All terms contained herein were initially derived from the following sources:  Ecosystem Charter for the Great Lakes - Glossary of Terms, Minnesota Sea Grant Glossary of the Great Lakes, various NOAA-GLERL web pages, from the NOAA Coastal Ocean Program, Science-Based Restoration Monitoring of Coastal Habitats and from the USGS Water Science Glossary of Terms. Modifications of these terms have been made by the Rivermouth Collaboratory membership to reflect current interpretations of these terms.

Relevant Terms:

Alongshore

Connecting Channels: See Interconnecting Waterways

Conservation: 

The protection, preservation, management, or restoration of natural environments and the ecological communities that inhabit them. Conservation is generally held to include the management of human use of natural resources for current public benefit and sustainable social and economic utilization. conservation. (n.d.). The American Heritage® Science Dictionary. Retrieved December 20, 2010, from Dictionary.com website: http://dictionary.reference.com/browse/conservation

Freshwater Estuary:

A freshwater estuary is a geomorphically  semi-enclosed rivermouth (transition zone between a terrestrial  drainage system and its' receiving waters)  in which transitional gradients in hydraulics, chemistry and temperature are enhanced by physical protection from dispersion by coastal currents.

Hydrodynamics

Interconnecting Waterway

 A stream or river emenating from a larger water body and eventually connecting to another large water body.  Within the Great Lakes context, this refers to rivers that connect one Great Lake to another.

Nearshore

Littoral Cell

Littoral System

Offshore

Rivermouth:

A rivermouth is the ecological transition zone occurring at the confluence of riverine and lacustrine ecosystems; typically characterized by dynamic hydraulic gradients, and high rates of deposition and biological assimilation of fluvial material loads.

Science Agenda

Upstream Terminus

 

Need to be Defined:

Adfluvial:  Migratory between lake and river, as in adfluvial fishes.  

Armoring

   The placement of stone, concrete, or other hard material along shorelines or on lake or stream beds to reduce wave- or flow-induced erosion.  Armoring is often done by humans to protect important structures (e.g., roads and bridges), although some natural sediment processes can lead to armored banks. 

Artificial or Hardened Shoreline

   Shorelines that are armored artificially to reduce wave- or flow-induced erosion.  These shorelines typically lack extensive vegetation or floodplain benches, although some artificial shorelines incorporate these features. 

Backwater Effect:

A diminution or reversal of flow driven by the attenuation of the dominant hydraulic energy gradient.

Baymouth / Barrier Beach Complex

Channel

Delta

   The area of sediment deposition associated with the mouth of a river or stream entering a large, slow moving water body.

Drowned rivermouth

  An area where a downcutting river channel is subsequently flooded by increasing lake/sea/ocean levels.

Groins or Groynes

Marsh and Marshland

Plume or River Plume 

   A body of water emerging from a rivermouth that remains chemically (e.g. dissolved elements) or physically (e.g. temperature) distinct from the surrounding lake/sea/ocean water.  The plume ends where it is no longer detectibly distinct from the surrounding waters.  

Receiving Basin or Receiving Waters

Revetment

Riparian

   The area along a stream channel where vegetation is influenced by the flow regime and hydrology of the stream.

Riverine

   Of, like, resembling, relating to, or derived from a river or stream.

Wetlands

Previously accepted definitions:

Abiotic - non-living.

Acidic - Any compound capable of neutralizing alkalis; having a pH of less than 7.

Acute Toxicity - Adverse effects to a plant or animal that result from an acute exposure to a stimulant such as a pollutant. The exposure usually does not constitute a substantial portion of the life span of the organism. In standard laboratory toxicity tests with aquatic organisms, an effect observed in 96 hours or less is typically considered acute. Also described as a stimulus severe enough to induce an effect.

Aerobic - A term that describes organisms or processes that require the presence of molecular oxygen.

Aerosol - very fine airborne droplets.

Air Toxics -Substances that cause or contribute to air pollution and which can cause serious health and environmental hazards, such as cancer or other illnesses.

Algae - Simple plants found in water and elsewhere that have no roots, flowers or seeds. These are usually microscopic plants and are the primary producers in lakes. See also phytoplankton and periphyton.

Algal bloom - A condition which occurs when excessive nutrient levels and other physical and chemical conditions facilitate rapid growth of algae. Algal blooms may cause changes in water color. The decay of the algal bloom may reduce dissolved oxygen levels in the water.

Alkaline - Acting like a base; having a pH of more than 7.

Alkalinity - measure of the ability of a solution to neutralize acids. Sum of the bases in solution.

Alluvial plain - the floodplain of a river, where the soils are deposited by the overflowing river.

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..

Amphibian - a member of the class Amphibia, which includes frogs and salamanders. A vertebrate animal which begins life as an aquatic larvae with gills and transforms to a terrestrial or semi-terrestrial adult with lungs.

