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Indiana Department of Environmental Management

IDEM > Your Environment > Source Water Protection - Drinking Water > Ground Water Glossary Ground Water Glossary


natural underground layer, often of sand or gravel that has the ability to receive, store, and transmit water.
Aquifer (confined):
An aquifer where the ground water is bounded between layers of impermeable substances like clay or dense rock. When tapped by a well, water in confined aquifers is forced up, sometimes above the soil surface. This is how a flowing artesian well is formed. Also known as artesian or pressure aquifers.
Aquifer (unconfined):
An aquifer in which the water table is at or near atmospheric pressure and is the upper boundary of the aquifer. Because the aquifer is not under pressure the water level in a well is the same as the water table outside the well.
Artesian Well:
well tapping a confined aquifer. Water in the well rises above the top of the aquifer under artesian pressure, but does not necessarily reach the land surface; a flowing artesian well is a well in which the static water level is above the land surface.
The solid rock beneath the soil and superficial rock. A general term for solid bedrock that lies beneath soil, loose sediments, or other unconsolidated material.
Best Management Practices (BMPs):
Structural, nonstructural, and managerial techniques recognized to be the most effective and practical means to reduce surface water and ground water contamination while still allowing the productive use of resources. 
A group of related bacteria whose presence in drinking water may indicate contamination by disease-causing microorganisms.
Community Public Water Supply System (CPWSS):
public water system that provides water for human consumption to at least 15 service connections used by year-round residents, or one that regularly serves at least 25 year-round residents (e.g., municipalities, subdivisions, and mobile home parks).
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 extremely slow.
Anything found in water (including microorganisms, minerals, chemicals, radionuclides, etc.) which may be harmful to human health.
microorganism commonly found in lakes and rivers which is highly resistant to disinfection. Cryptosporidium has caused several large outbreaks of gastrointestinal illness, with symptoms that include diarrhea, nausea, and/or stomach cramps. People with severely weakened immune systems (that is, severely immuno-compromised) are likely to have more severe and more persistent symptoms than healthy individuals.
An outflow of water from a stream, pipe, ground water aquifer, or watershed; the opposite of recharge.
Any process that destroys or removes disease-causing organisms such as viruses, bacteria or protozoa. It is used as part of the purification of drinking water. Commonly done with chemicals (chlorine, chloramine, or ozone) or a physical process (e.g., ultraviolet light).
Distribution System:
network of pipes leading from a treatment plant to customers' plumbing systems.
lowering of the ground water level caused by pumping.
Drinking Water Standards:
A threshold concentration for a constituent or compound in a public drinking-water supply, designed to protect human health. As defined here, standards are EPA regulations that specify the maximum contamination levels for public water systems required to protect the public health and welfare.
Finished Water:
Water that has been treated and is ready to be delivered to customers.
Giardia Lamblia:
microorganism frequently found in rivers and lakes, which, if not treated properly, may cause diarrhea, fatigue, and cramps after ingestion.
Ground Water:
The water that systems pump from aquifers (natural reservoirs below the earth's surface) and is found in the spaces between soil particles and cracks in rocks underground.
The study of the interrelationships of geologic materials and processes with water, especially ground water. 
Hydrologic Cycle:
The paths water takes through its various states--vapor, liquid, solid--as it moves throughout the oceans, atmosphere, ground water, streams, etc. Also known as the water cycle.
The study of the occurrence, distribution, and chemistry of all waters of the earth. 
Impermeable Layer:
layer of material (such as clay) in an aquifer through which water does not pass.
Flow of water from the land surface into the subsurface. 
Injection Well:
well constructed for the purpose of injecting treated water, often wastewater, directly into the ground. Water is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that are not used as a drinking water source, unused aquifers, or below freshwater levels.
Integrated Management:
Any combination of physical, technical, administrative, and legal practices relating to surface water and ground water in a manner designed to increase combined benefits or achieve a more equitable apportionment of benefits from both sources. Also referred to as conjunctive use.
Inorganic Contaminants:
Mineral-based compounds such as metals, nitrates, and asbestos. These contaminants are naturally-occurring in some water, but can also get into water through farming, chemical manufacturing, and other human activities.
geologic formation of irregular limestone deposits with sink holes, underground streams, and caverns.
Large Public Water Supply System:
public water supply system serving greater than fifty thousand (50,000) customers.
