| A |
- Adaptive management
- Approach where source controls are initiated while additional monitoring data are collected to provide a basis for future review and revision of the TMDL (as well as management activities).
- Aggradation
- The raising of the bed of a watercourse by the deposition of sediment.
- Allocations
- That portion of a receiving water's loading capacity that is attributed to one of its existing or future pollution sources (nonpoint or point) or to natural background sources. (A wasteload allocation [WLA] is that portion of the loading capacity allocated to an existing or future point source, and a load allocation [LA] is that portion allocated to an existing or future nonpoint source or to natural background source. Load allocations are best estimates of the loading, which can range from reasonably accurate estimates to gross allotments, depending on the availability of data and appropriate techniques for predicting loading.)
- Alluvium
- Sediment deposited by flowing water, such as in a riverbed, floodplain, or delta. Ambient water quality. Natural concentration of water quality constituents prior to mixing of either point or nonpoint source load of contaminants. Reference ambient concentration is used to indicate the concentration of a chemical that will not cause adverse impact to human health.
- Ambient water quality
- Natural concentration of water quality constituents prior to mixing of either point or nonpoint source load of contaminants. Reference ambient concentration is used to indicate the concentration of a chemical that will not cause adverse impact to human health.
- Anthropogenic
- Pertains to the [environmental] influence of human activities.
- Anti-degradation policies
- Policies that are part of each state's water quality standards. These policies are designed to protect water quality and provide a method of assessing activities that may impact the integrity of waterbodies.
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- Aquatic buffers
- Streamside vegetation that filters stormwater and protects stream banks.
- Aquatic classification system
- Assigns a classification to a waterbody reflecting the water quality and the biological health (integrity). Classification is determined through use of biological indices (see IBI). Examples of classifications include oligosaprobic (cleanest water quality) and polysaprobic (highly polluted water).
- Aquatic corridor
- The area where land and water meet. This can include floodplains, stream channels, springs and seeps, small estuarine coves, littoral areas, stream crossings, shorelines, riparian forest, caves, and sinkholes.
- Aquatic ecosystem
- Complex of biotic and abiotic components of natural waters. The aquatic ecosystem is an ecological unit that includes the physical characteristics (such as flow or velocity and depth), the biological community of the water column and benthos, and the chemical characteristics such as dissolved solids, dissolved oxygen, and nutrients. Both living and nonliving components of the aquatic ecosystem interact and influence the properties and status of each component.
- Aquatic life use
- A use designation in State/Tribal water quality standards that generally provides for survival and reproduction of desirable fish, shellfish, and other aquatic organisms; classifications specified in state water quality standards relating to the level of protection afforded to the resident biological community.
- Assimilative capacity
- The amount of contaminant load that can be discharged to a specific waterbody without exceeding water quality standards or criteria. Assimilative capacity is used to define the ability of a waterbody to naturally absorb and use a discharged substance without impairing water quality or harming aquatic life.
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| B |
- Background levels
- Levels representing the chemical, physical, and biological conditions that would result from natural geomorphological processes such as weathering or dissolution.
- Base level
- Lowest point to which a stream may erode its channel; the ultimate base level is sea level; temporary or local base levels are defined by rock, hardpan, or other strata that resist downcutting and force erosional processes laterally.
- BASINS (Better Assessment Science Integrating Point and Nonpoint Sources)
- A computer-run tool that contains an assessment and planning component that allows users to organize and display geographic information for selected watersheds. It also contains a modeling component to examine impacts of pollutant loadings from point and nonpoint sources and to characterize the overall condition of specific watersheds.
- Bedload sediment
- Portion of sediment load transported downstream by sliding, rolling, &/or bouncing along the channel bottom. Generally consists of particles >1 mm.
- Benthic
- Refers to material, especially sediment, at the bottom of an aquatic ecosystem. It can be used to describe the organisms that live on, or in, the bottom of a waterbody.
- Benthic organisms
- Organisms living in, or on, bottom substrates in aquatic ecosystems.
- Best management practices (BMPs)
- Methods, measures, or practices that are determined to be reasonable and cost-effective means for a land owner to meet certain, generally nonpoint source, pollution control needs. BMPs include structural and nonstructural controls and operation and maintenance procedures.