Amphipod - An omnivorous member of a group of small crustaceans that includes shrimp, sea lice and sand fleas.

Anadromous - migrating upstream to breed, usually from saltwater to freshwater.

Anaerobic - A term that describes processes that occur in the absence of molecular oxygen. See also anoxia.

Anoxia - The absence of oxygen or a deficiency of oxygen that is harmful to living organisms. Anoxic conditions can develop in a lake bottom when oxygen is depleted by decomposition processes. This often happens in eutrophic lakes and can result in fish kills. See also anaerobic.

Anthropogenic - Anything that is human-caused or derived.

Aquaculture - cultivation of aquatic organisms, fish farming.

Aquatic - living in the water

Aquatic Nuisance Species (ANS) - Water-borne plants or animals that pose a threat to humans, agriculture, fisheries, and/or wildlife resources. See also, non-indigenous species, zebra mussel, Bythotrephes, Eurasian ruffe, Eurasian watermilfoil.

Aquatic Nuisance Species Task Force - An international organization that develops and implements programs to prevent the introduction and distribution of aquatic nuisance species. Their goal is to monitor, control, and study these species, and to disseminate technical and educational information. Made up of 19 provincial, state, and federal organizations.

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.

Area of Concern (AOC) - Areas of the Great Lakes identified by the International Joint Commission as having serious water pollution problems requiring remedial action and the development of a Remedial Action Plan. AOCs are defined in the Great Lakes Water Quality Agreement as follows: ... a geographic area that fails to meet the general or specific objectives of the Great Lakes Water Quality Agreement, or where such failure has caused or is likely to cause impairment of beneficial use or of the areas ability to support aquatic life. Initially, there were 43 AOCs in the Great Lakes Basin. The 8 AOCs in Lake Superior are; Deer and Torch Lakes in Michigan, St. Louis River in Minnesota and Wisconsin, Jackfish Bay, Nipigon Bay, Thunder Bay, and Peninsula Harbour in Ontario, and St. Marys River in Michigan and Ontario. Related Programs - Great Lakes Water Quality Agreement, Remedial Action Plans

Artesian - 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.

Arthropod - literally, joint-foot. A member of the phylum Arthropoda, which includes insects, arachnids and crustacea. Invertebrates with a hard chitonous exoskeleton, a segmented body with appendages

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.

Asexual - without sex. Reproduction with only one parent and no mixing of genes producing offspring identical to the parent.

Assemblage - Collection: several things grouped together or considered as a whole.

Atmospheric Deposition - Pollution that travels through the air and falls on land and water. Related Programs - Clean Air Act, Great Lakes Toxic Reduction Effort

Attenuation - to lessen the amount, force, magnitude, or value of.

Backwater - a body of water in which the flow is slowed or turned back by an obstruction such as a bridge or dam, an opposing current, or the movement of the tide or lake seiche phenomena.

Bacterium, bacteria (pl) -unicellular organism of the Kingdom Monera. Prokaryotes in which the cells have no defined nucleus, but the genetic material (DNA) is scattered throughout the cell.

Ballast - device or weight used to stabilize a ship, especially when it is not loaded with cargo.

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.

Baseline measurements - a set of measurements taken to assess the current or pre-restoration condition of a community or ecosystem.

Bathymetric - Pertaining to the measurement of depth in bodies of water; also, pertaining to the distribution of organisms over various depths.

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.

Beneficial organisms - Organisms inhabiting the Great Lakes-St. Lawrence Basin Ecosystem that are not known to threaten ecosystem integrity or otherwise have any harmful impacts on the ecosystem or the beneficial uses of ecosystem resources.

Beneficial uses - Those activities that are dependent on the chemical, physical and biological integrity of the waters of the Great Lakes system; the impairment of which is identified under Annex 2 of the Great Lakes Water Quality Agreement.

Beneficial Use-Impairment - A negative change in the health of a water body making it unusable for a beneficial use that has been assigned to it. Examples of these use impairments as designated in the Great Lakes Water Quality Agreement include: restrictions on fish and wildlife consumption, beach closings, degradation to aesthetics, loss of fish and wildlife habitat, and restrictions on drinking water consumption.

Benthic - A term that describes both organisms and processes that occur in, on, or near, a lakes bottom sediments. See also benthos.

Benthic Invertebrate - Refers to animals with no backbone or internal skeleton that live on the bottom of lakes, ponds, wetlands, rivers and streams and among aquatic plants. Benthic invertebrates provide an essential source of food for young and adult fish, wildlife and other animals. Examples include caddisflies, midge larvae, scuds, waterfleas, crayfish, sponges, snails, worms, leeches, and nymphs of mayflies, dragonflies and damselflies. The benthic invertebrate Diaporeia, is an ecosystem indicator.

