Hydrogeology

Question 1

Area of Influence

Answer 1

The area within which the potentiometric surface is lowered by withdrawal or raised by injection of water through a well.

Question 2

Aquifer

Answer 2

A geologic unit that is saturated and sufficiently permeable to transmit significant economic quantities of water to wells and springs.

Question 3

Capillary Fringe

Answer 3

The lowest part of the vadose zone, immediately above the water table, where water is under pressure that is less than atmospheric pressure.

Question 4

Confined Aquifer

Answer 4

An aquifer overlain by a confining layer of low permeability.

Question 5

Connate Water

Answer 5

(Fossil Water) Water trapped in the pores of a sedimentary rock at the time of deposition.

Question 6

Darcy

Answer 6

A unit of intrinsic permeability = 9.87x10-9cm2

Question 7

Darcy’s Law

Answer 7

This equation describes groundwater flow.
Q=KiA.

Question 8

Discharge Area

Answer 8

An area where subsurface water is discharged to land, bodies of water, or the atmosphere.

Question 9

Effective Porosity

Answer 9

The percentage of the total volume of a soil or rock that consists of interconnected pore space.

Question 10

Field Capacity

Answer 10

The quantity of water held by the soil or rock against the pull of gravity. It is dependent on the length of time the soil or rock has been undergoing gravity drainage.

Question 11

Flow Net

Answer 11

Two-dimensional representation of flow lines and equipotentials

(equipotential lines are perpendicular to flow lines)

(Flow line traces path of water particle, visualizes groundwater flow direction)

Question 12

Ghyben-Herzberg Principle

Answer 12

The principle that states that the depth to which fresh water extends below sea-level is approximately 40 times the height of the water table above sea level.

Question 13

Head

Answer 13

A measure of the potential energy of a fluid at any given point with respect to a given datum.

Th elevation to which water rises at a given point as a result of reservoir pressure.

Question 14

Hydraulic Conductivity (K)

Answer 14

The capacity of a porous medium to transmit water.

The rate at which fluid can move through a permeable medium depends on properties of the fluid (viscosity and specific weight) and properties of the medium (intrinsic permeability).

Question 15

Hydraulic Gradient (I)

Answer 15

Rate of change in total head per unit of distance of flow in a given direction

Question 16

Intrinsic Permeability (k_i)

Answer 16

A property of the porous medium that measures the relative ease with which a fluid can be transmitted through it under a hydraulic gradient.

It is dependent upon the pore size and is measured in Darcys.

Question 17

Juvenile Water

Answer 17

Water that is derived directly from magma and is thought to have come to the Earth’s surface for the first time.

Question 18

Meinzer

Answer 18

A unit of hydraulic conductivity in gpd/ft2.

The rate of flow in gallons per day through a cross section of 1 square foot under a hydraulic gradient at 60ºF.

Question 19

Perched Groundwater

Answer 19

Unconfined groundwater separated from an underlying body of groundwater by an unsaturated zone.

Question 20

Permeability

Answer 20

The property of a porous rock or soil for transmitting a fluid.

It measure the relative ease of flow under unequal pressure.

Question 21

Porosity (n)

Answer 21

The percentage of the bulk volume of a rock or soil that is occupied by void space.

Question 22

Potentiometric Surface

Answer 22

A surface that represents the total head of groundwater and is defined by the level to which water will rise in a well.

Question 23

Recharge Area

Answer 23

An area where water infiltrates downward in to the saturated zone.

Question 24

Runoff (R)

Answer 24

That part of precipitation appearing in surface streams.

Question 25

Specific Retention (S\_r)

Answer 25

Ration of the volume of water a soil or rock can retain against gravity drainage to the total volume of the soil or rock, usually a percentage.

Question 26

Specific Storage (S-s)

Answer 26

Amount of water per unit volume of a saturated formation that is stored or expelled from storage due to compressibility of mineral skeleton and pore water per unit change in head.

Question 27

Specific Yield (S_y)

Answer 27

Ratio of the volume of water that drains from a saturated soil or rock due to gravity to the total volume of soil or rock. A percentage. Specific yield = effective porosity!

Question 28

Storativity or Storage Coefficient (S)

Answer 28

Volume of water that a permeable unit releases from or takes into storage per unit surface area of the aquifer per unit change in head.

Question 29

Transmissivity (T)

Answer 29

The capacity of an aquifer to transmit water of the prevailing kinematic viscosity. T=Kb. where b = saturated thickness of the aquifer.

Question 30

Unconfined aquifer

Answer 30

An aquifer with a water table.

Question 31

Underflow (U)

Answer 31

Groundwater that flows beneath the bed or alluvial plain of a surface stream, especially in arid regions.

Question 32

Vadose Zone or Zone of Aeration

Answer 32

A subsurface zone containing water under pressure that is less than atmospheric pressure. It is measured from ground surface to the water table.

Question 33

Water Table

Answer 33

The depth where the fluid pressure in the pores of the rock or soil is exactly atmospheric pressure

Question 34

Watershed

Answer 34

The region drained by a stream or body of water or a drainage divide.

