Oct 21 Lecture (Water as a resource)

Question 1

if you followed a water molecule all the way through the water cycle, it would take ___yrs

Answer 1

40,000

Question 2

regionally, water is a renewable resource, but may not be ___

Answer 2

locally

Question 3

how does groundwater form?

Answer 3

forms as rain infiltrates through soil and unconsolidated material, progressively moving into the bedrock
- the only space for water is pore spaces b/w the grains that comprise the bedrock or space in fractures

Question 4

rocks that store and transmit water are called ___

Answer 4

aquifers

Question 5

compared to surface water, groundwater has many advantages:

• it’s naturally ____ through aquifer rock
• it’s less susceptible to ____ and _____ ____

Answer 5

filtered

evaporation
seasonal variations

Question 6

porosity=

Answer 6

portion of void space in material (soil or rock) where fluid can be stored

Question 7

permeability=

Answer 7

measures how readily a fluid passes through a material

Question 8

____ are very porous

___ is not very porous/ permeable

Answer 8

sandstones

clay

Question 9

porosity varies with:
1.
2.
3.

Answer 9

1. % cement
2. sorting
3. fracturing

Question 10

gravity will pull water down into the ground until an impermeable layer (an ____) halts it

Answer 10

aquitard

Question 11

what is the saturated zone?

Answer 11

aka phreatic zone

below the water table; fills with water (all pore spaces)

Question 12

what is the unsaturated zone?

Answer 12

aka vadose zone

above the water table, above saturated zone

pore spaces are filled with water and air

Question 13

the water table is at the top of the _____ ___

Answer 13

saturated zone

the water table separates the unsaturated and saturated zones

Question 14

water stored and transmitted at rates sufficient enough to be useful is called a(n) _____

Answer 14

aquifer

Question 15

water moving into an aquifer is called ____

Answer 15

recharge

Question 16

when ___ and ___ are balanced, the groundwater reservoir and water table remain constant

Answer 16

recharge and discharge

Question 17

an aquifer without an aquitard above it is called a(n) ____ _____

Answer 17

unconfined aquifer

Question 18

an aquifer with an aquitard above and below it is a(n) ___ ___

Answer 18

confined aquifer

Question 19

a confined aquifer may see hydrostatic water pressure increase and form a(n) ____ ___

Answer 19

artesian system

Question 20

what happens if you drill into a confined aquifer that’s under pressure?

Answer 20

it’ll cause water to rise above the aquifer

- the potentiometric surface is the height to which the water would rise

Question 21

what is the potential energy in an aquifer called?

Answer 21

hydraulic head

Question 22

the higher the water table, the ___ the hydraulic head

the higher the potentiometric surface in a confined aquifer, the ___ the hydraulic head

Answer 22

higher

higher

Question 23

groundwater flows spontaneously from areas of ___ hydraulic head to areas with ___ hydraulic head

Answer 23

high to low

Question 24

discharge is the:

it’s influenced by:

Answer 24

amount of water flowing past a point over a period of time

the porosity and permeability of the rock or sediment of the aquifer

Question 25

what is a perched water table?

Answer 25

groundwater that forms a “table” above an aquitard well above the actual water table.
caused by distribution of aquitard lenses

Question 26

describe cones of depression

Answer 26

pumping ground water will lower the water table and form a cone of depression around the well
if not enough recharge, well can run dry

Question 27

why does saltwater intrusion occur?

Answer 27

because freshwater is less dense than saltwater
- saltwater near a coastline may push freshwater lenses back if recharge is not sufficient to push seawater back towards the sea

Question 28

What is the GRACE satellite?

Answer 28

2 satellites that can tell how much groundwater has been extracted

• based on mass of earth/ gravitational pull
• originally used for greenland ice caps

Question 29

what did the GRACE satellites find in India?

Answer 29

India’s groundwater has been nearly depleted