The zone immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. Plant roots can capture the moisture passing through this zone, but it cannot provide water for wells. Also known as the unsaturated zone.
Cone of depression
The zone around a well in an unconfined aquifer that is normally saturated, but becomes unsaturated as a well is pumped, leaving an area where the water table dips down to form a cone shape. The shape of the cone is influenced by porosity and the water yield or pumping rate of the well.
Geologic material with little or no permeability or hydraulic conductivity. Water does not pass through this layer or the rate of movement is extremely slow.
The loss of water from surface wafer reservoirs or groundwater aquifers at a rate greater than that of recharge.
An outflow of water from a stream, pipe, groundwater aquifer, or watershed; the opposite of recharge.
The time required for a volume of groundwater to move between points. Typically groundwater moves very slowly-sometimes only inches per year.
Water found in the spaces between soil particles and cracks in rocks underground (located in the saturation zone). It is a natural resource that is used for drinking, recreation, industry, and growing crops.
The paths water takes through its various states- vapor, liquid, solid- as it moves throughout the oceans, atmosphere, groundwater, streams, etc. Also known as the water cycle
A layer of material (such as clay) in an aquifer through which water does not pass.
The quantity of water that enters the soil surface in a specified time interval. Often expressed in volume of water per unit of soil surface area per unit of time.
A non-pumping well, generally of small diameter, that is used to measure the elevation of a water table or water quality.
Withdrawal of groundwater over a period of time that exceeds the recharge rate of the supply aquifer. Also referred to as overdraft or mining the aquifer.
Capable of transmitting water (porous rock, sediment, or soil); the rate at which water moves through rocks or soil.
A layer of porous material (rock, soil, unconsolidated sediment); in an aquifer, the layer through which water freely passes as it moves through the ground.
In groundwater, it is an underground pattern of contaminant concentrations created by the movement of groundwater beneath a contaminant source. Contaminants spread mostly laterally in the direction of groundwater movement. The source site has the highest concentration, and the concentration decreases away from the source.
Openings between geologic material found underground. Also referred to as void space or interstices.
The ratio of the volume of void or air spaces in a rock or sediment to the total volume of the rock or sediment. The capacity of rock or soil to hold water varies with the material. (example: saturated sand contains about 20% water; gravel, 25%; and clay, 48%.)
Water added to an aquifer. (example: when rain wafer seeps into the ground.) It may occur artificially through injection wells or by spreading water over groundwater reservoirs.
Recharge zone or area
An area where permeable soil or rock allows water to deep into the ground to replenish an aquifer.
Containment, treatment, or removal of contaminated groundwater. May also include containment, treatment, or removal of contaminated soil above the water table.
The annual amount of wafer that can be taken from a source of supply over a period of years without depleting that source beyond its ability to be replenished naturally in "wet years." Also called sustainable yield.
Salt water intrusion
Process by which an aquifer is overdrafted creating a flow imbalance within an area that results in salt water enroaching into fresh water supply.
A depression of the land surface as a result of groundwater being pumped. Cracks and fissures can appear in the land. It is virtually an irreversible process.
Water above the surface of land, including lakes, rivers, streams, ponds, floodwater, and runoff.
The top of an unconfined aquifer; indicates the level below which soil and rock are saturated with water. It is the upper surface of the saturation zone where it is open to atmospheric pressure.
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.
The process of sealing a well that is no longer being used to prevent groundwater contamination and harm to people and animals.
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 and subsurface zone surrounding a well or well field supplying a public water system to keep contaminants from reaching the well water.
Putting water back into groundwater storage from surface water supplies such as irrigation, or induced infiltration from streams or wells.
A type of wetland in which water is present for only part of the year, usually during wet or rainy seasons; also known as vernal pools.
A layer within the earth's crust that generally consists of the same kinds of soils or rock material
Points of higher ground that separate two adjacent streams or watersheds; also known as divides.
The potential level to which water will rise above the water level in an aquifer in a well that penetrates a confined aquifer