Principles of Groundwater Flow to Wells

Question 1

Three energy that groundwater posseses

Answer 1

mechanical, chemical, and thermal

Question 2

Three external forces acting on groundwater

Answer 2

molecular attraction, gravity, external pressure

Question 3

two forces resisting the fluid movement of groundwater

Answer 3

shear stress
normal stress

Question 4

stress acting tangentially to the surface of the solid

Answer 4

shear stress

Question 5

stress acting perpendicularly to the surface of the solid

Answer 5

normal stress

Question 6

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

Answer 6

internal molecular attraction

Question 7

this shearing resistance is known as the ____ of the fluid

Answer 7

viscosity

Question 8

a device used to measure liquid pressure in a system

Answer 8

piezometer

Question 9

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

Answer 9

piezometric head

Question 10

what does the piezometer measure

Answer 10

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

Question 11

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

Answer 11

T

Question 12

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

Answer 12

total head

Question 13

formula for total head

Answer 13

h = z + hp

Question 14

formula for hydraulic head

Answer 14

Hh = surface elevation - depth to water

Question 15

formula for pressure head

Answer 15

Hp = depth of piezometer - depth to water

Question 16

formula for elevation head

Answer 16

z = surface elevation - depth of piezometer

Question 17

formula for vertical hydraulic gradient

Answer 17

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

Question 18

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

Answer 18

T

Question 19

groundwater flows in the direction of ______ hydraulic head

Answer 19

decreasing

Question 20

The pressure at the tip of the piezometer is the ____

Answer 20

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

Question 21

density variation in water is due to variation in

Answer 21

salinity

Question 22

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

Answer 22

Point-water head

Question 23

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

Answer 23

Fresh-water head

Question 24

formula for point-water pressure head

Answer 24

PWPH = PWH - Elevation head

Question 25

formula for fresh water pressure head

Answer 25

FWPH = PWPH x Pp/Pf

Question 26

formula for fresh water head

Answer 26

FWH = FWPH + Elevation head

Question 27

Total mechanical energy per unit mass

Answer 27

Force Potential

Question 28

driving impetus behind groundwater flow

Answer 28

force potential

Question 29

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

Answer 29

kinetic energy, elevation energy, and pressure

Question 30

force potential formula

Answer 30

hydraulic head x gravity

Question 31

t or f: high hydraulic head means high force potential

Answer 31

True

Question 32

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

Answer 32

F (decreases)

Question 33

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

Answer 33

T

Question 34

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

Answer 34

mechanical ; thermal

Question 35

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

Answer 35

F (NOT MEASURABLE)

Question 36

slowly moving fluids are dominated by

Answer 36

viscous forces

Question 37

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

Answer 37

low ; laminar

Question 38

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

Answer 38

streamlines

Question 39

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.

Answer 39

kinetic energy inertial forces viscous forces turbulent flow

Question 40

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

Answer 40

Reynold's number

Question 41

formula for reynold's number

Answer 41

R = pqd / mew reynold's = fluid density x discharge velocity x diameter of passageway through which fluid moves divided by the viscosity

Question 42

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

Answer 42

2000

Question 43

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

Answer 43

T

Question 44

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

Answer 44

60-600

Question 45

600 reynold's number in groundwater flow are present if

Answer 45

the aqufier is cavernous

Question 46

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

Answer 46

T

Question 47

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

Answer 47

less than 1-10

Question 48

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

Answer 48

T

Question 49

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

Answer 49

flow line

Question 50

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

Answer 50

isotropic aquifer

Question 51

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

Answer 51

an angle

Question 52

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

Answer 52

degree of anisotropy orientation of the gradient to the hydraulic tensor ellipsoid

Question 53

a network of equipotential lines and associated flow lines

Answer 53

flow net

Question 54

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

Answer 54

steady-flow conditions

Question 55

method of flow net construction is based on the following assumption

Answer 55

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

Question 56

three types of boundary conditions

Answer 56

no-flow boundary water table boundary constant-head boundary

Question 57

boundary where groundwater cannot pass through

Answer 57

no-flow boundary

Question 58

boundary where the head is same everywhere

Answer 58

constant-head boundary

Question 59

boundary representing equipotential lines

Answer 59

constant-head boundary

Question 60

boundary for unconfined aquifers

Answer 60

water table boundary

Question 61

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

Answer 61

oblique angle water table

Question 62

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

Answer 62

parallel

Question 63

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

Answer 63

flow net

Question 64

steps for making flow net

Answer 64

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