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Groundwater Glossary

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acre-foot (af)

The volume of water necessary to cover one acre to a depth of one foot; equal to 43,560 cubic feet or 325,851 gallons.

A case that has been heard and decided by a judge. In the context of an adjudicated groundwater basin, landowners or other parties have turned to the courts to settle disputes over how much groundwater can be extracted by each party to the decision.

Of or pertaining to or composed of alluvium.

A general term for clay, silt, sand, gravel, or similar unconsolidated detrital material, deposited during comparatively recent geologic time by a stream or other body of running water, as a sorted or semi sorted sediment in the bed of the stream or on its floodplain or delta, as a cone or fan at the base of a mountain slope.

appropriative right
The right to use water that is diverted or extracted by a nonriparian or nonoverlying
party for nonriparian or nonoverlying uses. In California, surface water appropriative rights are subject to a statutory permitting process while groundwater appropriation is not.

A confining bed and/or formation composed of rock or sediment that retards but does not prevent the flow of water to or from an adjacent aquifer. It does not readily yield water to wells or springs, but stores ground water.

A body of rock or sediment that is sufficiently porous and permeable to store, transmit, and yield significant or economic quantities of groundwater to wells and springs.

artesian aquifer
A body of rock or sediment containing groundwater that is under greater than hydrostatic pressure; that is, a confined aquifer. When an artesian aquifer is penetrated by a well, the water level will rise above the top of the aquifer.

artesian pressure
Hydrostatic pressure of artesian water, often expressed in terms of pounds per square
inch; or the height, in feet above the land surface, of a column of water that would be supported by the pressure.

artificial recharge
The addition of water to a groundwater reservoir by human activity, such as putting surface water into dug or constructed spreading basins or injecting water through wells.

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borehole geophysics

The general field of geophysics developed around the lowering of a variety of probes into a boring or well. Borehole logging provides additional information concerning physical, electrical, acoustic, nuclear and chemical aspects of the soils and rock encountered during drilling.

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confined aquifer

An aquifer that is bounded above and below by formations of distinctly lower
permeability than that of the aquifer itself. An aquifer containing confined ground water. See artesian aquifer.

conjunctive use
The coordinated and planned management of both surface and groundwater resources in order to maximize the efficient use of the resource; that is, the planned and managed operation of a groundwater basin and a surface water storage system combined through a coordinated conveyance infrastructure. Water is stored in the groundwater basin for later and planned use by intentionally recharging the basin during years of above-average surface water supply.

Any substance or property preventing the use or reducing the usability of the water for ordinary purposes such as drinking, preparing food, bathing washing, recreation, and cooling. Any solute or cause of change in physical properties that renders water unfit for a given use. (Generally considered synonymous with pollutant).

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deep percolation

Percolation of water through the ground and beyond the lower limit of the root zone of plants into groundwater.

A process that converts seawater or brackish water to fresh water or an otherwise more usable condition through removal of dissolved solids.

domestic well
A water well used to supply water for the domestic needs of an individual residence or systems of four or fewer service connections.

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elastic deformation
Deformation that is temporary. Body will return to it's original volume after force is removed.

electrical conductivity (EC)
The measure of the ability of water to conduct an electrical current, the magnitude of which depends on the dissolved mineral content of the water.

effective porosity
The volume of voids or open spaces in alluvium and rocks that is interconnected and can
transmit fluids.

evapotranspiration (ET)
The quantity of water transpired (given off), retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces.

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groundwater basin

An alluvial aquifer or a stacked series of alluvial aquifers with reasonably well-defined boundaries in a lateral direction and having a definable bottom.

groundwater mining
The process, deliberate or inadvertent, of extracting groundwater from a source at a rate in excess of the replenishment rate such that the groundwater level declines persistently, threatening exhaustion of the supply or at least a decline of pumping levels to uneconomic depths.pits, ditches, furrows, streambed modifications, or injection wells.

groundwater recharge
The natural or intentional infiltration of surface water into the zone of saturation.

groundwater table
The upper surface of the zone of saturation in an unconfined aquifer.

Water that occurs beneath the land surface and fills the pore spaces of the alluvium, soil, or
rock formation in which it is situated. It excludes soil moisture, which refers to water held by capillary action in the upper unsaturated zones of soil or rock.

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Pressure created by the height of fluid above a given point.

hydraulic barrier
A barrier created by injecting fresh water to control seawater intrusion in an aquifer, or created by water injection to control migration of contaminants in an aquifer.

hydraulic conductivity
A measure of the capacity for a rock or soil to transmit water; generally has the units of feet/day or cm/sec.

Compaction of soil after an initial wetting event. A previously unsaturated soil compacts after saturation due to soil particles reorienting into a more compact form.

A graph that shows some property of groundwater or surface water as a function of time.

hydrologic cycle
The circulation of water from the ocean through the atmosphere to the land and ultimately
back to the ocean.

hydrostatic pressure
Pressure exerted by the weight of fluid.

A geologic framework consisting of a body of rock having considerable lateral extent and composing a reasonably distinct hydrologic system.

hyporheic zone
The region of saturated sediments beneath and beside the active channel and that contain some proportion of surface water that was part of the flow in the surface channel and went back underground and can mix with groundwater.

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inelastic deformation
Deformation that is permanent. Body will not return to its original volume after force is removed.

The flow of water downward from the land surface into and through the upper soil layers.

infiltration capacity
The maximum rate at which infiltration can occur under specific conditions of soil moisture.

in-lieu recharge
The practice of providing surplus surface water to historic groundwater users, thereby leaving groundwater in storage for later use.

