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Water Science Glossary of Terms

Here's a list of water-related terms that might help you understand our site better. It is compiled from a number of sources and should not be considered an "official" U.S. Geological Survey water glossary. A detailed water glossary is kept by the Water Quality Association.

A acequia--acequias were important forms of irrigation in the development of agriculture in the American Southwest. The proliferation of cotton, pecans and green chile as major agricultual staples owe their progress to the acequia system.

acid--a substance that has a pH of less than 7, which is neutral. Specifically, an acid has more free hydrogen ions (H+) than hydroxyl ions (OH-).

acre-foot (acre-ft)--the volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic meters.

alkaline--sometimes water or soils contain an amount of alkali (strongly basic) substances sufficient to raise the pH value above 7.0 and be harmful to the growth of crops.

alkalinity--the capacity of water for neutralizing an acid solution.

alluvium--deposits of clay, silt, sand, gravel, or other particulate material that has been deposited by a stream or other body of running water in a streambed, on a flood plain, on a delta, or at the base of a mountain.

appropriation doctrine--the system for allocating water to private individuals used in most Western states. The doctrine of Prior Appropriation was in common use throughout the arid west as early settlers and miners began to develop the land. The prior appropriation doctrine is based on the concept of "First in Time, First in Right." The first person to take a quantity of water and put it to Beneficial Use has a higher priority of right than a subsequent user. Under drought conditions, higher priority users are satisfied before junior users receive water. Appropriative rights can be lost through nonuse; they can also be sold or transferred apart from the land. Contrasts with Riparian Water Rights.

aquaculture--farming of plants and animals that live in water, such as fish, shellfish, and algae.

aqueduct--a pipe, conduit, or channel designed to transport water from a remote source, usually by gravity.

aquifer--a geologic formation(s) that is water bearing. A geological formation or structure that stores and/or transmits water, such as to wells and springs. Use of the term is usually restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people's uses.

aquifer (confined)--soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.

aquifer (unconfined)--an aquifer whose upper water surface (water table) is at atmospheric pressure, and thus is able to rise and fall.

artesian water--ground water that is under pressure when tapped by a well and is able to rise above the level at which it is first encountered. It may or may not flow out at ground level. The pressure in such an aquifer commonly is called artesian pressure, and the formation containing artesian water is an artesian aquifer or confined aquifer. See flowing well

artificial recharge--an process where water is put back into ground-water storage from surface-water supplies such as irrigation, or induced infiltration from streams or wells.

B base flow--sustained flow of a stream in the absence of direct runoff. It includes natural and human-induced streamflows. Natural base flow is sustained largely by ground-water discharges.

base--a substance that has a pH of more than 7, which is neutral. A base has less free hydrogen ions (H+) than hydroxyl ions (OH-).

bedrock--the solid rock beneath the soil and superficial rock. A general term for solid rock that lies beneath soil, loose sediments, or other unconsolidated material.

  C capillary action--the means by which liquid moves through the porous spaces in a solid, such as soil, plant roots, and the capillary blood vessels in our bodies due to the forces of adhesion, cohesion, and surface tension. Capillary action is essential in carrying substances and nutrients from one place to another in plants and animals.

commercial water use--water used for motels, hotels, restaurants, office buildings, other commercial facilities, and institutions. Water for commercial uses comes both from public-supplied sources, such as a county water department, and self-supplied sources, such as local wells.

condensation--the process of water vapor in the air turning into liquid water. Water drops on the outside of a cold glass of water are condensed water. Condensation is the opposite process of evaporation.

consumptive use--that part of water withdrawn that is evaporated, transpired by plants, incorporated into products or crops, consumed by humans or livestock, or otherwise removed from the immediate water environment. Also referred to as water consumed.

conveyance loss--water that is lost in transit from a pipe, canal, or ditch by leakage or evaporation. Generally, the water is not available for further use; however, leakage from an irrigation ditch, for example, may percolate to a ground-water source and be available for further use.

cubic feet per second (cfs)--a rate of the flow, in streams and rivers, for example. It is equal to a volume of water one foot high and one foot wide flowing a distance of one foot in one second. One "cfs" is equal to 7.48 gallons of water flowing each second. As an example, if your car's gas tank is 2 feet by 1 foot by 1 foot (2 cubic feet), then gas flowing at a rate of 1 cubic foot/second would fill the tank in two seconds.

D desalinization--the removal of salts from saline water to provide freshwater. This method is becoming a more popular way of providing freshwater to populations.

discharge--the volume of water that passes a given location within a given period of time. Usually expressed in cubic feet per second.

domestic water use--water used for household purposes, such as drinking, food preparation, bathing, washing clothes, dishes, and dogs, flushing toilets, and watering lawns and gardens. About 85% of domestic water is delivered to homes by a public-supply facility, such as a county water department. About 15% of the Nation's population supply their own water, mainly from wells.

drainage basin--land area where precipitation runs off into streams, rivers, lakes, and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins, like the area that drains into the Mississippi River contain thousands of smaller drainage basins. Also called a "watershed."

drip irrigation--a common irrigation method where pipes or tubes filled with water slowly drip onto crops. Drip irrigation is a low-pressure method of irrigation and less water is lost to evaporation than high-pressure spray irrigation.

drawdown--a lowering of the ground-water surface caused by pumping.

E effluent--water that flows from a sewage treatment plant after it has been treated.

erosion--the process in which a material is worn away by a stream of liquid (water) or air, often due to the presence of abrasive particles in the stream.

estuary--a place where fresh and salt water mix, such as a bay, salt marsh, or where a river enters an ocean.

evaporation--the process of liquid water becoming water vapor, including vaporization from water surfaces, land surfaces, and snow fields, but not from leaf surfaces. See transpiration

evapotranspiration--the sum of evaporation and transpiration.

F flood--An overflow of water onto lands that are used or usable by man and not normally covered by water. Floods have two essential characteristics: The inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river, stream, lake, or ocean.

flood, 100-year--A 100-year flood does not refer to a flood that occurs once every 100 years, but to a flood level with a 1 percent chance of being equaled or exceeded in any given year.

flood plain--a strip of relatively flat and normally dry land alongside a stream, river, or lake that is covered by water during a flood.

flood stage--The elevation at which overflow of the natural banks of a stream or body of water begins in the reach or area in which the elevation is measured.

flowing well/spring--a well or spring that taps ground water under pressure so that water rises without pumping. If the water rises above the surface, it is known as a flowing well.

freshwater, freshwater--water that contains less than 1,000 milligrams per liter (mg/L) of dissolved solids; generally, more than 500 mg/L of dissolved solids is undesirable for drinking and many industrial uses.

  G gage height--the height of the water surface above the gage datum (zero point). Gage height is often used interchangeably with the more general term, stage, although gage height is more appropriate when used with a gage reading.

gaging station--a site on a stream, lake, reservoir or other body of water where observations and hydrologic data are obtained. The U.S. Geological Survey measures stream discharge at gaging stations.

geyser--a geothermal feature of the Earth where there is an opening in the surface that contains superheated water that periodically erupts in a shower of water and steam.

giardiasis--a disease that results from an infection by the protozoan parasite Giardia Intestinalis, caused by drinking water that is either not filtered or not chlorinated. The disorder is more prevalent in children than in adults and is characterized by abdominal discomfort, nausea, and alternating constipation and diarrhea.

glacier--a huge mass of ice, formed on land by the compaction and recrystallization of snow, that moves very slowly downslope or outward due to its own weight.

greywater--wastewater from clothes washing machines, showers, bathtubs, hand washing, lavatories and sinks.

ground water--(1) water that flows or seeps downward and saturates soil or rock, supplying springs and wells. The upper surface of the saturate zone is called the water table. (2) Water stored underground in rock crevices and in the pores of geologic materials that make up the Earth's crust.

ground water, confined--ground water under pressure significantly greater than atmospheric, with its upper limit the bottom of a bed with hydraulic conductivity distinctly lower than that of the material in which the confined water occurs.

ground-water recharge--inflow of water to a ground-water reservoir from the surface. Infiltration of precipitation and its movement to the water table is one form of natural recharge. Also, the volume of water added by this process.

ground water, unconfined--water in an aquifer that has a water table that is exposed to the atmosphere.

H hardness--a water-quality indication of the concentration of alkaline salts in water, mainly calcium and magnesium. If the water you use is "hard" then more soap, detergent or shampoo is necessary to raise a lather.

headwater(s)--(1) the source and upper reaches of a stream; also the upper reaches of a reservoir. (2) the water upstream from a structure or point on a stream. (3) the small streams that come together to form a river. Also may be thought of as any and all parts of a river basin except the mainstream river and main tributaries.

hydroelectric power water use--the use of water in the generation of electricity at plants where the turbine generators are driven by falling water.

hydrologic cycle--the cyclic transfer of water vapor from the Earth's surface via evapotranspiration into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into the oceans.

