ASTM D6106-97(2010)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6106 − 97 (Reapproved 2010)
Standard Guide for
Establishing Nomenclature of Groundwater Aquifers
This standard is issued under the fixed designation D6106; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.8 This guide is a modification of a previously published
report (1).
1.1 This guide covers a series of options but does not
1.9 This guide offers an organized collection of information
specify a course of action. It should not be used as the sole
or a series of options and does not recommend a specific
criterion or basis of comparison and does not replace or relieve
course of action. This guide cannot replace education or
professional judgement.
experienceandshouldbeusedinconjunctionwithprofessional
1.2 This guide contains instructions and suggestions for
judgment. Not all aspects of this guide may be applicable in all
authors of groundwater (hydrogeologic) reports in assigning
circumstances. This guide is not intended to represent or
appropriately derived and formatted aquifer nomenclature.
replace the standard of care by which the adequacy of a given
Discussed are the water-bearing units that may require name
professional service must be judged, nor should this guide be
identification, which are, ranked from largest to smallest,
applied without consideration of a project’s many unique
aquifer system, aquifer, and zone. Guidance is given on
aspects. The word “Standard” in the title of this document
choosing the source of aquifer names, those are from lithologic
means only that the document has been approved through the
terms, rock-stratigraphic units, and geographic names.
ASTM consensus process.
1.3 Included are examples of comparison charts and tables
2. Referenced Documents
that can be used to define the hydrogeologic framework.
Illustrationsofelevendifferenthypotheticalaquifersettingsare
2.1 ASTM Standards:
presented to demonstrate the naming process.
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
1.4 Categories of items not suggested as a source of aquifer
D1129 Terminology Relating to Water
names are reviewed because, although they should be avoided,
D5409 Guide for Set of Data Elements to Describe a
they occur in published documents. These categories are the
Ground-Water Site; Part Two—Physical Descriptors
following: time-stratigraphic names, relative position, alpha-
D5434 Guide for Field Logging of Subsurface Explorations
numeric designations, depositional environment, depth of
of Soil and Rock
occurrence, acronyms, and hydrologic conditions.
D5474 Guide for Selection of Data Elements for Groundwa-
1.5 Confining units are discussed with the suggestion that
ter Investigations
these units should not be named unless doing so clearly
promotes an understanding of a particular aquifer system. 3. Terminology
Suggested sources of names for confining units correspond to
3.1 Definitions—Except as discussed as follows, all defini-
those for aquifer names, which are lithologic terms, rock-
tions are in accordance with Terminologies D653 and D1129.
stratigraphic units, and geographic names.
The following terms are examined in detail in order to clarify
the method of assigning nomenclature to the aquifers and
1.6 It is suggested that in reports that involve hydrogeology,
associated units:
the author should consider first not naming aquifers (see 6.2).
3.2 Introduction—Aquifers do not lend themselves to brief,
1.7 Formatandexpressionstylesareassessedalongwiththe
neat, and simple definitions; therefore, a flexible hierarchy of
general cautions related to name selection of aquifers and
terms is used in these guidelines. The terms that are used for
confining units.
water-yielding rocks from largest to smallest are: aquifer
1 2
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock The boldface numbers in parentheses refer to the list of references at the end of
and is under the direct responsibility of Subcommittee D18.21 on Groundwater and this standard.
Vadose Zone Investigations. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2010. Published September 2010. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1997. Last previous edition approved in 2004 as D6106 – 97 (2004). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D6106-97R10. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6106 − 97 (2010)
system (2), aquifer (3), and zone (4). Confining units (3) are greater importance to understanding the flow system than do
discussed because of the stratigraphic relationship with the the individual formational boundaries. A definition that places
water-bearing units. less emphasis on the formal term formation (6) and more on
3.2.1 Parallelism between the hierarchy of terms for water- permeable rocks has merit. For example, aquifer is defined in
yielding rocks and rock-stratigraphic terms, namely, aquifer the Glossary of Geology (7) as “a body of rock that is
system (group), aquifer (formation), and zone (member), sufficiently permeable to conduct groundwater and to yield
should be avoided because water-yielding rocks can cross the economically significant quantities of water to wells and
boundaries of geologic units or constitute only part of a springs.”
