Chapter 12 - Groundwater

Question 1

Whats the % of groundwater compared to total water. So how much drinking water do we have?

Answer 1

0. 625%

- EVEN LESS DRINKING WATER, AS WE CANT EVEN DRINK ALL GROUNDWATER

Question 2

Define groundwater

Answer 2

water contained in pores within bedrock or regolith

• in groundwater, there is a saturated zone – most of the water is contained
• above, there is a zone of aeration(no water in pores)
• there is an area between saturation zone and aeration zone, called water table

Question 3

Relative sizes of zone of aeration and zone of saturation

Answer 3

cm to tons of m - zone of aeration

1m to 100s of m - zone of saturation

Question 4

What are outcrops of water table?

Answer 4

Lakes

Question 5

What is the potable/usable depth of saturation (depth that we can drink groundwater). What is the max depth

Answer 5

Max depth/potable/usable of saturation: 750m

they lower you go, the ore minerals get dissolved in groundwater, the more salty

Question 6

Does groundwater stay in its place or does it move?

Answer 6

Most groundwater moves several cm to meters per year

Question 7

Define porosity. What does it depend on?

Answer 7

% of rock that is pore space

Depends on sorting and cementation

Question 8

Define permeability . What does it depend on

Answer 8

Easy of fluid flow through porous medium

-depends on pore size + connectivity + viscosity

Question 9

Rank permeability between the 3 A’s

Answer 9

Aquifer: high perm - carries water
Aquitard: Low perm - movement of water is retarded (slow)
Aquiclude: No perm

Question 10

What is structured water?

Answer 10

Thin water coating on edges of pores of rocks.

-structured water’s permeability depends on the pores of rocks (big pores big permeability)

Question 11

Rank permeability of
(I)sand, silt, clay
(ii)sandstone, shale, solution activity in limestone, dolostone

Answer 11

(I) sand - high perm
silt - medium perm
clay - low perm
(ii) soln permeability in limestone/dolostone - very high
sandstone - high
shale - low
(THIS ALL DEPENDS ON POROSITY)

Question 12

Aquifer porosity?

Answer 12

High

Question 13

Aquitard porosity?

Answer 13

medium

Question 14

Aquiclude porosity?

Answer 14

low

Question 15

Correlation of porosity and permeability?

Answer 15

High porosity = lots of white space beteween rocks = high permeability

Question 16

Recharge and discharge areas - groundwater flow paths; Unconfined aquifers

Answer 16

For unconfined aquifers:
Water moves in an idealized fashion
-water frickles through ground surfaces and goes back to nearest stream
-flow velocity of water is variable: Faster at top, and the deeper you get it gets slower

Question 17

Rates of velocity of water in unconfined aquifer. What about the rate of our drinking water? How do they create streams if they slow? OH WAIT THEYRE not.. nvm no spoiler

Answer 17

-flow velocity of water is variable: Faster at top, and the deeper you get it gets slower

Rates: shallow water takes ~1000 days for any given molecule to rain down and come back out along river system and back to ocean
if you go deeper, it can take 100 yrs, 10 centuries, to a millennia

The water we drink flows fast
-when it rains, it fills up pore space in ground water, until It gets up to surface level, then starts to create streams

Question 18

Confined aquifers

Answer 18

Floridan aquifer (our example)

• water flows through stricted layer of rocks
• recharge and discharge,

Question 19

How to tell which way groundwater flows in confined aquifer? And can you drill into ground to get fresh ground water?

Answer 19

Water wells are called artesian wells in this case, they may or may not flow. We basically determine the level up to which the water rises from the bottom of the well. So you drill down to the ground water, and you see how high the water rises. Then at another point a few distance away. Connect the highest the water rises from both points, and then you get a plane. This plane describes how the water flows.

Question 20

What word do we use to describe a water well that may or may not flow on their own?

Answer 20

“Artesian”(may or may not flow) water well

Question 21

When do springs appear? Do springs appear in confined, or unconfined aquifers?

Answer 21

In unconfined and confined aquifers, springs appear where a boundary of aquifer to aquitard intersects the land surface

Question 22

TOP 10 GROUNDWATER PROBLEMS: 10 IS MOST DANGEROUS, 1 IS LEAST

Answer 22

Ten groundwater problems:
Problem 1: things may not stay buried / in the ground. Ex) in new Orleans, the ground water is so shallow, and it pushes things out of the ground. In coffins, that are buried in the ground, they put them on the ground so groundwater doesn’t push them out
Shallow ground water could push things out of the ground.

Problem 2: land subsidence: the ground can sink, *Structural damage to roads, buildings, bridges

problem 3: dry wells due to cones of depression in unconfined aquifers : water cannot get replenished at the same rate it is being pumped out
-to avoid these dry wells, you space the wells at a large distance, and you pump less.

Problem 4: salt contamination due to cone of ascension in unconfined aquifers
Usually happens in coastal area, the wells causes a cone of ascension which causes contact with salt water and thus contamination
at some depth the water is eventually gonna turn salty, because its beside a sea
-to fix this, you have to stop pumping, and then wait for the fresh water to come back in

Problem 5: contamination due to spills, leakage, garbage dumps

Problem 6: drying up of water well and or contamination from CBM extraction .. The wells could also be contaminated from the methane or fossil fuels they extract

Problem 7a: Drowning of salt mines - Radioactive contamination
7b: drowning of salt mines - Loss of mining operation

Problem 8: drought - non cultivated land turning into desert –> habit destruction, species migration

Problem 9: agricultural land turning desert, little or no water for agriculture and drinking

Problem 10: wars over water:

Question 23

difference between confined and unconfined aquifer

Answer 23

unconfined aquifer: water table is upper boundary
confined aquifer:
confined aquifer: water is bound above and below by beds (deeper than unconfined)