supply reasonable amounts to wells

Front 2

Define Aquitard:

Back 2

A layer of low permeability along an aquifer; A Geologic unit of low permeability that restricts flow of water. generally not entirely impermeable, but we can pretend they are for the sake of calculation

Front 3

With reference to the groundwater cycle, how does the travel time of groundwater scale with distance to a water body of constant head?

Back 3

The further you are from the body of water, the longer it will take; because of the way equipotentials look in the subsurface, water very close to a lake will take a few days, while water furhter away will have to very deep in the subsurface to reach the lake, so it might take millenia.

Front 4

Give approximate porosities for sand, gravel, sand mixed with gravel and silt/clay

Back 4

Well sorted sand OR gravel: φ=25-50

Mixed sand AND gravel: φ=20-35

Silt/Clay: φ=35-50

Front 5

Define k (Intrinsic permeability)

Define K (Hydraulic conductivity) with words and numbers

Back 5

k: intrinsic permeability is a measure of the ability of a porous material to allow fluids to pass through it.

K describes the ease with which a fluid (usually water) can move through pore spaces or fractures in a porous medium - it is a function of the intrinsic permeability of the medium, the density and viscosity of the fluid, and the acceleration due to gravity

Front 6

What is the density of water? what is the viscosity of water at 25°C

Back 6

ϱ_water =1kg/L, 1000Kg/m^3, 1g/cm^3

μ_water = 0.01 Kg/m*s=0.01poise

Front 7

Define Q

Define q

Back 7

Q: Discharge is the Volume rate of water flow that is transported through a given cross-sectional area in a porous medium

q: Darcy flux: Discharge per unit area

Front 8

Define REV

Back 8

The REV (representative elementary volume) is the volumeacross which a property can be effectively averaged or can be consideredconstant. (so like, a large enough volume of measurement such that you're getting a good average rather than a small area of measurement that provides you with a biased one?

Front 9

Define Anisotropic with reference to soils

Define Heterogenous with reference to soils

Back 9

An anisotropic soil will have different properties depending on the direction of measurement

Heterogenous soils have properties that vary through space

Front 10

How does pressure change with depth in a fluid?

how does this change if the fluid's density changes?

Back 10

Pressure scales linearly with depth in a fluid, and the denser the fluid is, the greater the increase in pressure per unit depth

Front 11

Why do montoring wells have a screen installed?

Back 11

slits are cut so that water can flow through to be monitored: the slits are surrounded by a clean sand pack so that gunk like clays and silt don’t end up gumming up the screen

Front 12

Define h

State the bernoulli equation (for hydraulic head) in values and in words and explain how we can

Back 12

h=Hydraulic head, a measure of fluid energy per unit weight

h= z+ P/(ρ_w*g)+ v^2/2g

Front 13

Define Pressure, Interfacial tension, and Capillary pressure

Back 13

Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed (**TLDR: force per unit area**)

Interfacial tension exists between two immiscible fluids; it is the force that holds the surface of a particular phase together and is measured in units of force/length. for water and air this is equal to 0.072N/m

Capillary pressure is the isthe pressure difference across the interface between two immiscible fluidsarising from the capillary forces. These capillary forces are surface tensionand interfacial tension. (P_c=P_a-P_w)

Front 14

What is the difference between a water content VS pressure curve and a Saturation VS capillary pressure curve?

Back 14

Water content VS pressure curve:

Saturation VS capillary pressure curve:

Front 15

What are the 6 kinds of pumping tests that we can run?

Back 15

Steady state Unconfined

Steady state Confined

Unsteady state Confined THEIS

Unsteady state Confined Cooper-Jacob

Unsteady state Confined Modified (leaky)

Hvorslev Slug test

Front 16

Define S, S_s and S_y

Back 16

S is Storativity: the volume of water released from a volumeof soil per unit decline in hydraulic head in the aquifer, per unit area of theaquifer,

S_s is specific storage: the space available in a given soil to store water. it is dependant on the compressibility of water and air and porosity

S_y is the volume of water that can be extracted from a soil by desaturating it. In a confined aquifer, S_y is ZERO

Front 17

Define dispersion?. Why does it occur?

What does it depend on?

Back 17

Dispersion is a factor which quantifies how much contaminants stray away from the path of the groundwater which is carrying it. it is dependant on Mechanical and chemical dispersivity (chemical AKA diffusion)

mechanical dispersivity occurs dur to inhomogenous nature of subsurface- water particles "choose" to go around soil particles in any which direction and as a result, contaminants at the edges of the plume can be spread around. depending on the path taken, the contaminants may move through at different speeds- generally GW speed is faster in the centre of the pore throat, adn teh faster the GW speed is, the greater mechanical disersivity is. This causes the net concentration of the central part of the contaminant plume to deacrease.

diffusion is a chemical process that occurs due to random motions of particles in a solute. diffusion is largely not relevant to the dispersion.

Front 18

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Back 18

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