Glossary of Terms
| Glossary Term | Definition |
| 303(d) list | A list of waters that fail to meet any applicable water quality standards, that states are required, under section 303(d) of the Clean Water Act, to assemble and update once every 2 years. EPA is required to determine the completeness of such lists. |
| Abiotic factors | Pertaining to any non-biological factor or influence, such as geological or meteorological characteristics. |
| Algae | Unicellular or multicellular photosynthetic organisms that lack true roots, stems, or leaves. Includes tiny, single-celled planktonic phytoplankton, as well as large, multicellular benthic macroalgae. Common primary producers and sources of food and oxygen in freshwater and marine food web. |
| Alpine glacial lake | Lakes formed by glacial activity at high elevation and above the tree line. |
| Antidegradation | Policies which ensure protection of water quality for a particular water body where the water quality exceeds levels necessary to protect fish and wildlife propagation and recreation on and in the water. This also includes existing instream water uses and the level of water quality necessary to protect the existing uses shall be maintained and protected. |
| Assessment endpoint | Explicit expressions of the actual environmental value that is to be protected, operationally defined by an ecological entity and its attributes. |
| Bathymetry | The varying physical characteristics including depth, contour, and shape of the bottom of a body of water. |
| Benthic community | Bottom-dwelling community. Benthic organisms spend at least part of their lives in, on, or near the bottom of aquatic environments. |
| Benthic flux rates | Flux of nutrients across the sediment-water interface in a waterbody. |
| Best attainable use | The “use” of a water body is the most fundamental articulation of its role in the aquatic and human environments. “Best attainable” means the highest possible goal for the water. |
| Best management practices (BMPs) | Schedules of activities, prohibitions of practices, maintenance procedures, and other management practices other than traditional physical, chemical, or biological wastewater treatment. BMPs can be either nonstructural (good housekeeping practices, pollution prevention, contour plowing, cover crops) or structural (wet or dry detention ponds), and can include treatment requirements, operating procedures, and practices to control site runoff, spillage, or leaks. BMPs can be applied to both nonpoint and point sources of water pollution and can be employed as part of either regulatory or voluntary programs. |
| Biocriteria | Numerical values or narrative expressions describing the “reference” biological condition of aquatic communities inhabiting waters of a given designated aquatic life use. Biocriteria are benchmarks for evaluation and management of water resources. |
| Biological condition index | An indicator of watershed health, in terms of aquatic organisms and communities: For example, multimetric indices measure the presence, numbers and condition of aquatic organisms and communities in an aquatic ecosystem. They are intended to represent the biological condition of an aquatic ecosystem relative to some regionally-defined reference condition. |
| Biological indicators | An organism, species, or community whose characteristics show the presence of specific environmental conditions. |
| Biomass | The amount of a living species, expressed as a concentration or weight per unit area or volume. |
| Biotic community | A naturally occurring assemblage of plants and animals that live in the same environment and are mutually sustaining and interdependent. |
| Carbonaceous biochemical oxygen demand | Oxygen demand exerted by organic carbon compounds present; oxygen required to convert organic carbon to carbon dioxide. |
| Causal variables (in the context of nutrient criteria) | Parameters (e.g., total nitrogen and total phosphorus) whose presence result in a change in an identified response variable (e.g., chlrophyll a). |
| Characterizing ecological effects | The process for examining effects; evaluates stressor- response relationships or evidence that exposure to stressors causes an observed response. |
| Coastal water | Marine systems that lie between the mean highwater mark of the coastal baseline and the shelf break, or approximately 20 nautical miles offshore when the continental shelf is extensive. |
| Competition | An interaction between members of two or more species that, as a consequence either of exploitation of a shared resource or of interference related to that resource, has a negative effect on fitness-related characteristics of at least one of the species. |
