Lecture 14: Groundwater

Question 1

What is groundwater

Answer 1

Water below the Earth’s surface the fills voids in soils and rocks.

Question 2

How does recharge occur?

Answer 2

It occurs when water enters into the subsurface and becomes groundwater by percolating into soil or rocks at the surface.

Question 3

What are the two zones of groundwater?

Answer 3

1. The Vadose Zone

2. The Saturated Zone

Question 4

The Vadose Zone

Answer 4

That region nearest to the surface where pores or fractures in the subsurface are not entirely filled with water.

Question 5

The Saturated Zone

Answer 5

That region under the vadose zone that is filled with water.

-Where an aquifer begins

Question 6

Water table

Answer 6

The surface where the vadose zone meets the saturated zone.

Question 7

Porosity

Answer 7

The amount of pore space in a geologic medium.

Question 8

Permeability

Answer 8

A measure of the ease with which a fluid can flow through a geologic medium.

Question 9

How does the water table change with the landscape and seasons?

Answer 9

• Subdued imitation of the landscape (rises with hills and becomes lower in valleys)
• Position varies with seasons

Question 10

What drives groundwater flow?

Answer 10

Flows from regions of lower pressure, driven by the force of gravity.

Question 11

What does the hydraulic head do?

Answer 11

Measures the pressure difference that drives groundwater flow.

Question 12

Groundwater discharge

Answer 12

A region at which groundwater emerges at the surface.

-Common discharge areas include surface water bodies.

Question 13

What are springs?

Answer 13

They are natural points of groundwater discharge that occur when the water table or a permeability boundary intersects the land surface.

Question 14

What is an aquifer?

Answer 14

Are units if geologic media that have sufficient capacity and high enough permeability to supply water at a rate useful to humans.
-Google definition: A body of permeable rock which can contain or transmit groundwater.

Question 15

What is an aquiclude?

Answer 15

Are units of geologic media that considerably slow or stop the flow of water.
-Google definition: Any geological formation that absorbs and holds water but does not transmit it at a sufficient rate to supply springs, wells, etc.

Question 16

What are the two kinds of aquifer?

Answer 16

1. Unconfined aquifer

2. Confined aquifer

Question 17

What is an unconfined aquifer?

Answer 17

Is an aquifer where the upper boundary is defined by the water table.

Question 18

What is a confined aquifer?

Answer 18

Is an aquifer where the upper boundary is defined by an aquiclude.

Question 19

How can a cone of depression form in the water table with a well in an unconfined aquifer?

Answer 19

If rate of groundwater withdrawal exceeds rate of local groundwater flow at a well.

Question 20

Wells in confined (artesian) aquifers

Answer 20

Water is often under pressure.
-If a well is drilled into a confined aquifer, the water can rise to a level close to that of the water table in the recharge area.

Question 21

What does the dissolution of minerals depend on?

Answer 21

Depends on the groundwater chemistry, especially pH.

-Occurs when minerals dissolve into the groundwater.

Question 22

What is the precipitation of minerals?

Answer 22

Occurs when ions dissolved in groundwater come out of the solution due to changes in factors such as pH, temperature, pressure or effects of evaporation.

Question 23

What are types of karst topography?

Answer 23

• Cave systems
• Sinkholes (collapsed cave roof)
• Pillars of rock isolated by dissolution of surrounding materials.

Question 24

What are stalactites?

Answer 24

An icicle-shaped formation that hangs from the ceiling of a cave and is produced by minerals that re-precipitate from water dripping through the cave ceiling.

Question 25

What are stalagmites?

Answer 25

A formation that rises from the floor of a cave due to the accumulation of re-precipitated minerals dripping off of stalactites.

Question 26

What is cement?

Answer 26

Mineral deposits in small pore spaces of sediment or rocks.