Question 35

Input Sources

Answer 35

1. Deep percolation from precipitation 2. Seepage from surface water 3. Groundwater underflow into aquifer 4. Artificial recharge from irrigation, recharge wells, etc. 5. Leakage through confining beds

Question 36

Losses of Groundwater (output sources)

Answer 36

1. Evapotranspiration 2. Seepage to surface water 3. Groundwater underflow from aquifer 4. Discharge to springs 5. Artificial discharge from wells, infiltration galleries, and drainage systems 6. Discharge through confining beds.

Question 37

What is below the water table?

Answer 37

Groundwater

Question 38

What is above the water table?

Answer 38

The capillary fringe

Question 39

What units are used for change in storage (dS)?

Answer 39

acre-feet-per year (AFY) or gallons per year (GPY)

Question 40

What is 1 square mile in acres?

Answer 40

640 acres

Question 41

What is 1 mile in feet?

Answer 41

5280 feet

Question 42

Where is hydraulic pressure greater than atmospheric pressure?

Answer 42

Below the water table

Question 43

Why is the vadose zone important?

Answer 43

It supplies water and nutrients to plants, is a zone of human activity, and is the medium that transports water and contaminants and recharges aquifers.

Question 44

Where is hydraulic pressure negative (less than atmospheric pressure)?

Answer 44

Above the water table in the capillary fringe.

Question 45

3 types of Preferential Flow:

Answer 45

1. Macro pore flow that occurs along worm holes, root holes, or fractures. 2. Funneled or focused flow along lenses that may concentrate and deflect the direction of flow. 3. Unstable flow. i.e flow that breaks through interfaces and creates fungers that become more conducive to water flow, as compared to adjacent areas that are dry,

Question 46

What does the Soil Water Retention Curve show?

Answer 46

As the water content increases the metric potential decreases until it approaches zero.

Question 47

The area within which the potentiometric surface is lowered by withdrawal or raised by injection of water through a well.

Answer 47

Area of Influence

Question 48

A geologic unit that is saturated and sufficiently permeable to transmit significant economic quantities of water to wells and springs.

Answer 48

Aquifer

Question 49

The lowest part of the vadose zone, immediately above the water table, where water is under pressure that is less than atmospheric pressure.

Answer 49

Capillary Fringe

Question 50

An aquifer overlain by a confining layer of low permeability.

Answer 50

Confined Aquifer

Question 51

(Fossil Water) Water trapped in the pores of a sedimentary rock at the time of deposition.

Answer 51

Connate Water

Question 52

A unit of intrinsic permeability = 9.87x10-9cm2

Answer 52

Darcy

Question 53

This equation describes groundwater flow. Q=KiA.

Answer 53

Darcy's Law

Question 54

An area where subsurface water is discharged to land, bodies of water, or the atmosphere.

Answer 54

Discharge Area

Question 55

The percentage of the total volume of a soil or rock that consists of interconnected pore space.

Answer 55

Effective Porosity

Question 56

The quantity of water held by the soil or rock against the pull of gravity. It is dependent on the length of time the soil or rock has been undergoing gravity drainage.

Answer 56

Field Capacity

Question 57

Two-dimensional representation of flow lines and equipotentials

Answer 57

Flow Net

Question 58

The principle that states that the depth to which fresh water extends below sea-level is approximately 40 times the height of the water table above sea level.

Answer 58

Ghyben-Herzberg Principle

Question 59

A measure of the potential energy of a fluid at any given point with respect to a given datum. Th elevation to which water rises at a given point as a result of reservoir pressure.

Answer 59

Head

Question 60

The capacity of a porous medium to transmit water. The rate at which fluid can move through a permeable medium depends on properties of the fluid (viscosity and specific weight) and properties of the medium (intrinsic permeability).

Answer 60

Hydraulic Conductivity (K)

Question 61

Rate of change in total head per unit of distance of flow in a given direction

Answer 61

Hydraulic Gradient (I)

Question 62

A property of the porous medium that measures the relative ease with which a fluid can be transmitted through it under a hydraulic gradient. It is dependent upon the pore size and is measured in Darcys.

Answer 62

Intrinsic Permeability (k\_i)

Question 63

Water that is derived directly from magma and is thought to have come to the Earth's surface for the first time.

Answer 63

Juvenile Water

Question 64

A unit of hydraulic conductivity in gpd/ft2. The rate of flow in gallons per day through a cross section of 1 square foot under a hydraulic gradient at 60ºF.

Answer 64

Meinzer

Question 65

Unconfined groundwater separated from an underlying body of groundwater by an unsaturated zone.

Answer 65

Perched Groundwater

Question 66

The property of a porous rock or soil for transmitting a fluid. It measure the relative ease of flow under unequal pressure.

Answer 66

Permeability

Question 67

The percentage of the bulk volume of a rock or soil that is occupied by void space.

Answer 67

Porosity (n)

Question 68

A surface that represents the total head of groundwater and is defined by the level to which water will rise in a well.

Answer 68

Potentiometric Surface

Question 69

An area where water infiltrates downward in to the saturated zone.

Answer 69

Recharge Area

Question 70

That part of precipitation appearing in surface streams.