| Conceptual model | A conceptual model in problem formulation is a written description and visual representation of predicted relationships between ecological entities and the stressors to which they may be exposed. |
| Cyanobacteria | A group of phytoplankton which often cause nuisance conditions in water, so called because they contain a blue pigment in addition to chlorophyll (also called “blue-green algae”). Blue-green algae are often associated with problem blooms in lakes. Some produce chemicals toxic to other organisms, including humans. They often form floating scum as they die. Many can fix nitrogen (N2) from the air to provide their own nutrient. |
| Cyanotoxin | Cyanotoxins are produced and contained within the cyanobacterial cells (intracellular). The release of these toxins in an algal bloom into the surrounding water occurs mostly during cell death and lysis (i.e., cell rupture) as opposed to continuous excretion from the cyanobacterial cells. However, some cyanobacteria species are capable of releasing toxins into the water without cell rupture or death. |
| Delta plain | The level (or nearly level) surface that makes up the landward part of a large delta; strictly, a flood plain characterized by repeated channel bifurcation and divergence, multiple distributary channels, and interdistributary flood basins. |
| Deposition | The accumulation of material dropped because of a slackening movement of the transporting medium, e.g., water or wind. |
| Designated use | Terminology used in the Clean Water Act to describe classes of expectations for water bodies. The classification of water bodies must take into consideration the use and value of water for public water supplies, protection and propagation of fish, shellfish and wildlife, recreation in and on the water, agricultural, industrial, and other purposes including navigation. |
| Detritus | Organic debris from dead organisms that is often an important source of food in a food web. |
| Diatoms | Microscopic algae with cell walls made of silicon and of two separating halves. |
| Discharger | Dischargers can be either “direct dischargers,” that are sources that discharge directly to waters of the United States, or “indirect dischargers,” that are sources that introduce pollutants to publicly owned treatment works (POTWs). |
| Downstream waters | EPA interprets “downstream waters” to include both intra- and interstate waters, as well as waters that form a boundary between adjacent jurisdictions. Regulation at 40 CFR 131.10(b) requires that “(i)n designating uses of a water body and the appropriate criteria for those uses, the State shall take into consideration the water quality standards of downstream waters and shall ensure that its water quality standards provide for the attainment and maintenance of the water quality standards of downstream waters.” |
| Duration (in the context of nutrient criteria) | The time period over which exposure is averaged (i.e., the averaging period) to limit the time of exposure to elevated concentrations. |
| Dynamic | Marked by usually continuous and productive activity or change. |
| Ecological effects profile | An assessment that describes the available effects information for various plants and animals and an interpretation of available incidents information and effects monitoring data. |
| Ecological risk | The likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. |
| Ecoregion | A geographic area having relatively uniform ecological properties (e.g., landform, natural vegetation, hydrology). |
| Ecosystem | The biotic community and abiotic environment within a specified location in space and time. |
| Epiphyte | Narrowly, an organism that grows on a plant. Often used loosely, it refers to the community of algae, microfauna, and particulate matter existing on the surface of submerged aquatic vegetation. The epiphyte does not consume the plant on which it grows, but mainly uses the plant for structural support or as a way to get off the benthic surface and into the canopy environment. |
| Estuary | A partially enclosed body of water where fresh water from rivers and streams mixes with salt water from the ocean. It is an area of transition from land to sea. |
| Eutrophication | Enrichment of a water body with nutrients, often resulting in high levels of primary production. |
| Evapotranspiration | The loss of water from the soil both by evaporation and by transpiration from the plants growing in the soil. |
| Exposure profile | The product of characterization of exposure in the analysis phase of ecological risk assessment. The exposure profile summarizes the magnitude and spatial and temporal patterns of exposure for the scenarios described in the conceptual model. |
