L15: Groundwater

Question 1

Groundwater

Answer 1

water below the Earth’s surface that fills voids in soils and rocks. It probably comprises less than 1% of Earth’s water, but this is somewhat uncertain because quantifying the exact amount, especially at depth, is difficult.

Question 2

Recharge

Answer 2

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

Question 3

THere’s approximately ______ more groundwater than there is surface water

Answer 3

35x

Question 4

What are the 2 primary zones of groundwater?

Answer 4

the vadose zone and the saturated zone

Question 5

Vadose zone

Answer 5

that region nearer to the surface where pores or fractures in the subsurface are not entirely filled with water

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 (soil, sediment, or rock), normally given between 0 to 1, or 0% to 100%

Question 8

Permeability

Answer 8

a measure of the ease with which a fluid (water in this case) can flow through a geologic medium. Related to both porosity and connectedness of pores.

Question 9

Does high porosity mean high permeability?

Answer 9

No

Question 10

Form of the water table

Answer 10

Notebook

Question 11

What drives groundwater flow?

Answer 11

Groundwater flows from regions of higher pressure to regions of lower pressure, driven ultimately by the force of gravity.

Question 12

Hydraulic head

Answer 12

measures the pressure difference that drives groundwater flow.

Question 13

Groundwater discharge

Answer 13

A region of discharge is one at which groundwater emerges at the surface. Common discharge areas include surface water bodies (rivers, lakes, streams, wetlands) and springs.

Question 14

Aquifer

Answer 14

units of geologic media that have sufficient capacity and high enough permeability to supply water at a rate useful to humans

Question 15

What are springs?

Answer 15

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

Question 16

What are the 2 types of aquifers?

Answer 16

Confined and unconfined

Question 17

Confined aquifer

Answer 17

one in which the upper boundary is defined by an aquiclude

Question 18

Unconfined aquifer

Answer 18

one in which the upper boundary is defined by the water table

Question 19

Aquiclude

Answer 19

units of geologic media that considerably slow or stop the flow of water (that is, they have low permeability).

Question 20

Wells in unconfined aquifers

Answer 20

If rate of groundwater withdrawal (pumping) exceeds rate of local groundwater flow at a well, this can lead to the formation of a cone of depression in the water table surrounding the well

Question 21

Wells in confined aquifer

Answer 21

• Artesian
• 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 22

Groundwater is a _____________ that causes considerable mass transport, via the dissolution and precipitation of minerals in geologic media.

Answer 22

Geologic agent

Question 23

What is the dissolution of minerals dependent on?

Answer 23

• the groundwater chemistry, especially pH

- More in notebook

Question 24

Karst

Answer 24

Dissolution of limestone and other soluble rock types leads to the formation of cave systems, sinkholes (collapsed cave roofs),and pillars of rock isolated by dissolution of surrounding materials

Question 25

Stalactites

Answer 25

hanging from ceiling

Question 26

Stalagmites

Answer 26

growing from the floor

Question 27

Precipitation of groundwater

Answer 27

Dissolved ions in groundwater may re-precipitate to form stalactites or stalagmites in caves, due to evaporation and other changes in groundwater chemistry

Question 28

Cements

Answer 28

more abundant, are mineral deposits in small pore spaces, called cement. Cement may convert a loose sand into a hard sandstone, an aquifer into an aquiclude, and make a potential oil reservoir into a non-porous non-reservoir