Benthos - A term applied to organisms that live on or in a lakes bottom and/or bottom sediments. See also benthic.

Best Management Practice (BMP) - Methods used to control nonpoint source pollution by modifying existing management practices. BMPs include the best structural and non-structural controls and operation and maintenance procedures available. BMPs can be applied before, during and after pollution-producing activities, to reduce or eliminate the introduction of pollutants into receiving waters.

Biennial - every two years. A plant which produces flowers every second year.

Bioaccumulation - Any substance that has the ability to bioaccumulate, where bioaccumulate means the retention of a chemical in the tissues of an organism as a result of uptake from all routes of exposure (i.e., absorption, consumption). The net accumulation of a substance by an organism as a result of uptake from all environmental sources. As an organism ages it can accumulate more of these substances, either from its food or directly from the environment. Bioaccumulation of a toxic substance has the potential to cause harm to organisms, particularly to those at the top of the food chain. The pesticide, DDT, is an example of a chemical that bioaccumlates in fish and then in humans, birds, and other animals eating those fish. See also accumulation and biomagnification.

Bioavailability - A measure of how available a toxic pollutant is to the biological processes of an organism. The less the bioavailability of a toxic substance, the less its toxic effect on an organism.

Biochemical - chemical found in or produced by a living organism

Biocontrol - control using biological means. Usually implies deliberately introducing one type of organism to control another.

Bioindicator - An organism and/or biological process whose change in numbers, structure or function points to changes in the integrity or quality of the environment.

Biofouling - biological fouling. Undesirable accumulation of organisms on underwater objects including ship hulls, intake pipes, etc.

Biological Control - A method of controlling a disease-causing organism or pathogen or an exotic species. A biochemical product or bioengineered or naturally-occurring organism is used to cause death, inhibit growth, or inhibit the reproduction of an unwanted organism. One example is the import and use of the European beetle that feeds exclusively on Purple Loofestrife.

Biological diversity/biodiversity - The full range of variety and variability within and among living organisms and the natural associations in which they occur.

Biological Oxygen Demand (BOD) - This is a measurement of the oxygen depletion in a water sample incubated under controlled conditions over a period of time. The aerobic decomposition of organic matter by bacteria in the sample requires oxygen. BOD is an important measurement of the impact that sewage discharge may have upon a water body because a certain amount of oxygen will be used in the breakdown of the wastewater.

Biomagnification - The process by which the concentration of a substance increases in different organisms at higher levels in the food chain. For example, if an organism is eaten by another organism these substances move up the food chain and become more concentrated at each step. See also bioaccumulation and accumulation.

Biomass - the mass (weight) of a living organism or organisms

Biomonitor - similar to a bioindicator, but the correlation between the indicator and environmental variable is sufficiently strong to quantify the impact.

Bivalve - with two shells. Organisms of the Class Bivalvia, which includes clams and mussels.

Blue-green alga - also known as cyanobacteria. Photosynthetic prokaryotes.

Boreal - northern, colder waters

Boundary Waters Treaty - The international treaty between the United States and Great Britain signed on January 11, 1909, regarding the waters joining the two nations and relating to questions arising between the United States and Canada. It gave rise to the International Joint Commission.

Brachiopod - Two-valved marine animals which somewhat resemble bivalve mollusks but do not belong in the Mollusca.

Brackish - intermediate salinity between fresh and marine salt concentrations.

Brood - young hatched or cared for at one time. To care for young.

Buoyant - Floats easily, and is less dense than water.

Business Case - The business need that a project intends to address. A business case includes the reasons for the project, the expected benefits, options and alternatives, and expected costs.

Calcareous - a sediment, sedimentary rock, or soil type which is formed from or contains a high proportion of calcium carbonate in the form of calcite or aragonite.

Calcified - Hardened from the deposit of calcium salts; become unchanging or inflexible.

Canal - channel. Artificial waterway.

Carcinogenic - cancer-causing

Cardinal - of foremost importance

Carnivore - consumes food from trophic levels 2 or above, i.e., animal food.

Carrier - one who carries a disease, parasite, medical condition or genetic trait without showing symptoms.

Catchment - the land area drained by a river or stream; also known as "watershed" or "drainage basin"; the area is determined by topography that divides drainage between watersheds.

Causal - cause.

Cell - small compartment, basic structural and functional unit of all organisms.

Chlordane - A critical pollutant that was used as a pesticide until banned by the U.S. in 1983 (except for use in controlling underground termites). Chlordane bioaccumulates in the food chain. Concentrations are highest in fat and liver tissue of predatory species. It has been detected in lake trout and other wildlife.

Chloride - One of seven major ions in most natural waters; Increased levels of chloride will heighten the corrosive effects of water; combined with sodium, causes a salty taste.