| Fjord | A long, narrow arm of the sea, usually formed by entrance of the sea into a deep glacial trough. |
| Frequency (in the context of nutrient criteria) | How often the magnitude/duration condition may be exceeded and still protect the designated use. |
| Geology | The science that studies the physical nature and history of the earth. |
| Harmful algal blooms | Overgrowths of algae in water. Some produce dangerous toxins in fresh or marine water, but even nontoxic blooms hurt the environment and local economies. |
| Headwaters | (1) The source and upper reaches of a stream; also the upper reaches of a, lake, reservoir, or estuary. (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. The water from which a river originates. |
| Historical condition | Water quality conditions observed prior to significant anthropogenic impacts that provide a basis for comparison. |
| Hydrodynamics | The branch of science that deals with the dynamics of fluids, especially incompressible fluids, in motion. |
| Hydrology | The science dealing with the properties, distribution, and circulation of water. |
| Hypolimnetic anoxia | Deep-water depletion of dissolved oxygen. |
| Hypoxia | A condition in which oxygen levels in water are very low. |
| Impaired | A state of a waterbody that does not meet state water quality standards. Under the Clean Water Act, section 303(d), states, territories and authorized tribes are required to develop prioritized lists of impaired waters. |
| In situ | In place. |
| Integrity | Refers to a condition in which the natural structure and function of ecosystems is maintained. |
| Karst | A type of terrain where there are numerous sinkholes and large voids such as caves. Karst is created when water dissolves rocks such as limestone, halite (salt) and gypsum. |
| Kinetics | The mechanism by which a physical or chemical change is affected. |
| Lacustrine | Pertaining to, produced by, or formed in a lake. |
| Lake | A natural inland body of water, fresh or salt, occupying a basin or hollow on the earth’s surface, which may or may not have a current or single direction of flow. |
| Land application systems | The addition of biosolids to soil to supply nutrients and replenish soil organic matter. |
| Least disturbed condition | Describes minimally impacted conditions. |
| Lentic waters | Ponds or lakes (standing water). |
| Light attenuation coefficient | A numerical value that describes the light penetration in water or water clarity. |
| Lines of evidence | Information derived from different sources or by different techniques that can be used to describe and interpret risk estimates. Unlike the term “weight of evidence,” it does not necessarily imply assignment of quantitative weightings to information. |
| Loading (pollutant loading) | Amount of a substance entering the environment (e.g., soil, water, pollutants, air). |
| Macrophyte | Aquatic plants growing in or near water. They may be either emergent (i.e., with upright portions above the water surface), submerged or floating. |
| Management goal | Narrative statement that expresses the desired condition of an aquatic system. |
| Measure of effect | A change in an attribute of an assessment endpoint or its surrogate in response to a stressor to which it is exposed. |
| Mechanistic model | A model that has a structure that explicitly represents an understanding of physical, chemical, and/or biological processes. Mechanistic models quantitatively describe the relationship between some phenomenon and underlying first principles of cause. Hence, in theory, they are useful for inferring solutions outside of the domain that the initial data was collected and used to parameterize the mechanisms. |
| Minimally disturbed | Biological conditions found in water bodies with minimum human disturbance. |
| Natural lake | Those without evidence of a dam or where available information indicated the lake was natural even if a dam exists to augment the depth of the lake. |
| Natural nutrient source | Sources of naturally derived nitrogen and phosphorus. Nitrogen and phosphorus are nutrients that are natural parts of aquatic ecosystems. Nitrogen is also the most abundant element in the air we breathe. Nitrogen and phosphorus support the growth of algae and aquatic plants, which provide food and habitat for fish, shellfish and smaller organisms that live in water. |
| Nonpoint source | A diffuse source of water pollution that is not collected and discharged through a discrete man-made conveyance. (i.e, any source of pollutants not considered a point source under the CWA.) Atmospheric deposition and hydromodification are also nonpoint sources of pollution. |