Liquids that have percolated through a soil and that carry substances in solution or suspension.
The process by which soluble materials in the soil, such as salts, nutrients, pesticide chemicals, or contaminants, are washed into a lower layer of soil or are dissolved and carried away by water.
Maximum Contaminant Level (MCL):
The highest level of a contaminant that EPA allows in drinking water. MCLs ensure that drinking water does not pose either a short-term or long-term health risk. EPA sets MCLs at levels that are economically and technologically feasible. Some states set MCLs which are more strict than EPA's.
Medium Public Water Supply System:
public water supply system serving from three thousand three hundred and one (3,301), up to and including, fifty thousand (50,000) customers.
Tiny living organisms that can be seen only with the aid of a microscope. Some microorganisms can cause acute health problems when consumed in drinking water. Also known as microbes.
Testing that water systems must perform to detect and measure contaminants. A water system that does not follow EPA's monitoring methodology or schedule is in violation, and may be subject to legal action.
Monitoring Well:
non-pumping well, generally of small diameter, that is used to measure the elevation of a water table or water quality. A piezometer, which is open only at the top and bottom of its casing, is one type of monitoring well. 
Non-Community Water System:
A public water system that provides water for human consumption to at least 15 service connections used by individuals other than year-round residents for at least 60 days a year, or serves 25 or more people at least 60 days a year (e.g., schools, factories, rest stops, Interstate carrier conveyances).
Nonpoint Source Pollution:
Pollution discharged over a wide land area, not from one specific location. These are forms of diffuse pollution caused by sediment, nutrients, organic and toxic substances originating from land use activities which are carried to lakes and streams by surface runoff. Nonpoint source pollution is contamination that occurs when rainwater, snowmelt, or irrigation washes off plowed fields, city streets, or suburban backyards. As this runoff moves across the land surface, it picks up soil particles and pollutants, such as nutrients and pesticides. 
Non-Transient, Non-Community Water System:
non-community water system that serves at least 25 of the same persons over six months per year (e.g., schools, factories, industrial parks, office buildings).
Organic Contaminants:
Carbon-based chemicals, such as solvents and pesticides, which can get into water through runoff from cropland or discharge from factories, home septic systems, gas stations and many other land use activities.
Parts per million:
The number of "parts" by weight of a substance per million parts of water.
Parts per billion:
The number of "parts" by weight of a substance per billion parts of water.
disease-causing organism.
Permeable Layer:
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 ground water, a plume is an underground pattern of contaminant concentrations created by the movement of ground water through a contaminant source. Contaminants spread mostly laterally in the direction of ground water movement. The source site has the highest concentration, and the concentration decreases away from the source. 
Point Source Pollution:
Pollutants discharged from any identifiable point, including pipes, ditches, channels, sewers, tunnels, and containers of various types.
An alteration in the character or quality of the environment, or any of its components, that renders it less suited for certain uses. The alteration of the physical, chemical, or biological properties of water by the introduction of any substance that renders the water harmful to use.
Potable Water:
Water of a quality suitable for drinking.
Potential Source of Contamination:
facility, site, practice, or activity that possesses the ability to contaminate source water.
Production Well:
well used to withdraw water from an aquifer.
Public Water System (PWS):
Any water system which provides water to at least 25 people for at least 60 days annually. There are more than 170,000 PWSs providing water from wells, rivers and other sources to about 250 million Americans. The others drink water from private wells. There are differing standards for PWSs of different sizes and types.
Any man-made or natural element that emits radiation and that may cause cancer after many years of exposure through drinking water.
Raw Water:
Water in its natural state, prior to any treatment for drinking.
Water added to an aquifer. For example, when rainwater seeps into the ground. Recharge may occur artificially through injection wells or by spreading water over ground water reservoirs.
Containment, treatment or removal of contaminated ground water. May also include containment, treatment or removal of contaminated soil above the water table.
Precipitation that flows over land to surface streams, rivers, and lakes.
The water that is analyzed for the presence of EPA-regulated drinking water contaminants. Depending on the regulation, EPA requires water systems and states to take samples from source water, from water leaving the treatment facility, or from the taps of selected consumers.
Sanitary Setback Area:
An area established around a Community Public Water Supply System production well to protect ground water from direct contamination.
