Glossary of Groundwater Terms

Acre-Feet –

The amount of water that would be contained in volume defined as one acre by a depth of one-foot. Equivalent to 325,851 gallons.-

Area of Influence –

The area surrounding a pumping or recharging well within which the potentiometric surface has been changed.-

Aquiclude –

A hydrogeologic unit which, although porous and capable of storing water, does not transmit it at rates sufficient to furnish an appreciable supply for a well or spring Preferred term confining unit.-

Aquifer –

A formation, a group of formations, or a part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells and springs.-

Aquifer System –

A body of permeable and poorly permeable material that functions regionally as a water-yielding unit; it comprises two or more permeable beds separated at least locally by confining beds that impede ground-water movement but do not greatly affect the regional hydraulic continuity of the system; includes both saturated and unsaturated parts of permeable material.-

Aquifer Units –

Aquifers or a sub-set of aquifers in an aquifer system.-

Aquitard –

A confining bed that retards but does not prevent the flow of water to or from an adjacent aquifer; a leaky confining bed. It does not readily yield water to wells or springs, but may serve as a storage unit for ground water.

Attribute Table –

A type of table used in a geographic information system (GIS) that contains the characteristics of the data being used in an analysis.-

Baseflow –

That part of the stream discharge that is not attributable to direct runoff from precipitation or melting snow; it is usually sustained by ground-water discharge.-

Baseline –

Accumulation of available data that is analyzed and becomes a point of departure for further studies.-

Bedrock –

The first native consolidated rock underlying the ground surface. Usually, an area of broken and weathered unconsolidated material exists between the bedrock and the surface.-

Bedrock-High –

An area of high elevation on the bedrock topographic surface.-

Borehole Log Data –

Data collected from borehole soil sampling as a borehole is advanced.-

Boulder(s) –

A clastic mineral particle of any composition that has a grain size greater than 600 mm.-

Build-Out –

Planning term used to describe the maximum amount of development that can occur in an area.-

Buffer –

An area bordering the study area that is included in the study to provide additional information of conditions at the border if conditions at the border are not clear.-

Clastic –

A sedimentary rock (such as shale, siltstone, sandstone or conglomerate) or sediment (such as mud, silt, sand, or pebbles). An accumulation of transported weathering debris or a material originating from the weathering of rocks.-

Clay –

A clastic mineral particle of any composition that has a grain size smaller than 1/256 mm.-

Cobble(s) –

A clastic mineral particle of any composition that has a grain size in the range of 76 to 250 mm.-

Competent Bedrock –

Solid non-weathered bedrock.-

Confining Layer (Unit) –

A hydrogeologic unit which, although porous and capable of storing water, does not transmit it at rates sufficient to furnish an appreciable supply for a well or spring.-

Critical Recharge –

An area where precipitation rapidly recharges the groundwater. Because of the rapid recharge these areas are very susceptible to contamination.-

Critical Water Level –

The groundwater level in an unconsolidated aquifer that, if maintained for a long period of time, would damage the area’s ecology and environment.-

Cross-Sections –

The area of a surface cut by a plane passing through the body and perpendicular to the long axis of the body. A plane showing the vertical distribution of materials below the ground surface.-

Datum –

A mark used as a basis for calculations or measurements, such as a level (bench mark) from which elevations and depths are measured in surveying.-

Deep Bedrock Aquifers –

The rock aquifers located below the Maquoketa shale aquiclude.-

Digital Elevation Model (DEM) –

A model provided by the USGS that represents the detailed topography of an area and was used in this study to establish the surface elevation of well locations.-

Dolomite –

A carbonate rock (similar to limestone) made up predominately of the mineral dolomite, CaMg(C03)2.-

Drainage Channel –

A channel carved into the bedrock prior to glaciation.-

Drawdown –

A lowering of the water table around a producing well. The drawdown at any given location will be the vertical change between the original water table and the level of the water table reduced by pumping.-

Drift (Glacial Drift) –

Unconsolidated materials deposited by retreating glaciers.-

Easting Coordinates –

In geographic mapping, the horizontal coordinate equivalent to the “X” axis in mathematical graphing.-