| Numeric nutrient criteria | Quantitative expressions of nutrient levels needed to support water quality management goals. |
| Nutrient pollution | Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern. |
| Nutrient source | Excessive nitrogen and phosphorus that washes into water bodies and is released into the air are often the direct result of human activities. The primary sources of nutrient pollution are: agriculture, stormwater, wastewater, fossil fuels, and in and around the home. |
| Periphyton | Microscopic underwater plants and animals that are firmly attached to solid surfaces such as rocks, logs, and pilings. |
| Physiography | Physical geography, or geography that deals with the exterior physical features and changes of the earth. |
| Plankton | Small and microscopic free-floating plants, animals and bacteria. Plankton have limited or no swimming ability and are generally transported by currents and tides. |
| Playa | Generally, a dry or intermittently dry lakebed in the lowest spot of a closed valley. Also, a nearly level area at the bottom of an undrained desert basin, sometimes temporarily covered with water. Salt contents are generally quite high. |
| Point source | A source of pollution that can be attributed to a specific physical location — an identifiable, end-of-pipe “point.” The vast majority of point source discharges of nutrients are from wastewater treatment plants, although some come from industries. |
| Primary productivity | The rate of formation of organic matter from inorganic carbon by photosynthesizing organisms |
| Receptor | The ecological entity exposed to the stressor. |
| Reference condition | Set of selected measurements or conditions of minimally disturbed waterbodies characteristic of a waterbody type in a region. |
| Regression analysis | A statistical process that produces a mathematical function (regression equation) that relates a dependent variable (biological effect) to independent variable, e.g., dose rate, duration of exposure, age. |
| Reservoir | A natural or artificial place where water is collected or stored for use, especially water for supplying a community, irrigating land and furnishing power. |
| Respiration rate | The sum total of the physical and chemical processes in an organism by which oxygen is conveyed to tissues and cells, and the oxidation products, carbon dioxide and water, are given off. |
| Response variables (in the context of nutrient criteria) | Quantifiable parameters (e.g., chlorophyll a, turbidity) that are used to indicate and measure change in causal variable (e.g., total nitrogen, total phosphorus) inputs. |
| Retention time | The interval of time that a pollutant, fluid, or other material remains in a water body. |
| Riparian | The area of land next to a body of water. Riparian areas form the transition between terrestrial and aquatic environments. |
| Risk characterization | The final phase of ecological risk assessment and the culmination of the planning, problem formulation, and analysis of predicted or observed adverse ecological effects related to the assessment endpoints. Completing risk characterization allows risk assessors to clarify the relationships between stressors, effects, and ecological entities and to reach conclusions regarding the occurrence of exposure and the adversity of existing or anticipated effects. |
| Risk hypotheses | Proposed answers to questions risk assessors have about what responses assessment endpoints will show when they are exposed to stressors and how exposure will occur. Risk hypotheses clarify and articulate relationships that are posited through the consideration of available data, information from scientific literature, and the best professional judgment of risk assessors developing the conceptual models. |
| Risk management | The process of evaluating and selecting alternative regulatory and non-regulatory responses to risk. The selection process necessarily requires the consideration of legal, economic, and behavioral factors. |
| River | A natural stream of water of considerable volume, larger than a brook or creek. |
| Secchi depth | A measurement of the transparency of surface water. The depth at which a Secchi Disk can no longer be seen. |
| Sediment diagenesis | Diagenesis refers to the sum of all the processes that bring about changes (e g., composition and texture) in a sediment or sedimentary rock subsequent to deposition in water. The processes may be physical, chemical, and/or biological in nature and may occur at any time subsequent to the arrival of a particle at the sediment‐water interface. |
