Geohazards - Water

Question 1

what does porosity mean and what is it affected by? (3 points)

Answer 1

• amount of cavities between grains fractures and joints
• how much liquid is being held
• affected by sorting shape, shape, packing and cementation

Question 2

what does permeability mean and what is it affected by? (3 points)

Answer 2

• measure of how fast water can move through a rock
• governed by connectivity
• affected by grain size

Question 3

what is an aquifer? (3 marks)

Answer 3

• can hold and extract water
• permeable and porous
• limestones and sandstones

Question 4

what is an aquitard? (3 points)

Answer 4

• can hold water but only extracted via pumping
• shale
• semi-pervious

Question 5

what is an aquiclude? (3 points)

Answer 5

• can’t store or extract water
• shale
• impervious

Question 6

what is a confined aquifer?

Answer 6

water can’t seeps directly into the aquifer

water can flow in from the side

Question 7

what is an unconfined aquifer?

Answer 7

water will seep directly into an underlying unit of permeable rock

Question 8

what is a spring?

Answer 8

water flows from an aquifer to the surface

Question 9

what is the cone of depression and why does it form

Answer 9

its the lowering of the regional water table

forms when the extraction rate greater than recharge

Question 10

what is subsidence?

Answer 10

water removal means that pore pressure decreases which then causes the ground to sink

Question 11

what is saltwater incursion?

Answer 11

when extraction is greater the recharge and the water re-entering is saltwater rather than freshwater

Question 12

what do you look for when building a reservoir where or dam? (7 points)

Answer 12

Porosity/permeability
Faults
Folds
Rock strength 
Lithology
Recharge 
SA/volume of area