Lesson 14: Ground Water

Question 1

What is the main use of groundwater in the U.S.?

Answer 1

Irrigation (Agriculture)

Question 2

Where does the groundwater stay in the rock?

Answer 2

in open spaces (pores) within rocks and unconsolidated sediments.

Question 3

What is porosity?

Answer 3

The percentage of open pore space within an unconsolidated sediment/rock

Question 4

What is permeability?

Answer 4

How connected the pore spaces are to one another; controlled solely by pore geometry

Question 5

Compare porosity and permeability

Answer 5

Porosity: determines how much groundwater can be stored
Permeability: determines how well water can flow from one pore to another

Question 6

Define vadose zone.

Answer 6

The unsaturated zone above the zone of saturation; includes both air and water

Question 7

Define saturated zone.

Answer 7

The zone of saturation where all pore spaces are completely filled with water; water in this zone is groundwater

Question 8

Define water table.

Answer 8

The upper limit of the zone of saturation.

Question 9

Compare losing and gaining streams.

Answer 9

Losing Streams: streams lose water to the groundwater system by outflow through the streambed; the water table is lower than the level of a stream

Gaining Streams: streams gain water from the inflow of groundwater through the streambed; the water table is higher than the level of the stream.

Question 10

What is an Aquitard?

Answer 10

an impermeable layer that hinders/prevents groundwater movement

Question 11

What is an Aquifer?

Answer 11

A porous and permeable zone that is saturated with water that is recharged as surface water seeps downward

Question 12

What types of rocks make an aquitard?

Answer 12

Shale/mudrock and clay

Question 13

What types of rock make an Aquifer?

Answer 13

Sand and glacial till

Question 14

What is a confined aquifer?

Answer 14

An aquifer that has permeable rock units enclosed within impermeable rock units; recharged in highlands where permeable rocks are exposed

Question 15

What is an unconfined aquifer?

Answer 15

An aquifer that is connected to the surface by open pore spaces through which it can be recharged

Question 16

What is a perched aquifer?

Answer 16

When there is a limited aquitard; it may be a good source of water during some parts of the year, but is very thin and small, and can be depleted easily.

Question 17

What is drawdown?

Answer 17

As water is withdrawn from a well, the surrounding water table is lowered.

Question 18

Where do drawdowns form?

Answer 18

at the water table

Question 19

What is a cone of depression?

Answer 19

the lowering effect on the water table

Question 20

Where does a cone of depression form?

Answer 20

at the base of a well stem

Question 21

What are artesian wells?

Answer 21

a system where groundwater under pressure rises above the level of the aquifer

Question 22

Where do artesian wells form?

Answer 22

in a confined and inclined aquifer

Question 23

What is the main corrosive component in groundwater?

Answer 23

Carbonic acid

Question 24

How is Carlsbad Cavern in New Mexico different than most other caverns?

Answer 24

they formed due to reactions with sulfuric acid-bearing water

Question 25

What are the 5 common rocks that easily dissolve?

Answer 25

1. Limestone 2. Dolostone 3. Halite/rock salt 4. Gypsum/Rock Gypsum 5. Marble

Question 26

What is Karst topography?

Answer 26

a landscape that has been shaped mainly by the dissolving power of groundwater

Question 27

What are the different karst landscapes?

Answer 27

1. Sinkholes 2. Caves/caverns 3. Tower karst 4. Disappearing streams 5. Springs

Question 28

How do sinkholes form? (3) types

Answer 28

1. Dissolution: Rainfall and surface water percolate through joints of a limestone, dissolved carbonate rock is carried away from the surface, and a depression gradually forms 2. Cover-Subsidence: Granular sediments spall into secondary openings in the underlying rocks, and a column of overlying sediments settles into the vacated spaces, forming a noticeable depression in the land surface 3. Cover-Collapse: Sediments spall into a cavity as spalling continues the cohesive covering sediments form a structural arch. The cavity migrates up by progressive roof collapse and eventually branches creating a sudden and dramatic sinkhole

Question 29

How do caves form?

Answer 29

By chemical dissolution resulting from circulating groundwater

Question 30

How do tower karsts form?

Answer 30

limestone rises above the surrounding landscape in highly eroded karst regions

Question 31

What are disappearing streams?

Answer 31

streams that disappear into cave openings that flow directly into the groundwater system.

Question 32

What are springs?

Answer 32

Groundwater that is becoming surface water

Question 33

What is speleothem?

Answer 33

A general name for dripstone features

Question 34

How do stalactites differ from stalagmites?

Answer 34

Stalactites hang from the ceiling Stalagmites form from the ground

Question 35

___ accounts for the largest percentage of groundwater usage in the US

Answer 35

Irrigation

Question 36

Porosity may be defined as:

Answer 36

the percentage of pore spaces in a rock/sediment

Question 37

_____ refers to how connected pore spaces are to one another.

Answer 37

Permeability

Question 38

______ are characteristics found in all good aquifers.

Answer 38

High porosity and high permeability

Question 39

The unsaturated (vadose) zone...

Answer 39

lies above the water table

Question 40

Highly impermeable layers such as compacted clay/shale are known as _____.

Answer 40

Aquitards.

Question 41

The lowering effect on the water table at the base of the well stem is called a ______.

Answer 41

cone of depression

Question 42

In an ______ system groundwater under pressure rises above the level of the aquifer.

Answer 42

artesian

Question 43

Does permeability depend on fluid properties?

Answer 43

No

Question 44

Which of the following sedimentary rocks is NOT easily dissolved? a. limestone b. sandstone c. dolostone d. Halite

Answer 44

b. sandstone

Question 45

____ topography is a landscape that has been shaped mainly by the dissolving power of groundwater.

Answer 45

Karst