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Hydrogeology > Geology of Groundwater Occurence > Flashcards

Geology of Groundwater Occurence Flashcards

1
Q

The Philippines has complex geology owing to presence of:

A

various tectonic and structural formation

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2
Q

where does groundwater inevitably occur?

A

geologic formations

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3
Q

t or f: earth is heterogenous

A

T

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4
Q

groundwater studies of an area necessarily includes:

A

review of previous geological studies

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5
Q

t or f: groundwater is more abundant than surface water

A

T

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6
Q

a ______________ must be made along groundwater study

A

detailed geological study

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7
Q

concerned with the distribution of earth material as they affect porosity and hydraulic conductivity of the earth

A

hydrogeologist

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8
Q

amount of voids contained in a particular volume of rock mass

A

porosity

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9
Q

porosity ranges for sedimentary materials

A

soil
clay
silt
medium to coarse sand
uniform sand
fine to medium sand
gravel
sand and gravel
sandstone
shale
limestone

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10
Q

capacity of a porous rock or soil to transmit a fluid

A

permeability / hydraulic conductivity

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11
Q

t or f: large interconnected pore openings are associated with high permeability

A

t

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12
Q

three types of limestone bedrock

A

karstified, fissured, compact

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13
Q

t or f: in groundwater assessment, using large ranges of hydraulic conductivity is not safe

A

t

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14
Q

the water that cannot be pumped out of a well

A

specific retention (Sr)

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15
Q

specific retention is left as a _____ on the rock surface

A

film

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16
Q

the water that can be pumped from a well

A

Specific yield (Sy)

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17
Q

part of the water that would be drained under the influence of gravity

A

Specific yield

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18
Q

what is the material with highest specific yield by (heath 1983)?

A

soil

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19
Q

what is the material with lowest specific yield by (heath 1983)?

A

granite

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20
Q

dumoy aquifer is under what watershed?

A

Talomo-Lipadas watershed

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21
Q

Dumoy aquifer is of what material?

A

volcaniclastics

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22
Q

this watershed supplies 90% of the drinking water serviced by Davao City Water Districts

A

Talomo-Lipadas watershed

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23
Q

target areas of groundwater exploration (2):

A

fllodplain ; malayo sa dagat

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24
Q

t or f: air allows passage of electrical currents

A

F (air does not allow electrical passage)

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25
Q

probability of sinkhole may reflect a _______ (high/low) electrical resistivity

A

high

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26
Q

this allows one and two dimensional acquisition of resistivity values of subsurface and generate long signature

A

Vertical electrical sounding (VES)

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27
Q

estimate lateral and vertical variations in ground resistivity values (allows 2D and 3D)

A

Electrical Resistivity Tomography (ERT)

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28
Q

a gently sloping plain consisting of alluvium

A

alluvial valleys

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29
Q

a dry lake bed

A

playa

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30
Q

playas and floodplains are good prospects of groundwater exploration because they have

A

unconsolidated sediments

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31
Q

an aquifer where water is held in pore spaces between grains of sand, gravel, clays, or rock fragments

A

unconsolidated aquifer

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32
Q

alluvial valleys are normally delimited by _______ on either side that rise above the level of the valley to varying heights

A

uplands

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33
Q

t or f: the alluvial valley of a stream is the portion of its alluvial plain that is on the upstream of its deltaic plain

A

T

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34
Q

basins formed by faulting or erosion are both filled with ______________; coarse grained deposits form ______

A

unconsolidated deposits ; productive aquifers

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35
Q

t or f: lake mainit is a graben

A

t

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36
Q

t or f: marikina valley is a graben formed by fault

A

T

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37
Q

emptied oxbow lake, remnants of a meandering water channel

A

meander scar

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38
Q

A lake formed as a river finds a different, shorter, course

A

oxbow lake

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39
Q

t or f: many major valley systems are products of tectonic activities rather than of fluvial and glacial erosion

A

t

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40
Q

during mountain-building episodes, the uplift of mountain masses will result in _____________ being formed

A

intermontane basins

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41
Q

An alluvium-filled valley between mountain ranges, often formed over a graben

A

intermontane basin

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42
Q

major aquifers in intermontane basins are composed of _____________ that overlie _________ aged rocks

