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Geog322 > groundwater > Flashcards

groundwater Flashcards

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
Q

hydro horizon and water pressure

A

unsaturated soil: negative P
saturated : positive P
water table: P = 0

26
Q

water table

A

fluctuates up and down with precipi
usually parallel to soil surface

27
Q

measuring soil water tension

A

Tensiometer -> tube partially filled with water with low-permeability porous cup at bottom that balance with soil pressure

28
Q

Hydraulic conductivity (K)

A

ease at which water can move through pore spaces/ soil fractures
-larger for sand VS smaller for clay

29
Q

Rainfall rate (i)

A

rainfall intensity = amount per time

30
Q

infiltration capacity (fc)

A

max rate soil can absorb water through surface

31
Q

infiltration fate f(t)

A

time-variable rate of water entering soil via surface

32
Q

how does f(t) vary throughout rainfall event

A

at first, decrease rapidly
then plateau near fc

33
Q

Wetting front

A

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
Q

Cumulative infiltration F(t)

A

accumulated depth of infiltration from beginning of rainfall to given time -> area under curve of f(t)

35
Q

Time of ponding H(t)

A

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
Q

Horton & Philip models

A

Both measure f(t) , F(t) and H(t)
Horton -> include f0 and fc
Philip -> use suction and K

37
Q

what controls infiltration

A

soil surface condition
subsurface conditions
influencing factors
flow influence
hydrophobicity

38
Q

Subsurface conditiond

A

soil characteristics (porosity, depth, etc.)
root system
water table depth
subsurface drainage
hydraulic conductivity

39
Q

soil surface conditions

A

land use
vegetation cover
roughness and slope
cracking/ crusting
surface sealing

40
Q

factor influencing surface/ subsurface conditions

A

mechanical process
freeze-thaw cycle
litter layer
compaction
antecedent soil water conditions
chem activity
bio activtiy
microbial activity

41
Q

hydrophobicity

A

dryness
heat
plant chem
aromatic oils
fire
other chem

42
Q

Flow influence

A

ponding
soil and water temperature

43
Q

Saturated flow

A

movement of water via saturated pores & fractures
-relatively slow BUT higher in limestone

44
Q

Flow velocity depends on:

A

slope of water table
permeability of rock/ sediment of aquifer

45
Q

aquifer

A

saturated, permeable, geologic unit transmitting significant amount of GW under ordinary gradient

46
Q

aquiclude

A

saturated, geologic unit doesnt transmit significant amount of GW under ordinary gradient

47
Q

Aquifer types

A

unconfined
confined
perched

48
Q

unconfined aquifer

A

aquifer with lower barrier bc of aquiclude below BUT not upper barrier -> water fluctuates upwards
-partially filled and rapidly recharged

49
Q

confined aquifer

A

aquifer with lower and higher barrier bc aquiclude above and below
-completely filled and slow to recharge

50
Q

perched aquifer

A

unconfined water zone sitting on top of clay and separated from main aquifer below

Geog322 (9 decks)

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