GLOSSARY
The terms in this glossary were compiled from numerous sources. Some definitions have been modified and may not be the only valid ones for these terms.
- Acre-foot
- A volume of water equal to 1 foot in depth and covering 1 acre; equivalent to 43,560 cubic feet or 325,851 gallons.
- Algae
- Chlorophyll-bearing, nonvascular, primarily aquatic species that have no true roots, stems, or leaves; most algae are microscopic, but some species can be as large as vascular plants.
- Alluvial aquifer
- A water-bearing deposit of unconsolidated material (sand and gravel) left behind by a river or other flowing water.
- Anthropogenic
- Occurring because of, or influenced by, human activity.
- Aquatic-life criteria
- Water-quality guidelines for protection of aquatic life. Often refers to U.S. Environmental Protection Agency water-quality criteria for protection of aquatic organisms. See also Water-quality guidelines, Water-quality criteria.
- Aquifer
- A water-bearing layer of soil, sand, gravel, or rock that will yield usable quantities of water to a well.
- Bed sediment
- The material that temporarily is stationary in the bottom of a stream or other watercourse.
- Benthic invertebrates
- Insects, mollusks, crustaceans, worms, and other organisms without a backbone that live in, on, or near the bottom of lakes, streams, or oceans.
- Breakdown product
- A compound derived by chemical, biological, or physical action upon a pesticide. The breakdown is a natural process which may result in a more toxic or a less toxic compound and a more persistent or less persistent compound.
- Concentration
- The amount or mass of a substance present in a given volume or mass of sample. Usually expressed as micrograms per liter (water sample) or micrograms per kilogram (sediment or tissue sample).
- Consumptive use
- The quantity of water that is not available for immediate reuse because it has been evaporated, transpired, or incorporated into products, plant tissue, or animal tissue. Also referred to as "water consumption."
- Criterion
- A standard rule or test on which a judgment or decision can be based.
- Cubic foot per second
- (ft3/s, or cfs) rate of water discharge representing a volume of 1 cubic foot passing a given point during 1 second, equivalent to approximately 7.48 gallons per second or 448.8 gallons per minute or 0.02832 cubic meter per second.
- Discharge
- Rate of fluid flow passing a given point at a given moment in time, expressed as volume per unit of time.
- Dissolved solids
- Amount of minerals, such as salt, that is dissolved in water; amount of dissolved solids is an indicator of salinity or hardness.
- Drainage basin
- The portion of the surface of the Earth that contributes water to a stream through overland runoff, including tributaries and impoundments.
- Drinking-water standard or guideline
- A threshold concentration in a public drinking-water supply, designed to protect human health. As defined here, standards are U.S. Environmental Protection Agency regulations that specify the maximum contamination levels for public water systems required to protect the public welfare; guidelines have no regulatory status and are issued in an advisory capacity.
- Ecoregion
- An area of similar climate, landform, soil, potential natural vegetation, hydrology, or other ecologically relevant variables.
- Eutrophication
- The process by which water becomes enriched with plant nutrients, most commonly phosphorus and nitrogen.
- Health advisory
- Nonregulatory levels of contaminants in drinking water that may be used as guidance in the absence of regulatory limits. Advisories consist of estimates of concentrations that would result in no known or anticipated health effects (for carcinogens, a specified cancer risk) determined for a child or for an adult for various exposure periods.
- Herbicide
- A chemical or other agent applied for the purpose of killing undesirable plants. See also Pesticide.
- Insecticide
- A substance or mixture of substances intended to destroy or repel insects.See alsoPesticide.
- Load
- General term that refers to a material or constituent in solution, in suspension, or in transport; usually expressed in terms of mass or volume.
- Major ions
- Constituents commonly present in concentrations exceeding 1.0 milligram per liter. Dissolved cations generally are calcium, magnesium, sodium, and potassium; the major anions are sulfate, chloride, fluoride, nitrate, and those contributing to alkalinity, most generally assumed to be bicarbonate and carbonate.
- Mouth
- The place where a stream discharges to a larger stream, a lake, or the sea.