I impermeable layer--a layer of solid material, such as rock or clay, which does not allow water to pass through.

industrial water use--water used for industrial purposes in such industries as steel, chemical, paper, and petroleum refining. Nationally, water for industrial uses comes mainly (80%) from self-supplied sources, such as a local wells or withdrawal points in a river, but some water comes from public-supplied sources, such as the county/city water department.

infiltration--flow of water from the land surface into the subsurface.

injection well--refers to a well constructed for the purpose of injecting treated wastewater directly into the ground. Wastewater is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that don't deliver drinking water, unused aquifers, or below freshwater levels.

irrigation--the controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall. 

irrigation water use--water application on lands to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands, such as parks and golf courses.

  K kilogram--one thousand grams.

kilowatthour (KWH)--a power demand of 1,000 watts for one hour. Power company utility rates are typically expressed in cents per kilowatt-hour.

  L leaching--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.

lentic waters--ponds or lakes (standing water).

levee--a natural or manmade earthen barrier along the edge of a stream, lake, or river. Land alongside rivers can be protected from flooding by levees.

livestock water use--water used for livestock watering, feed lots, dairy operations, fish farming, and other on-farm needs.

lotic waters--flowing waters, as in streams and rivers.

  M maximum contaminant level (MCL)--the designation given by the U.S. Environmental Protection Agency (EPA) to water-quality standards promulgated under the Safe Drinking Water Act. The MCL is the greatest amount of a contaminant that can be present in drinking water without causing a risk to human health.

milligram (mg)--One-thousandth of a gram.

milligrams per liter (mg/l)--a unit of the concentration of a constituent in water or wastewater. It represents 0.001 gram of a constituent in 1 liter of water. It is approximately equal to one part per million (PPM).

million gallons per day (Mgd)--a rate of flow of water equal to 133,680.56 cubic feet per day, or 1.5472 cubic feet per second, or 3.0689 acre-feet per day. A flow of one million gallons per day for one year equals 1,120 acre-feet (365 million gallons).

mining water use--water use during quarrying rocks and extracting minerals from the land.

municipal water system--a water system that has at least five service connections or which regularly serves 25 individuals for 60 days; also called a public water system

  N nephelometric turbidity unit (NTU)--unit of measure for the turbidity of water. Essentially, a measure of the cloudiness of water as measured by a nephelometer. Turbidity is based on the amount of light that is reflected off particles in the water.

NGVD--National Geodetic Vertical Datum. (1) As corrrected in 1929, a vertical control measure used as a reference for establishing varying elevations. (2) Elevation datum plane previously used by the Federal Emergency Management Agency (FEMA) for the determination of flood elevations. FEMA current uses the North American Vertical Datum Plane.

NGVD of 1929--National Geodetic Vertical Datum of 1929. A geodetic datum derived from a general adjustment of the first order level nets of the United States and Canada. It was formerly called "Sea Level Datum of 1929" or "mean sea level" in the USGS series of reports. Although the datum was derived from the average sea level over a period of many years at 26 tide stations along the Atlantic, Gulf of Mexico, and Pacific Coasts, it does not necessarily represent local mean sea level at any particular place.

non-point source (NPS) 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. Non-point 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.

  O organic matter--plant and animal residues, or substances made by living organisms. All are based upon carbon compounds.

osmosis--the movement of water molecules through a thin membrane. The osmosis process occurs in our bodies and is also one method of desalinizing saline water.

outfall--the place where a sewer, drain, or stream discharges; the outlet or structure through which reclaimed water or treated effluent is finally discharged to a receiving water body.

oxygen demand--the need for molecular oxygen to meet the needs of biological and chemical processes in water. Even though very little oxygen will dissolve in water, it is extremely important in biological and chemical processes.

  P pH--a measure of the relative acidity or alkalinity of water. Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity, while pH levels higher than 7 indicate increasingly basic solutions.

particle size--the diameter, in millimeters, of suspended sediment or bed material. Particle-size classifications are:
[1] Clay—0.00024-0.004 millimeters (mm);
[2] Silt—0.004-0.062 mm;
[3] Sand—0.062-2.0 mm; and
[4] Gravel—2.0-64.0 mm.

parts per billion--the number of "parts" by weight of a substance per billion parts of water. Used to measure extremely small concentrations.

parts per million--the number of "parts" by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations.

pathogen--a disease-producing agent; usually applied to a living organism. Generally, any viruses, bacteria, or fungi that cause disease.

peak flow--the maximum instantaneous discharge of a stream or river at a given location. It usually occurs at or near the time of maximum stage.

per capita use--the average amount of water used per person during a standard time period, generally per day.

percolation--(1) The movement of water through the openings in rock or soil. (2) the entrance of a portion of the streamflow into the channel materials to contribute to ground water replenishment.

permeability--the ability of a material to allow the passage of a liquid, such as water through rocks. Permeable materials, such as gravel and sand, allow water to move quickly through them, whereas unpermeable material, such as clay, don't allow water to flow freely.

point-source pollution--water pollution coming from a single point, such as a sewage-outflow pipe.

polychlorinated biphenyls (PCBs)--a group of synthetic, toxic industrial chemical compounds once used in making paint and electrical transformers, which are chemically inert and not biodegradable. PCBs were frequently found in industrial wastes, and subsequently found their way into surface and ground waters. As a result of their persistence, they tend to accumulate in the environment. In terms of streams and rivers, PCBs are drawn to sediment, to which they attach and can remain virtually indefinitely. Although virtually banned in 1979 with the passage of the Toxic Substances Control Act, they continue to appear in the flesh of fish and other animals.

porosity--a measure of the water-bearing capacity of subsurface rock. With respect to water movement, it is not just the total magnitude of porosity that is important, but the size of the voids and the extent to which they are interconnected, as the pores in a formation may be open, or interconnected, or closed and isolated. For example, clay may have a very high porosity with respect to potential water content, but it constitutes a poor medium as an aquifer because the pores are usually so small.

potable water--water of a quality suitable for drinking.

precipitation--rain, snow, hail, sleet, dew, and frost.

primary wastewater treatment--the first stage of the wastewater-treatment process where mechanical methods, such as filters and scrapers, are used to remove pollutants. Solid material in sewage also settles out in this process.

prior appropriation doctrine--the system for allocating water to private individuals used in most Western states. The doctrine of Prior Appropriation was in common use throughout the arid West as early settlers and miners began to develop the land. The prior appropriation doctrine is based on the concept of "First in Time, First in Right." The first person to take a quantity of water and put it to beneficial use has a higher priority of right than a subsequent user. The rights can be lost through nonuse; they can also be sold or transferred apart from the land. Contrasts with riparian water rights.

public supply--water withdrawn by public governments and agencies, such as a county water department, and by private companies that is then delivered to users. Public suppliers provide water for domestic, commercial, thermoelectric power, industrial, and public water users. Most people's household water is delivered by a public water supplier. The systems have at least 15 service connections (such as households, businesses, or schools) or regularly serve at least 25 individuals daily for at least 60 days out of the year.

public water use--water supplied from a public-water supply and used for such purposes as firefighting, street washing, and municipal parks and swimming pools.

  R rating curve--A drawn curve showing the relation between gage height and discharge of a stream at a given gaging station.

recharge--water added to an aquifer. For instance, rainfall that seeps into the ground.

reclaimed wastewater--treated wastewater that can be used for beneficial purposes, such as irrigating certain plants.

recycled water--water that is used more than one time before it passes back into the natural hydrologic system.

reservoir--a pond, lake, or basin, either natural or artificial, for the storage, regulation, and control of water.

return flow--(1) That part of a diverted flow that is not consumptively used and returned to its original source or another body of water. (2) (Irrigation) Drainage water from irrigated farmlands that re-enters the water system to be used further downstream.

returnflow (irrigation)--irrigation water that is applied to an area and which is not consumed in evaporation or transpiration and returns to a surface stream or aquifer.

reverse osmosis--(1) (Desalination) The process of removing salts from water using a membrane. With reverse osmosis, the product water passes through a fine membrane that the salts are unable to pass through, while the salt waste (brine) is removed and disposed. This process differs from electrodialysis, where the salts are extracted from the feedwater by using a membrane with an electrical current to separate the ions. The positive ions go through one membrane, while the negative ions flow through a different membrane, leaving the end product of freshwater. (2) (Water Quality) An advanced method of water or wastewater treatment that relies on a semi-permeable membrane to separate waters from pollutants. An external force is used to reverse the normal osmotic process resulting in the solvent moving from a solution of higher concentration to one of lower concentration.

riparian water rights--the rights of an owner whose land abuts water. They differ from state to state and often depend on whether the water is a river, lake, or ocean. The doctrine of riparian rights is an old one, having its origins in English common law. Specifically, persons who own land adjacent to a stream have the right to make reasonable use of the stream. Riparian users of a stream share the streamflow among themselves, and the concept of priority of use (Prior Appropriation Doctrine) is not applicable. Riparian rights cannot be sold or transferred for use on nonriparian land.

river--A natural stream of water of considerable volume, larger than a brook or creek.

runoff--(1) That part of the precipitation, snow melt, or irrigation water that appears in uncontrolled surface streams, rivers, drains or sewers. Runoff may be classified according to speed of appearance after rainfall or melting snow as direct runoff or base runoff, and according to source as surface runoff, storm interflow, or ground-water runoff. (2) The total discharge described in (1), above, during a specified period of time. (3) Also defined as the depth to which a drainage area would be covered if all of the runoff for a given period of time were uniformly distributed over it.