geologic unit. The scale of the study also may determine the
3.3.1.5 Regardless of the fine points in any definition,
best usage. For example, at the local scale, an aquifer system
delineating permeable rocks should be the major goal of
could be defined totally within a single formation, and at the
hydrogeologists in mapping and describing an aquifer. By the
regionalscale,aformationorgroupcouldbetotallywithinand
same token, detailed knowledge of the stratigraphic units and
only a part of a single aquifer or an aquifer system.Again, the
post-depositional processes, such as solution, cementation,
guidelines for aquifer nomenclature must remain flexible to
folding, and faulting, are essential in determining where the
meet a variety of hydrogeologic scales and settings.
boundaries of the aquifer are located and in understanding the
3.2.2 A discussion of the terms aquifer, aquifer system,
flow system. In addition, hydraulic properties (hydraulic con-
zone, and confining unit is provided here to give authors a
ductivity and storage coefficient) throughout the aquifer usu-
common reference base. Although complete agreement on
ally are not determined directly but are estimated by indirect
these definitions has not been achieved, the terms are adequate
means, such as aquifer tests, analyses of drill cuttings and
to transfer knowledge from authors to readers of reports. It is
cores, borehole geophysical logging, and surface geophysical
not the purpose of these guidelines to formally redefine the
surveys.
terms or to define new terms to take their place.
3.3.1.6 In many situations, hydrologic estimates and ex-
trapolations can be made on the basis of rock type alone
3.3 Definitions of Terms Specific to This Standard:
without any determination of hydrologic properties. For
3.3.1 aquifer, n—This term probably has more shades of
example, a wide-spread, thick clay separating two sand units
meaningthananyotherterminhydrology (5),seeTerminology
tentatively could be designated as a confining unit on the basis
D653. It can mean different things to different people and
of geologists’ logs and borehole geophysical logs alone with-
different things to the same person at different times.
out any hydrologic data.
3.3.1.1 Discussion—Meinzer (5) defined an aquifer as “a
3.3.2 aquifer system, n—Poland and others (2) define an
rock formation or stratum that will yield water in sufficient
aquifer system as “a heterogeneous body of intercalated
quantitytobeofconsequenceasasourceofsupplyiscalledan
permeable and poorly permeable material that functions re-
aquifer, or simply a water-bearing formation, water-bearing
gionally as a water-yielding hydraulic unit; it comprises two or
stratum,orwater-bearer.Itiswater-bearing,notinthesenseof
more permeable beds (aquifers) separated at least locally by
holdingwater,butinthesenseofcarryingorconveyingwater.”
aquitards(confiningunits)thatimpedegroundwatermovement
3.3.1.2 Lohman and others (3) refined Meinzer’s definition
of an aquifer as “a formation, group of formations, or part of a butdonotgreatlyaffecttheregionalhydrauliccontinuityofthe
system.”
formation that contains sufficient saturated permeable material
to yield significant quantities of water to wells and springs.”
3.3.2.1 Discussion—The definition could be moregeneralif
3.3.1.3 Both of these definitions imply that the aquifer is
the term aquifers were used in place of permeable beds. Bed
bounded by or is included within the formation(s) (or stratum),
implies a single stratigraphic unit, whereas, the individual
but the concept of the aquifer extending across formational
aquifer could include or cross many beds.
boundaries is not indicated explicitly. In many local studies
3.3.2.2 Confining unit should be used instead of aquitard
covering a few tens to a few hundred square miles, the aquifer
because the definition of confining unit is broad enough to
and the formation may be the same. In these studies, few
include varying degrees of leakiness.
problems may exist in defining the aquifer. However, since the
3.3.2.3 The hierarchy of aquifer and aquifer-system names
late 1970s, studies of regional aquifers that may cover hun-
may not always be consistent in practice. Because of differ-
dreds of thousands of square miles have been made under the
ences in scales of investigations, individual aquifers may be
Regional Aquifer-System Analysis (RASA) Program. Results
combined into a single aquifer system, which may be only a
from several of the RASA studies have shown that regional
part of another aquifer system over a larger area.Authors have
aquifers may include numerous formations and rock types and
the responsibility to explain these relationships clearly with
that the aquifers cut across formational and lithologic bound-
comparison charts and descriptions in the text.
aries so that no one formation is completely representative of
3.3.3 confining unit, n—confining bed was defined by
the aquifer.