| Simple linear regression | Linear regression is an approach for quantifying the relationship between a dependent (response) variable and an independent (explanatory) variable. In a simple linear regression, there is only one explanatory variable. |
| Sediment oxygen demand | The amount of dissolved oxygen removed from the water covering the sediment in a waterbody because of biological, chemical, and physical processes. |
| Stakeholders | People or organizations with an interest in the outcome of an assessment. |
| Steady-state | A state or condition of a system or process that does not change in time. |
| Stratification | The formation of separate layers (of temperature, salinity, plant, or animal life) in a water body. Each layer has similar characteristics such as all water in the layer has the same temperature. |
| Stream | In comparison to a river, a smaller flow of water in a channel or bed, also referred to as a brook, rivulet, or small river. |
| Stream order | A classification based on stream/tributary relationships. The uppermost channels in a drainage network (i.e., headwater channels with no upstream tributaries) are designated as first-order streams down to their first confluence. A second-order stream is formed below the confluence of two first-order channels. Third-order streams are created when two second-order channels join, and so on. Note that the intersection of a channel with another channel of lower order does not raise the order of the stream below the intersection (e.g., a fourth-order stream intersecting with a second-order stream is still a fourth- order stream below the intersection). |
| Stressor | Any physical, chemical, or biological entity that can induce an adverse response. |
| Stressor-response | The relationship between the intensity, frequency, or duration of exposure to a stressor and the intensity, frequency, or duration of a biological response. |
| Subaqueous | Existing, formed, or taking place in or under water. |
| Submerged aquatic vegetation (SAV) | Rooted, vascular plants that grow completely underwater except for periods of brief exposure at low tides. The term SAV is generally used for marine, estuarine, and riverine angiosperms, and macrophytes. |
| Temporal reference approach | Reference approach that collects observations during reference time periods. |
| Thalwegs | Longitudinal outline/trace/survey of a deepest part of riverbed from source to mouth (upstream/downstream). Line of steepest descent along the stream. |
| Tidal amplitude | The difference in elevation between mean sea level and high or low tide. |
| TMDL | Total Maximum Daily Loads, or TMDLs, is a calculation of the maximum amount of a pollutant that a waterbody can receive and still safely meet water quality standards. |
| Total suspended solids | Total suspended solids, or TSS, is a measure of filterable material suspended in water |
| Transition zone | The intervening area between distinct environments. |
| Type I error | False positive; the error made when the null hypothesis is rejected in favor of the alternative, when in fact the null hypothesis is true. |
| Type II error | False negative; the error made when the null hypothesis is accepted when in fact the alternative hypothesis is true. |
| Wadeable stream | A stream, creek, or small river that is shallow enough to be sampled using methods that involve wading into the water. Sometimes Ddefined as 1st, 2nd, 3rd order streams. |
| Water quality targets ((in the context of nutrient criteria) | Targets used in developing nutrient criteria to quantitatively define the level of nutrients that represents the ecological condition expressed by the management goal. |
| Weight-of-evidence | Describes the process of evaluating multiple lines of evidence, which includes quantitative weightings to information, in addition to other factors. |
| Zooplankton | Planktonic animals that float in the water and range in size from single-celled protozoa to comb jellies. |
| Acronym/Unit | Meaning |
|---|---|
| µg/L | Microgram per Liter |
| µM | Micromole |
| 1-D | 1 Dimensional |
| 2-D | 2 Dimensional |
| 3-D | 3 Dimensional |
| 3DEP | 3D Elevation Program |
| AAC | Academic Advisory Committee |
| ACWA | Association of Clean Water Administrators |
| AFDM | Ash Free Dry Mass |
| AGWA | Automated Geospatial Watershed Assessment |
| AHPS | Advanced Hydrologic Prediction Service |
| AIRMoN | Atmospheric Integrated Research Monitoring Network |
| ALI | Aquatic Life Indicators |
| AMoN | Ammonia Monitoring Network |
| ARS | Agriculltural Research Service |
| ASCII | American Standard Code for Information Interchange |
| AT2K | AlgaeTransect2K |
| ATTAINS | Assessment and Total Maximum Daily Load Tracking and Implementation System |
| BBST | Benthic Biomass Spreadsheet Tool |