  S saline water--water that contains significant amounts of dissolved solids.

Here are our parameters for saline water:
Fresh water - Less than 1,000 parts per million (ppm)
Slightly saline water - From 1,000 ppm to 3,000 ppm
Moderatly saline water - From 3,000 ppm to 10,000 ppm
Highly saline water - From 10,000 ppm to 35,000 ppm

secondary wastewater treatment--treatment (following primary wastewater treatment) involving the biological process of reducing suspended, colloidal, and dissolved organic matter in effluent from primary treatment systems and which generally removes 80 to 95 percent of the Biochemical Oxygen Demand (BOD) and suspended matter. Secondary wastewater treatment may be accomplished by biological or chemical-physical methods. Activated sludge and trickling filters are two of the most common means of secondary treatment. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settleable solids and about 90 percent of the oxygen-demanding substances and suspended solids. Disinfection is the final stage of secondary treatment.

sediment--usually applied to material in suspension in water or recently deposited from suspension. In the plural the word is applied to all kinds of deposits from the waters of streams, lakes, or seas.

sedimentary rock--rock formed of sediment, and specifically: (1) sandstone and shale, formed of fragments of other rock transported from their sources and deposited in water; and (2) rocks formed by or from secretions of organisms, such as most limestone. Many sedimentary rocks show distinct layering, which is the result of different types of sediment being deposited in succession.

sedimentation tanks--wastewater tanks in which floating wastes are skimmed off and settled solids are removed for disposal.

self-supplied water--water withdrawn from a surface- or ground-water source by a user rather than being obtained from a public supply. An example would be homeowners getting their water from their own well.

seepage--(1) The slow movement of water through small cracks, pores, Interstices, etc., of a material into or out of a body of surface or subsurface water. (2) 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.

septic tank--a tank used to detain domestic wastes to allow the settling of solids prior to distribution to a leach field for soil absorption. Septic tanks are used when a sewer line is not available to carry them to a treatment plant. A settling tank in which settled sludge is in immediate contact with sewage flowing through the tank, and wherein solids are decomposed by anaerobic bacterial action.

settling pond (water quality)--an open lagoon into which wastewater contaminated with solid pollutants is placed and allowed to stand. The solid pollutants suspended in the water sink to the bottom of the lagoon and the liquid is allowed to overflow out of the enclosure.

sewage treatment plant--a facility designed to receive the wastewater from domestic sources and to remove materials that damage water quality and threaten public health and safety when discharged into receiving streams or bodies of water. The substances removed are classified into four basic areas:
[1] greases and fats;
[2] solids from human waste and other sources;
[3] dissolved pollutants from human waste and decomposition products; and
[4] dangerous microorganisms.
Most facilities employ a combination of mechanical removal steps and bacterial decomposition to achieve the desired results. Chlorine is often added to discharges from the plants to reduce the danger of spreading disease by the release of pathogenic bacteria.

sewer--a system of underground pipes that collect and deliver wastewater to treatment facilities or streams.

sinkhole--a depression in the Earth's surface caused by dissolving of underlying limestone, salt, or gypsum. Drainage is provided through underground channels that may be enlarged by the collapse of a cavern roof.

solute--a substance that is dissolved in another substance, thus forming a solution.

solution--a mixture of a solvent and a solute. In some solutions, such as sugar water, the substances mix so thoroughly that the solute cannot be seen. But in other solutions, such as water mixed with dye, the solution is visibly changed.

solvent--a substance that dissolves other substances, thus forming a solution. Water dissolves more substances than any other, and is known as the "universal solvent".

specific conductance--a measure of the ability of water to conduct an electrical current as measured using a 1-cm cell and expressed in units of electrical conductance, i.e., Siemens per centimeter at 25 degrees Celsius. Specific conductance can be used for approximating the total dissolved solids content of water by testing its capacity to carry an electrical current. In water quality, specific conductance is used in ground water monitoring as an indication of the presence of ions of chemical substances that may have been released by a leaking landfill or other waste storage or disposal facility. A higher specific conductance in water drawn from downgradient wells when compared to upgradient wells indicates possible contamination from the facility.

spray irrigation--an common irrigation method where water is shot from high-pressure sprayers onto crops. Because water is shot high into the air onto crops, some water is lost to evaporation.

storm sewer--a sewer that carries only surface runoff, street wash, and snow melt from the land. In a separate sewer system, storm sewers are completely separate from those that carry domestic and commercial wastewater (sanitary sewers).

stream--a general term for a body of flowing water; natural water course containing water at least part of the year. In hydrology, it is generally applied to the water flowing in a natural channel as distinct from a canal.

streamflow--the water discharge that occurs in a natural channel. A more general term than runoff, streamflow may be applied to discharge whether or not it is affected by diversion or regulation.

subsidence--a dropping of the land surface as a result of ground water being pumped. Cracks and fissures can appear in the land. Subsidence is virtually an irreversible process.

surface tension--the attraction of molecules to each other on a liquid's surface. Thus, a barrier is created between the air and the liquid.

surface water--water that is on the Earth's surface, such as in a stream, river, lake, or reservoir.

suspended sediment--very fine soil particles that remain in suspension in water for a considerable period of time without contact with the bottom. Such material remains in suspension due to the upward components of turbulence and currents and/or by suspension.

suspended-sediment concentration--the ratio of the mass of dry sediment in a water-sediment mixture to the mass of the water-sediment mixture. Typically expressed in milligrams of dry sediment per liter of water-sediment mixture.

suspended-sediment discharge--the quantity of suspended sediment passing a point in a stream over a specified period of time. When expressed in tons per day, it is computed by multiplying water discharge (in cubic feet per second) by the suspended-sediment concentration (in milligrams per liter) and by the factor 0.0027.

suspended solids--solids that are not in true solution and that can be removed by filtration. Such suspended solids usually contribute directly to turbidity. Defined in waste management, these are small particles of solid pollutants that resist separation by conventional methods.

  T tertiary wastewater treatment--selected biological, physical, and chemical separation processes to remove organic and inorganic substances that resist conventional treatment practices; the additional treatment of effluent beyond that of primary and secondary treatment methods to obtain a very high quality of effluent. The complete wastewater treatment process typically involves a three-phase process: (1) First, in the primary wastewater treatment process, which incorporates physical aspects, untreated water is passed through a series of screens to remove solid wastes; (2) Second, in the secondary wastewater treatment process, typically involving biological and chemical processes, screened wastewater is then passed a series of holding and aeration tanks and ponds; and (3) Third, the tertiary wastewater treatment process consists of flocculation basins, clarifiers, filters, and chlorine basins or ozone or ultraviolet radiation processes.

thermal pollution--a reduction in water quality caused by increasing its temperature, often due to disposal of waste heat from industrial or power generation processes. Thermally polluted water can harm the environment because plants and animals can have a hard time adapting to it.

thermoelectric power water use--water used in the process of the generation of thermoelectric power. Power plants that burn coal and oil are examples of thermoelectric-power facilities.

transmissibility (ground water)--the capacity of a rock to transmit water under pressure. The coefficient of transmissibility is the rate of flow of water, at the prevailing water temperature, in gallons per day, through a vertical strip of the aquifer one foot wide, extending the full saturated height of the aquifer under a hydraulic gradient of 100-percent. A hydraulic gradient of 100-percent means a one foot drop in head in one foot of flow distance.

transpiration--process by which water that is absorbed by plants, usually through the roots, is evaporated into the atmosphere from the plant surface, such as leaf pores. 

Tributary--a smaller river or stream that flows into a larger river or stream. Usually, a number of smaller tributaries merge to form a river.

turbidity--the amount of solid particles that are suspended in water and that cause light rays shining through the water to scatter. Thus, turbidity makes the water cloudy or even opaque in extreme cases. Turbidity is measured in nephelometric turbidity units (NTU).

  U unsaturated zone--the zone immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. These zones differ from an aquifer, where the pores are saturated with water.