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- Bioassessment
- Biological assessment; the evaluation of an ecosystem using integrated assessments of habitat and biological communities in comparison to empirically defined reference conditions. Biochemical oxygen demand (BOD)
- The amount of oxygen per unit volume of water required to bacterially or chemically oxidize (stabilize) the oxidizable matter in water. Biochemical oxygen demand measurements are usually conducted over specific time intervals (5, 10, 20, 30 days). The term BOD generally refers to a standard 5-day BOD test.
- Biochemical oxygen demand (BOD)
- The amount of oxygen per unit volume of water required to bacterially or chemically oxidize (stabilize) the oxidizable matter in water. Biochemical oxygen demand measurements are usually conducted over specific time intervals (5, 10, 20, 30 days). The term BOD generally refers to a standard 5-day BOD test.
- Biological criteria
- Also known as biocriteria, biological criteria are narrative expressions or numeric values of the biological characteristics of aquatic communities based on appropriate reference conditions. Biological criteria serve as an index of aquatic community health.
- Biomass
- The amount, or weight, of a species, or group of biological organisms, within a specific volume or area of an ecosystem.
- Boundary conditions
- Values or functions representing the state of a system at its boundary limits.
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| C |
- Calcareous
- Pertaining to or containing calcium carbonate.
- Calibration
- The process of adjusting model parameters within physically defensible ranges until the resulting predictions give a best possible good fit to observed data.
- Carbonaceous
- Pertaining to or containing carbon derived from plant and animal residues.
- Cation exchange capacity
- The sum total of exchangeable cations that a soil can adsorb. Expressed in centimoles per kilogram of soil (or of other adsorbing material such as clay.)
- Channel
- A natural stream that conveys water; a ditch or channel excavated for the flow of water.
- Channel improvement
- The improvement of the flow characteristics of a channel by clearing, excavation, realignment, lining, or other means in order to increase its capacity. Sometimes used to connote channel stabilization.
- Channel morphology
- The change in a stream channel's width or the shape of the stream banks. Increased erosion often causes a stream channel to widen and to deepen. Additional aspects of channel morphology include height, angle, and extent of bank erosion, substrate embeddedness, sediment deposition, and substrate.
- Channel stabilization
- Erosion prevention and stabilization of velocity distribution in a channel using jetties, drops, revetments, vegetation, and other measures.
- Chloride
- An atom of chlorine in solution; an ion bearing a single negative charge.
- Clean sediment
- Sediment that is not contaminated by chemical substances. Pollution caused by clean sediment refers to the quantity of sediment, as opposed to the presence of pollutant-contaminated sediment.
- Clean Water Act (CWA)
- The Clean Water Act (formerly referred to as the Federal Water Pollution Control Act or Federal Water Pollution Control Act Amendments of 1972), Public Law 92-500, as amended by Public Law 96-483 and Public Law 97-117, 33 U.S.C. 1251 et seq. The Clean Water Act (CWA) contains a number of provisions to restore and maintain the quality of the nation's water resources. One of these provisions is section 303(d), which establishes the TMDL program.
- Coastal zone
- Lands and waters adjacent to the coast that exert an influence on the uses of the sea and its ecology, or whose uses and ecology are affected by the sea.
- Colluvium
- Soil and rock debris on a hillslope that has been transported from its original location.
- Concentration
- Amount of a substance or material in a given unit volume of solution; usually measured in milligrams per liter (mg/L) or parts per million (ppm).
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- Concentration-based limit
- A limit based on the relative strength of a pollutant in a wastestream, usually expressed in milligrams per liter (mg/L).
- Contaminated sediments
- Deposited or accumulated sediments, typically on the bottom of a waterbody, that contain contaminants. These may or may not be toxic as revealed by a whole sediment toxicity test, or as predicted by equilibrium partitioning.
- Contamination
- The act of polluting or making impure; any indication of chemical, sediment, or biological impurities.
- Continuous discharge
- A discharge that occurs without interruption throughout the operating hours of a facility, except for infrequent shutdowns for maintenance, process changes, or other similar activities.
- Conventional pollutants
- As specified under the Clean Water Act, conventional contaminants include suspended solids, coliform bacteria, high biochemical oxygen demand, pH, and oil and grease.
- Cost-share program
- A program that allocates project funds to pay a percentage of the cost of constructing or implementing a best management practice. The remainder of the costs are paid by the producer.
- Criteria
- (1) Under section 304(a) of the Clean Water Act, EPA publishes scientific information regarding concentrations of specific chemicals or levels of parameters in water that protect aquatic life and human health.
