CHPTR 16 Groundwater

Question 1

what percentage of water is groundwater

Answer 1

1%

Question 2

what percentage of fresh water (excluding ice) is groundwater

Answer 2

90%

Question 3

phreatic zone

Answer 3

saturated zone; water in this zone is called ground water

Question 4

soil moisture

Answer 4

some groundwater stays near the surface in the soil

Question 5

water table

Answer 5

top of the saturated (phreatic) zone

Question 6

vadose zone

Answer 6

zone of aeration

Question 7

capillary fringe

Answer 7

random water in the ground outside of the phreatic zone

Question 8

how can we see the water table

Answer 8

• tops of rivers
• bottoms of wells

Question 9

porosity

Answer 9

fraction of rock volume that is voids (water or air + joints, faults, caves)

Question 10

primary porosity

Answer 10

is in structures present when rock forms

Question 11

secondary porosity

Answer 11

develops in structures after the rock has formed

Question 12

permeability

Answer 12

measure of how easily fluid can flow through a rock

Question 13

Specific yield

Answer 13

fraction of groundwater that will drain under influence of gravity

Question 14

specific retention

Answer 14

fraction of groundwater that will remain under influence of gravity

Question 15

Porosity equation

Answer 15

Porosity% = Specific Yield% + Specific Retention%

Question 16

Aquitard

Answer 16

impermeable layer that hinders or prevents groundwater flow

Question 17

Aquifer

Answer 17

permeable layer that holds enough groundwater to be a useful source

Question 18

Porosity and permeability of crystalline igneous rock

Answer 18

low porosity
low permeability

Question 19

Porosity and permeability of shale (clay layers)

Answer 19

hi porosity
low permeability

Question 20

porosity and permeability of quartz sandstone

Answer 20

hi porosity
hi permeability

Question 21

porosity and permeability of glacial till

Answer 21

low porosity
low permeability

Question 22

Darcy’s Law + give it

Answer 22

equation for the calculation of groundwater velocity

V= (kh / pL)

k = constant
h = height
L = horizontal distance
p = porosity

Question 23

how can we increase the velocity of groundwater

Answer 23

• increase height

Question 24

how can we decrease he velocity of groundwater

Answer 24

• increase porosity
• increase horizontal distance

Question 25

perched water table

Answer 25

when an aquitard is situated above the main water table; producing a localized zone of saturation

Question 26

geyser

Answer 26

produce regular “eruptions” of hot water

Question 27

cone of depression

Answer 27

area of drawdown that forms around a well. occurs because groundwater flows relatively in response to extraction from aquifer. eventually the flow will level the water table

Question 28

drawdown

Answer 28

lowering of water table due to withdrawl of water

Question 29

confined aquifer

Answer 29

an inclined aquifer is surrounded by impermeable beds

Question 30

unconfined aquifer

Answer 30

overlain by permeable rocks and soil. pressure increased by elevation changes

Question 31

artesian well

Answer 31

water is in a confined aquifer and rises to a level above the aquifer due to pressure from changing elevations

Question 32

subsidence

Answer 32

the grounds sinks because of how much and how quickly groundwater is being removed

Question 33

saltwater intrusion

Answer 33

a natural barrier between salt and freshwater due to the density of seawater being higher than freshwater

Question 34

brackish water

Answer 34

mixture of seawater and freshwater

Question 35

acceptable tds in drinking water

Answer 35

500 mg / l

Question 36

hard water

Answer 36

substantial amounts of dissolved calcium and magnesium

Question 37

where do most caves form

Answer 37

at or just below the water table in the zone of saturation due to erosion

Question 38

speleothems

Answer 38

features formed by deposition of chemical sediment

ie. stalactites and stalagmites

Question 39

stalactite

Answer 39

hangs from the cieling

Question 40

stalagmite

Answer 40

upward growing mound

Question 41

Karst topography

Answer 41

groundwater erosion forms distinct features on the surface of the Earth:

• sinks and sinkholes form
• lack of surface streams

Question 42

most useful paramaters to finding water

Answer 42

electrical resistivity