  W wastewater--water that has been used in homes, industries, and businesses that is not for reuse unless it is treated.

wastewater-treatment return flow--water returned to the environment by wastewater-treatment facilities.

water cycle--the circuit of water movement from the oceans to the atmosphere and to the Earth and return to the atmosphere through various stages or processes such as precipitation, interception, runoff, infiltration, percolation, storage, evaporation, and transportation.

water quality--a term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose.

water table--the top of the water surface in the saturated part of an aquifer.

water use--water that is used for a specific purpose, such as for domestic use, irrigation, or industrial processing. Water use pertains to human's interaction with and influence on the hydrologic cycle, and includes elements, such as water withdrawal from surface- and ground-water sources, water delivery to homes and businesses, consumptive use of water, water released from wastewater-treatment plants, water returned to the environment, and instream uses, such as using water to produce hydroelectric power.

watershed--the land area that drains water to a particular stream, river, or lake. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large watersheds, like the Mississippi River basin contain thousands of smaller watersheds.

watthour (Wh)--an electrical energy unit of measure equal to one watt of power supplied to, or taken from, an electrical circuit steadily for one hour.

well (water)--an artificial excavation put down by any method for the purposes of withdrawing water from the underground aquifers. 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 or oil, or to store or bury fluids below ground.

withdrawal--water removed from a ground- or surface-water source for use.

  X xeriscaping--a method of landscaping that uses plants that are well adapted to the local area and are drought-resistant. Xeriscaping is becoming more popular as a way of saving water at home.

  Y

yield--mass per unit time per unit area

 

Glossary of Terms
 

absorption
The process by which substances in gaseous, liquid, or solid form dissolve or mix with other substances.

adsorption
The attraction and adhesion of ions from an aqueous solution to the surface of solids.

air sparging
The process of injection of air below the water table to strip volatile contaminants from the saturated zone.

air stripping
A remediation process for removing VOCs from groundwater by aeration.

alluvial
Pertaining to, or composed of, alluvium or deposited by a stream or running water.

Alluvium
A general term for clay, silt, sand and gravel, or similar unconsolidated material deposited by a river as a sorted or semi-sorted sediment in the bed of the river or on its floodplain or delta.

analytical model
A mathematical model that provides an exact or approximate solution of a differential equation (and the associated initial and boundary conditions) for subsurface water movement or transport.

anisotropy
The conditions under which one or more of the hydraulic properties of an aquifer vary with direction. (See also isotropy.)

aquiclude
A geologic formation which may contain water (sometimes in appreciable quantities), but is incapable of transmitting significant quantities under ordinary field conditions.

aquifer
A geologic formation, group of formations or part of a formation that contains saturated permeable material that yields sufficient, economical quantities of groundwater.

aquifer system
Two or more permeable units separated at least locally by confining units that impede groundwater movement but do not greatly affect the regional hydraulic continuity of the system.

aquifer test
See pumping test.

aquifuge
An impervious formation which neither contains nor transmits water.

aquitard
A semi-pervious geologic formation which can store water but transmits water at a overflow rate compared to the aquifer.

area of influence
Area surrounding a pumping or recharging wen within which the water table or potentiometric surface has been changed due to the well's pumping or recharge. Also called zone of influence.

artesian aquifer
Commonly used expression, generally synonymous with (but less favored term than)confined aquifer. The term "artesian" takes its name from the basin of Artois in France.

artesian well
A well deriving its water from a confined ("artesian") aquifer.

artificial recharge
The process by which water can be injected or added to an aquifer. Dug basins, wells, or the spread of water across the land surface are all means of artificial recharge.

attenuation
The process of diminishing contaminant concentrations in groundwater, due to filtration,biodegradation, dilution, sorption, volatilization, and other processes.

backreamer
A tool attached to the end of the drill string and pulled through the bore to enlarge the hole and mix the cuttings with the drilling fluid.

bailer
A device used to withdraw a water sample from a small-diameter well or piezometer. It is typically a piece of pipe having a check valve in the bottom.

bail-down test
A type of slug test performed by using a bailer to remove a volume of water-from a small-diameter well.

baseflow
That part of a stream discharge not attributable to direct runoff from precipitation or snowmelt, usually sustained by groundwater discharging into the stream.

bedrock
A general term for the rock formation, usually solid, that underlies soil or other unconsolidated materials.

bentonite
An absorbent aluminum silicate clay formed from volcanic ash. When thoroughly mixed with water, bentonite breaks down into small particles called platelets. The platelets plaster or shingle off the wall of the hole and form a filter cake that cuts off the flow of water into the surrounding sand or gravel.

bioaugmentation
Similar to bioremediation, but involving the introduction of organisms to affect cleanup.

biodegradation
A subset of biotransforination, it is the biologically mediated conversion of a compound to more simple products.

bioremediation
A cleanup method involving the stimulation of naturally occurring organic substances in the soil.

bioventing
A process by which air is injected into the subsurface to stimulate biodegradation by microbes.
bore

1. A hole made in the ground by drilling or pushing.

2. The act of making a hole in the ground by drilling or pushing.

BORE-GEL
A single-sack boring fluid system, which consists of bentonite, polymer, and soda ash,specially formulated by Baroid Drilling Fluids, Inc., for use in trenchless technology construction applications. Processed from premium grade Wyoming sodium bentonite with an extra high yield, enhanced to provide superior hole stabilizing properties and cuttings support with improved lubrication and torque reduction.

box
The female thread portion of a drill pipe.

bubbling pressure
The pressure at which air enters saturated zone (or air entry value or threshold pressure).

build-up
The potentiometric surface (or the water table) rise in the vicinity of a' recharge wen. It is the vertical distance between the initial and the new potentiometric surface (or the water table in the case of an unconfined aquifer) at a given point.

bulk density
The mass of a soil per unit bulk volume of soil; the mass is measured after all water has been extracted and the volume includes the volume of the soil itself and the pore volume.

cable sonde
A probe or transmitter that operates with a wire attached to the drill rack for locating purposes.

calibration of models
Refinement of estimates of the input parameters and boundary conditions of a model until model results match the field-observed data. Also known as "history matching."

caliche
A geological formation often found in the Southwestern United States that can be as hard as rock but more closely resembles very dry layered clay which becomes sticky when wet.

capillary form
Interfacial forces between immiscible fluid phases, resulting in pressure differences between the two phases.

capillary fringe
The zone immediately above the water table within which the water is drawn by capillary forces (fluid is under tension). The capillary fringe is saturated, and it is considered to be part of the unsaturated zone.

carbonate
A sediment formed by the organic or inorganic precipitation from aqueous solution of carbonates of calcium, magnesium, or iron.

carbonate rock
A rock consisting chiefly of carbonate minerals, such as limestone and dolomite.

Chinese Finger
A woven wire device used to pull product back through the bore. It is slipped over the outside diameter of the product and attached to the drill string. The harder it is pulled, the tighter it gets.

clastic
Pertaining to a rock or sediment composed principally of broken fragments that are derived from pre-existing rocks or minerals and that have been transported some, distance from their places of origin.

coarse
The term used to denote sand and gravel. The use of bentonite in the drilling fluid is recommended when boring in this type of soil conditions.

compactor
A reamer that enlarges the hole by compressing the soil as it is pulled through the bore.

concentration gradient
The change in concentration with distance across a fluid medium.

CON-DETO
A clear arnber liquid blend of water soluble anionic surfactant manufactured by Baroid Drilling Fluids, Inc. It can be used in conjunction with Quik-Gelo® to aid in reducing the tendency of the hole-boring tools being stuck by adhesive.

cone of depression
A depression in the groundwater table (or potentiometric surface) that has the shape of an inverted cone and develops around a discharge well.

confined aquifer
An aquifer bounded above and below by confining layers of distinctly lower permeability than the aquifer material and the one containing confined groundwater. When a well is installed in a confined aquifer, the water level in the well rises above the top of the aquifer.

confining unit
A hydro geologic unit of relatively low hydraulic conductivity, bounding one or more aquifers. (See also aquitard, aquifuge, and aquiclude.)

conservation solute
A non-reactive constituent that does not undergo chemical reaction during substance migration.

contaminant
Toxic substances found in soils and groundwater.

contamination
The degradation of natural water quality as a result of man's activities. There is no implication of any specific limits, since the degree of permissible contamination depends upon the intended end use of the water.

cosolvency
The interaction of one or more organic contaminants that may cause them to behave differently than if they were present alone in their pure form.

cuttings
Soil particles, also known as drilling spoils, created during the boring process..Use of the proper drilling fluid will help to suspend the cuttings which reduces the risk of getting stuck while boring and backreaming.

