TMDL glossary

A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U 

303(d) — The section of the Clean Water Act that has the TMDL requirements. The 303(d) list is a list of all impaired or threatened waters within the jurisdiction of a State, Territory, or authorized Tribe.

305(b) — The section of the Clean Water Act requiring states to report on progress in meeting the "fishable, swimmable" goals of the act.

Acute Water Quality Standards — Acute toxicity means a substance has been introduced that is severe enough to rapidly induce a response. In toxicity tests, a response is normally observed in 96 hours or less. Acute effects are often measured in terms of mortality or other debilitating effects. Acute water quality standards are set for individual pollutants at a level designed to protect 95 percent of the species in an aquatic community from acute effects, 95 percent of the time.

Aquatic life — Fish, invertebrates and other organisms that live in the water.

Bioassessment — An evaluation of the biological condition of a waterbody that uses biological surveys and other direct measurements of resident biota in surface waters. Most often evaluated is the fish population, the bottom dwelling insects and other invertebrates, and plants or attached algae. Data collected from bioassessments can be used to determine whether the biological health of the waterbody is what would be expected if pollution and other water quality stressors were not causing an effect. Bioassessment data are the foundation for developing biocriteria.

Biological criteria (biocriteria) — Numeric values or narrative expressions that are used to describe the reference biological condition of aquatic communities inhabiting waters of a given designated aquatic life use. Biologists and other natural resource scientists using bioassessments to characterize the ecoregion reference conditions for a state or tribe's waterbodies develop them. Biocriteria can be used in a variety of ways by water quality managers to determine if waters are affected by chemical pollution or other factors.

Biological integrity — The ability to support and maintain a balanced, integrated, and adaptive community of organisms having a species composition, diversity, and functional organization comparable to those of natural habitats within a region. Biological integrity is equated with pristine conditions or those conditions with no or minimal disturbance, and it is used as the baseline for the IBI.

Biotic impairment — A divergence from the expected biological condition of a lake, stream, or wetland. Practical methods exist for assessing impairment to a biological community, and they must be tested and refined for application to Minnesota. The methodology for Minnesota is being used as it is developed.

Chronic Water Quality Standards — The highest water concentration of a toxicant to which organisms can be exposed indefinitely without causing chronic toxicity. Chronic toxicity is a negative stimulus that lingers or continues for a long period of time, often one-tenth the life span or more. A chronic effect can be mortality, reduced growth, reproduction impairment, harmful changes in behavior, or other nonlethal effects. Chronic water quality standards are set for individual pollutants at a level designed to protect the aquatic community, or human or wildlife consumers of aquatic organisms, from any long-term adverse effects.

Condition monitoring — The purpose of this monitoring is to establish status and trends. Condition monitoring is designed to assess the condition of the state's waters, both in general and specific. This monitoring will identify problems, but may not collect enough data to identify the causes or sources of the problems. With adequate design considerations, condition monitoring can be used to determine trends over time or across areas of the state.

Conventional pollutants — Conventional pollutants include excessive nutrients, bacteria, turbidity, chlorides or stressors not related to bioaccumulative toxins such as mercury and PCBs. "Conventional TMDLs" are total maximum daily load projects addressing lakes or streams polluted by conventional pollutants.

Critical conditions — Critical conditions are the waterbody conditions associated with flow, season, water temperature, loading, beneficial use impacts, monitoring site location, and other water quality factors. 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.

Cultural eutrophication — Eutrophication caused by excess nutrients (in particular nitrogen and phosphorus) from anthropogenic sources, or sources that result from human activities.

Designated Uses — Specific uses identified for all waterbodies in the state, both surface water and ground water. Waters of the state are protected for multiple uses and water quality standards exist to protect those uses. Examples of designated uses are drinking water, aquatic life and recreation, agriculture, wildlife, industrial consumption, aesthetic enjoyment, and navigation.

DO — dissolved oxygen. Oxygen is necessary to maintain a healthy ecosystem for fish and other aquatic life in a waterbody.

Ecoregions — Areas where the land form, land use and water resources are similar. Ecoregions have been mapped by EPA for the lower 48 states based on overlying maps of land form, soil type, land use, and potential natural vegetation. Minnesota has seven ecoregions.

Ecoregion criteria — Data gathered from representative, minimally impacted (reference) lakes within each ecoregion are used as a basis for comparing the water quality and characteristics of other lakes in that ecoregion.

Effectiveness monitoring — The purpose of this monitoring is to determine the extent to which purposeful interventions had an effect on water conditions.

Eutrophic — high in nutrients, with high organic production. Eutrophic lakes contain more phytoplankton (algae) than other lakes, and are common among more naturally fertile lowland regions in which human activity provides an increased supply of nutrients.

Eutrophication — The aging process by which lakes are fertilized with nutrients. Natural eutrophication will very gradually change the character of a lake. Cultural eutrophication is the accelerated aging of a lake as a result of human activities.