Chlorinated Organic Compounds - Organic chemicals that contain chlorine, including many pesticides and industrial chemicals such as PCBs, DDT, chlorinated dioxins and furans, dieldrin, and hexachlorobenzene. Also called organochlorines, chlorinated organics.

Chlorine - A common, naturally-occurring element. One form of chlorine is a highly poisonous gas that is typically used for water disinfection, sewage treatment and the manufacture of bleach and other chemicals.

Chlorophyll -  pigment found in photosynthetic organisms, all algae have chlorophyll a; chlorophylls b, c, and d are found in one or more groups of algae

Chlorophyll A (Chla) - A measurement of a specific green pigment found in all plants including microscopic plants such as algae. It is used as an estimate of algal biomass of algae.

Chromosome - A structure in the cell nucleus that contains DNA, histone protein, and other structural proteins.

Chronic - marked by long duration or frequent recurrence

Chronic Toxicity - A harmful and delayed response (such as death, unusual growth, reduced reproduction, disorientation to a chemical that causes adverse effects over a long period of time, relative to an organisms natural life span. In standard laboratory tests an effect observed in 96 hours or more is considered a chronic effect.

Class - Major division of a phylum. There are six (or seven) classes in Mollusca.

Clean Air Act (CAA) - Federal law originally passed in 1970 for the purpose of protecting and enhancing the quality of the nation's air resources. legislation was passed in 1990 that amended the Clean Air Act, which resulted in major changes further limiting the generation of air pollution in the United States.

Clean Water Act (CWA) -  A federal law that identifies national requirements to protect the nation's waters. Originally known as the Federal Water Pollution Control Act. The act is divided into six Subchapters (33 U.S.C. 1251-1387).

Clone - a group of genetically identical cells or organisms derived from a single cell or individual by some kind of asexual reproduction.

Coastal habitat restoration - the process of reestablishing a self-sustaining habitat in coastal areas that in time can come to closely resemble a natural condition in terms of structure and function.

Coastal Waters - In the Great Lakes Basin, coastal waters are defined in the Coastal Zone Management Act as the waters within the territorial jurisdiction of the United States consisting of the Great Lakes, their connecting waters, harbors, roadsteads, and estuary-type areas such as bays, shallows, and marshes.

Coastal Zone - Each state defines its coastal zone differently. While some use specific "distance from the high water mark" to define the upland boundary of their coastal zone, other states include the entire coastal watershed. In the Great Lakes basin, the seaward boundary of each state, pursuant to the Submerged Lands Act , extends "to the international boundary between the United States and Canada" (43 USC 1312 (2005)). The only exception to this rule is in Lake Michigan, which lies entirely within the United States; there the state jurisdictional boundaries have been defined by the states that border that lake (MCL 2.201 (1947)). All considered, the "coastal zone" of the 8 Great Lakes states is more than 14,000 square miles, larger than the surface area of Lake Erie. (see http://www.glin.net/envt/air-land/coastal.html)

Coastal Zone Management Act (CZMA) - A federal law enacted in 1972 to deal with increasing stresses on the nation's coastal areas, including the Great Lakes. Administered by National Oceanic and Atmospheric Administration, the CZMA provides money, technical help, and policy guidance to states for balancing conservation and development of coastal resources. Under CZMA, states voluntarily develop their own Coastal Zone Management programs.

Cobble - A particular size of rock, larger than gravel.

Collaboratory - A "collaboratory" is a recent term describing a working environment where regionally-dispersed scientists and resource managers can commit to development and implementation of a common science-based partnership. Participants make use of computing and communication technologies to access shared instruments and data, as well as to communicate with others (Wikipedia 2010). Participants make use of computing and communication technologies to access shared instruments and data, as well as to communicate with others (Wikipedia 2010) .A collaboratory, as defined by William Wulf in 1989, is a "center without walls, in which the nation's researchers can perform their research without regard to physical location, interacting with colleagues, accessing instrumentation, sharing data and computational resources, and accessing information in digital libraries". This environment encourages: 1) vigorous, critical discussions of science approaches; 2) broad sharing of ideas, knowledge and tools; 3) inter-disciplinary, and inter-agency working partnerships; and 4) an ongoing, iterative, adaptive science process at a regional scale.

Colony - a group of individuals living and acting together, often functioning as a single individual.

Combined Sewer Overflow - Occurs when heavy rainfall or thaw conditions overload a sewer system designed to carry both waste and stormwater. The result is the discharge of untreated sewage into receiving waters. Also refers to the outfall structures themselves.

Community - a group of interdependent organisms inhabiting the same region and interacting with each other.

