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Glossary of Water Terms

acre-foot​

volume of water that would cover 1 acre of land to a depth of 1 foot, the equivalent of 325,581 gallons.

alluvial​

deposited by running water

aquiclude​

A saturated geological formation that may contain water but does not transmit significant quantities.

aquifer​

an underground geologic formation that is able to store and yield water

artesian well​

a well in which water rises to the surface on its own.

cone of depression​

the spatial pattern of drawdown in an aquifer as a result of pumping. The downward-pointing, cone-shaped surface of the water table in a location where the water table was previously saturated but has become unsaturated due to pumping. The shape of the cone is influenced by porosity and the water yield or pumping rate of the well.

confining layer​

geologic material with little or no permeability or hydraulic conductivity. Water does not pass through this layer or the rate of movement is very slow.

discharge​

loss of water from the surface water reservoirs or groundwater through natural processes such as springs and rivers, or artificially by pumping wells. The opposite of recharge.

drawdown​

a lowering of the groundwater level caused by pumping.

ephemeral​

a term used to describe streams and arroyos that only flow in response to local rainfall or snowmelt events.

evaporation​

the physical process involving a phase change from liquid to vapor from soils, lakes, streams and oceans.

evapotranspiration​

The sum of evaporation from bodies of water and the ground surface and transpiration from plants and animals.

flow rate​

the time required for a volume of groundwater to move between points. Typically groundwater moves very slowly, sometimes as little as inches per year.

gaining stream​

a reach of a river or stream where groundwater is entering the channel through the riverbed and increasing the flow in the river and the volume of surface water.

groundwater​

water that resides under the water table in a saturated zone of the subsurface, mostly in pores or cracks of rocks and sediments.

groundwater mining​

prolonged pumping of groundwater at rates that exceed the rate of replenishment by recharge in an aquifer.

hydraulic conductivity​

volume of water that will move through a unit area of saturated material, typically expressed as gpd/ft^2)

hydrograph​

a continuous record of streamflow (stage or discharge) or groundwater level in a well as a function of time.

hydrology​

the study of the occurrence and movement of water on and beneath the surface of the Earth, the properties of water, and its relationship with the living and material components of the environment.

impermeable​

said of a water-bearing material that does not readily transmit or yield water to wells (such as clay).

infiltration​

the movement of rain or melting snow into the subsurface.

karst​

a type of topography formed where groundwater dissolves limestone, dolostone, or gypsum to form underground opening or caverns, the roofs of which have collapsed in places to form closed depressions at the surface known as sinkholes.

monitoring well​

a non-pumping well, generally of small diameter, that is used to measure the elevation of the water table of the water quality. A piezometer, which is only open at the top and bottom of its casing, is one type of monitoring well.

perennial​

said of a stream that flows year-round.

permeability​

the degree to which a material allows fluids to pass through it via an interconnected network of pores and cracks.

pH​

measure of hydrogen ion concentration in a liquid; 1-7 is acidic, 7 is neutral, 7-14 is alkaline.

plume​

a groundwater plume is an underground pattern of containment concentrations created by the movement of groundwater beneath a contaminant source. Contaminants typically spread laterally in the direction of groundwater movement.

porosity​

the ratio of empty or air space (pore space) in a material such as rock, sediment, or soil to the total volume of the rock or sediment.The capacity of rock or soil to hold water varies with the material. For example, saturated sand contains about 20% water.

potentiometric surface​

level to which groundwater will rise in wells.

precipitation​

the dominant process by which water vapor in the atmosphere is returned to the Earth’s surface either as liquid drops (e.g. rain) or solid particles (e.g. snow) under the influence of gravity.

produced water​

water that is produced during the extraction of petroleum from underground reservoirs. These reservoirs contain a mixture of water and petroleum so produced water is an inevitable byproduct of the extraction process.

pumping water level​

the level of groundwater in a well after pumping has lowered the water table by creating a cone of depression.

recharge​

when water enters the ground and infiltrates into an aquifer.

diffuse recharge​

when water infiltrates into an aquifer across a broad area through the soil.

focused recharge​

when water infiltrates into an aquifer at a discrete location, such as through a stream channel bed or artificially through an injection well

recharge area​

a location where water enters the ground and infiltrates down to the water table; also called a recharge zone.

remediation​

containment, treatment, or removal of contaminated groundwater or the contaminated soil above the water table.

residence time​

the period of time that groundwater remains in the aquifer.

runoff​

water flowing over the land surface.

saturated thickness​

total water-bearing thickness of an aquifer.

spring​

a natural outlet from which groundwater flows up onto the ground surface.

static water level​

the water table elevation under natural, stable conditions, i.e. when there are no pumping influences

subsidence​

a depression of the land surface as a result of groundwater being pumped. Cracks and fissures can appear in the land. Subsidence is a virtually irreversible process.

surface water​

water above the land surface, including lakes, rivers, streams, ponds, floodwater, and runoff.

surface runoff​

water from rainfall or snowmelt that runs over the surface of the Earth in sheets, rivulets, streams, and rivers.

sustainable yield​

see safe yield.

transpiration​

the physical process by which water changes phase from liquid to vapor, is released through the stomata of a plant, and returns to the atmosphere.

unsaturated zone​

the zone in a soil or rock between the Earth’s surface and the water table; pores in the unsaturated zone are partly filled with water and partly filled with air. Also called the vadose zone.

water table​

The boundary, typically parallel to the Earth’s surface, between saturated subsurface layers (the pore spaces are filled with water) and non-saturated layers (the pores are filled with mostly air and some water).

well​

a bored, drilled, or driven shaft, or a dug hole whose depth is greater than the largest surface dimension and whose purpose is to reach underground water supplies to inject, extract or monitor water.

well casing​

a pipe, typically steel or PVC, that serves to line a well.

well closure​

the process of sealing a well that is no longer being used to prevent groundwater contamination and harm to people and animals; also referred to as well plugging, or plugging and abandoning.

well screen​

a section at the end of a well casing that allows water to enter the well; construction may be holes drilled or slots cut in a pipe or may be a wire mesh material.

well siting​

location of a well placed to best protect water quality, access adequate water quantity, and allow for inspection and maintenance of the well.

wellhead protection area​

a protected surface or subsurface zone surrounding a well or well field supplying a public water system to keep contaminants from reaching the well water.

withdrawal​

the quantity of water extracted from a ground- or surface-water source.