Eutrophic Lake — A nutrient-rich lake, usually shallow, green in color, and with limited oxygen in the bottom layer of water.

Exceedences — The number of times a water quality standard or a permit limit was exceeded. Violations of a permit limit or a water quality standard.

Fecal Coliform bacteria — Bacteria that originate in the intestinal tract of a mammal. Not all fecal coliform bacteria cause disease, but this relatively simple test is used as an indicator that fecal matter is getting into the waterbody, and that other potentially harmful contaminants may be also be entering the waterbody. The main sources of these bacteria are from animal and human waste. Animal sources of bacteria include feedlot and manure runoff, urban runoff, and wildlife. Improperly treated human waste may come from overflows from sewage treatment systems in cities and towns, unsewered areas with inadequate community or individual wastewater treatment, or a single home with a failing septic system.

Geometric Mean — The geometric mean of 'n' fecal coliform samples is the nth root of their product. For example, the geometric mean of 5 values is the 5th root of the product of the 5 values.

Geomorphology — The geologic field that investigates physical processes that shape the surface of the earth, such as erosion and flooding and how rivers work. The study of the evolution and configuration of landforms. Often used in reference to the structure and shape of a stream or river channel.

GLI — The Great Lakes Water Quality Initiative established uniform water quality standards, implementation procedures, and nondegradation procedures for toxic chemicals in the Great Lakes basin. Particular emphasis was placed on persistent, bioaccumulative toxic chemicals. Standards and procedures applying to the Minnesota portion of the Lake Superior basin are included in Minnesota Rules Chapter 7052. All waters in the Lake Superior basin are GLI waterbodies.

IBI — The index of biotic integrity is a regionally based index used to measure the integrity of rivers and streams, and to determine the level of their biotic impairment. The IBI relies on multiple parameters (termed "metrics") based on fish community structure and function, to evaluate a complex biotic system. In order to implement biological criteria, a formal method for sampling the biota of streams, evaluating the resulting data, and clearly describing the condition of sampled stream reaches is needed. The IBI incorporates professional judgment with quantitative criteria that enables determination of a continuum between very poor and excellent conditions. An important key to successful restoration, mitigation and conservation efforts is having an objective way to assess and compare the biological integrity of damaged sites. The IBI provides a tool for doing so and, at the same time, allows managers to set specific biological integrity targets for restoration programs.

Impaired waterbody — A waterbody that does not meet water quality standards and designated uses because of pollutant(s), pollution, or unknown causes of impairment.

Load — The quantity that is or can be carried at one time, as compared to a concentration. A pollutant load is the quantity of a pollutant that a waterbody is carrying measured at a point in time.

Mercury — A metal that recycles between land, air and water. Mercury accumulates in fish and often results in fish consumption advisories for lakes and rivers. Mercury can have toxic effects on the nervous system of animals, including humans, that eat large quantities of fish. Mercury is naturally occurring, but most of the mercury entering waterbodies comes from mercury released by human activities. The main pathway of mercury to surface water is through atmospheric deposition. Major sources of mercury to the atmosphere include the burning coal and petroleum, metal smelting, and the use of mercury in manufacturing and products (such as switches, dental amalgam, and measuring instruments).

Metrics — Indices or parameters used in the IBI that measure an aspect of the structure, function, or other characteristic of the biological community that changes in some predictable way with changes in human influence. Since the metrics are differentially sensitive to various perturbations (e.g., siltation or toxic chemicals), as well as various degrees or levels of change within the range of integrity, conditions at a site can be determined with considerable accuracy. Some examples of fish community metrics used in the IBI are species richness and composition, trophic and reproductive constituents, and fish abundance and condition.

Minnesota Fish Consumption Advisory (MFCA) — Guidelines developed by the Minnesota Department of Health for how often fish in the state's waters can be safely eaten. Chemicals such as mercury, polychlorinated biphenyls (PCBs), toxaphene and dioxin have been found in some fish from certain waters. The advisory is a guide for choosing fish that are low in contaminants.

MN R Ch 7050 & 7052 — Minnesota Rules Chapters 7050 and 7052. These chapters contain the water quality standards for all waters of the state, both surface water and ground water. Chapter 7050 has the overall water quality standards for the state as well as specific standards for waterbodies, and Chapter 7052 has the water quality standards for waters in the Lake Superior Basin.

Multiple metrics — Multiple metrics can be used to assess the biological condition of a biotic system. Multimetric biological indexes calculated from biological monitoring data provide an integrative approach for measuring condition and "diagnosing" causes in complex ecological systems. Evaluations that measure multiple components of communities are recommended because they tend to be more reliable (e.g., measures of fish and macroinvertebrates combined will provide more information than measures of fish communities alone). The weaknesses of one measure or index can often be compensated by combining it with the strengths of other community measurements.

ng/l — nanograms per liter, or 0.000000001 grams per liter, or parts per trillion.