| BCG | Biological Condition Gradient |
| BEACON | BEach Advisory and Closing Online Notification |
| BMI | Benthic Macroinvertebrate |
| BMP | Best Management Practice |
| BOD | Biochemical Oxygen Demand |
| CADDIS | Causal Analysis/Diagnosis Decision Information System |
| CAS | Chemical Abstracts Service |
| CASRN | Chemical Abstracts Service Registry Number |
| CBOD | Carbonaceous Biochemical Oxygen Demand |
| CBP | Chesapeake Bay Program |
| CBP | Chesapeake Bay Program |
| CDFs | Cumulative Distribution Functions |
| CDL | Cropland Data Layer |
| CDMO | Centralized Data Management Office |
| CDOM | Colored Dissolved Organic Matter |
| CeNCOOS | Central and Northern California Ocean Observing System |
| chl-a | Chlorophyll a |
| chlorophyllRS | Remotely Sensed Chlorophyll a |
| CO2 | Carbon Dioxide |
| CSV | Comma-Separated Values |
| CWA | Clean Water Act |
| DB | Database |
| DB2 | Database 2 |
| DD | Decimal Degrees |
| DEMs | Digital Elevation Models |
| DEP | Departent of Environmental Protection |
| DEP | Department of Environmental Protection |
| DEQ | Department of Environmental Quality |
| DHI | Danish Hydraulic Institute |
| DIN | Dissolved Inorganic Nitrogen |
| DIP | Dissolved Inorganic Phosphorus |
| DL | Detection Limit |
| DMR | Discharge Monitoring Report |
| DMS | Degrees, Minutes, and Seconds |
| DNA | Deoxyribonucleic Acid |
| DO | Dissolved Oxygen |
| DOC | Dissolved Organic Carbon |
| DOM | Dissolved Organic Matter |
| DON | Dissolved Organic Nitrogen |
| DOP | Dissolved Organic Phosphorus |
| DPV | Downstream Protection Value |
| DSM | Digital Surface Model |
| DWPC | Division of Water Pollution Control |
| ECOMSED | Estuary and Coastal Ocean Model with Sediment Transport |
| EDM | Estuary Data Mapper |
| EIA | Ecosystems Integration and Assessment |
| ELOHA | Ecological Limits of Hydrologic Alteration |
| EMAP | Environmental Monitoring and Assessmetn Program |
| EPA | Environmental Protection Agency |
| EPT | Ephemeroptera, Plecoptera and Trichoptera |
| ESRI | Environmental Systems Research Institute |
| FDEP | Florida Department of Environmental Protection |
| FE&C | Federal Enforement and Compliance |
| FTP | File Transfer Protocol |
| g/m2 | Gram per Square Meter |
| GA EDP | Georgia Department of Natural Resources |
| GBIF | Global Biodiversity Information Facility |
| GDG | Geospatial Data Gateway |
| GIS | Geigraphic Information System |
| GLOS | Great Lakes Observing System |
| GOMA | Gulf of Mexico Alliance |
| ha | Hectare |
| HAB | Harmful Algal Bloom |
| HABS | Harmful Algal BloomS |
| HABSOS | Harmful Algal BloomS Observing System |
| HAWQS | Hydrologic and Water Quality System |
| HBN | Hydrologic Benchmark Network |
| HDR | High Dose Rate |
| HUC | Hydrological Unit Code |
| IBI | Index of Biotic Integrity |
| IBWC | International Boundary and Water Commission |
| ICD | Interactive conceptual diagram |
| ICIS | Integrated Compliance Information System |
| IOOS | Integrated Ocean Observing System |
| ITIS | Intigrated Taxonomic Information System |
| IWR | Impaired Water Rule |
| kg | Kilogram |
| km | Kilometer |
| LAS | Land Application Systems |
| LPOC | Labile Particulate Organic Carbon |
| LPON | Labile Particulate Organic Nitrogen |
| LPOP | Labile Particulate Organic Phosphorus |
| LSPC | Loading Simulation Program in C++ |
| m | Meter |
| m2 | Square Meter |
| MA DEP | Massachusetts Department of Environmental Protection |
| MAF | Master Address File |
| MDEQ | Mississippi Department of Environmental Quality |
| MDL | Method Detection Limit |
| MEP | Massachusetts Estuaries Project |
| MERIS | Medium Resolution Imaging Spectroradiometer |
| mg | Milligram |
| mg/L | Milligram per Liter |
| mg/mg2 | Milligram per Square Meter |
| mg/m3 | Milligram per Cubic Meter |
| MMI | Multimetric Indices |
| MODIS | Moderate Resolution Imaging Spectroradiometer Aqua |
| MPCA | Minnesota Pollution Control Agency |
| MRLC | Multi-Resolution Land Characteristics Consortium |
| MS | Microsoft |
| MSDT | Model Selection Decision Tool |
| MSX | Multinucleated Sphere Unknown |
| MXD | Map Exchange Document |
| N | Nitrogen |
| NAD | North American Datum |
| NADED | North American Diatom Ecological Database |
| NADP | National Atmospheric Deposition Program |
| NANOOS | Northwest Association of Networked Ocean Observing systems |
| NARS | National Aquatic Resource Surveys |
| NASA | National Aeronautics and Space Administration |
| NASQAN | National Stream Quality Accounting Network |
| NASS | National Agricultural Statistics Service |
| NAWQA | National Water-Quality Assessment Program |
| NCC | Nutrient Criteria Committee |
| NCDC | National Climatic Data Center |