Answer 70

Runoff (R)

Question 71

Ration of the volume of water a soil or rock can retain against gravity drainage to the total volume of the soil or rock, usually a percentage.

Answer 71

Specific Retention (S\_r)

Question 72

Amount of water per unit volume of a saturated formation that is stored or expelled from storage due to compressibility of mineral skeleton and pore water per unit change in head.

Answer 72

Specific Storage (S-s)

Question 73

Ratio of the volume of water that drains from a saturated soil or rock due to gravity to the total volume of soil or rock. A percentage.

Answer 73

Specific Yield (S\_y)

Question 74

Volume of water that a permeable unit releases from or takes into storage per unit surface area of the aquifer per unit change in head.

Answer 74

Storativity or Storage Coefficient (S)

Question 75

The capacity of an aquifer to transmit water of the prevailing kinematic viscosity. T=Kb. where b = saturated thickness of the aquifer.

Answer 75

Transmissivity (T)

Question 76

An aquifer with a water table.

Answer 76

Unconfined aquifer

Question 77

Groundwater that flows beneath the bed or alluvial plain of a surface stream, especially in arid regions.

Answer 77

Underflow (U)

Question 78

A subsurface zone containing water under pressure that is less than atmospheric pressure. It is measured from ground surface to the water table.

Answer 78

Vadose Zone or Zone of Aeration

Question 79

The depth where the fluid pressure in the pores of the rock or soil is exactly atmospheric pressure

Answer 79

Water Table

Question 80

The region drained by a stream or body of water or a drainage divide.

Answer 80

Watershed

Question 81

1. Deep percolation from precipitation 2. Seepage from surface water 3. Groundwater underflow into aquifer 4. Artificial recharge from irrigation, recharge wells, etc. 5. Leakage through confining beds

Answer 81

Input Sources

Question 82

1. Evapotranspiration 2. Seepage to surface water 3. Groundwater underflow from aquifer 4. Discharge to springs 5. Artificial discharge from wells, infiltration galleries, and drainage systems 6. Discharge through confining beds.

Answer 82

Losses of Groundwater (output sources)

Question 83

Groundwater

Answer 83

What is below the water table?

Question 84

The capillary fringe

Answer 84

What is above the water table?

Question 85

acre-feet-per year (AFY) or gallons per year (GPY)

Answer 85

What units are used for change in storage (dS)?

Question 86

640 acres

Answer 86

What is 1 square mile in acres?

Question 87

5280 feet

Answer 87

What is 1 mile in feet?

Question 88

Below the water table

Answer 88

Where is hydraulic pressure greater than atmospheric pressure?

Question 89

It supplies water and nutrients to plants, is a zone of human activity, and is the medium that transports water and contaminants and recharges aquifers.

Answer 89

Why is the vadose zone important?

Question 90

Above the water table in the capillary fringe.

Answer 90

Where is hydraulic pressure negative (less than atmospheric pressure)?

Question 91

1. Macro pore flow that occurs along worm holes, root holes, or fractures. 2. Funneled or focused flow along lenses that may concentrate and deflect the direction of flow. 3. Unstable flow. i.e flow that breaks through interfaces and creates fungers that become more conducive to water flow, as compared to adjacent areas that are dry,

Answer 91

3 types of Preferential Flow:

Question 92

As the water content increases the metric potential decreases until it approaches zero.

Answer 92

What does the Soil Water Retention Curve show?

Question 93

1 Meinzer equals:

Question 94

1 darcy equals:

Question 95

Transmissivity Equation

Question 96

Hydraulic Gradient Equation

Answer 96

i = dh/l = h₁ - h₂ / l hydraulic gradient = change in head / distance between two points where heads are measured

Question 97

Darcy's Law:

Answer 97

v_d = -K (h₁ - h₂ / *l*) = Q / A

Question 98

Darcy's Law in terms of Transmissivity:

Answer 98

Q = T \* i \* w

Question 99

Flow rate equation

Answer 99

Q = v_d \*A or v_d = K\*i

Question 100

Seepage velocity equation

Answer 100

v_s = K\*i/n_e

Question 101

Ghyben-Herzberg Principle equation

Answer 101

Z = 40\*ht

Question 102

Methods used to control and prevent salt water intrusion into a fresh water aquifer

Answer 102

1. Controlled pumping to maintatin seaward hydraulic gradient in the fresh-water aquifer 2. Artificial recharge at the ground surface to maintain seaward gradient. 3. Placement of pumping trough between ocean and water-supply wells. 4. Creation of an injection barrier ridge between ocean and water-supply wells. 5. Construction of a man-made subsurface barrier.

Question 103

Isotopes used to date young groundwater:

Answer 103

Tritium (Hydrogen-3) Chlorofluorocarbons (CFC-11, CFC-12, CFC-113) Krypton-85

Question 104

Isotopes used to date Old Groundwater (60 - 50,000 years)

Answer 104

Radiocarbon (C-12, C-13, C-14)

Question 105

Isotopes used to date Very Old Groundwater

Answer 105

Chlorine-36 Krypton-81 ⁸¹Kr Helium-4