Lohman and others (3) as “ . . . a termwhich willnowsupplant
3.3.1.4 In studies of regional scope, the shape and the
the terms aquiclude, aquitard, and aquifuge in reports of the
boundaries of the permeable rocks that form the aquifer have
U.S. Geological Survey and is defined as a body of imperme-
ablematerialstratigraphicallyadjacenttooneormoreaquifers.
RASA, Regional Aquifer-System Analysis Program, a systematic study of a
In nature, however, its hydraulic conductivity may range from
number of regional groundwater systems that represent a significant part of the
nearly zero to some value distinctly lower than that of the
water supply of the United States. These studies are managed by the Water
Resources Division of the U.S. Geological Survey. aquifer. Its conductivity relative to that of the aquifer it
D6106 − 97 (2010)
confinesshouldbespecifiedorindicatedbyasuitablemodifier, 3.4.1 The term aquifer may be less precise than we would
such as slightly permeable or moderately permeable.” like,butithasbeenusedandacceptedwidelyinthehydrologic
3.3.3.1 Discussion—Although the Lohman and others (3) literature since it was defined originally.
definition of confining bed is descriptive and should be used, 3.4.2 Coining new terms for aquifer and aquifer system that
the term confining unit is more general and appropriate than either are synonyms or defined with slightly different meaning
confining bed, especially where more than a single bed makes is not an advancement. It only creates confusion especially
up the confining unit. among people who are not hydrogeologists. Use of the term
3.3.3.2 The term bed is not correct usage for a thick aquiformation also infers an equivalence between aquifer and
formation that is not always correct.
sequence of stratigraphic units that could be of member or
formationrank. Bedisparticularlyinappropriatewhenusedfor
4. Significance and Use
intrusive igneous rocks beneath an aquifer. The term bed has a
formal definition in the 1983 North American Stratigraphic 4.1 An essential requirement of hydrogeologists in evaluat-
Code (6) and should not be used in definitions of aquifer ing the hydraulic properties of a segment of earth materials is
nomenclature. to define and map hydrogeologic units, aquifers, and confining
3.3.3.3 Many confining units are leaky and in some areas, units, which are determined on the basis of relative permeabil-
ity. Discussion of the hydrogeologic units is facilitated by
undernaturalconditions,maycontributesignificantamountsof
water to the aquifers they confine, and even larger quantities of individual designations (see Practices D5409, D5434, and
D5474).
water as heads are lowered in the aquifer by pumping. In areas
where withdrawals from aquifers have caused large declines in
4.2 Determinations of hydrogeologic units are based on
head, considerable amounts of water may be derived from
indirect methods, knowledge of the geologic materials (geo-
water stored in the confining unit.
logic mapping, surface geophysical surveys, borehole geo-
3.3.3.4 Poland and others (2) retained the terms aquiclude
physical logs, drill-cuttings and core descriptions, and so
and aquitard in their definitions related to studies of the
forth), and hydraulic testing (aquifer tests, laboratory perme-
mechanics of aquifer systems and land subsidence due to fluid
ability tests on core samples, and so forth).
withdrawal. An aquiclude was defined as a body of saturated
4.3 The physical properties of all rock units will change if
but relatively impermeable material that is characterized by
traced laterally and vertically. The rock units are broken by
very low values of leakance (the ratio of vertical hydraulic
unconformities and faults, which may or may not affect the
conductivity to thickness) and transmits negligible interaquifer
flow of groundwater. The process of designating and naming
flow.
aquifers and confining units, therefore, is a somewhat subjec-
3.3.3.5 An aquitard is a saturated poorly permeable bed that
tive undertaking, and, if not thoroughly documented, can lead
has values of leakance that range from relatively low to
to confusion.
relatively
...