Comparative Risk Analysis - A procedure for ranking environmental problems by their seriousness (relative risk) for the purpose of assigning them program priorities. Typically, teams of experts put together a list of problems, sort the problems by types of risk, then rank them by measuring them against standards, such as the severity of effects, the likelihood of the problem occurring among those exposed, the number of people exposed and the like. Relative risk is then used to set priorities. See also risk assessment, risk management, ecological risk assessment.

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.

Conductivity - the transmission of heat or electricity or sound.

Confined Disposal Facility (CDF) - A facility providing a contained disposal area for contaminated sediments removed during dredging operations.

Confluence - The transect where two or more rivers or streams meet to flow together as to form one.

Contiguous - Connected, touching, abutting; adjacent, neighboring; connecting without a break.

Copepod - minute marine or freshwater crustaceans usually having six pairs of limbs on the thorax; some abundant in plankton and others parasitic on fish.

Council of Great Lakes Research Managers - A binational advisory group to the International Joint Commission to evaluate the status of Great Lakes research.

Criteria Pollutants - A group of air and water pollutants regulated by the EPA under the Clean Air Act and Clean Water Act on the basis of criteria that includes information on health and environmental effects. Criteria pollutants include particulates, some metals, organic compounds and other substances attributable to discharges.

Critical Pollutant - Chemicals that persist at levels that are causing or could cause impairment of beneficial uses lakewide. Other critical pollutants will be added to the list, but the Lake Superior Lakewide Management Program will first focus on the same nine critical pollutants identified in the zero discharge demonstration program (TCDD, OCS, HCB, Chlordane, DDT, Dieldrin, Toxaphene, PCBs, and Mercury). See also Great Lakes Critical Pollutants.

Crustaceans - any mainly aquatic arthropod usually having a segmented body and chitinous exoskeleton.

Cyanobacteria - Group of mostly freshwater algae with blue-green pigment; often referred to as blue-green algae; may occur as a single cell or as a colony of cells.

Decomposition - The breakdown of complex organic substances into more simple organic chemicals or substances. The ultimate product of decomposition in an aerobic environment is carbon dioxide.

Debris- detritus, the remains of something that has been destroyed or broken up

Decompose - break down.

Degeneration - passing from a more complex to a simpler biological form.

Demographic - Of or relating to demography (the statistical study of populations).

Desiccation- dehydration: dryness resulting from the removal of water.

Designated Uses - The role that a water body is slated to fulfill, such as a drinking water source. Uses are specified in water quality standards for each water body or segment, whether or not the current water quality is high enough to allow the designated use. Other typical uses of a water body include propagation of fish and wildlife, recreation, agriculture, industry, and navigation.

Deterioration - a symptom of reduced quality or strength

Detrimental - causing harm or injury

Detritus - Litter formed from fragments of dead material in aquatic environments.

Diadromous - migratory between fresh and salt waters.

Diatom - microscopic unicellular marine or freshwater colonial alga having cell walls impregnated with silica.

Diatomaceous earth - siliceous geological deposits made up of diatom frustules.

Dichlorodiphenyltrichloroethane (DDT) - DDT, one of the nine critical pollutants, was commonly used as an insecticide after World War II and is now banned in the U.S. and Canada. DDT and its metabolites are toxic pollutants with long-term persistence in soil and water. They concentrate in the fat of wildlife and humans and may disrupt the human body's chemical system of hormones and enzymes. DDT caused eggshell thinning in a number of fish-eating birds and is associated with the mortality of embryos and sterility in wildlife, especially birds. DDT still enters the Great Lakes, probably from a number of sources including airborne transport from other countries, leakage from dumps, and the illegal use of old stocks.

Dieldrin - Dieldrin, a critical pollutant, was used as a pesticide for veterinary uses and to control soil insects. In the U.S. and Canada, its use is now restricted to termite control. Dieldrin has a long half-life in shallow waters compared to most chlorinated organic compounds. It is acutely toxic and poses a potential carcinogenic threat to humans. This chemical enters the Great Lakes System from the air or contaminated sediments and has been detected in fish and wildlife in all of the Great Lakes.

Dioxin (TCDD) -  A critical pollutant considered to be highly toxic, 2,3,7,8 tetrachlorodibenzo-p-dioxin or TCDD is a variant in a family of 75 chlorinated organic compounds referred to as dioxins. An unwanted chemical byproduct of incineration and some industrial processes that use chlorine, dioxin tends to accumulate in the fatty tissue of fish. Dioxin is a suspected human carcinogen. 

Discharge - Any release or unloading of a substance or materials from a pipe, or other emission source. The addition of any pollutant to the Waters of the State or to any disposal system from a point source.

Discharge of Dredged or Fill Material - Any addition of dredged or fill material into navigable waters or into the waters of the United States. This includes the driving of pilings and the addition of any material that changes the bottom elevation or configuration of a water body or material that might destroy or degrade any navigable water. 

