question

subsurface water

answer

the sum of soil moisture (above the water table) and groundwater (below it) (3)

question

saturated zone

answer

the zone where all pores are filled with water; the water table is the upper boundary; also called phreatic zone

question

phreatic zone

answer

same of the saturated zone

question

unsaturated zone

answer

the are above the water table where pores are only partially filled; the zone also called *soil moisture*

question

vadose zone

answer

same as unsaturated zone

question

soil moisture

answer

same as the unsaturated zone or vadose zone

question

soil zone

answer

one of two division of the unsaturated zone; the uppermost layer of earth which is usually dry as plant root-suction remove this moisture; plant water use is lost through transpiration

question

transpiration

answer

the release of water vapor to the atmosphere from plant leafs and stems

question

root-suction base

answer

the base of the soil zone; the maximum distance plants can draw water

question

sub-soil zone

answer

the area between root-suction and the water table

question

capillary fringe

answer

the area above the saturated zone that also saturated, but hydraulically resembles the unsaturated zone; can extend a fraction of mm to several meters depending on the soul (5)

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underground streams

answer

page 7

question

atmospheric pressure

answer

prevents water from flowing into a dug well; unsaturated zone is less than atmospheric pressure & saturated zone is greater than atmospheric pressure; the boundary should = 1 atmosphere; 10 tonnes/m^2

question

subsurface horizon

answer

that area where pore pressure and atmospheric pressure are the same

question

aquifer

answer

a body of saturated rock that both stores and transmits groundwater (9, 12)

question

aquitard

answer

a saturated body of rock that impedes groundwater movement; impedes rather than stops; low-permeability rock (9)

question

aquifuge

answer

obsolete term for aquitard

question

aquiclude

answer

obsolete term for aquitard

question

unconfined aquifer

answer

where the upper limit of saturation is the water table (11)

question

confined aquifer

answer

lying below an aquitard where there is no unsaturated zone; a dug well would rise to the piezometric surface

question

piezometric surface

answer

the line at which a water table extends; the waters of confined aquifers when punctured reach this level (see p. 10 illus.); if pressure drops and the water table drops below the aquitard the aquifer is unconfined (12)

question

perched aquifer (lens)

answer

small aquifers that pool water and sit above the regional water table; care must be made not to confuse this aquifer, which is limited, with the regional aquifer (12)

question

storage and transmission

answer

key terms in groundwater systems; geological factors control both: (i) volume and size of pores of rock, (2) rock mass strength when compressed by the weight of the overlying ground (12)

question

porosity

answer

the proportion of a given volume of rock that occupied by pores; hydrogeologist are concerned with interconnected pore space or effective porosity (12)

question

effective porosity

answer

the ratio of the volume of interconnected pores to the total rock volume; cf. porosity which concerned rock pores in general; a necessary condition for permeability but not sufficient (cf. pore neck size); it is prerequisite, but pore neck size determines magnitude (12)

question

intergranular porosity

answer

the type of porosity found in sands and gravels; grain size does not correlate with effective porosity

question

variables of effective porosity

answer

aspects of sediment that effect effective porosity: 1. grain shape: the more platy (flat) or angular, the lower the effective porosity 2. grain sorting: uniform grain-size is more porous than non-uniform grains which fill-in and reduce porosity 3. grain packing: depositional processes that align grains parallel to one another have less porosity than those randomly placed

question

diagenesis

answer

the physical and chemical changes - including pressure, heat, and chemical reactions - by which buried sediments are lithified into sedimentary rocks; from sediment to lithification

question

primary effective porosity

answer

porosity found in the original rock; in time, diagenesis can alter this; cf. secondary effective porosity

question

secondary effective porosity

answer

in time, low-porosity rocks can become more porous; intergranular effective porosity can increase with the disillusionment of cements and sediment grains (esp important on petroleum reserves); fracture porosity (13)

question

fracture porosity

answer

1.5.3

question

permeability

answer

the ability to transmit water; there is no correlation between effective porosity and ______________; the real control of __________ is the size of pore necks which are generally far smaller than then pores they interconnect; small necks causes water to seep very slowly in a laminar fashion (contra turbulent surface water) (14)

question

pore neck size

answer

determines permeability; the bigger the grain the higher the permeability since ______________ would be broader; low porosity rocks (e.g., cavernous limestone, 1%) are very permeable; while mudstone is very porous (50%) not very permeable (14)