Darcy's law
An empirically derived equation for the flow of fluids through porous media. It is based on the assumptions that flow is laminar and inertia can be neglected, and states that the specific discharge, q, is directly proportional to the hydraulic conductivity, K, and the hydraulic gradient, J.

darcy, unit
A unit of intrinsic permeability, k (I darcy = 9.87 x 10-9 cm2). The relationship between hydraulic conductivity, K, and the permeability, k, is given as K = kpg/u where p is the fluid density, g is the gravitational constant, and u is the dynamic viscosity.

deflection
The amount of flex applied to the drill stem while steering the head.

density
The mass of a substance per unit volume [ML-3] Units are pounds per cubic foot (Ib/ft3),kilograms per cubic meter (kg/m3), or grams per cubic centimeter (g/cm3).

depth
Refers to the depth of the drill head during a bore.

desorption
See adsorption, which is the reverse process.

diffusion coefficient
See molecular diffusion.

discharge area
An area in which groundwater is discharged to the land surface, surface water, or atmosphere. An area in which there are upward components of hydraulic head in the aquifer. Groundwater is flowing toward the surface in a discharge area and may escape as a spring, seep, or base flow, or by evaporation and transpiration.

dispersion
The spreading and mixing of chemical constituents in groundwater caused by diffusion and mixing (due to microscopic variations in velocities within and between pores).

dispersion coefficient
A measure of the spreading of a flowing substance due to the nature of the porous medium(and specific substance or fluid properties), with interconnected channels distributed at random in all directions. Also the sum of the coefficients of mechanical dispersion and molecular diffusion in porous medium.

dispersivity
A property of a porous medium (and the specific substance of fluid) that determines the dispersion characteristics of the contaminant in that medium by relating the components of pore velocity to the dispersion coefficient.

distribution (partitioning) coefficient
Relates the quantity of a solute sorbed per unit weight of the solid phase and the quantity of the solute dissolved in water per unit volume of water.

DNAPL
Dense Non Aqueous Phase Liquid. A liquid consisting of a solution of organic compounds (e.g., chlorinated hydrocarbons) and which is denser than water.

drainage basin
The land area from which surface runoff drains into a stream.
drawdown
A lowering of the water table of an unconfined aquifer or the potentiometric surface of a confined aquifer caused by pumping of groundwater from wells. The vertical distance between the original water level and the new water level.

dry hole
If not enough drilling fluid is used, a dry hole occurs and the product becomes lodged in the ground.

duckbill
The drilling bit that attaches to the front of the boring head. It mounts to the head at an angle and also is bent. This angle is what provides the steering capability while pushing the drill pipe.

effective grain size
The grain size corresponding to the 10% finer by weight on the grain-size distribution curve.

effective porosity
The interconnected pore space through which fluids can pass, expressed as a percent of bulk volume. Part of the total porosity will be occupied by static fluid being held to mineral surface by surface tension, so effective porosity will be less than total porosity.

effluent stream
See gaining stream.

entrance pit
The area where the drill pipe enters the ground after the drill machine is set up.

entry angle
The angle at which the drill head enters the ground or the degree that the rack is set at.

EPA
The Environmental Protection Agency. The federal authority responsible for enforcing the various laws dealing with environmental standards.

equipotential line
A line in a two-dimensional groundwater flow field along which the total hydraulic head(the groundwater potential) is constant.

evapotranspiration, actual
The evaporation that actually occurred under given climatic and soil-moisture conditions.

evapotranspiration, potential
The evaporation that would occur under given conditions if there were unlimited soil moisture.

exit pit
The area where the drill pipe exits the ground and the service lines are pulled back in.

extraction well
A discharge well used to remove groundwater or air.

EZ-MUD®
A premium grade, high molecular weight PUPA polymer manufactured by Baroid Company. When this is added to bentonite in the drilling fluid, it provides extended high viscosity and gel strength. It also lowers the filtration rate and increases lubrication. It is an excellent shale/clay stabilizer which minimizes swelling.

Fick's Law
The mass flux due to the molecular diffusion is proportional to the concentration gradient and the diffusion coefficient.

field capacity
The amount of moisture remaining in the soil after an extended period of gravity drainage without additional supply of water at the soil surface.

filter cake
The zone where the bentonite platelets plaster or shingle off the wall of the hole.

filtrate
The water portion of the drilling fluid that seeps through the filter cake.

fines
Term used to denote clay and shale soils. The use of polymer is recommended in these soil conditions to reduce swelling while at the same time improving lubrication and torque reduction.

flow
When the drilling fluid moves or runs smoothly with unbroken continuity through the entire length of the bore.

flowline or pathline
The general path that a particle of water follows under laminar flow conditions., Flow lines are perpendicular to equipotential lines in an isotropic aquifer.

flow model
A digital computer model that calculates a hydraulic head field for the modeling domain using numerical methods to arrive at an approximate solution to the differential equation of groundwater flow.

flow, steady
A characteristic of a flow system, where the magnitude and direction of specific discharge are constant in time at any point. If the specific discharge has the same magnitude and direction at any point, the flow is uniform.

flow, unsteady (transient)
A characteristic of a flow system where the magnitude and/or direction of the specific discharge changes with time.

forged upset
The area at each end of a FIRESTICK drill stem where it tapers to a larger diameter. This larger diameter is achieved by heating the ends of the rod to temperatures in excess of 2000º F and striking it with tremendous force in a die set. To achieve this, the metal has to start out 3' longer than the desired finished length of the drill stem.

frac out
In certain conditions, the drilling fluid can build tremendous pressure in the bore. If the pressure becomes great enough, the ground will fracture to the surface. The drilling fluid escapes the bore through this rupture, and the pressure is relieved.

fracture
A general term for any break in a rock, which includes cracks, joints and faults.

fracture trace
Visible on aerial photographs, fracture traces are natural linear-drainage, soil-tonal, and topographic alignments that are probably the surface manifestation of underlying zones of fractures.

front locate point
The point in front of the drill head where the DIGITRAKTM locator goes from + to -. This point is also referred to as the front negative locate point.

gaining stream
A stream or reach of a stream, the flow of which is being increased by inflow of groundwater. Also known as an effluent stream.

gel strength
The ability of the drilling fluid to support and suspend the cuttings. The use of bentonite in the drilling fluid greatly increases these characteristics.

geostatistics
A methodology for the analysis of spatially correlated data. The characteristic feature is in the use of variograms or related techniques to quantify and model the spatial correlation structure. Also includes various techniques such as kriging, which utilize spatial correlation models.

ghost
False signals received by the locator.

glacial drift
A general term for unconsolidated sediment transported by glaciers and deposited directly on land or in the sea.

glacial outwash
Well-sorted sand, or sand and gravel, deposited by the meltdown from a glacier.

glacial till
A glacial deposit composed of mostly unsorted sand, silt, clay, and boulders and laid down directly by the melting ice.

gravitational head
Component of total hydraulic head related to the vertical position of a given mass of water relative to an arbitrary datum.

gravitational water
Water that moves into, through, or out of a soil or rock mass under the influence of gravity.

ground stake
A long copper rod with a T handle and auger bit that is screwed into the ground and attached to the boring machine to provide an additional path for electricity to flow in the event of an electrical strike.

groundwater
The water contained in interconnected pores below the water table in an unconfined aquifer or in a confined aquifer.

groundwater barrier
Rock or artificial material with a relatively low permeability that occurs (or is placed) below ground surface, where it impedes the movement of groundwater and thus causes a pronounced difference in the heads on opposite sides of the barrier.

groundwater basin
General term used to define a groundwater flow system that has defined boundaries and may include more than one aquifer underlain by permeable materials that are capable of storing or furnishing a significant water supply. The basin includes both the surface area and the permeable materials beneath it.

groundwater divide
Ridge in the water table, or potentiometric surface, from which groundwater moves away at right angles in both directions. Line of highest hydraulic head in the water table or potentiometric surface.

groundwater flow
The movement of water through openings in sediment and rock that occurs in the zone of saturation.

groundwater model
A simplified conceptual or mathematical image of a groundwater system, describing the feature essential to the purpose for which the model was developed and including various assumptions pertinent to the system. Mathematical groundwater models can include numerical and analytical models.

groundwater mound
Raised area in a water table or other potentiometric surface, created by groundwater recharge.

groundwater recharge
Process of water addition to the saturated zone, or the volume of water added by this process.

HAZMAT
A term used in the environmental industry to identify materials classified as hazardous by the EPA.

heat-treat
To treat metal by alternate heating and cooling in order to produce desired characteristics,such as increased hardness; temper.