Dissolved oxygen - oxygen dissolved in water and available to aquatic organisms; one of the most important indicators of the condition of a water body; concentrations below 5 mg/l are stressful and may be lethal to many fish and other species.

Diurnal - having a daily cycle or occurring every day.

Dominant species — a plant species that exerts a controlling influence on or defines the character of a community.

Downwelling - the process of build-up and sinking of warm surface waters along coastlines.

Drainage - watershed; the land, rivers, etc draining into a water body.

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 Great Lakes contain thousands of smaller drainage basins. Also called a "watershed."

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

Dreissenid - belonging to a family of small freshwater mussels, aquatic bivalve mollusks. They attach themselves to stones or to any other hard surface using filaments. For the Great Lakes, includes zebra and quagga mussels.

Drift line - A line of debris left by waves at the high-tide line in marine environments or at the ordinary high water mark in freshwater environments.

Dry Deposition - The deposition of pollutants from the atmosphere that occurs during dry weather periods (such as dust and particulate matter). Dry deposition rates are often drastically different than wet deposition rates.

Duration - a span or interval of time.

Ebb - a period of fading away; low tide.

Echolocate - Locate and discriminate among objects by producing sounds and then hearing the echo.

Emergent Vegetation - Plants that are rooted in the water but with most of the plant growing above the surface of the water, such as cattails and wild rice.

Ecological Risk Assessment - An organized procedure to evaluate the likelihood that adverse ecological effects will occur as a result of exposure to stressors related to human activities, such as the draining of wetlands or release of chemicals.

Ecological processes - The flow of energy and nutrients (including water) through an ecosystem.

Ecology - The study of the effect and relationship of environment on an organism.

Ecosystem - A biological community and its environment working together as a functional system, including transferring and circulating energy and matter. An interacting system consisting of groups of organisms and their non-living or physical environment, which are highly interrelated.

Ecosystem approach - An approach to perceiving, managing and otherwise living in an ecosystem that recognizes the need to preserve the ecosystem's biochemical pathways upon which the welfare of all life depends in the context of multifaceted relationships (biological, social, economic, etc.) that distinguish that particular ecosystem.

Ecosystem-based management - Stewardship of our living natural resources to maintain the functional integrity of large, complex environmental units called ecosystems. Ecosystem-based management is an active process that emphasizes the maintenance of biological diversity, of natural relationships among species, and dynamic processes that make ecosystems sustainable.

Ecosystem Indicator - An organism or community of organisms that is used to assess the health of an ecosystem as a whole. For example, the Binational Program has selected the lake trout and Diaporeia (a benthic invertebrate) to be indicator species for Lake Superior.

Ecosystem integrity - The ability of an ecosystem to maintain its organization (i.e., structures, processes, diversity) when confronted with environmental disturbance and change.

Ecotype - a genetically distinct geographic population within species (or among closely related), which is adapted to specific environmental conditions such as local selective pressure or physical isolation.

Effluent - Liquid wastes that are discharged into the environment as a by-product of human-oriented processes, such as waste material, liquid industrial refuse, or sewage.

Egg Bank - large number of diapausing eggs found in pond and lake sediments. Their presence is thought to ensure survival in temporary ponds or in permanent bodies of water to ensure the continuation of a population through periods of poor recruitment and help create conditions for the coexestence of competing species.

Ellipsoid - Being the figure of revolution of an ellipse, an ellipsoid, when rotated around the major axis. 3 dimensional oval.

Endangered Species Act (ESA) - Federal statutes passed in 1973 that protect endangered and threatened species. The act has 16 sections.

Endemic - Native to, and restricted to, a particular geographical region. Highly endemic species are those with very restricted natural ranges; they are especially vulnerable to extinction if their natural habitat is eliminated or significantly disturbed.

Environmental Impact Assessment (EIA) - A decision-making process mandated under the National Environmental Policy Act which may require a detailed environmental impact statement analyzing the potential significant environmental impacts and alternatives to the action before the action is permitted. A public comment period takes place on each EIA.

Environmental Impact Statement (EIS) - A statement detailing the environmental impacts of and the alternatives to an action. See Environmental Impact Assessment.

Environmental Monitoring and Assessment Program (EMAP) - A federal program initiated by the EPA in 1988 to provide improved information on the current status and long-term trends in the condition of the nation's ecological resources. Seven resource categories are defined: near coastal waters, the Great Lakes, inland surface waters, wetlands, forests, arid lands, and agroecosystems.

Epifaunal - animals living on the surface of the sediment or other substrate such as debris.

Epiphyte - plant that derives moisture and nutrients from the air and rain; usually grows on another plant but not parasitic on it.

Erosion - The wearing away of the land surface by running waters, glaciers, winds, and waves. Erosion occurs naturally from weather or runoff but can be intensified by land-clearing practices related to farming, residential or industrial development, road building, or timber cutting.