Saturation Zone:
The portion below the earth's surface that is saturated with water is called the zone of saturation. The upper surface of this zone, open to atmospheric pressure, is known as the water table.
Secondary Drinking Water Standards:
Non-enforceable federal guidelines regarding cosmetic effects (such as tooth or skin discoloration) or aesthetic effects (such as taste, odor, or color) of drinking water.
Septic System:
Used to treat household sewage and wastewater by allowing the solids to decompose and settle in a tank, then letting the liquid flow through a drainage field. The liquid is absorbed by the soil in the drainage field. Septic systems are used when a sewer line is not available to carry wastes to a sewage treatment plant. Also called an onsite wastewater treatment system.
Small Public Water Supply System:
public water supply system serving up to and including three thousand three hundred (3,300) customers.
The top layer of the Earth's surface, containing unconsolidated rock and mineral particles mixed with organic material.
Sole Source Aquifer:
An aquifer that supplies 50 percent or more of the drinking water of an area and for which there are no reasonably available alternative sources should the aquifer become contaminated.
Source Water:
Water in its natural state, prior to any treatment for drinking.
Source Water Assessment:
process in which the land area that impacts a public drinking water source is delineated, possible sources of contaminants that could impact that drinking water source are identified, and a determination of the likelihood that the contaminants will reach the drinking water source is made. The federal Safe Drinking Water Act requires states to provide each public water system with a source water assessment. Public water systems are then required to make the assessments available to the public. A community may verify, refine or expand the list of potential contaminants. See source water protection.
Source Water Protection:
Voluntary action taken to prevent the pollution of drinking water sources, including ground water, lakes, rivers, and streams. Source water protection is developing and implementing a plan to manage land uses and potential contaminants. To be effective, source water protection should be directed to major threats to the drinking water source identified in the source water assessment. As part of the source water protection plan, a contingency plan for use in the event of an emergency is developed. Source water protection for ground water is also called wellhead protection. See source water assessment. 
Static Water Level:
(1) Elevation or level of the water table in a well when the pump is not operating. (2) The level or elevation to which water would rise in a tube connected to an artesian aquifer or basin in a conduit under pressure.
Storm Drain:
Constructed opening in a road system through which runoff from the road surface flows into an underground system.
layer of material beneath the surface soil.
Susceptibility Assessment:
An evaluation of drinking water source quality and its vulnerability to contamination by pathogens and toxic chemicals.
Surface Water:
The water that systems pump and treat from sources open to the atmosphere, such as rivers, lakes, and reservoirs.
Time of Travel:
The calculated length of time a particle of water takes to reach a community public water supply system production well from a certain point.
Transient, Non-Community Water System:
non-community water system that does not meet the definition of a non-transient, non-community water system because the people served do not stay at the location, rather differ from day to day (e.g., highway rest stops, restaurants, motels, golf courses, parks).
Treatment Technique:
required process intended to reduce the level of a contaminant in drinking water.
The cloudy appearance of water caused by the presence of tiny particles. High levels of turbidity may interfere with proper water treatment and monitoring.
Unconsolidated Rock:
Loosely bound geologic formation composed of sands and gravel.
Unsaturated Zone:
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 vadose zone.
Water that contains unwanted materials from homes, businesses, and industries; a mixture of water and dissolved or suspended substances.
Wastewater treatment:
Any of the mechanical or chemical processes used to modify the quality of wastewater in order to make it more compatible or acceptable to humans and the environment.
The land area from which surface runoff drains into a stream, channel, lake, reservoir, or other body of water; also called a drainage basin.
Water Table:
The top of an unconfined aquifer; indicates the level below which soil and rock are saturated with water. The upper surface of the saturation zone.
Water Treatment Plants:
Facilities that treat water to remove contaminants so that it can be safely used.
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 Abandonment:
The process of sealing an unused well. This action can prevent ground water contamination, causing potential harm to people or animals.
Well Field:
An area in which productive wells are drilled.
Well Log:
drilling record that describes the subsurface formations that have been drilled through and gives details of well construction. A copy of this record must be filed with the Indiana Department of Natural Resources, Water Division, for any water well drilled after 1968.
Wellhead Protection Area:
designated area which surrounds a drinking water supply well or well field. The boundaries are usually determined by a mathematical ground water but can be a fixed radius when certain requirements are met. The area is provided special safeguards and other measures to protect the drinking water from becoming contaminated.

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