groundwater Flashcards

(50 cards)

1
Q

Hydrologic horizons in order

A

root zone
intermediate zone
capillary fringe
water table
groundwater zone
impermeable layer

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2
Q

2 main zone of hydrologic soil horizons

A

Vadose (unsaturated) = water fills some pores
Phreatic (saturated) = water fills all pores

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3
Q

Capillary fringe

A

Belt of variable thickness presenting wet envr in saturated zone due to capillary rise

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4
Q

Process affecting water in subsurface

A

Infilitration
percolation
recharge
capillary rise
interflow/ subsurface flow
GW flow

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5
Q

Infiltration

A

movement of water from soil surface downwards

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6
Q

Percolation

A

downward movement of water in unsaturated zone

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7
Q

recharge

A

addition of water to saturated zone

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8
Q

capillary rise

A

movement of water from saturated zone upwards into unsaturated zone

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9
Q

Interflow/ subsurface flow

A

flow occuring in unsaturated zone in lateral direction

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10
Q

GW flow

A

flow in saturated zone

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11
Q

Soil texture

A

describes grain size distribution for particles below 2mm -> influence infilitration, runoff, etc.

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12
Q

total porosity (n) equation

A

n = V voids/ V total

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13
Q

Void ratio (e)

A

V voids/ V solids

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14
Q

soil water content volumetric

A

V water / V total

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15
Q

soil water content gravimetric

A

(Mass wet - mass dry )/ mass dry

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16
Q

Relating gravimetric to volumetric

A

(Bulk density soil/ bulk density water) x mass

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17
Q

Degree of Saturation (S)

A

S = V water / (V water + V gas)

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18
Q

soil water storage type

A

Gravitational: excess drained under gravity at saturation
Capillary: held in soil pore in intermediate/wet conditions
Hygroscopic: thin films holding onto soil grains in dry conditions

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19
Q

Soil moisture critical values

A

Field capacity
permanent wilting point
plant available water

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20
Q

Field capacity

A

max amount of water soil holds after gravitation drainage

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21
Q

PWP

A

Minimum soil moisture content after gravity drainage AND plant evapotranspi

22
Q

Plant available water

A

difference between FC and PWP

23
Q

hydro horizon and critical moisture value:

A

root: PWP < moisture < n
intermediate: FC < moisture < n
capillary : moisture = n
saturated: moisture = n

24
Q

Water migration caused by

A

water pressure difference:
-from higher to lower pressure

25
hydro horizon and water pressure
unsaturated soil: negative P saturated : positive P water table: P = 0
26
water table
fluctuates up and down with precipi usually parallel to soil surface
27
measuring soil water tension
Tensiometer -> tube partially filled with water with low-permeability porous cup at bottom that balance with soil pressure
28
Hydraulic conductivity (K)
ease at which water can move through pore spaces/ soil fractures -larger for sand VS smaller for clay
29
Rainfall rate (i)
rainfall intensity = amount per time
30
infiltration capacity (fc)
max rate soil can absorb water through surface
31
infiltration fate f(t)
time-variable rate of water entering soil via surface
32
how does f(t) vary throughout rainfall event
at first, decrease rapidly then plateau near fc
33
Wetting front
sharp discontinuity in soil profile with dry below and wet above -> created by change of soil moisture with depth due to top-down infiltration BUT not always at constant depth -> preferential flow
34
Cumulative infiltration F(t)
accumulated depth of infiltration from beginning of rainfall to given time -> area under curve of f(t)
35
Time of ponding H(t)
time a which surface layer is saturated with rainfall rate exceeding hydraulic conductivity 2 conditions: fully saturated soil OR higher rainfall rate than infiltration rate
36
Horton & Philip models
Both measure f(t) , F(t) and H(t) Horton -> include f0 and fc Philip -> use suction and K
37
what controls infiltration
soil surface condition subsurface conditions influencing factors flow influence hydrophobicity
38
Subsurface conditiond
soil characteristics (porosity, depth, etc.) root system water table depth subsurface drainage hydraulic conductivity
39
soil surface conditions
land use vegetation cover roughness and slope cracking/ crusting surface sealing
40
factor influencing surface/ subsurface conditions
mechanical process freeze-thaw cycle litter layer compaction antecedent soil water conditions chem activity bio activtiy microbial activity
41
hydrophobicity
dryness heat plant chem aromatic oils fire other chem
42
Flow influence
ponding soil and water temperature
43
Saturated flow
movement of water via saturated pores & fractures -relatively slow BUT higher in limestone
44
Flow velocity depends on:
slope of water table permeability of rock/ sediment of aquifer
45
aquifer
saturated, permeable, geologic unit transmitting significant amount of GW under ordinary gradient
46
aquiclude
saturated, geologic unit doesnt transmit significant amount of GW under ordinary gradient
47
Aquifer types
unconfined confined perched
48
unconfined aquifer
aquifer with lower barrier bc of aquiclude below BUT not upper barrier -> water fluctuates upwards -partially filled and rapidly recharged
49
confined aquifer
aquifer with lower and higher barrier bc aquiclude above and below -completely filled and slow to recharge
50
perched aquifer
unconfined water zone sitting on top of clay and separated from main aquifer below