Groundwater

Question 1

Estimated that there is 3000x more water stored as groundwater in the upper 800m of

Answer 1

the continental crust than water found in ALL the rivers and streams

Question 2

Groundwater is our most important:

Answer 2

source of freshwater

Question 3

About 30% of the Canadian pop depends on:

Answer 3

groundwater

Question 4

Groundwater is present where:

Answer 4

the crust has pores (like sand) or fractures (breaks in rocks)

Question 5

What is the water table?

Answer 5

The level below which the ground is saturated with water, fills all pore spaces, fluctuates with flooding, etc.

Question 6

What is the capillary fringe?

Answer 6

the boundary zone b/w unsaturated and saturated zones

Question 7

Water Table rises and falls with:

Answer 7

The seasons, and is not flat. Has muted topography.

Question 8

Porosity

Answer 8

• Pores are open spaces within any sediment or rock
• The total volume of open space is term porosity
• Geologic materials exhibit a wide range of porosities (i.e crystal size)

Question 9

Two categories of porosity:

Answer 9

primary and secondary

Question 10

Primary porosity

Answer 10

originally formed with the material, ie voids in sediment, vesicles in basalt

Question 11

Secondary porosity

Answer 11

develops later = fracturing, faulting, dissolution

Question 12

Permeability

Answer 12

• The ease of water flow due to pore interconnectedness
• Highly permeable material allows water to flow readily
• Water cannot flow through impermeable material
• Many large and straight flow paths enhance permeability

Question 13

Aquifer

Answer 13

a body of rock or unconsolidated sediment through which groundwater can flow, transmits water easily

Question 14

Aquitard

Answer 14

impermeable or low permeability sediment or rock that hinders water flow

Question 15

Why should deep groundwater take many times longer to reach the discharge area than shallow groundwater?

Answer 15

Travels longer distance, works its way far down and recharging is slower rate

Question 16

Unconfined vs Confined Aquifers

Answer 16

• Unconfined: an aquifer that intersects the surface, in contact with the atmosphere, easily contaminated
• Confined: an aquifer beneath an aquitard, isolated from the surface, less susceptible to pollution

Question 17

Hydraulic Gradient

Answer 17

• Hydraulic gradient is the slope of the water table
  = (h1 - h2)/L
• basically rise over run for water table
• Steeper slope means faster water table flows

Question 18

Darcy’s Law

Answer 18

V = K(dh/dL) or K(h1-h2)/L
V is groundwater flow velocity
K is the coefficient of permeability
(h1-h2)/L or (dh/dL) = hydraulic gradient

Question 19

Most water wells are drilled with

Answer 19

truck-mounted drill rigs

Question 20

Groundwater is fed by

Answer 20

snowmelt and rainfall in recharge areas

Question 21

In some situations, groundwater contributes to the base flow of a stream. In others:

Answer 21

streams contribute to the groundwater

Question 22

Gaining stream:

Answer 22

water table is above base flow so gains water

Question 23

Losing stream (connected):

Answer 23

water table is below, but connected to stream, loses water to ground

Question 24

Losing stream (disconnected):

Answer 24

water table is super far below stream, loses water

Question 25

Groundwater can maintain a 3D surface because:

Answer 25

pore water moves super slow = topography

Question 26

Wetlands are critically important for:

Answer 26

storage of both surface and groundwater

Question 27

Groundwater moves in response to

Answer 27

gravity and hydraulic pressure (pressure from behind)

Question 28

Aquiclude

Answer 28

aquitard = impermeable layer

Question 29

Confined or artesian aquifer

Answer 29

contained between 2 aquicludes

Question 30

Potentiometric surface

Answer 30

an imaginary plane where a given reservoir of fluid will “equalize out to” if allowed to flow, based on hydraulic principles.

Question 31

Potentiometric surface vs water table:

Answer 31

the difference between the naturally occurring surface of the water in a groundwater aquifer and the surface of the water in a monitoring well in a confined aquifer.

Question 32

Groundwater is vulnerable to many different sources of

Answer 32

pollution

Question 33

Any other fluid released into the ground will

Answer 33

try to do as water does

Question 34

Groundwater contains a wide range of dissolved

Answer 34

ions, most at levels that are higher than in surface water

Question 35

Hard water

Answer 35

• Water with high levels of calcium or magnesium
• often leaves coatings of white precipitates on plumbing fixtures
• related to the history of where the water has flowed in sediments

Question 36

Saltwater Intrusion

Answer 36

• Well creates a cone of depression and used so much of freshwater so now where saltwater flows in, near the coast

Question 37

What can people living near the coast do to reduce the likelihood of saltwater intrusion?

Answer 37

Dig well further inland, limit water use

Question 38

An improperly functioning septic tank can be a source of

Answer 38

groundwater contamination

Question 39

Springs (where the water table intersects with topography) exist where

Answer 39

groundwater naturally comes to the surface

Question 40

Karst topography

Answer 40

A landscape that is characterized by numerous caves, sinkholes, fissures, and underground streams

• usually forms in regions of plentiful rainfall where bedrock consists of carbonate-rich rock that is easily dissolved
• i.e hydrothermal activity like geysers, hot springs, fumaroles