Nonpoint Sources — Pollution in runoff and seepage from land areas. The major origins of nonpoint source pollution include agricultural runoff; pesticide and fertilizer use; feedlot runoff; urban runoff from streets, yards, and construction sites; leachate from septic systems; runoff from forestry and mining activities; highway de-icing chemicals; and dredging and drainage activities.

NTU — nephelometric turbidity units. A unit of measure for turbidity values. Turbidity measured in NTU uses nephelometric methods that depend on passing specific light of a specific wavelength through the sample.

Point Sources — Pollution from municipal and industrial facilities, usually entering a waterbody via discharge from a pipe or a discrete channel.

Pollutant — Any sewage, industrial waste or other wastes, discharged into a disposal system or to waters of the state.

Pollutant load — See 'Load."

Pollution — Pollution of water, water pollution, or pollute the water means: (a) the discharge of any pollutant into any waters of the state or the contamination of any waters of the state so as to create a nuisance or render such waters unclean, or noxious, or impure so as to be actually or potentially harmful or detrimental or injurious to public health, safety or welfare, to domestic, agricultural, commercial, industrial, recreational or other legitimate uses, or to livestock, animals, birds, fish or other aquatic life; or (b) the alteration made or induced by human activity of the chemical, physical, biological, or radiological integrity of waters of the state. [Mn. Chapter 115.01; Subd. 5]

Priority Ranking — The "priority ranking" of an impaired water is indicated by the target start/completion schedule for each impairment on the current impaired waters list. The earlier the start date, the higher the priority for completing a TMDL project for that waterbody.

Project schedules are determined by looking at existing priorities in the basin that were set through the basin management process, and at local priorities set through the local water-planning process. Other local, state or federal priority considerations are also taken into account, ranging from severity of the impairment and risk to human health to readiness of public agencies to lead a TMDL project.

Problem investigation monitoring — The purpose of this monitoring is to develop a description of the causes and sources of impairment to the waterbody. Problem investigation monitoring is designed to focus on the inputs to the lake, stream, wetland or ground water aquifer with poor water quality conditions. Investigative monitoring provides information about the sources of stress to the system, thus allowing for a management plan to remove the stressors.

Reach — A section of a river or stream that generally extends from one tributary to another, or sometimes from a tributary to a dam or other feature. A reach is typically less than 20 miles in length. Water quality assessments of use support are made on individual river reaches using monitoring data for that reach, and other supporting data and information.

Reference conditions — The chemical, physical, or biological quality or condition exhibited at either a single site or an aggregation of sites that are representative of the least-impacted and attainable condition. Reference conditions are used to describe reference sites.

Reference site — Reference sites are used as the benchmark against which test sites are to be compared. The MPCA uses a regional reference site approach to develop and calibrate the IBI for specific regions of Minnesota.

Regional reference condition is a description of the chemical, physical, or biological condition based on an aggregation of data from least-impacted sites that are representative of a waterbody type in an ecoregion, subecoregion, watershed, or political unit. Using regional reference conditions is preferable to using data from a single reference site from which to compare biosurvey results.

Represented Reach — A reach that is represented by data collected on another, usually adjacent reach.

Riparian — Of, on or relating to the banks of a natural course of water. The landscape areas adjacent to a stream or river that have vegetation, soil, and hydrologic mosaics that are distinct from the predominate landscape surface types. In a broad sense, the riparian zone is both a transition and interface between riverine and upland systems. Functionally and structurally, riparian areas are different from surrounding uplands because of proximity to a watercourse. Riparian areas have unique features that provide desirable habitat for a variety of species. The same features that make these ecosystems relatively rare and important also make them relatively sensitive. Hydrologic changes to the waterbody also alter the associated riparian ecosystem. Riparian ecosystems generally occupy relatively small areas, and their occurrence along waterways makes them vulnerable to severe alteration caused by a variety of development activities.

Suspended Solids — Suspended solids limit sunlight, inhibit oxygen uptake by fish and alter aquatic habitat.

Threatened waterbody — A waterbody that currently attains water quality standards, but data and information indicate declining trends such that water quality standards will likely be exceeded in the next two years.

TMDL — Total maximum daily load. The maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. TMDL also refers to the process of allocating pollutant loadings among point and nonpoint sources.

EPA's proposed definition is: "A written plan and analysis of an impaired waterbody established to ensure that the water quality standards will be attained and maintained throughout the waterbody in the event of reasonably foreseeable increases in pollutant loads."

Trophic status — The level of growth or productivity of a lake as measured by phosphorus content, algae abundance, and depth of light penetration.

Trophy — of a lake refers to the rate at which organic matter is supplied by or to the lake per unit of time. Trophy is an expression of the combined effects of organic matter supplied to the lake. The trophic concept refers to the pelagial-zone (open water)-planktonic portion of the lake ecosystem.

Turbidity — Measures particles in the water, such as sediment and algae. Related to the depth sunlight can penetrate into the water. Higher turbidities reduce the penetration of sunlight in the water and can affect species of aquatic life that survive in the waterbody.

Un-ionized Ammonia — A form of ammonia that is toxic to fish.