A

unconsolidated deposits ; pre-Miocene

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43
Q

are also created by down-dropping of large crustal pieces along faults

A

fault-block valleys

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44
Q

basins bounded by impermeable rock may form ________

A

local or single-valley flow systems

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45
Q

if the interbasin rock is permeable, __________ may form

A

regional flow systems

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46
Q

in closed basins, ground water discharges into _______

A

playas

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47
Q

playas are discharged by

A

evaporation and transpiration by phreatophytes

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48
Q

closed basins are also called

A

endorheic basins

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49
Q

much of the drainage in this basin occurs underground

A

cryptorheic basins

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50
Q

a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation

A

closed / endorheic basin

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51
Q

one of the most productive terrains for recovering groundwater

A

alluvial valleys

52
Q

these form a large part of the stream alluvium

A

sand and gravel

53
Q

likely to tap a good aquifer or series of aquifer

A

alluvial valleys

54
Q

t or f: individual aquifers in alluvial valleys do not usually extend far

A

T

55
Q

t or f: the number and depth of water-bearing sand and gravels change rapidly from place to place in an alluvial valley

A

t

56
Q

t or f: lithified sedimentary rocks have lesser hydraulic conductivity

A

t

57
Q

clastic sedimentary rocks are typically composed of

A

silicate, carbonate, or clay minerals

58
Q

chemically precipitated sedimentary rocks are primarily

A

limestone, dolomite, salt, or gypsum

59
Q

chemically precipitated sedimentary rocks that are good aquifers

A

limestone and dolostone

60
Q

salt or gypsum can be a material that prohibit petroleum deposits from leaking out, also known as ______

A

petroleum caprocks

61
Q

can also be considered to be sedimentary deposits with the original sediments being organic

A

coal and lignite

62
Q

t or f: sedimentary rock sequences are formed with younger beds laid down upon older ones

A

t

63
Q

t or s: sedimentary rocks can occur as single unit

A

T (but rarely)

64
Q

t or f: horizontally dipping beds are not common in the Philippines

A

T

65
Q

t or f: folded and faulted rocks are common in the Philippines

A

T

66
Q

how many wells are needed to locate in order to determine groundwater flow?

A

at least 3

67
Q

this is a very real hindrance to groundwater exploration

A

complex stratigraphy

68
Q

can create a very complex hydrogeologic systems in which the determination of recharge and discharge zones and flow systems are confounded

A

faulting and folding

69
Q

in addition to determining hydraulic characteristics of rock units and measuring of ground-water levels, _________ must also be evaluated

A

detailed geology

70
Q

three steps in determining groundwater flow systems

A

-determine hydraulic characteristics or rock units
-measure groundwater levels in wells
-evaluation of detailed geology

71
Q

t or f: structure may or may not help with the formation of groundwater, but often than not, they help by increasing porosity

A

t

72
Q

t or f: silangan is composed of hard rocks but is highly fractured so it has high recharge rates

A

t

73
Q

________ and _________ must be reconciled with the pre-existing geologic knowledge

A

logs of test wells and borings

74
Q

hydraulic conductivity of clastic sedimentary rocks are based on _______

A

primary permeability

75
Q

primary permeability of clastic sed rx is a function of:

A

grain size, shape, and sorting of original sediments

76
Q

carbonate aquifers have _____ dissolution and ________ pore spaces

A

high dissolution ; interconnected

77
Q

t or f: primary porosity of limestone and dolomite varies

A

t

78
Q

can be zones of high primary porosity and permeability in carbonate rocks

A

bedding planes

79
Q

why is drilling limestones or karst lithology not recommended?

A

-when drill bit reaches the cavity/hollow, it detaches
- it is unfeasible to develop if maglagay ng pebbles and casing

80
Q

explain the stages of growth of a carbonate aquifer

A

a.) first, most joints in the recharge area undergo solution enlargement
b.) as the solution passes grow, they join and become fewer
c.) eventually, one outlet appears at the discharge zone

81
Q

t or f: growth of carbonate aquifers starts in recharge area towards the discharge area

A

t

82
Q

this make the best aquifer

A

coarse-grained unconsolidated sediments

83
Q

search for groundwater starts with investigations of

A

non-indurated sediments

84
Q

properties of unconsolidated sediment aquifers

A
  1. easy to drill / dig = rapid and cheap
  2. found in valleys = shallow groundwater level
  3. favorable locations = recharge from rivers
  4. permeabilities are much higher
85
Q

good aquifers of consolidated sediments

A

coarse-grained rocks

86
Q

permeability of consolidated sediments depends on the degrees of

A

compaction, cementation, and fracturing

87
Q

these acts as impermeable beds in a consolidated sedimentary rocks

A

finer sediments

88
Q

properties of consolidated sediment aquifers:

