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ENCN342 > Groundwater > Flashcards

Groundwater Flashcards

1
Q

Aquifer

A

The temporary storage of infiltrating precipitation with slow release to lakes and streams

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2
Q

Vadose Zone

A

Area close to the surface where pore spaces are filled with a mixture of water and air

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3
Q

Phreatic Zone

A

Depth where all pore spaces are saturated

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4
Q

Aquitards

A

Low porosity and conductivity, provide protection for aquifers from surface contamination

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5
Q

Gaining stream

A

Water table above base of stream, baseflow recharges stream

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6
Q

Losing stream

A

Water table below base of stream

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7
Q

Perched aquifer

A

Infiltrating water becomes trapped and cannot flow out

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7
Q

Seepage face

A

Aquifer-aquitard contact outcrops at cliff face, causes groundwater to seep out

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8
Q

Artesian well

A

Water table level sits above ground surface, flows out of ground naturally

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9
Q

Groundwater well

A

Hole drilled into ground to target an aquifer

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10
Q

Well screen

A

Outer casing that allows water to flow into well while filtering out large particles

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11
Q

Groundwater head

A

Level to which water would rise in an infinite straw that is open to just that aquifer

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12
Q

Piezometric surface

A

Contours of constant head within an aquifer

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13
Q

Dupoit-Forchheimer Flow

A

Parabolic head profile in an unconfined aquifer assuming steady state conditions

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14
Q

Drawdown

A

Change in head compared to an original pre-pumped state

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15
Q

Hantush-Jacob Solution

A

Semi-confined aquifer with leakage, modelled by extra parameter, c, characterising the hydraulic resistance of the confining layer

16
Q

Moench-Neuman Solution

A

Model of delayed yield in unconfined aquifers

17
Q

Well yield

A

Maximum volume rate over a specified time period that introduces a drawdown no larger than Hmax

18
Q

Calculating the drawdown due to more than 1 well

A

Use the principle of superposition since Theis solution is linear

19
Q

Pump test with lateral flow barriers or a recharge source

A

Place an image well to model the effect of the flow boundary/recharge

20
Q

Using an image well for a lateral flow barrier

A

Place image well at equal distance from the lateral confinement as the pumped well
Drawdown at observation well is the sum of the image well and the pumped well

21
Q

Pump rate changes from x to y from time a to b

A

Drawdown is the sum of head due to x till time b, and the head due to (y - x) for time (b - a)

22
Q

Wellbore skin

A

Transmissivity reduction due to water level dropping more than expected

23
Q

Rorabaugh Method

A

Step-rate test to quantify transmissivity reduction using estimates from a pumping test

24
Q

Driven well

A

Pipe with pointed steel tip driven into ground to break through pebbles and layers of hard material

25
Q

Drilled well

A

Drill rig used to excavate hole, then casing and screen is placed.

26
Q

Well casing

A

The tubular components used in the construction of water wells

27
Q

Well screen intake

A

For wells in unconsolidated formations, prevent the pump from being clogged with aquifer material

28
Q

What is the maximum desirable screen entrance velocity related to?

A

Hydraulic conductivity of aquifer material

29
Q

Well screening for confined aquifers

A

Entire thickness of aquifer

30
Q

Well screening for unconfined aquifers

A

Lower one-third to one-half of the saturated thickness

31
Q

Why are longer screen lengths preferable?

A

Higher pumping rates per unit drawdown

32
Q

Common groundwater pump

A

Vertical turbine pump

33
Q

Grouting

A

Protection between well casing and borehole to prevent polluted surface water from contaminating the aquifer

34
Q

Performance assessment of groundwater wells

A

Pumping rate per unit drawdown

35
Q

Goal of wellfield design

A

Meet total pumping demand using as few whiles as possible while being constrained to a maximum drawdown

36
Q

Time of travel

A

Distance from a well where it will take a certain time for contaminants/water to reach the well

ENCN342 (3 decks)

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