Effective Porosity –

The ratio of the volume of the voids of a soil or rock mass that can be drained by gravity to the total volume of the mass.-

Equilibrium Groundwater Conditions –

The condition when there is no variation in the flow elements of a water balance and the magnitudes of recharge and discharge are equal.-

Gamma Ray Logging –

A method of using natural gamma radiation to characterize the rock or soils in a borehole.-

Geographic Information System (GIS) –

A system for capturing, storing, analyzing and managing data and associated attributes which are spatially referenced to the earth.-

Geology –

Encompasses such things as rocks, soil, and gemstones, geology studies the composition, structure, physical properties, history, and the processes that shape Earth's components.-

Geophysical Data –

Data collected by measuring magnetic fields, force of gravity, electrical properties, seismic-wave paths and velocities, radioactivity, and heat flow.-

GIS Querying Techniques –

Techniques use to isolate data required to conduct a particular analysis.-

Glacier –

A large, slow moving river of ice, formed from compacted layers of snow, that slowly deform and flow in response to gravity.-

Glacial Deposits –

Unconsolidated materials deposited by retreating glaciers.-

Global Positioning System (GPS) –

Is the only fully functional Global Navigation Satellite System (GNSS). Utilizing a constellation of at least 24 Medium Earth Orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its location, speed, direction, and time.-

Gradient –

Slope of stratum, stream bed or land surface; expressed in percent, as feet per mile, or meters per kilometer, or in degrees.-

Grain Size –

Particle size-

Gravel –

Clastic sedimentary particles of any composition that are over 2 mm in diameter.-

Gravity Water –

Water in the transition zone between the soil horizon and the capillary fringe.-

Gray Water –

Treated sewerage water.-

Groundwater –

All water that occurs below the land surface. It includes water within the unsaturated and saturated zones.-

Groundwater Discharge –

The seeping of groundwater out of geologic formations to surface features such as streams, lakes, and wetlands.-

Groundwater Hydrograph –

A graph that shows the change groundwater level elevation (or depth below the ground surface), over time. -

Groundwater Inflow –

Flow into the sides of a three-dimensional block that represents the study area in a water balance analysis. -

Groundwater Level –

The elevation of/or the depth of the water table below the ground surface.

Groundwater Management Level –

The level of groundwater that when reached signifies a warning that the critical water level is being approached.-

Groundwater Modeling –

a mathematical representation of the characteristics of a study area that can be used to analyze cause-and-effect scenarios.-

Groundwater Outflow –

Flow out of the sides of a three-dimensional block that represents the study area in a water balance analysis.-

Groundwater Resource –

The amount of recoverable groundwater available in an aquifer system.-

Groundwater Sustainability –

The development and use of groundwater to meet both current and future beneficial purposes without causing unacceptable consequences. Groundwater sustainability involves minimizing net losses from the hydrologic reservoir (resource renewability), management of groundwater as an integrated part of the hydrologic cycle, development of manmade infrastructure based on an understanding of the natural hydrologic system, wise and efficient water use, and fair allocation and monitoring of water for human as well as environmental and ecological needs.-

Head (Static) –

The height above a standard datum of the surface of a column of water (or other liquid) that can be supported by the static pressure at a given point. The static head is the sum of the elevation head and the pressure head.-

Holocene Epoch –

The current post-glacial period, beginning about 10,000 years ago.-

Hydraulic Conductivity –

A measure of how well a material can transmit water. Materials such as gravel, that transmit water quickly, have high hydraulic conductivity values. Materials such as shale, that transmit water poorly, have low values. Hydraulic conductivity is primarily determined by the size of the pore spaces and their degree of interconnection. Hydraulic conductivity measures are expressed in units of velocity, such as centimeters per second, and assume a gradient of one vertical foot of drop per linear foot.-

Hydraulically Connected –

Two or more separated aquifers that have a connection that facilitates the sharing of water.-

Hydrogeologic Units –

Strata or groups of strata having common hydrogeologic characteristics.-

Hydrogeology –

The science of Earth's water, its movement, abundance, chemistry and distribution below Earth's surface.-