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land subsidence

The lowering of the natural land surface due to groundwater (or oil and gas) extraction.

leaky confining layer
A low-permeability layer that can transmit water at sufficient rates to furnish some recharge from an adjacent aquifer to a well.

lithologic log
A record of the lithology of the soils, sediments and/or rock encountered in a borehole from
the surface to the bottom.

The description of rocks, especially in hand specimen and in outcrop, on the basis of such characteristics as color, mineralogic composition, and grain size.

losing stream
A stream or reach of a stream that is losing water by seepage into the ground.

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natural recharge

Natural replenishment of an aquifer generally from snowmelt and runoff; through seepage from the surface.

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overlying right

Property owners above a common aquifer possess a mutual right to the reasonable and beneficial use of a groundwater resource on land overlying the aquifer from which the water is taken. Overlying rights are correlative (related to each other) and overlying users of a common water source must share the resource on a pro rata basis in times of shortage. A proper overlying use takes precedence over all non-overlying uses.

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perched groundwater

Groundwater supported by a zone of material of low permeability located above an
underlying main body of groundwater.

The capability of soil or other geologic formations to transmit water. See hydraulic

Pleistocence-Holocene age aquitards
Confined beds deposited during the last 1.8 million years.

The ratio of the voids or open spaces in alluvium and rocks to the total volume of the alluvium or
rock mass.

pre-consolidation pressure
The maximum effective stress that a geologic unit has been subjected to.

prescriptive right
Rights obtained through the open and notorious adverse use of another's water rights. By definition, adverse use is not use of a surplus, but the use of non-surplus water to the direct detriment of the original rights holder.

primary porosity
Voids or open spaces that were present when alluvium and rocks were originallydeposited or formed.

pueblo right
A water right possessed by a municipality which, as a successor of a Spanish or Mexican pueblo, entitled to the beneficial use of all needed, naturally-occurring surface and groundwater of the original pueblo watershed Pueblo rights are paramount to all other claims.

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Water added to an aquifer or the process of adding water to an aquifer. Ground water recharge occurs either naturally as the net gain from precipitation, or artificially as the result of human influence. See artificial recharge.

recharge basin
A surface facility constructed to infiltrate surface water into a groundwater basin.

riparian right
A right to use surface water, such right derived from the fact that the land in question abuts
upon the banks of streams.

The volume of surface flow from an area.

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safe yield

The maximum quantity of water that can be continuously withdrawn from a groundwater basin without adverse effect.

Generally, the concentration of mineral salts dissolved in water. Salinity may be expressed in terms of a concentration or as electrical conductivity. When describing salinity influenced by seawater, salinity often refers to the concentration of chlorides in the water. See also total dissolved solids.

saline intrusion
The movement of salt water into a body of fresh water. It can occur in either surface water
or groundwater bodies.

saturated zone
The zone in which all interconnected openings are filled with water, usually underlying the
unsaturated zone.

seawater intrusion barrier
A system designed to retard, cease or repel the advancement of seawater
intrusion into potable groundwater supplies along coastal portions of California. The system may be a series of specifically placed injection wells where water is injected to form a hydraulic barrier.

secondary porosity
Voids in a rock formed after the rock has been deposited; not formed with the genesis of
the rock, but later due to other processes. Fractures in granite and caverns in limestone are examples of secondary openings.

The gradual movement of water into, through or from a porous medium. Also the loss of water by
infiltration into the soil from a canal, ditches, laterals, watercourse, reservoir, storage facilities, or other body of water, or from a field.

semi-confined aquifer
A semi-confined aquifer or leaky confined aquifer is an aquifer that has aquitards
either above or below that allow water to leak into or out of the aquifer depending on the direction of the hydraulic gradient.

specific retention
The ratio of the volume of water a rock or sediment will retain against the pull of gravity
to the total volume of the rock or sediment.

specific yield
The ratio of the volume of water a rock or soil will yield by gravity drainage to the total volume of the rock or soil.

A location where groundwater flows naturally to the land surface or a surface water body.

The science of rocks: It is concerned with the original succession and age relations of rock strata and their form, distribution, lithologic composition, fossil content, geophysical and geochemical properties-all characters and attributes of rocks as strata-and their interpretation in terms of environment and mode of origin and geologic history.

subterranean stream
Subterranean streams "flowing through known and definite channels" are regulated by California's surface water rights system.

surface supply
Water supply obtained from streams, lakes, and reservoirs.

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The product of hydraulic conductivity and aquifer thickness; a measure of a volume of water to move through an aquifer. Transmissivity generally has the units of ft2/day or gallons per day/foot. Transmissivity is a measure of the subsurface's ability to transmit groundwater horizontally through its entire saturated thickness and affects the potential yield of wells.

An essential physiological process in which plant tissues give off water vapor to the

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unconfined aquifer

An aquifer which is not bounded on top by an aquitard. The upper surface of an
unconfined aquifer is the water table.

underground stream
Body of water flowing as a definite current in a distinct channel below the surface of the ground, usually in an area characterized by joints or fissures. Application of the term to ordinary aquifers is incorrect.

unsaturated zone
The zone below the land surface in which pore space contains both water and air.

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water quality

Description of the chemical, physical, and biological characteristics of water, usually in
regard to its suitability for a particular purpose or use.

water table
See groundwater table

The land area from which water drains into a stream, river, or reservoir.

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