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 zone of aeration, immediately above the water table, where water is under pressure that is less than atmospheric pressure

Question 4

Cone of depression

Answer 4

A depression in the potentiometric surface of ground water that has the shape of an inverted cone and develops around a well from which water is being withdrawn. It defines the area of influence of a well.

Question 5

connate water

Answer 5

water trapped in the pores of a sedimentary rock at the time of deposition; fossil water

Question 6

Darcy

Answer 6

A unit of intrinsic permeability = 9.87 * 10e-9 cm2

Question 7

Darcy’s Law

Answer 7

Q = KiA

Question 8

Effective porosity

Answer 8

The percentage of the total volume of a soil or rock that consists of interconnected pore space. The term is sometimes used analogously to specific yield.

Question 9

Field Capacity

Answer 9

The quantity of water held by the soil or rock against the pull of gravity. Field capacity is dependent on the length of the time the soil or rock has been undergoing gravity drainage, while specific retention is not.

Question 10

Flow Net

Answer 10

two-dimensional representation of flow lines and equipotentials

Question 11

head

Answer 11

a measure of the potential energy of a fluid at any given point with respect to a given datum. In practice, it is the elevation to which water rises at a given point as a result of reservoir pressure.

Question 12

Hydraulic conductivity

Answer 12

the capacity of a porous medium to transmit water. units are L/T

Question 13

hydraulic gradient (i)

Answer 13

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

Question 14

intrinsic permeability (ki)

Answer 14

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 measured in darcys.

Question 15

Juvenile water

Answer 15

water that is derived directly from magma and is thought to have come to earth’s surface for the first time

Question 16

Meinzer

Answer 16

a unit of hydraulic conductivity in gpd/ft2. Rate of flow in gallons per day through a cross-section of one square foot under a hydraulic gradient at 60F

Question 17

Packer Test

Answer 17

An aquifer test in which two inflatablwe seals (or packers) are set in an open borehole to prevent movement of groundwater in the test section while the permeability of the isolated rock is determined.

Question 18

Perched groundwater

Answer 18

unconfined groundwater separated from an underlying body of groundwater by an unsaturated zone

Question 19

Percolation test

Answer 19

A test made by digging a hole, filling it with water, and measuring the decline of the water level.

Question 20

Permeability

Answer 20

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

Question 21

Potentiometric surface

Answer 21

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

Question 22

Runoff (R)

Answer 22

The part of precipitation appearing in surface streams

Question 23

slug test

Answer 23

an aquifer test where you pour a small charge of water into a well or where you remove a slug of water from the well. The removal of water from the well is also called a bail-down test

Question 24

Specific retention (St)

Answer 24

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

Question 25

Specific Storage (Ss)

Answer 25

amount of water per unit volume of a saturated formation that is stored or expelled from storage due to the compressibility of mineral skeleton and pore water per unit change in head. Units are in ft^-1

Question 26

Specific Yield (Sy)

Answer 26

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, stated as a percentage

Question 27

Storativity or Storage Coefficient (S)

Answer 27

Volume of water that a permeable unit releases from or takes into storage per unit of surface area of the aquifer per unit change in head. In an unconfined aquifer, storage = specific yield.

Question 28

Transmissivity (T)

Answer 28

The capacity of an aquifer to transmit water of the prevailing kinematic viscosity. T = Kb, where b = saturated thickness of the aquifer. Dimensions are in gpd/ft or ft2/day

Question 29

Unconfined Aquifer

Answer 29

an aquifer with a water table

Question 30

Underflow (u)

Answer 30

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

Question 31

Vadose Zone or Zone of Aeration

Answer 31

A subsurface zone containing water under pressure that is less than atmospheric pressure.

Question 32

Water table

Answer 32

The surface within unconfined groundwater at which the hydraulic pressure is equal to atmospheric pressure

Question 33

Well Efficiency

Answer 33

The ratio in percent of theoretical drawdown to actual drawdown measured in a well

Question 34

Permeability vs hydraulic conductivity

Answer 34

The proportionality constant specifically for the flow of water through a porous media is called the hydraulic conductivity; permeability is a portion of this, and is a property of the porous media only, not the fluid. Given the value of hydraulic conductivity for a subsurface system, the permeability can be calculated as follows:

k=K(mu/(rho*g))
where
k is the permeability, m2
K is the hydraulic conductivity, m/s
mu is the dynamic viscosity of the fluid, Pa·s
rho is the density of the fluid, kg/m3
g is the acceleration due to gravity, m/s2.