question

storage properties (SP) of aquifers

answer

rock porosity is directly related to SP

question

∇

answer

symbol of water table elevation

question

fillable effective porosity (FEP)

answer

the amount of space available to be filled in porous rock; e.g. a 100 mm of rainfall causes an aquifer to rise 400 mm -- his is because only 25% of the rock was porous; FEP ideally equals *total* effective porosity (TEP), but some of the pore space may already be occupied by water which is why FEP is generally less than TEP (14-15)

question

electrostatic attraction

answer

how water molecules adhere to rock, its strength determined by rock chemistry (e.g., quartz low ESA, iron and clay high); narrow necks favor water retention (< 10 µm, but plant suction can overcome this)

question

specific yield

answer

the amount of water which drains freely from a unit volume of initially saturated rock per unit decline in water table elevation; express the same way as effective porosity (as % of fraction); a more elegant term for "fillable" & "drainable" effective porosity; cf. specific retention (15-16)

question

specific retention

answer

the amount that remains after gravity has removed the specific yield; effective porosity = specific yield + __________; "meniscus fillings" & "pendant droplets"

question

effective porosity

answer

= specific yield + specific retention

question

meniscus fillings

answer

water retained interstitially; cf. specific retention

question

pendant droplets

answer

water electrostatically held onto a grain; cf. specific retention

question

confined aquifer pressure

answer

as long as an aquifer is confined it is completely saturated to the base of the overlaying aquitard; pressure places force on pore walls; as water is drained the pressure drops while full-saturation remains; water also compresses; cf. a balloon filled with air: even as air is let out the balloon is still filled with air (16-17)

question

elastic storage (ES)

answer

the ability of pores to expand under pressure like a balloon expands under pressure; removed confined water relieves pressure, but water volume is still maintained; KEY: pore expansion and water compression; ES occurs in all aquifers but it is much less important in unconfined aquifers (16-17)

question

storativity (S)

answer

the amount of water which can be removed from a unit volume of confined aquifer per unit decline in water level; confined aquifers have far less storage space per unit volume compared to unconfined aquifers; although many compare S and Sy (specific yield in unconfined aquifers), the magnitude of the former is quite small when compared to the later (see p. 17)

question

hydrostratigraphy

answer

is the identifying, naming, and specifying the extents and properties of the aquifers and aquitards in a given geographical area (18-20)

question

common types of aquifer rock

answer

i. unconsolidated sands and gravels ii. sandstones iii. limestones iv. basaltic lava flows More than 80% of aquifers the author has encountered correspond to one of these types (there are cases where the latter 3 are aquitards)

question

common types of aquitard rocks

answer

i. mudstones ii. siltstones iii. metamorphic rocks iv. plutonic rocks

question

rocks type that can be either an aquifer or aquitard

answer

volcanic tuffs, coals, and many evaporites (local geological history determines which is which) (20)

question

sands and gravel

answer

archetypal aquifer materials; but burial and diagenesis, compaction and cementation reduce permeability (20)

question

sandstones

answer

another good aquifer material, that when consolidated loses its primary effective porosity; however, through "extension" and deformation "clean" fractures develop which allows enough permeability (20)

question

limestone

answer

another good aquifer material prone to fractures, dolines, and "karst" landscapes; limestone massifs (21)

question

massifs

answer

a block of the earth's crust bounded by faults and shifted to form peaks of a mountain range

question

lava flows

answer

good aquifer material; e.g., Columbia Lave Plateau of the NW US, the Hawaiian Islands, Iceland, the Canary Islands, Sicily, & the Deccan Traps of India (cf. the prolific springs of Mt Etna)

question

breccia

answer

A coarsely clastic rock consisting of relatively large angular fragments bonded in a matrix of finer particles. Conglomerate.

question

structural framework

answer

the geology and tectonic forces that effect aquifers and aquitards (21-22)

question

antiform

answer

∩ or "up-fold"

question

synform

answer

U or "down-fold"

question

plane of angular noncomformity

answer

Fig. 1.10

question

extensional fault

answer

Fig. 1.10

question

compressional fault

answer

Fig. 1.10

question

hanging wall

answer

overlying block over a foot wall (either extensional or compressional faults); influence groundwater movement (23f)

question

foot wall

answer

underlying block under a hanging wall (either extensional or compressional faults); influence groundwater movement (23f)

question

mylonites

answer

glassy materials formed by metamorphic pressure and heat

question

faults

answer

can limit or reduce groundwater flow or can enhance it (cf. karst terrain, carbonite rock) (23f)

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