(2)Levels of individual pollutants, or water quality characteristics, or descriptions of conditions of a water body, adopted into State water quality standards that, if met, will generally protect the designated use of the water. In many cases, States make use of the criteria developed by EPA under definition #1 above.
- Critical condition
- The critical condition can be thought of as the "worst case" scenario of environmental conditions in the waterbody in which the loading expressed in the TMDL for the pollutant of concern will continue to meet water quality standards. Critical conditions are the combination of environmental factors (e.g., flow, temperature, etc.) that results in attaining and maintaining the water quality criterion and has an acceptably low frequency of occurrence.
- Cross-sectional area
- Wet area of a waterbody normal to the longitudinal component of the flow.
- Cryptosporidium
- See protozoa.
- Cumulative impacts
- Describes situations when the effects of an action are added to or interact with other effects in a particular place and within a particular time. A multi-purpose practice used for the removal of sediment that accumulates at the bottom of water bodies.
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| D |
- Decay
- The gradual decrease in the amount of a given substance in a given system due to various sink processes including chemical and biological transformation, dissipation to other environmental media, or deposition into storage areas.
- Decomposition
- Metabolic breakdown of organic materials; the formation of by-products of decomposition releases energy and simple organic and inorganic compounds. (See also, Respiration.)
- Design stream flow
- The stream flow used to conduct steady-state wasteload allocation modeling.
- Designated uses
- Those uses specified in State/Tribal water quality standards for each water body or segment whether or not they are being attained. Sometimes referred to as Beneficial Uses, i.e., desirable uses that water quality should support. Examples are drinking water supply, primary contact recreation (such as swimming), and aquatic life support.
- Deterministic model
- A model that does not include built-in variability: same input will always equal the same output.
- Detritus
- Any loose material produced directly from disintegration processes. Organic detritus consists of material resulting from the decomposition of dead organic remains.
- Diagenesis
- Production of sediment fluxes as a result of the flux of particulate organic carbon in the sediment and its decomposition. The diagenesis reaction can be thought of as producing oxygen equivalents released by various reduced species.
- Diel ("die´-el")
- Involving a 24-hour period.
- Dilution
- The addition of some quantity of less concentrated liquid (water) that results in a decrease in the original concentration.
- Direct runoff
- Water that flows over the ground surface or through the ground directly into streams, rivers, and lakes.
- Discharge
- Flow of surface water in a stream or canal or the outflow of groundwater from a flowing artesian well, ditch, or spring. Can also apply to discharge of liquid effluent from a facility or to chemical emissions into the air through designated venting mechanisms.
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- Discharge monitoring report (DMR)
- Report of effluent characteristics submitted by a municipal or industrial facility that has been granted an NPDES discharge permit.
- Discharge permits (NPDES)
- A permit issued by the U.S. EPA or a State regulatory agency that sets specific limits on the type and amount of pollutants that a municipality or industry can discharge to a receiving water; it also includes a compliance schedule for achieving those limits. It is called the NPDES because the permit process was established under the National Pollutant Discharge Elimination System, under provisions of the Federal Clean Water Act.
- Dispersion
- The spreading of chemical or biological constituents, including pollutants, in various directions from a point source, at varying velocities depending on the differential in-stream flow characteristics.
- Dissolved oxygen (DO)
- The amount of oxygen that is dissolved in water. This term also refers to a measure of the amount of oxygen available for biochemical activity in a waterbody, and is an indicator of the quality of that water.
- Domestic wastewater
- Also called sanitary wastewater, consists of wastewater discharged from residences and from commercial, institutional, and similar facilities.
- Drainage basin
- A part of a land area enclosed by a topographic divide from which direct surface runoff from precipitation normally drains by gravity into a receiving water. Also referred to as a watershed, river basin, or hydrologic unit.
- Dry ravel
- Sloughing of sediment due to loss of cohesion in surface materials.
- Dynamic model
- A mathematical formulation describing and simulating the physical behavior of a system or a process and its temporal variability.
- Dynamic simulation
- Modeling of the behavior of physical, chemical, and/or biological phenomena and their variation over time.
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| E |
- Ecological function
- Potentially impacted by changes in channel morphology, stream hydrology, water quality, and habitat structure. Ecological function can be measured by fish diversity, macroinvertebrate diversity, biological integrity, EPA Rapid Bioassessment Protocol, fish barriers, and the leaf pack processing rate.
- Ecoregion
- A physical region that is defined by its ecology, which includes meteorological factors, elevation, plant and animal speciation, landscape position, and soils.