- National Academy of Sciences/National Academy of Engineering (NAS/NAE) recommended maximum concentration in water
- Numerical guidelines recommended by two joint NAS/NAE committees for the protection of freshwater and marine aquatic life, respec-tively. These guidelines were based on available aquatic toxicity studies and were considered preliminary even when formulated (1972). The guidelines used in the summary reports are for freshwater.
- Nonpoint source
- A pollution source that cannot be defined as originating from discrete points such as pipe discharge. Areas of fertilizer and pesticide applications, atmospheric deposition, manure, and natural inputs from plants and trees are types of nonpoint source pollution.
- Organochlorine compound
- Synthetic organic compounds containing chlorine. As generally used, term refers to compounds containing mostly or exclusively carbon, hydrogen, and chlorine. Examples include organochlorine insecticides, polychlorinated biphenyls, and some solvents containing chlorine.
- Pesticide
- A chemical applied to crops, rights of way, lawns, or residences to control weeds, insects, fungi, nematodes, rodents, or other "pests."
- Point source
- A source at a discrete location such as a discharge pipe, drainage ditch, tunnel, well, concentrated livestock operation, or floating craft.
- Polychlorinated biphenyls (PCBs)
- A mixture of chlorinated derivatives of biphenyl, marketed under the trade name Aroclor with a number designating the chlorine content (such as Aroclor 1260). PCBs were used in transformers and capacitors for insulating purposes and in gas pipeline systems as a lubricant. Further sale for new use was banned by law in 1979.
- Radon
- A naturally occurring, colorless, odorless, radioactive gas formed by the disintegration of the element radium; damaging to human lungs when inhaled.
- Riparian
- Areas adjacent to rivers and streams with a high density, diversity, and productivity of plant and animal species relative to nearby uplands.
- Runoff
- Rainwater or snowmelt that is transported to streams by overland flow, tile drains, or ground water.
- Sediment
- Particles, derived from rocks or biological materials, that have been transported by a fluid or other natural process and are suspended or settled in water.
- Semivolatile organic compounds (SVOCs)
- Operationally defined as a group of synthetic organic compounds that are solvent-extractable and can be determined by gas chromatography/mass spectrometry. SVOCs include phenols, phthalates, and polycyclic aromatic hydrocarbons (PAHs).
- Streamflow
- A type of channel flow, applied to that part of surface runoff in a stream whether or not it is affected by diversion or regulation.
- Suspended sediment
- Particles of rock, sand, soil, and organic detritus carried in suspension in the water column, in contrast to sediment that moves on or near the streambed.
- Tolerant species
- Those species that are adaptable to (tolerant of) human effects on the environment.
- Trace element
- An element found in only minor amounts (concentrations less than 1.0 milligram per liter) in water or sediment; includes arsenic, cadmium, chromium, copper, lead, mercury, nickel, and zinc.
- Volatile organic compounds (VOCs)
- Organic chemicals that have a high vapor pressure relative to their water solubility. VOCs include components of gasoline, fuel oils, and lubricants, as well as organic solvents, fumigants, some inert ingredients in pesticides, and some byproducts of chlorine disinfection.
- Water-quality criteria
- Specific levels of water quality which, if reached, are expected to render a body of water unsuitable for its designated use. Commonly refers to water-quality criteria established by the U.S. Environmental Protection Agency. Water-quality criteria are based on specific levels of pollutants that would make the water harmful if used for drinking, swimming, farming, fish production, or industrial processes.
- Water-quality guidelines
- Specific levels of water quality which, if reached, may adversely affect human health or aquatic life. These are nonenforceable guidelines issued by a governmental agency or other institution.
- Water-quality standards
- State-adopted and U.S. Environmental Protection Agency-approved ambient standards for water bodies. Standards include the use of the water body and the water-quality criteria that must be met to protect the designated use or uses.
- Water year
- The continuous 12-month period, October 1 through September 30, in U.S. Geological Survey reports dealing with the surface-water supply. The water year is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus, the year ending September 30, 1980, is referred to as the "1980" water year.
