Groundwater

Question 1

What is the role of hydrology for water resources management ?

Answer 1

Estimation of water resources availability
Estimation and reduction of hydrological risks
Development of hydrological scenarios
Ensure proper information to decision makers

Question 2

Zone of aeration/ vadose zone

Answer 2

A zone that contains both water and air

Question 3

Saturated zone

Answer 3

Where all the interconnected openings between rock particles are filled with water

Question 4

Soil moisture:

Answer 4

Water in the upper layers of zone of aeration

Question 5

Groundwater

Answer 5

Called the water in the zone of saturation

Question 6

Capillary fringe/ tension-saturated zone

Answer 6

The lower subdivision of the zone of aeration that overlies the zone of saturation and in which the pressure of water in the interstices is lower than atmospheric

Question 7

The water table

Answer 7

the surface where hydraulic head or water pressure head is equal to the atmospheric pressure

Question 8

Hydraulic head

Answer 8

specific measurement of water pressure which helps the water to rise above a datum

Question 9

Atmospheric pressure

Answer 9

force per unit area exerted on a surface by the weight of air above that surface in the atmosphere of Earth

Question 10

Aquifer

Answer 10

underground layer of water-bearing permeable rock or unconsolidated materials that can produce significant quantities of water to springs and wells

Question 11

Confined aquifer

Answer 11

Sandwiched between confining beds (layers of impermeable materials such as clay which impede the movement of water into and out of the aquifer)
Because of the confining beds, ground water in these aquifers is under high pressure
Because of the high pressure, the water level in a well
will rise to a level higher than the water level at the top
of the aquifer

The water level in the well is referred to as the Potentiometric Surface or pressure surface

Question 12

Does a confined aquifer have a water table ?

Answer 12

Confined aquifer does not have a water table.
It is completely filled with groundwater.
The water levels in wells drilled into a confined aquifer correspond
instead to the potentiometric surface of the aquifer, also
known as pressure head or confined head.

If the pressure head falls below the top of the aquifer, the aquifer is no
longer confined.

Question 13

Unconfined Aquifer

Answer 13

A groundwateraquiferis said to beunconfinedwhen its upper surface (water table) is open to the atmosphere through permeable material

As opposed to a confinedaquifer, the water table in anunconfined aquifersystem has no overlying impervious rock layer to separate it from the atmosphere

Question 14

What makes water flow?

Answer 14

Heat conducts from high to low temperature
Electricity flows from high to low voltage
Water flows from high to low fluid potential
Fluid potential is the mechanical energy per unit mass = work to move unit mass
Groundwater flow is a mechanical process, forces driving fluid must overcome frictional forces between porous media and fluid

Question 15

What is hydraulic conductivity?

Answer 15

𝐾 is a property of both media and fluid.

Experiments show:

• 𝒌 is the intrinsic permeability (L2), a property of media only
• 𝜌 is the mass density (M/L3)
• 𝜇 is the dynamic viscosity (M/LT) and measures the resistance of fluid to shearing that is necessary for flow

Question 16

What are the types of porosity?

Answer 16

Intergranular
Between grains, mostly part of the effect
of porosity, but also dead-end pores

• Intragranular
Within grains
Usually not considered part of the effective porosity
Incredible wide range of widths and length scales

Question 17

Specific retention - 𝑺_𝒓

Answer 17

Ratio of volume of water it will retain after saturation against the force of gravity to its own volume

Question 18

Specific Yield - 𝑺_𝒚

Answer 18

Ratio of volume of water that, after saturation, can be drained by gravity to its own volume

Question 19

Storativity (S)

Answer 19

Volume of water released from storage per unit surface area of an aquifer per unit decline in hydraulic head
Storativity is also known as Coefficient of Storage andStorage Coefficient

Question 20

Specific storage (SS)

Answer 20

Volume of water that a unit volume of aquifer releases from storage under a unit decline in head by the expansion of water and compression of the soil or rock skeleton
Ss=ρg(α+ neβ)

Question 21

Transmissivity (T)

Answer 21

Rate of flow under a unit hydraulic gradient through a unit width of aquifer of given saturated thickness
The transmissivity of an aquifer is related to its hydraulic conductivity as follows:
T = Kb
whereTistransmissivity[L2/T] andbisaquifer thickness[L]

Question 22

Why do the arrows that indicate the leakage point upward?

Answer 22

The piezometric surface of the lower aquifer is higher than the phreatic surface, which is also the piezometric surface of the upper aquifer. WE ASSUME that in both aquifers, the flow is essentially horizontal. The leakage across the aquitard is from low to high piezometric head, hence it iupwards.