Estuary (Freshwater) - Areas of interaction between rivers and nearshore lake waters, where seiche activity and river flow create a mixing of lake and river water. These areas may include bays, mouths of rivers, marshes, and lagoons. These ecosystems shelter and feed fish, birds, and wildlife. Most importantly, Great Lakes estuaries provide habitat for wildlife and for young-of-the-year and juvenile fish.

Eulittoral - refers to that part of the shoreline that is situated between the highest and lowest seasonal water levels.

Euphotic - Refers to the surface layer of the ocean that receives enough sunlight for photosynthesis.

Eurasia - region of eastern Europe and western Asia.

Eurasian Ruffe - A non-indigenous species, which is a member of the perch family. It is usually less than 6 inches long, has a perch-like body shape and is very slimy when handled. This fish may be competing with native perch and other fish for food. There is a great deal of concern over the potential for this fish to expand its range into other North American waters. It has also been called the European ruffe and river ruffe. See also aquatic nuisance species.

Eurasian Watermilfoil - An exotic aquatic macrophyte that forms thick underwater stands of tangled stems and vast mats of vegetation on the surface of inland lakes. In many shallow areas this plant can crowd out native plants and interfere with water recreation such as boating, fishing and swimming. The plant can spread from lake to lake by stem fragments that cling to boats and trailers. Public education campaigns aimed at preventing unintentional transport of the plant by boaters have successfully slowed its spread in some states. See also aquatic nuisance species.

Eutrophic - A term used to classify those lakes of high primary productivity as indicated by high algal concentrations or high nutrient levels. Having waters rich in mineral and organic nutrients that promote a proliferation of plant life, especially algae, which reduces the dissolved oxygen content and often causes the extinction of other organisms.See also eutrophication.

Eutrophic - designating a body of water in which the increase of mineral and organic nutrients has reduced the dissolved oxygen, producing an environment that favors plant over animal life.

Eutrophication - The process of physical, biological, and chemical changes that occurs in a lake when enriched by nutrients, organic matter, and/or silt and sediments. The process can occur naturally, but if accelerated by human activities such as agriculture, urbanization, and industrial discharge, it is called cultural eutrophication.

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

Evapotranspiration - the combination of water that is evaporated and transpired by plants as a part of their metabolic processes.

Exotic Species - See non-indigenous species.

Exposure - Contact with a chemical or physical agent.

Exposure Assessment - Estimates the amount of a substance something is exposed to.

Extirpation - local extinction, removal of all of a type of organism from a specific geographic area.

Family - taxonomic classification, group of genera collectively showing relationship.

Fauna - Animal life of a particular area or epoch; as opposed to Flora, for all plant life.

Fecal Coliform - any of several bacilli, especially of the genera Escherichia, found in the intestines of animals. Their presence in water suggests contamination with sewage of feces, which in turn could mean that disease-causing bacteria or viruses are present. Fecal coliform bacteria are used to indicate possible sewage contamination. Fecal coliform bacteria are not harmful themselves, but indicate the possible presence of disease-causing bacteria, viruses, and protozoans that live in human and animal digestive systems. In addition to the possible health risks associated with them, the bacteria can also cause cloudy water, unpleasant odors, and decrease dissolved oxygen in the water.

Fetch - the distance along open water or land over which the wind blows.

Fill Material - Material used to convert a water body into dry land or change its configuration or bottom elevation.

Filter-feeder - Any aquatic animal that obtains nourishment by filtering particles of food from the water in which it lives.

Fish Consumption Advisory - An advisory issued by a government agency recommending that the public limit their consumption of fish. Advisories are issued to limit exposure to toxic substances in the fish that have the potential to impact human health. Fish caught from selected lakes and streams are tested for toxic substances (mercury, sometimes PCBs and dioxins). Many of the lakes tested have restrictions on fish consumption due to high mercury levels. PCBs and dioxin levels in fish have also resulted in suggested restrictions on fish consumption in some lakes and streams.

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.

Flooding regime - pattern of flooding over time.

Floodplain - a strip of relatively flat land bordering a stream channel that may be overflowed at times of high water; the amount of land inundated during a flood is relative to the severity of a flood event.

Flora - plants collectively, especially the plants of a particular region or time

Fluctuate - 1. To vary irregularly. 2. To rise and fall in or as if in waves; undulate.

Fluvial - of, relating to, or living in a stream or river.

Flushing Time - See residence time.

Food chain - interrelations of organisms that feed upon each other, transferring energy and nutrients; typically solar energy is processed by plants who are eaten by herbivores which in turn are eaten by carnivores: sun -> grass -> mouse -> owl.

Food Webs - Interacting food chains in an ecological community.

Forage - wander and feed

Foreshore - The intertidal zone. ????