Hydrograph –

A graph that shows the change of a water-related variable, such as water level elevation, over time. -

Hydrologic Cycle –

The natural cycling of Earth's water between the atmosphere, surface and subsurface through the processes of evaporation, transpiration, percolation, infiltration, runoff and precipitation.-

Hydrologic Soil Groups –

Refers to soils grouped according to their runoff-producing characteristics. The chief consideration is the inherent capacity of soil bare of vegetation to permit infiltration. The slope and the kind of plant cover are not considered but are separate factors in predicting runoff. Soils are assigned to four groups. In group A are soils having a high infiltration rate when thoroughly wet and having a low runoff potential. They are mainly deep, well drained, an-d sandy or gravelly. In group D, at the other extreme, are soils having a very slow infiltration rate and thus a high runoff potential. They have a clay layer at or near the surface, have a permanent high water table, or are shallow over nearly impervious bedrock or other material. A soil is assigned to two hydrologic groups if part of the acreage is artificially drained and part is undrained.-

Hydrology –

The science of Earth's water, its movement, abundance, chemistry and distribution on, above and below Earth's surface.-

Infiltration –

The movement of surface water into porous soil.-

Isopach –

Thickness of a unit or a group of units.-

Isopleth –

A line composed of points having equal values such as elevations.-

Kriging Method –

Kriging is an optimal prediction method designed for geophysical variables with a continuous distribution. This method was used to prepare most of the maps presented in this study.-

Leaky Aquifer –

Aquifers, whether artesian or water table, that lose or gain water through adjacent less permeable layers.-

Limestone –

A sedimentary rock composed principally of calcium carbonate (CaCO2), usually as the mineral calcite.-

Log Value –

Logarithm to the base 10. Mathematical procedure that facilitates the manipulation of large numbers.-

Mapping –

The process of creating a representation to a definite scale on a horizontal plane of the physical features of a portion of the Earth's surface (natural or artificial or both) by means of symbols, which may emphasize, generalize, or omit certain features as conditions may warrant.-

Monitoring Wells –

A small diameter well used for obtaining groundwater samples and for measuring water levels.-

Northing Coordinates –

In geographic mapping, the vertical coordinate equivalent to the “Y” axis in mathematical graphing.-

Observation Well –

A small diameter well used for obtaining groundwater samples and for measuring water levels.-

Outcrop –

The part of a rock formation that appears at the surface of the ground or appears at the surface of an overlying formation. -

Particle/Grain Size Analysis –

Determination of the statistical proportions or distribution of particles of defined size fractions of a soil, sediment, or rock.-

Perched Water Table –

A water table that is isolated from and higher than the regional water table. This can occur when a hilltop is underlain by an impermeable rock or soil unit. Infiltrating waters stack up on the impermeable unit, creating an isolated water table that is higher than the water table of the surrounding land.-

Percolate –

The movement of surface water into porous soil.-

Permeability –

See Hydraulic Conductivity-

Permeable Deposits –

Deposits composed of materials having a high hydraulic conductivity such as sand, gravel, sandstone, etc.-

Piezometer –

An instrument for measuring water levels (pressure head); usually consisting of a small diameter pipe placed into a small borehole and set at a level of interest.-

Piezometric Surface –

See potentiometric surface.-

Pore(s) –

An opening in a rock or soil that is not occupied by solid matter.-

Pore Spaces –

The open spaces or voids in a rock taken collectively.-

Potentiometric Surface –

An imaginary surface representing the total head of ground water; defined by the level to which water will rise in a well. The water table is a particular potentiometric surface.-

Precambrian Rock –

Rock formed greater than 600 million years ago.-

Production Well –

A large capacity well used for municipal, industrial or commercial needs.-

Proportion Factor –

A value used to represent the relative importance of the soil particles making up the components of a soil sample.-

Pump Test –

A test to determine hydrologic properties of the aquifer involving the withdrawal of measured quantities of water from or addition of water to a well and the measurement of resulting changes in head in the aquifer both during and after the period of discharge or additions.-

Quaternary Period –

The past 2 to 3 million years. Includes the Holocene and Pleistocene Epochs.-

Querying Techniques –

Techniques use in GIS analyses to isolate data required to conduct a particular analysis.-