- Ecosystem
- An interactive system that includes the organisms of a natural community association together with their abiotic physical, chemical, and geochemical environment.
- Effluent
- Municipal sewage or industrial liquid waste (untreated, partially treated, or completely treated) that flows out of a treatment plant, septic system, pipe, etc.
- Effluent guidelines
- Technical EPA documents that set effluent limitations for given industries and pollutants.
- Effluent limitation
- Restrictions established by a state or EPA on quantities, rates, and concentrations in pollutant discharges.
- Effluent plume
- Delineates the extent of contamination in a given medium as a result of a distribution of effluent discharges (or spills). Usually shows the concentration gradient within the delineated areas or plume of flow of contaminants.
- Embeddedness
- The degree to which fine sediments (e.g., clays, silts) fill the spaces (interstices) between rocks, cobbles, and gravel on the bottom of a stream or river.
- Empirical model
- Use of statistical techniques to discern patterns or relationships underlying observed or measured data for large sample sets. Does not account for physical dynamics of waterbodies.
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- Endpoint
- An endpoint (or indicator/target) is a characteristic of an ecosystem that may be affected by exposure to a stressor. Assessment endpoints and measurement endpoints are two distinct types of endpoints commonly used by resource managers. An assessment endpoint is the formal expression of a valued environmental characteristic and should have societal relevance (an indicator). A measurement endpoint is the expression of an observed or measured response to a stress or disturbance. It is a measurable environmental characteristic that is related to the valued environmental characteristic chosen as the assessment endpoint. The numeric criteria that are part of traditional water quality standards are good examples of measurement endpoints (targets).
- Enhancement
- In the context of restoration ecology, any improvement of a structural or functional attribute.
- Environmental monitoring and assessment program (EMAP)
- A USEPA program to monitor and assess the ecological health of major ecosystems, including surface waters, forests, near-coastal waters, wetlands, agricultural lands, arid lands, and the Great Lakes, in an integrated, systematic manner. Although EMAP has been curtailed somewhat during recent years, the program is designed to operate at regional and national scales, for decades, and to evaluate the extent and condition of entire ecological resources by using a common sampling framework to sample approximately 12,500 locations in the conterminous United States.
- Estuary
- Brackish-water areas influenced by the tides where the mouth of a river meets the sea.
- Estuarine number
- A nondimensional parameter accounting for decay, tidal dispersion, and advection velocity; used for classification of tidal rivers and estuarine systems.
- Existing use
- Use actually attained in the waterbody on or after November 28, 1975, whether or not it is included in the water quality standards (40 CFR 131.3).
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| F |
- Fate of pollutants
- Physical, chemical, and biological transformation in the nature and changes of the amount of a pollutant in an environmental system. Transformation processes are pollutant-specific. Because they have comparable kinetics, different formulations for each pollutant are not required.
- Feedlot
- A confined area for the controlled feeding of animals. Tends to concentrate large amounts of animal waste that cannot be absorbed by the soil and, hence, may be carried to nearby streams or lakes by rainfall runoff.
- Fines
- Fine particulate material such as silt and clay particles typically of less than .85 mm diameter
- Flocculation
- The process by which suspended colloidal or very fine particles are assembled into larger masses or floccules that eventually settle out of suspension.
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- Fluvial geomorphology
- The effect of rainfall and runoff on the form and pattern of riverbeds and river channels.
- Flux
- Movement and transport of mass of any water quality constituent over a given period of time. Units of mass flux are mass per unit time.
- Forcing functions
- External empirical formulation used to provide input describing a number of processes. Typical forcing functions include parameters such as temperature, point and tributary sources, solar radiation, and waste loads and flow.
- Fry
- Young, newly hatched fish.
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| G |
- Geochemical
- Referring to chemical reactions involving earth materials such as soil, rocks, and water.
- Geomorphology
- The study of the evolution and configuration of landforms.
- Gradient
- The rate of change of the value of one quantity with respect to another; for example, the rate of decrease of temperature with depth in a lake.
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- Ground water
- The supply of fresh water found beneath the earth's surface, usually in aquifers, which supply wells and springs. Because ground water is a major source of drinking water, there is growing concern over contamination from leaching agricultural or industrial pollutants and leaking underground storage tanks.
- Gully erosion
- The erosion process whereby water accumulates in narrow channels and, over short periods, removes the soil form this narrow area to considerable depths, ranging from 1-2 feet to as much as 75-100 feet.
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Science & Technology