| NCEI | National Center for Environmental Information |
| NED | National Elevation Dataset |
| NEP | National Estuarine Programs |
| NERRS | National Estuarine Research Reserve System |
| NES | National Eutrophication Survey |
| NH4 | Ammonium |
| NHD | National Hydrography Dataset |
| NHDPlus | National Hydrography Dataset Plus |
| NHEP | New Hampshire Estuaries Project |
| NID | National Inventory of Dams |
| NLCD | National Land Cover Database |
| NNC | Numeric Nutrient Criteria |
| NNE | Nutrient Numeric Endpoint |
| NO2 | Nitrite |
| NO3 | Nitrate |
| NOAA | National Oceanographic and Atmospheric Administration |
| NPDAT | Nitrogen and Phosphorus Pollution Data Access Tool |
| NPDES | National Pollutant Discharge Elimination System |
| NPS | National Park Service |
| NPSCol2Row | National Park Service Column to Row Data Converter |
| NPSSTORET | National Park Service Storage and Retrieval |
| NSW | Nutrient Sensitive Waters |
| NSWS | National Surface Water Survey |
| NTN | National Trends Network |
| NWI | National Wetlands Inventory |
| NWIS | National Water Information System |
| NWQMC | National Water Quality Monitoring Council |
| NWRs | Nutrient Watershed Regions |
| NWS | National Weather Service |
| ODES | Ocean Data Evaluation System |
| OFS | Operational Forecast System |
| ORIs | Orthorectified Radar Intensity Images |
| ORSANCO | Ohio River Valley Water Sanitation Comission |
| P | Phosphorus |
| PAR | Photosynthetically Active Radiation |
| PBIAS | Percent Bias |
| PCS | Permit Compliance System |
| PFD | Precipitation Frequency Data Server |
| PIT | Priority Issue Team |
| PO4 | Phosphate |
| PO4-P | Soluble Reactive Phosphorus |
| PO4d | Dissolved Orthophosphate |
| PO4p | Particulate Orthophosphate |
| PO4t | Total Orthophosphate |
| POM | Princeton Ocean Model |
| ppb | parts per billion |
| ppm | parts per million |
| PQL | Practical Quantitation Limit |
| PTW | Phosphorus Technical Workgroup |
| QA | Quality Assurance |
| QAPP | Quality Assurance Project Plan |
| QC | Quality Control |
| QL | Quantitation Limit |
| RCA | Row-Column AESOP |
| RFC | River Forecast Center |
| RMS | Root Mean Squared |
| ROMS | Regional Ocean Modeling System |
| RPOC | Refractory Particulate Organic Carbon |
| RPON | Refractory Particulate Organic Nitrogen |
| RPOP | Refractory Particulate Organic Phosphorus |
| SA | Available Biogenic Silica |
| SAS | Statistical Analysis Software |
| SAV | Submerged Aquatic Vegetation |
| SCCOOS | Southern California Coastal Ocean Observing System |
| SCUBA | Self-Contained Underwater Breathing Apparatus |
| SeaWiFS | Sea-viewing Wide Field of View Sensor |
| Si | Silicon |
| SIM | STORET Import Module |
| SOD | Sediment Oxygen Demand |
| SPARROW | SPAtially Referenced Regression On Watershed Attributes |
| SPDES | State Pollution Discharge Elimination System |
| SQL | Structured Query Language |
| SRM | Stressor-Response Model |
| SRS | Sequence Retrieval System |
| SSURGO | Soil Survey Geographic database |
| STATSGO | State Soil Geographic database |
| STATSGO2 | State Soil Geographic database 2 |
| STEWARDS | Sustaining The Earth’s Watersheds – Agricultural Research Database System |
| STORET | STOrage and RETrieval and Water Quality eXchange |
| SU | Unavailable Silica |
| SWAT | Soil and Water Assessment Tool |
| SWCB | State Water Control Board |
| SWRCB | State Water Resources Control Board |
| TAC | Technical Advisory Committee |
| TCEQ | Texas Commission on Environmental Quality |
| TDP | Total Dissolved Phosphorus |
| TIAER | Texas Institute for Applied Environmental Research |
| TKN | Total Kjeldahl Nitrogen |
| TMDL | Total Maximum Daily Load |
| TN | Total Nitrogen |
| TP | Total Phosphorus |
| TSI | Trophic State Index |
| TSN | Taxonomic Serial Number |
| TSS | Total Suspended Solids |
| TVA | Tennessee Valley Authority |
| UMR-LPM | Upper Mississippi River-Lake Pepin Water Quality Model |
| URL | Uniform Resource Locator |
| USACE | U.S. Army Corps of Engineers |
| USDA | U.S. Department of Agriculture |
| USDOI | U.S. Department of the Interior |
| USFS | U.S. Forest Service |
| USGS | U.S. Geological Survey |
| UTM | Universal Transverse Mercator |
| VNRP | Voluntary Nutrient Reduction Program |
| WASP | Water Quality Analysis Simulation Program |
| WBD | Watershed Boundary Dataset |
| WDNR | Wisconsin Department of Natural Resources |
| WDS | World Geodetic System |
| WE&RF | Water Environment and Reuse Foundation |
| WEBB | Water, Energy, and Biogeochemical Budgets |
| WERF | Water Environment & Reuse Foundation |
| WIDNR | Wisconsin Department of Natural Resources |
| WQO | Water Quality Objective |
| WQP | Water Quality Portal |
| WQS | Water Quality Standards |
| WSS | Web Soil Survey |