Pump Test –

A test used to estimate aquifer characteristics. A well is pumped and the resulting drawdown of the water level is measured over time.-

Recharge –

The process by which water is added to the saturated zone.-

Recharge Area –

The area of land surface where groundwater recharge from precipitation occurs.-

Recharge Characteristics –

The physical characteristics of the soil, water, and air that affect the rate and effectiveness of water movement from the surface to the water table.-

Recoverable Groundwater Volume –

The amount of water in an aquifer that can be pumped from the unit.-

Rock(s) –

A clastic mineral particle of any composition that has a grain size in the range of 250 t0 600 mm.-

Sand –

Clastic materials having a particle size between 1/16 to 2 millimeters in diameter.-

Sandstone –

A sedimentary rock composed of grains from 1/16 to 2 millimeters in diameter, dominated in most sandstones by quartz, feldspar, and rock fragments, bound together by a cement of silica, carbonate, or other minerals or a matrix of clay minerals.-

Saturated Zone –

That part of the earth material beneath the water table in which all voids, large or small, are ideally filled with water under pressure greater than atmospheric-

Screen –

See well intake screen.-

Sedimentary Rock –

A rock formed from the accumulation and consolidation of sediment, usually in layered deposits.-

Semi-Confined Aquifer –

Aquifers, whether artesian or water-table, that lose or gain water through adjacent less permeable layers.-

Semi-Confined Well –

A well screened in a semi-confined aquifer.-

Shale –

a clastic sedimentary rock that is made up of clay-size (less than 1/256 millimeter in diameter) weathering debris. It typically breaks into thin flat pieces.-

Shallow Aquifer System –

The shallow aquifer system extends from the ground surface to the surface of the Maquoketa shale and includes the Silurian dolomite and the overlying unconsolidated material.-

Shallow Bedrock Aquifer –

Silurian dolomites and some shaly rocks of the Maquoketa Group that form the bedrock immediately underlying the glacial drift-

Shallow Sand and Gravel Aquifers –

Aquifers located in the unconsolidated material located between the ground surface and the Silurian dolomite bedrock.-

Shallow Soil –Water Zone –

Upper part of the unsaturated zone and contains three kinds of water: soil water, gravity water, and the capillary fringe respectively from the ground surface to the water table.-

Silt –

A clastic material with a particle size between 1/256 and 1/16 millimeter diameter.-

Soil –

Unconsolidated material located between the surface soil and the bedrock.-

Soil Horizon –

A natural, three-dimensional body at the earth's surface. It is capable of supporting plants and has properties resulting from the integrated effect of climate and living matter acting on earthy parent material, as conditioned by relief over periods of time.-

Soil Material –

A mixture of unconsolidated materials consisting of particles having particle sizes ranging from clay to boulders.-

Soil Profile –

A vertical strip of soil stretching from the surface down to the bedrock and including all of the successive soil horizons.-

Soil Survey –

A detailed investigation of the soils at a site, including boreholes and tests to determine their nature, thickness, strength, and depth to bedrock.-

Soil Texture –

A term commonly used to designate the proportionate distribution of the different sizes of mineral particles in a soil.-

Soil-Water Zone –

The area between the water table and the ground surface composed of areas having soil water, gravity water and the capillary fringe.-

Stack Mapping –

The process of stacking maps representing the distribution of desired characteristics in a horizontal plane (map) used to describe the vertical variation of the distributed characteristics.-

Stone(s) –

A clastic mineral particle of any composition that has a grain size in the range of 250 t0 600 mm.-

Strata –

Plural of stratum.-

Stratigraphic Data –

Data collected to define a sequence of soil or sedimentary rock layers found in a specific geographic area, arranged in the order of their deposition.-

Stratigraphic Model –

A model representing the sequence of soil layers found in the BACOG study area arranged in the order of their deposition.-

Stratigraphic Profile –

The sequence of soil or sedimentary rock layers found in a specific geographic area, arranged in the order of their deposition.-

Stratigraphic Units –

A layer or a series of layers in a stratigraphic profile.-

Stratigraphy –

The study of soil or sedimentary rock units, including their geographic extent, age, classification, characteristics and formation.-