Henry's Law
The relationship between the partial pressure of a compound and its equilibrium concentration in a dilute aqueous solution through a constant of proportionality known as the Henry's Law Constant.

heterogeneity
Characteristic of a medium in which material properties vary from point to point.

homogeneity
Characteristic of a medium in which material properties are identical throughout. Though heterogeneity or nonunifonnity is the characteristic of most aquifers, assumed homogeneity, with some other additional assumptions, allows use of analytical models as a valuable tool for approximate analyses of groundwater movement.

hydra-lock
A situation that has been known to occur while pulling product through the bore. In this condition, the bore acts as a huge hydraulic cylinder with the product string acting as a large hydraulic ram. The drilling fluid stops flowing in the bore and pressure begins to build. The pressure continues to build to the point where the boring machine can no longer pull the product string and you have a stuck situation. Increased pullback pressure with decreased rotational pressure is an indication that hydra-lock is occurring. This most often occurs in very tight soil conditions such as dry clay and can sometimes be cured by digging a burp hole to relieve the pressure or by letting everything set for a period of time while the pressure seeps past the product string.

hydraulic barrier
Modifications to a groundwater flow system that restrict or impede movement of contaminants.

hydraulic conductivity (K)
Proportionality constant relating hydraulic gradient to specific discharge, which, for an isotropic medium and homogeneous fluid, equals the volume of water at the existing kinematic viscosity that will move in unit time under a unit hydraulic gradient through a unit area measured at right angles to the direction flow. The rate of flow of water in gallons per day through a cross section of one square foot under a unit hydraulic gradient, at the prevailing temperature (gpd/ft2). In the standard International System, the units are m3/day/m2 or m/day. A coefficient of proportionality describing the rate at which water can move through a permeable medium. The density and kinematic viscosity of the water must be considered in determining hydraulic conductivity.

hydraulic conductivity, effective
Rate of water flow through a porous medium that contains more than one fluid (such as water and air in the unsaturated zone), which should be specified in terms of the fluid type,content and the existing pressure.

hydraulic gradient (J)
Slope of a water table or potentiometric surface. More specifically, change in the hydraulic head per unit of distance in the direction of the maximum rate of decrease. The difference in hydraulic heads (hl-h2), divided by the distance
(L) along the flowpath: J= (hl-h2)/L.

hydraulic head (h)
Height above a datum plane (such as mean sea level) of the column of water that can be supported by the hydraulic pressure at a given point in a groundwater system. Equal to the distance between the water level in a well and the datum plane.

hydrodynamic dispersion
Spreading (at the macroscopic level) of the solute front during transport resulting from both mechanical dispersion and molecular diffusion. The process by which groundwater containing a solute is diluted with uncontaminated groundwater as it moves through an aquifer (see dispersion coefficient).

hydrogeologic
Those factors that deal with subsurface waters and related geologic aspects of surface waters.

hydrogeologic parameters
Numerical parameters that describe the hydro geologic characteristics of an aquifer such as porosity, permeability, and transmissivity.

hydrogeologic pressure
Pressure exerted by the weight of water at any given point in a body of water at rest.

hydrogeologic unit
Any soil or rock unit or zone that has a distinct influence on the storage or movement of groundwater because of its hydraulic properties.

immiscible
The chemical property where two or more liquids or phases do not readily dissolve in one another, such as soil and water.

impermeability
Characteristic of geologic materials that limits their ability to transmit significant quantities of water under the pressure gradients normally found in the subsurface environment.

impermeable layer
An area in the subsurface that has zero air flow. Limits the range of influence of extraction wells in SVE systems.

infiltration
The downward entry of water into soil or rock.

infiltration rate
Rate at which soil or rock under specified conditions absorbs falling rain, melting snow, or surface water; expressed in depth of water per unit time. Also, the maximum rate at which water can enter soil or rock under specific conditions, including the presence of an excess of water; expressed in units of velocity.

influent stream
See losing stream.

insitu
Latin term for "in the site," used in environmental industry to describe the treatment of contaminants without removal from their immediate location.

intrinsic permeability
Pertaining to the relative ease with which a porous medium can transmit a liquid under a hydraulic or potential gradient. It is a property of the porous medium and is independent of the nature of the liquid or the potential field.

isochron
A line connecting all points having the same time of travel for contaminant particles to move through the saturated zone and reach a well.

isotropy
The condition in which the properties of interest (generally hydraulic properties of the aquifer) are the same in all directions.

joint
Where the male and female threads of the drill stem come together.

kinematic viscosity
The ratio of dynamic viscosity to mass density. It is obtained by dividing dynamic viscosity by the fluid density. Units of kinematic viscosity are square meters per second (M2/S).

klinkenberg effect
Gas slippage along pore walls. Darcy's Law assumes that the velocity of a fluid at the pore wall surface is zero.

kriging
A weight-moving-average interpolation method where the set of weights assigned to samples minimizes the estimation variance, which is computed as a function of the variogram model and locations of the samples relative to each other, and to the point or block being estimated.

laminar flow
Fluid flow in which the head loss is proportional to the first power of the velocity;synonymous with streamline flow and viscous flow. Type of flow in which the fluid particles follow paths that are smooth, straight, and parallel to the channel wars. In laminar flow, the viscosity of the fluid dampens out turbulent motion.

leaching
Removal of materials in solution from rock, soil, or waste; dissolving out of soluble constituents from a porous medium by percolation of water.

leakage
Flow of water from one hydrogeologic unit to another. This may be natural, as through a somewhat permeable confining layer, or anthropogenic, as through an uncased well. It may also be the natural loss of water from artificial structures, as a result of hydrostatic pressure.

leakage coefficient
The rate of flow across a unit (horizontal) area of a semi-pervious layer into (or out of) an aquifer under one unit of head difference across this layer.

leaky aquifer
An artesian or water table aquifer that loses or gains water through adjacent semipermeable confining units.

LNAPL
Lighter-than-water non aqueous phase liquid.

locator
The unit which picks up the signal from the drill head where the transmitter is housed.

losing stream
A stream or reach of a stream that is losing water by seepage into the ground. Also known as an influent stream.

lubricity
Slick or slippery as in lubricate. Polymer in the drilling fluid will increase "lubricity" in the bore.

macropores
Relatively large pores in porous medium that allow the enhanced movement of liquid and gas.

make-up
The fitting together of the pin and box sections of the drill stem.

mats
Stainless steel wire mesh that is part of the strike alert and grounding system. The function of the mats is to equalize the voltage around the machine in the event of an electrical strike.

matrix
Solid framework of a porous material or system.

mechanical dispersion
Process whereby solutes are mechanically mixed during advective transport, caused by the velocity variations at the microscopic level; synonymous with hydraulic dispersion. The coefficient of mechanical dispersion is the component of mass transport flux of solutes caused by velocity variations at the microscopic level.

moisture content
See water content.

molecular diffusion
Process in which solutes are transported at the microscopic level due to variations in the solute concentrations within the fluid phases.

monitoring well
A tube or pipe, open to the atmosphere at the top and to water at the bottom, usually along an interval of slotted screen, used for taking groundwater samples.

mud
Drilling fluid.

NAPL
Non aqueous phase liquids.

negative locate
One of two points where a Digitrak locator reading goes from + to -.

nonpoint source
A source discharging pollutants into the environment that is not a single point.

nozzle
Located on the drill head to spray drilling fluid into the bore.

observation well
A well drilled in a selected location for the purpose of observing parameters such as waterl evels and pressure changes. A non-pumping well used to observe the elevation of the water table or the potentiometric surface. An observation well is generally of larger diameter than a piezometer and typically is screened or slotted throughout the thickness of the aquifer.

organic carbon content
The amount of the organic carbon present in a soil. Organic chemicals in soil adsorb to soil organic carbon and the amount of adsorption can be related to the soil organic carbon content.

partial penetration
When the intake portion of the well is less than the full thickness of the aquifer. A well constructed in such a way that it draws water directly from a fractional part of the total thickness of the aquifer. The fractional part may be located at the top, the bottom, or anywhere else in the aquifer.

partitioning
Chemical equilibrium condition where a chemical's concentration is apportioned between two different phases according to the partition coefficient, which is the ratio of a chemical's concentration in one phase to its concentration in the other phase.

peclet number
Relationship between the advective and diffusive components of solute transport;
expressed as the ratio of the product of the average interstitial velocity and the characteristic length, divided by the coefficient of molecular diffusion. Small values indicate diffusion dominates; large values indicate advection dominates.

perched aquifer
A special case of phreatic aquifer which occurs wherever an impervious (or semi-pervious)layer of limited aerial extent is located between the water table of a phreatic aquifer and the ground surface.

perched water
Unconfined groundwater separated from an underlying main body of groundwater by an unsaturated zone.

percolation
Downward movement of water through the unsaturated zone; also defined as the downward flow of water in saturated or nearly saturated porous media at hydraulic gradients of 1.0 or less. The act of water seeping or filtering through the soil without a definite channel.

permeability coefficient
Rate of flow of water through a unit cross-sectional area under a unit hydraulic gradient at the prevailing temperature (field permeability coefficient), or adjusted to 15 degrees C.

permeability, effective
Observed permeability of a porous medium to one fluid phase, under conditions of physical interaction between the phase and other fluid phases present.