A

1.) good aquifers = often coarse grained
2.) permeability depends on degrees of compaction, cementation, and fracturing
3.) finer sediments act as the impermeable beds

89
Q

___________ igneous rocks are preferred for groundwater

A

extrusive igneous rocks

90
Q

igneous and metamorphic rocks conductivity depends on:

A

development of secondary porosity

91
Q

conductivity of metamorphic rocks depends on

A

degree of metamorphism
type of metamorphism

92
Q

for groundwater to occur on igneous and metamorphic rocks, there must be openings developed through:

A

fracturing, faulting, or weathering

93
Q

volcanic rocks have __________ permeabilities

A

low to high

94
Q

igneous rock that is originally not porous

A

plutonic

95
Q

recent volcanic aquifers may have high permeabilities due to:

A
  1. development of gas bubbles (vesicles)
  2. fracture/joints caused by buckling, faulting
  3. development of leached zone by weathering
  4. sand and gravel trapped between flows
96
Q

fractures of plutonic igneous rocks tend to close due to

A

compaction and crystallization of secondary minerals

97
Q

in plutonic rocks, groundwater is present in ____________ by tectonic processes and in ___________ or ________

A

open fractures ; leached or weathered zone

98
Q

what type of aquifer is metamorphic rocks

A

fractured aquifer

99
Q

metamorphic rocks have very low permeability except:

A

marble

100
Q

groundwater in metamorphic rocks occur and moves through

A

fractures and leached zones

101
Q

t or f: porosity and permeability of metamorphic rocks decrease with rapid depth

A

t

102
Q

porosity and permeability of metamorphic rocks decrease with rapid depth because of

A

weight of overlying material

103
Q

this metamorphic rock could have well developed solution openings or even caverns where large groundwater flow occurs

A

marble

104
Q

properties of metamorphic rock aquifer

A

1.) very low permeability (except marble)
2.) groundwater moves and occurs in fracture and leached zones
3.) porosity and permeability decreases with depth
4.) marble could have well-developed solution openigs or caverns

105
Q

t or f: arid regions have presence of groundwater but are difficult to find

A

t

106
Q

manifestation of groundwater in arid regions

A

presence of vegetation (oasis)

107
Q

desert areas receive ________ of precipitation or less each year

A

10 (25 cm)

108
Q

t or f: cold deserts can have great accumulations of water

A

t

109
Q

why is it that there is often virtually no local ground-water recharge in warm deserts?

A

the potential evapotranspiration is many times greater than annual precipitation

110
Q

t or f: bedrock and unconsolidated aquifers are known in desert areas

A

t

111
Q

unconsolidated materials in desert areas are often rather _____ and ______

A

coarse and permeable

112
Q

dry climate in arid regions promote ________ of rock

A

mechanical weathering

113
Q

vast bedrock aquifers are known to occur in the sedimentary basins of ____, ______, and _______

A

Egypt, Jordan, and Saudi Arabia

114
Q

The Sahara Desert is underlain by what aquifer?

A

Nubian aquifer

115
Q

what rock makes up Nubian aquifer? and how thick is it?

A

sandstone ; 3000 ft (900m) thick

116
Q

much of North Africa and Arabia have old groundwater exceeding ____________ years

A

35,000 radiocarbon years

117
Q

t or f: coastal plain aquifers are common in the Philippines

A

t

118
Q

they are regional features, bounded on the continental side by highlands and seaward by coastline

A

coastal-plain aquifers

119
Q

where do coastal plains exist?

A

in areas of stable basement rock;
in areas where the basement is sinking

120
Q

the coastal plain may include large areas of __________, and the geology of the coastal zone may be very similar to the ___________

A

former sea floor ; adjacent continental shelf

121
Q

transition between fresh and salt water

A

zone of diffusion

122
Q

t or f: aquifers located next to tidal bodies are subjected to short-term fluctuations in the head, due to the tide

A

T

123
Q

much of the aquifers in Davao City are located in?

A

south (bajada, talomo)

124
Q

t or f: Dumoy aquifer is a confined aquifer

A

t

125
Q

t or f: dumoy aquifer has low susceptibility to subsidence because it is made of hard and competent rocks

A

t

Hydrogeology (13 decks)

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