Groundwater

Question 1

Roughly _____% of Canada’s population is reliant on groundwater

Answer 1

25-40%

Question 2

Define Groundwater

Answer 2

water that lies beneath the surface

Question 3

Ground water makes up for __% of the hydrosphere’s fresh water, while glaciers make up for ___%

Answer 3

22% and 77%, respectively

Question 4

___% of total precipitation infiltrates the ground and sends up as ground water

Answer 4

15%

Question 5

True or False: ground water is static

Answer 5

False; it is slow moving

Question 6

True or False: groundwater is found most commonly in underground lakes and rivers

Answer 6

True, but barely. It can occur, but is extremely rare

Question 7

Where is groundwater most commonly found

Answer 7

pores of sediment and soil

fractures of bedrock

Question 8

Porosity

Answer 8

percentage of voids or pore space (vs total volume)

Question 9

What is porosity used to determine?

Answer 9

How much groundwater can be stored

Question 10

How to measure porosity

Answer 10

Take a column with a toal volume of 1000 mL and fill it with dry sand (dry sand has a porosity filled with air). replace the air with water. The porosity=volume water/Volume total

Question 11

Permeability or Conductivity

Answer 11

Capacity of rock or sediment to transmit a fluid

connected pores give a rock permeability

Question 12

Specific yield

Answer 12

% that can drain by gravity

Question 13

Specific retention

Answer 13

% that cannot drain by gravity

Question 14

Distribution of ground water is found in what three places?

Answer 14

1) Unsaturated zone
2) Water Table
3) Zone of saturation

Question 15

Unsaturated zone

Answer 15

• above water table
• voids filled by water and air
• water is under suction (negative pressure) due to capillary forces (think TLC)
• water cannot be pumped by wells

Question 16

Water Table

Answer 16

• Upper limit of zone of saturation
• surface of water level in ground
• depth varies seasonally

Question 17

Zone of Saturation

Answer 17

• below water table
• all voids are filled with water
• water is under positive pressure and can be sucked up by wells

Question 18

Pressure distribution

Answer 18

unsat:
a) Patmos. P
b) water under (+) pressure

Question 19

What factors control infiltration?

Answer 19

1) precipitation
2) slope
3) geological material
3) vegetation

Question 20

In what three places is groundwater stored?

Answer 20

1) Aquifer
2) Acquitard
3) Aquiclude

Question 21

Aquifer

Answer 21

permeable rock layer or sediment that stores and transmits groundwater

Question 22

Acquitard

Answer 22

semi-permeable rock layer

Question 23

Aquiclude

Answer 23

impermeable rock layer (exCLUDEs water)

Question 24

Types of aquifers

Answer 24

Unconfined and confined

Question 25

Unconfined aquifer

Answer 25

• no confining layer
• groundwater is not under pressure
• top of water table moves freely up and down

Question 26

Confined aquifer

Answer 26

• sandwiched between 2 confining layers (usually inclined to allow recharge)
• groundwater is under pressure
• top of water table is above confined aquifer

Question 27

Types of wells

Answer 27

Non-flowing artesian well and flowing artisan well

Question 28

Non-flowing artesian well

Answer 28

water table (pressure surface) of a confined aquifer lies below ground level (pressure is not great enough to bring water to the surface)

Question 29

Flowing artesian well

Answer 29

Water table of a confined aquifer rests above ground level; water reaches ground surface using natural pressure of the confined aquifer

Question 30

What is the general pattern of movement?

Answer 30

recharge (high) –> discharge (low)

Question 31

True or False: velocity is highest nearest the surface

Answer 31

true

Question 32

Darcy’s Law states:

Answer 32

States that if permeability remains uniform, the velocity of groundwater will increase as the slope of the water table (hydraulic gradient) increases

Question 33

Darcy’s Law equation

Answer 33

v=-(K/fancy n)(i), where K = hydraulic conductivity, n = porosity, i=hydraulic gradient=driving force, v=velocity

Question 34

Ground water and stream interactions

Answer 34

1) gaining streams
- gain water from the inflow of groundwater through streambed
2) losing streams
- loss of water to the groundwater system by outflow through streambed

Question 35

The water table is ____ than the stream bed in the gaining streams interaction

Answer 35

higher

Question 36

The water table is ____ than the stream bed in the losing streams interaction

Answer 36

lower

-zone of aeration present

Question 37

Sources of groundwater contamination

Answer 37

• road salt
• fertilizers
• pesticides
• chemical and industrial materials
• bacteria and viruses

Question 38

What are some problems associated with groundwater withdrawal?

Answer 38

Sewage contamination
-sewage often becomes purified as it passes through the aquifer composed of sand or permeable sandstone. However, in extremely permeable aquifers (ie. coarse gravel or fractured bedrock), the groudwater may travel long distances without being cleaned

Saltwater contamination
-excessive groundwater withdrawal causes saltwater to be drawn into wells

Question 39

What are the consequences of excessive pumping?

Answer 39

1) drawdown (lowering) of the W.T

2) cone of depression in the WT

Question 40

subsidence

Answer 40

Ground shrinks when water is pumped from wells faster than the recharge process can replace it

Question 41

Geysers

Answer 41

intermittent surface emission of hot water

occur when groundwater heats, changes to steam, and errupts

Question 42

Erosional features of groundwater

Answer 42

• caves (underground cavity)

- Karst topography (typically form in limestone bedrock) (ie. caves and sinkholes)

Question 43

Depositional features

Answer 43

• Groundwater is often mildly acidic, so it dissolves rocks (particularily limestone).
• if rxn reverts and CO2 escapes, CaCO3 is deposited, creating stalactite (point down), stalagmite (point up), column/pillar etc