permeability, intrinsic
Relative ease with which a porous medium can transmit a fluid under a potential gradient,as a property of the medium itself. Property of a medium expressing the relative ease with which fluids can pass through it.

phreatic aquifer
See water table aquifer.

piezometer
A tube or pipe, open to the atmosphere at the top and to water at the bottom, and sealed along its length, used to measure the hydraulic head in a geologic unit.

piezometer surface
See potentiometric surface.

pin
The male threads on the drill stem.

pitch
Measurement for the deviation from horizontal of the drill head.

platelet
A minute, disklike cytoplasmic body found in bentonite that plasters or shingles off the wall of the hole to form a filter cake that cuts off the flow of water into the surrounding sand or gravel. When broken down to its smallest dimension, there are enough platelets in a cubic inch of high-quality sodium bentonite to cover 66 football fields.

point source
Any discernible, confined, or discrete conveyance from which pollutants are or may be discharged, including (but not limited to) pipes, ditches, channels, tunnels, conduits,,wells,containers, rolling stock, concentrated animal feeding operations, or vessels.

pollutant
Any solute or cause of change in physical properties that renders water unfit for a
given use.

pollution
When the contaminant concentration levels restrict the potential use of groundwater.

polymer
Any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule. Polymer, when used in conjunction with bentonite in the drilling fluid, enhances viscosity and gel strength, lowers filtration rate, and increases lubricity. The use of a polymer is recommended when boring in clay or shale.

pore space
Total space in an aquifer medium not occupied by solid soil or rock particles.

porosity
Ratio of the total volume of voids to the total volume of a porous medium. The percentage of the bulk volume of a rock or soil that is occupied by interstices, whether isolated or connected. Porosity may be primary, formed during deposition or cementation of the material, or secondary formed after deposition or cementation, such as fractures.

positive locate
When locating with a Digitrak&, this is the point directly above the drill head where the locator readout changes from + to -.

potable water
Suitable for human consumption as drinking water.

potentiometric surface
A surface that represents the level to which water will rise in wells penetrating a confined aquifer. If the head varies significantly with depth in the aquifer, then there may be more than one potentiometric surface. The water table is a particular potentiometric surface for an unconfined aquifer.

pothole
A hole dug to expose underground utilities crossing the proposed bore path.

pressure aquifer
Also known as confined aquifer. (See confined aquifer.)

pressure head
Hydrostatic pressure expressed as the height (above a measurement point) of a column of water that the pressure can support.

pressure, static
Pressure exerted by a fluid at rest.

probe
An electronic device that fits inside the drill head and sends out a signal used to locate the head, read pitch and roll, and determine depth.

PRPs
Potential responsible parties. Waste generators who are responsible for the ultimate fate of toxic wastes. Includes property owners, industries, government agencies, etc. The current federal laws make the PRPs liable in perpetuity for these wastes.

pH
The specific gravity of water.

public water supply system
System for provision to the public of piped water for human consumption. Such a system has at least 15 service connections or regularly serves at least 25 individuals daily or at least60 days out of the year. The ten-n includes any collection, treatment, storage, and distribution facilities under control of the operator of such system and used primarily in connection with the system, and any collection or pretreatment storage facilities not under such control that are used primarily in connection with the system.

pumping test
A test that is conducted to determine aquifer or well characteristics. A test made by pumping a well for a period of time and observing the change in hydraulic head in the aquifer. A pumping test may be used to determine the capacity of the well and the hydraulic characteristics of the aquifer. Also called aquifer test.

PVC
Plastic pipe that can be used as well casing material.

quench
A step in the heat treating process to cool hot metal which causes it to harden. The most common quench mediums are brine, water, oil, and air. The greatest hardness and strength for most materials are obtained by brine or water quenching. However, this also produces the most distortion and cracking. Oil or air quenching will produce less distortion and cracking but also less strength and hardness.

QUIK-GEL®
Highest-grade sodium bentonite manufactured by Baroid Drilling Fluids, Inc. This drilling fluid mix develops a cost-effective low solids slurry with high viscosity, high gel strength,and controlled filtration rate to provide formation and hole stabilization.

QUIK-TROL®
A white granular pure grade polymer manufactured by Baroid Drilling Fluids, Inc. When added to a premixed bentonite slurry, it improves clay/shale stabilization and enhances all properties of a bentonite slurry used in boring.

rack
The actual boring machine which includes drive head, controls, vise, etc.

radial flow
The flow of water in an aquifer toward a vertical well.

radius of influence
The radial distance from the center of a wellbore to the point where there is no lowering of the water table or potentiometric surface (the edge of its cone of depression). The radial distance from an extraction well that has adequate air flow for effective removal of contaminants when a vacuum is applied to the extraction well.

range of influence
The area that can be remediated by an extraction well in an SVE system.

Raoult's Law
A physical law which describes the relationship between the vapor pressure of a component over a solution, the vapor pressure of the same component over pure liquid,and the mole fraction of the component in the solution.

reamer
Any of various tools attached to the end of the drill string and pulled through the bore to enlarge the hole and mix the cuttings with the drilling fluid.

rear locate point
The point behind the drill head where the readout on a Digitrak locator switches from + to -. This is also called the rear negative locate point.

receiver
an electronic unit that receives information from the transmitter. This is also referred to as the locator.

recharge
The addition of water to the zone of saturation; also, the amount of water added. Can be expressed as a rate (i.e., in/yr) or a volume.

recharge area
An area in which there are downward components of hydraulic head in the aquifer. Infiltration moves downward into the deeper parts of an aquifer in a recharge area.

recharge basin
A basin or pit excavated to provide a means of allowing water to soak into the ground at rates exceeding those that would occur naturally.

recharge boundary
An aquifer system boundary that adds water to the aquifer. Streams and lakes are typical recharge boundaries.

remedial construction
T'he business of implementing the methods for cleanup. Includes firms that specialize in underground storage tank removal and soil vacuum extraction.

remediation
The methods of cleanup used for contaminated soils and groundwaters.

remote
An auxiliary electronic readout that displays information received from the receiver.

residual saturation
Saturation below which fluid drainage will not occur.

retardation
The movement of a solute through a geologic medium at a velocity less than that of the flowing groundwater due to sorption or other removal of the solute.

Reynolds number
Dimensionless number expressing the ratio of inertial to viscous forces acting on the fluid,Re = pVd/u. The number can be used to determine whether the flow is laminar or turbulent.

rockwell
The most commonly used method for determining the hardness of a metal.

rod
A section of drill stem.

rod wiper
A donut-shaped neoprene disk that fits around the drill stem to help clean it during the pullback.

roll
The rotational position of the drill head as it relates to a clock face.

RPM
The speed of the drill stem turning in the ground. It also relates to how fast the reamer turns.

runoff
That part of precipitation flowing to surface streams. The total amount of water flowing in a stream. It includes overland flow, return flow, interflow, and baseflow.

safe yield
The amount of naturally occurring groundwater that can be withdrawn from an aquifer on a sustained basis without impairing the native groundwater quality or lowering water levels.

saturation
The ratio of the volume of a single fluid in the pores to pore volume expressed as a percentage or a fraction.

saturated zone
Portion of the subsurface environment in which all voids are ideally filled with water under pressure greater than atmospheric. The zone in which the voids in the rock or soil are filled with water at a pressure greater than atmospheric. The water table is the top of the saturated zone in an unconfined aquifer.

seepage face
Whenever a phreatic surface approaches the downstream external boundary of a flow domain, it always terminates on it at a point that is above the water table of the body of open water present outside the flow domain. The segment of the boundary above the water table and below the phreatic surface is called the seepage face.

semiconfined
An aquifer that has a "leaky" confining unit and displays characteristics of both confined and unconfined aquifers. (See leaky aquifer.)

sewer probe
This transmitter is designed to bore sewer pipe by allowing the bore to be on grade. The probe works on a 0. I% readout.

site characterization
T'he process of determining the geology, hydrology, type of contaminants and area of contamination. Done by engineering and consulting firms.

skin effect
The damage to the permeability in the proximity of a well due to drilling fluids.

slug test
A test for estimating hydraulic conductivity of an aquifer in which a rapid water-level change is produced in a piezometer or monitoring wen, usually by introducing or withdrawing a "slug" of water or a weight. The rise or decline in the water level is monitored.

slurry wall
A subsurface wall constructed by digging a trench and backfilling it with a slurry and designed to prevent groundwater flow.

soda ash
Sodium carbonate in powdery white form used to increase the PH level of hard water. This makes the mixing of bentonite and polymers into the drill fluid much easier.

soil venting, soil vapor extraction, soil vacuum extraction, "SVE"
All describe the process of using extraction wells as a means to deliver a vacuum in the subsurface, thereby pulling toxic vapors to the surface to be treated by an incineration,catalytic or absorptive process.

