Groundwater Flashcards

1
Q

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

A

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

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2
Q

Groundwater is our most important:

A

source of freshwater

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3
Q

About 30% of the Canadian pop depends on:

A

groundwater

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4
Q

Groundwater is present where:

A

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

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5
Q

What is the water table?

A

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

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6
Q

What is the capillary fringe?

A

the boundary zone b/w unsaturated and saturated zones

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7
Q

Water Table rises and falls with:

A

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

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8
Q

Porosity

A
  • 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)
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9
Q

Two categories of porosity:

A

primary and secondary

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10
Q

Primary porosity

A

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

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11
Q

Secondary porosity

A

develops later = fracturing, faulting, dissolution

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12
Q

Permeability

A
  • 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
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13
Q

Aquifer

A

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

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14
Q

Aquitard

A

impermeable or low permeability sediment or rock that hinders water flow

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15
Q

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

A

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

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16
Q

Unconfined vs Confined Aquifers

A
  • 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
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17
Q

Hydraulic Gradient

A
  • 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
18
Q

Darcy’s Law

A

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

19
Q

Most water wells are drilled with

A

truck-mounted drill rigs

20
Q

Groundwater is fed by

A

snowmelt and rainfall in recharge areas

21
Q

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

A

streams contribute to the groundwater

22
Q

Gaining stream:

A

water table is above base flow so gains water

23
Q

Losing stream (connected):

A

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

24
Q

Losing stream (disconnected):

A

water table is super far below stream, loses water

25
Groundwater can maintain a 3D surface because:
pore water moves super slow = topography
26
Wetlands are critically important for:
storage of both surface and groundwater
27
Groundwater moves in response to
gravity and hydraulic pressure (pressure from behind)
28
Aquiclude
aquitard = impermeable layer
29
Confined or artesian aquifer
contained between 2 aquicludes
30
Potentiometric surface
an imaginary plane where a given reservoir of fluid will "equalize out to" if allowed to flow, based on hydraulic principles.
31
Potentiometric surface vs water table:
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.
32
Groundwater is vulnerable to many different sources of
pollution
33
Any other fluid released into the ground will
try to do as water does
34
Groundwater contains a wide range of dissolved
ions, most at levels that are higher than in surface water
35
Hard water
- 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
36
Saltwater Intrusion
- Well creates a cone of depression and used so much of freshwater so now where saltwater flows in, near the coast
37
What can people living near the coast do to reduce the likelihood of saltwater intrusion?
Dig well further inland, limit water use
38
An improperly functioning septic tank can be a source of
groundwater contamination
39
Springs (where the water table intersects with topography) exist where
groundwater naturally comes to the surface
40
Karst topography
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