Stratum –

A bed or layer of rock or unconsolidated material. -

Surface Soil –

Superficial material that forms at earth's surface as result of organic and inorganic processes. Soil varies with climate, plant and animal life, time, slope of land, and parent material.-

Surface Water –

Water collecting on the ground or in a stream, river, lake, wetland, or ocean.-

Sustainable Development –

The development and use of groundwater to meet both current and future beneficial purposes without causing unacceptable consequences. Groundwater sustainability involves minimizing net losses from the hydrologic reservoir (resource renewability), management of groundwater as an integrated part of the hydrologic cycle, development of manmade infrastructure based on an understanding of the natural hydrologic system, wise and efficient water use, and fair allocation and monitoring of water for human as well as environmental and ecological needs.-

Till –

A mixture of clay, silt, sand, gravel and cobbles that was deposited by retreating glaciers.-

Topography –

The shape and physical features of surface.-

Topsoil –

The upper part of the soil, which is the most favorable material for plant growth. It is ordinarily rich in organic matter. -

Total Groundwater Volume (Storage)-

Transpiration –

A process of plants removing water from the soil and releasing it into the atmosphere through their leaves.-

Upgradient –

Upward direction of a slope of stratum, stream bed or land surface. -

Unconfined Aquifer –

An aquifer that has a water table.-

Unconsolidated Materials –

Materials consisting of loosely coherent or uncemented particles, whether occurring at the surface or at depth.-

Unsaturated Zone –

the area between the water table and the ground surface.-

Vadose Zone –

The unsaturated zone or the soil-water zone.-

Vertical Groundwater Movement –

vertical movement between separate aquifer units driven by the differences in water levels (head) between the two units.-

Vertical Inflow –

Flow into the bottom of a three-dimensional block that represents the study area in a water balance analysis.-

Vertical Outflow –

Flow out of the bottom of a three-dimensional block that represents the study area in a water balance analysis.

Void(s) –

An opening in a rock or soil that is not occupied by solid matter.

Water Balance –

Determination of the magnitude of groundwater flows in and out of a three-dimensional block representing the study area.

Water-Bearing Zone –

See saturated zone.

Water Law –

Laws governing the rights of water use.

Water Level –

The elevation above mean sea level of a surface water or groundwater body.

Water Planning –

Planning that determines the use, conservation and disposition of water.

Water Quality –

An assessment of the physical, chemical and biological characteristics of water, especially how they relate to the suitability of that water for a particular use.

Watershed –

The geographic area that contributes runoff to a stream. It can be outlined on a topographic map by tracing the points of highest elevation (usually ridge crests) between two adjacent stream valleys. The watershed of a large river usually contains the watersheds of many smaller streams.

Water Table –

A seasonally fluctuating boundary between the unsaturated zone and the saturated zone and where the water pressure in the porous medium equals atmospheric pressure.

Water Table Aquifer –

An aquifer that has a water table.

Water Table Well –

A well whose source of water is an unconfined or water table aquifer.

Weathered Bedrock –

Bedrock that has been exposed to the weathering process.

Weathering –

The destructive physical and chemical effects of the forces of weather on rock surfaces, as in forming soil or sand.

Well –

A hole or shaft in the earth dug or drilled to tap an underground supply of water, gas, oil, etc.

Well Capacity –

See well yield.

Well Drilling –

The process of drilling a borehole for the installation of a well.

Well Intake Screen –

The screen is the portion of the well casing that supports the borehole walls while allowing water to enter the well and keeps loose sand and gravel from entering the well.

Well Log –

See borehole log.

Well Siting –

The process of establishing a location for a new well.

Well Yield –

Well yield is the volume of water that can be pumped during a specific period of time. It is expressed as gallons per minute.

Wetland –

Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetations typically adapted for life in saturated soils. Wetlands generally include swamps, marshes, bogs, and similar areas.

Zone of Groundwater-Level Fluctuation –

The range between the maximum and minimum values of water depth or elevation in a hydrograph representing the long-term measurement of water levels.

Zone of Influence –

See area of influence.