solute transport
Net flux of solute through a hydrogeologic unit, controlled by the flow of subsurface -water and transport mechanisms.

solute transport model
Mathematical model used to predict the movement of solutes (generally contaminants) in an aquifer through time.

sonde
An electronic device that fits inside the drill head and transmits a signal used for locating purposes. Also referred to as a transmitter or probe.

sorption
Processes that remove solutes from the fluid phase and concentrate them on the solid phase of a medium; used to encompass absorption and adsorption.

sparging
A method of forcing VOCs from the saturated zone into the vadose zone by pushing air into the groundwater.

specific capacity
The rate of discharge of water from the well divided by the drawdown within the well.

specific discharge
The volume of water flowing through a unit cross-sectional area of an aquifer.

specific drawdown
The drawdown within a well divided by the discharge rate of water from the well (inverse of specific capacity).

specific gravity
The ratio of a substance's density to the density of some standard substance, usually water.

specific retention
As water is being drained from the interstices of soil, after drainage has stopped, the volume of water retained in an aquifer per unit area and unit drop of the water table.

specific storage
The amount of water released from or taken into storage per unit volume of a porous medium per unit change in head.

specific surface
The amount of surface area of a dispersed system per gram or per unit volume of the dispersed phase.

specific yield
The volume of water that a saturated rock or soil win yield by gravity (often used as a synonym for effective porosity or storage coefficient of unconfined aquifers).

spiral reamer
A specially designed back reamer that resembles a huge wood screw. This long tapered spiral design is well suited for pushing hard obstacles out of the way.

spring
Discrete place where groundwater flows naturally from rock or soil onto the land surface or into a surface water body.

stagnation point
A point in a groundwater flow field at which the groundwater is not moving. The magnitude of vectors of hydraulic head at the point are equal but opposite in direction.

static water level
The level of water in a well that is not being affected by withdrawal of groundwater.

stem
A section of drill pipe.

step potential
Describes the electrical voltage differential between two points.

strike alert
A warning system on all NAVIGATORs that is set off by contact with an electrical power source.

storage coefficient
The amount of water released from or taken into storage per porous medium column with a unit surface area per unit change in head. (See also storativity.)

storativity
A dimensionless term representing the volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head. It is equal to the product of specific storage and aquifer thickness. In an unconfined aquifer, the storativity is equivalent to the specific yield.

Superfund
The commonly used name for a federal law called "CERCLA." This act designated a portion of funds to be put away by generators of certain wastes for the research and implementation of remediation processes.

superposition
Principle used for linear problems, such as confined groundwater flow, that allows equation solutions to be added to form new solutions. For example, if within a well field,pumping rates of the pumped wells are known, the composite drawdown at a point can be determined by summing the drawdown caused by each individual pumped well.

surfactant
A soap based substance which acts as a wetting agent to reduce the tendency of clay cutting to stick together. It also reduces the tendency of boring tools becoming stuck by adhesion.

swivel
Attaches between the back reamer and the product being pulled back to keep the product from twisting.

tempered
Metal that is reheated after quenching for the purpose of making it more stress-free, crack-free, distortion-free and slightly softening it.

tensiometer
The instrument used for measuring the capillary pressure in an unsaturated zone.

thread compound
Used to lubricate the thread and shoulder area of the drill joint. Suitable thread compound should have a zinc base of 40-60% by weight to withstand the pressures and torque that is applied to the drill stem joints. Sometimes mistakenly referred to as grease.

thrust
This occurs when you push the drill stem into the ground without rotating.

time of travel (TOT)
The time required for a contaminant to move in the saturated zone from a specific point to well.

torque
The rotational force applied to the drill stem joints.

transmissivity
Rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of the aquifer under a unit hydraulic gradient. It is equal to an integration of the hydraulic conductivities across the saturated part of the aquifer perpendicular to the flow paths. The rate at which water is transmitted through a unit width of an aquifer under a unit hydraulic gradient. Transmissivity values are given in gallons per minute through a vertical section of an aquifer one foot wide and extending the full saturated height of an aquifer under a hydraulic gradient of one in the English Engineering System; in the Standard International System, transmissivity is given in cubic meters per day through a vertical section of an aquifer one meter wide and extending the full saturated height of an aquifer under a hydraulic gradient of one. It Is a function of properties of the liquid, the porous media, and the thickness of the porous media.

transmitter
An electronic device that fits inside the drill head and transmits a signal used for locating purposes. Also referred to as a sonde or probe.

turbulent flow
Water flow in which the flow lines are confused and heterogeneously mixed. It is typical of flow in surface water bodies (2). That type of flow in which the fluid particles move ' along very irregular paths. Momentum can be exchanged between one portion of the fluid and another. Compare with laminar flow.

unconfined
Conditions in which the upper surface of the zone of saturation forms a water table under atmospheric pressure.

unconfined aquifer
See water table aquifer.

unconsolidated aquifer
An aquifer made up of loose material, such as sand or gravel, that has not undergone lithification.

unsaturated flow
Movement of water in porous medium in which the pore spaces are not completely filled with water.

unsaturated zone
The zone between the land surface and the water table. It includes the root zone,intermediate zone, and capillary fringe. The pore spaces contain water, as well as air and other gases at less than atmospheric pressure. Saturated bodies, such as perched groundwater, may exist in the unsaturated zone, and water pressure within these may be greater than atmospheric. Replaces the older terms "zone of aeration" and "vadose zone."

USTs
Underground storage tanks used for the storage of fuels and other liquids. Most have leaked contaminants into the ground around them. A program to remove all old USTs is in place by the EPA and is scheduled to be completed by 1998.

vadose zone
The area immediately beneath the surface of the earth. Usually made up of soils, small rocks, gravels, clays, etc. Above saturated zone.

validation
The process of determining the degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model.

velocity, average interstitial
Average rate of groundwater flow in interstices expressed as the product of hydraulic conductivity and hydraulic gradient (specific discharge) divided by the effective porosity. It is synonymous with average linear groundwater velocity or effective velocity.

verification
The examination of the numerical technique in the computer code to ascertain that it truly represents the conceptual model and that there are no inherent problems with obtaining a solution.

viscosity
The internal friction within a fluid that causes it to resist flow.

voc
Volatile organic compounds, typically with a high vapor pressure and a tendency to evaporate rapidly.

volatilization
The transfer of a chemical from liquid to the gas phase. Solubility, molecular weight, and vapor pressure of the liquid, and the nature of the air-liquid interface, affect the rate of volatilization.

water budget
An evaluation of all the sources of supply and corresponding discharges with respect to an aquifer or drainage basin.

water table
Upper surface of a zone of saturation, where that surface is not formed by a confining unit;water pressure in the porous medium is equal to atmospheric pressure. The surface between the vadose zone and the groundwater; that surface of a body of unconfined groundwater at which the pressure is equal to that of the atmosphere.

water table aquifer
An aquifer in which the water table forms the upper boundary.

well field
An area containing two or more wells supplying a public water supply system.

well, fully penetrating
A well drilled to the bottom of an aquifer, constructed in such a way that it withdraws water from the entire thickness of the aquifer.

well interference
The condition occurring when the area of influence of a water well (the cone of depression)overlaps that of a neighboring well or wells, as when the wells are pumping from the same aquifer.

well screen
A filtering device used to permit the flow of liquid or air but prevents the passage of sediments or backfill particles.

well yield
The volume of water discharged from a well per unit time.

wellhead
The physical structure, facility, or devise at the land surface from or through which groundwater flows or is pumped from subsurface, water-bearing formations.

wellhead protection area (VHPA)
The surface and subsurface area surrounding a water well or well field, supplying a public water system, through which contaminants are reasonably likely to move toward and reach such water well or well field.

wetting agent
A substance that reduces the surface tension of a liquid, causing the liquid to spread across or penetrate more easily the surface of a solid. A soap-based wetting agent reduces the tendency of clay cuttings to stick together. It also reduces the tendency of boring tools becoming stuck due to adhesion.

wilting point
The soil-moisture content below which plants are unable to withdraw soil moisture.

wing cutter
A backreamer specially designed to cut, mix, and change the form of the material that is being pulled through to make it into a passable or manageable form.

zone of capture
Area surrounding a pumping well that encompasses all areas of features that supply groundwater recharge to the well.

zone of contribution (ZOC)
The area surrounding a pumping well that encompasses all areas or features that supply groundwater recharge to the well.

zone of influence (ZOI)
The area surrounding a pumping well within which the water table or potentiometric surfaces have been changed due to groundwater withdrawal.

zone of transport (ZOT)
The area surrounding a pumping well, bounded by an isochrone and/or isoconcentration contour, through which a contaminant may travel and reach the well.

Links

Oklahoma Water Resources Board

USGS

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