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Hydrogeology > Principles of Groundwater Flow to Wells > Flashcards

Principles of Groundwater Flow to Wells Flashcards

1
Q

Three energy that groundwater posseses

A

mechanical, chemical, and thermal

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2
Q

Three external forces acting on groundwater

A

molecular attraction, gravity, external pressure

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3
Q

two forces resisting the fluid movement of groundwater

A

shear stress
normal stress

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4
Q

stress acting tangentially to the surface of the solid

A

shear stress

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5
Q

stress acting perpendicularly to the surface of the solid

A

normal stress

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6
Q

the _____ of the fluid itself resist the movement of fluid past each other

A

internal molecular attraction

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7
Q

this shearing resistance is known as the ____ of the fluid

A

viscosity

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8
Q

a device used to measure liquid pressure in a system

A

piezometer

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9
Q

piezometer is a device which measures the pressure, more precisely the ____ of groundwater

A

piezometric head

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10
Q

what does the piezometer measure

A

the extent to which water level will rise against the force of gravity, or the pressure of the groundwater

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11
Q

t or f : the velocity of groundwater flowing in porous medium under natural hydraulic gradient is very low

A

T

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12
Q

it is equal to the pressure head (hp) plus the elevation head (z)

A

total head

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13
Q

formula for total head

A

h = z + hp

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14
Q

formula for hydraulic head

A

Hh = surface elevation - depth to water

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15
Q

formula for pressure head

A

Hp = depth of piezometer - depth to water

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16
Q

formula for elevation head

A

z = surface elevation - depth of piezometer

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17
Q

formula for vertical hydraulic gradient

A

Hg = Difference in total head / vertical distance between two piezometer

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18
Q

t or f: hydraulic head and total head are the same

A

T

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19
Q

groundwater flows in the direction of ______ hydraulic head

A

decreasing

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20
Q

The pressure at the tip of the piezometer is the ____

A

pressure = height of water in the piezometer x gravitational constant x density of the water

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21
Q

density variation in water is due to variation in

A

salinity

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22
Q

water level in well filled with water coming from a point in an aquifer and which is just enough to balance the pressure in the aquifer at that point

A

Point-water head

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23
Q

is the height of the column of fresh water in an aquifer which is just enough to balance the pressure in the aquifer at that point

A

Fresh-water head

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24
Q

formula for point-water pressure head

A

PWPH = PWH - Elevation head

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25
Q

formula for fresh water pressure head

A

FWPH = PWPH x Pp/Pf

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26
Q

formula for fresh water head

A

FWH = FWPH + Elevation head

27
Q

Total mechanical energy per unit mass

A

Force Potential

28
Q

driving impetus behind groundwater flow

A

force potential

29
Q

Force potential energy is equal t the sum of ___, ____ and ____

A

kinetic energy, elevation energy, and pressure

30
Q

force potential formula

A

hydraulic head x gravity

31
Q

t or f: high hydraulic head means high force potential

A

True

32
Q

t or f: hydraulic head increases in the direction of flow

A

F (decreases)

33
Q

t or f: as groundwater moves it encounters frictional resistance between the fluid and the porous media

A

T

34
Q

Groundwater is warmed slightly as it flows and ____ energy is turned into ____ energy

A

mechanical ; thermal

35
Q

t or f: undermost circumstance, the resulting change in temperature is measurable

A

F (NOT MEASURABLE)

36
Q

slowly moving fluids are dominated by

A

viscous forces

37
Q

if viscous forces are dominating in moving fluids, there is a ___ energy level, and the resulting fluid flow is ____

A

low ; laminar

38
Q

in laminar flow, molecules of water follow smooth lines called ___

A

streamlines

39
Q

As the velocity of the flow increases, the moving fluid gains _____. Eventually the _____ forces are more influential than the _____ forces. The result is a _____ flow in which water molecules no longer move along parallel streamlines.

A

kinetic energy
inertial forces
viscous forces
turbulent flow

40
Q

this relates the four factors that determine if a flow will be turbulent or laminar

A

Reynold’s number

41
Q

formula for reynold’s number

A

R = pqd / mew

reynold’s = fluid density x discharge velocity x diameter of passageway through which fluid moves divided by the viscosity

42
Q

if reynold’s value exceeds ____, it is considered to be a turbulent flow

A

2000

43
Q

t or f: turbulence flow in groundwater is difficult to detect

A

T

44
Q

the inception of turbulent flow in groundwater has been reported at a reynold’s number ranging from

A

60-600

45
Q

600 reynold’s number in groundwater flow are present if

A

the aqufier is cavernous

46
Q

t or f: Darcy’s law is valid only if the resistive forces of the viscosity predominates

A

T

47
Q

Darcy’s law is valid if the reynold’s number of the flow is

A

less than 1-10

48
Q

t or f: darcy’s law applies only to very slowly moving ground waters

A

T

49
Q

an imaginary line that traces the path that a particle of groundwater would follow as it flows to the aquifer

A

flow line

50
Q

in an _____, flow lines will cross equipotential lines at right angles

A

isotropic aquifer

51
Q

in an anisotropic aquifer flow lines will cross equipotential line at ____

A

an angle

52
Q

the angle of the flow line in an anisotropic aquifer is dictated by

A

degree of anisotropy

orientation of the gradient to the hydraulic tensor ellipsoid

53
Q

a network of equipotential lines and associated flow lines

A

flow net

54
Q

______ conditions may be solved by graphical construction of a flow net

A

steady-flow conditions

55
Q

method of flow net construction is based on the following assumption

A
  1. aquifer is homogenous
  2. aquifer is saturated
  3. aquifer is isotropic
  4. there no change in the potential field with time
  5. the soil and water are incompressible
  6. flow is laminar, darcy’s law is valid
  7. all boundary conditions are known
56
Q

three types of boundary conditions

A

no-flow boundary
water table boundary
constant-head boundary

57
Q

boundary where groundwater cannot pass through

A

no-flow boundary

58
Q

boundary where the head is same everywhere

A

constant-head boundary

59
Q

boundary representing equipotential lines

A

constant-head boundary

60
Q

boundary for unconfined aquifers

A

water table boundary

61
Q

if there is recharge or discharge across the water table, flow lines will be at an _____ to the _____.

A

oblique angle
water table

62
Q

if there is no recharge across the water table, flow line can be ____ to it

A

parallel

63
Q

a family of equipotential lines with sufficient orthogonal flow lines drawn so that a pattern of square figures results

A

flow net

64
Q

steps for making flow net

A
  1. sketch flow net system and identify prefixed equipotential and flow lines
  2. identify prefixed end positions of equipotential and flow lines
  3. draw trial set of flow lines
  4. draw trial set of equipotential lines orthogonal to flow lines

Hydrogeology (13 decks)

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