Fossil - Any hardened remains or traces of plant or animal life of some previous geological period, preserved in rock formations in the earth's crust.

Freighter - ship carrying freight (cargo).

Frequency - how often something happens.

Fresh water - water containing less than 0.5% salts.

Function - refers to how wetlands and riparian areas work - the physical, chemical, and biological processes that occur in these settings, which are a result of their physical and biological structure regardless of any human benefit.

Functional habitat characteristics - parameters that describe what ecological service a habitat provides and may be used as a measure to determine how well a particular place performs a specific function.

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.

Gastrointestinal - of or relating to the stomach and intestines.

Gastropod - a class of mollusks typically having a one-piece coiled shell and flattened muscular foot with a head bearing stalked eyes.

General Permit - An Army Corps of Engineers authorization that is issued on a nationwide or regional basis for categories of human activities within navigable waters of the U.S.  General permits are issued when: (1)these activities are substantially similar in nature and cause only minimal individual and cumulative environmental impacts; or (2) the general permit would result in avoiding unnecessary duplication of the regulatory control exercised by another federal, state, or local agency provided it has been determined that the environmental consequences of the action are individually and cumulatively minimal. There are three types of general permits, Regional Permits, Nationwide Permits, and Programmative Permits.

Geomorphic - pertaining to the form of the Earth or its surface features.

Geomorphology - the science that treats the general configuration of the Earth's surface; the description of landforms.

Genome - the full DNA sequence of an organism

Genotype - the genetic makeup of an individual; for a particular trait, you can't always tell the genotype by looking at the phenotype.

Genus - Group of genetically related species possessing certain characters in common and easily separable from other groups of species. A taxonomic rank for closely related species which share a common phylogenetic origin.

Germinate - To start or cause to start a process of growth or development; sprout.

GLIN GIS - The Maps and GIS section of the Great Lakes Information Network (GLIN) website (http://gis.glin.net) provides a centralized location to discover, publish, and acquire geospatial data for areas within the Great Lakes region.

Great Lakes Critical Pollutants (GLCP) -  Substances (a total of 138) currently identified as most critical to improving water quality under four major Great Lakes Initiatives: The Great Lakes Water Quality Initiative, the Lake Michigan Lakewide Management Plan, the Lake Ontario/Niagara River Four Party agreement, and the Lake Superior Binational Program Agreement. Each of the four initiatives may define critical pollutants differently.

Great Lakes Critical Programs Act - Federal legislation in which Congress amended Section 118 of the Clean Water Act in 1990 to improve the effectiveness of EPA's existing programs in the Great Lakes. The Critical Programs Act established the Great Lakes Water Quality Initiative and identified key treaty agreements between the United States and Canada in the Great Lakes Water Quality Agreement. The act required the EPA to establish statutory deadlines for treaty activities and increased federal resources for the program. It also requires the EPA to publish proposed water quality guidelines for the Great Lakes System. The guidelines must specify minimum requirements for waters in the Great Lakes system in three areas: water quality standards; anti-degradation policies; and implementation procedures.

Great Lakes Information Network (GLIN) - Since 1993, GLIN has been a recognized information service providing "one-stop shopping" for Great Lakes-related resources. Owing to its strong network of state, provincial, federal and regional partner agencies and organizations, GLIN has defacto become a necessary component of informed decisionmaking, and a reliable source of information for those who live, work or have an interest in the Great Lakes region.

Great Lakes Interagency Task Force (GLITF) - On 18 May 04, President Bush signed Executive Order (EO) 13340. The EO established the Great Lakes Interagency Task Force, composed of Secretaries from the Departments of State, Army, Agriculture, Commerce, HUD, Homeland Security, Interior, Transportation, the Administrator of the EPA and the Chairman of the Council on Environmental Quality.

Great Lakes States - The states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin.

Great Lakes States Air Permitting Agreement - A federal program signed by the environmental administrators of the Great Lakes States in 1988 to assure consistent implementation of the Toxic Substances Management in the Great Lakes Basin Through the Permitting Process Agreement.

Great Lakes - St. Lawrence Basin - The watershed, including all land and freshwater (both surface and ground water) within the confines of the drainage area defined by topographic high points surrounding the five Great Lakes and the St. Lawrence River to Beaupre, Quebec.

Great Lakes - St. Lawrence Basin Ecosystem - The interacting system consisting of groups of organisms and their non-living or physical environment, which are highly interrelated, as it pertains to the Great Lakes-St. Lawrence Basin.

Great Lakes Toxic Substances Control Agreement - An interstate agreement signed by the governors of the eight Great Lakes States in 1986, this agreement seeks uniform water quality standards for the Great Lakes. The purpose of the governors' agreement was to establish a framework for coordinated regional action in controlling toxic substances entering the Great Lakes system.

Great Lakes Water Quality Agreement (GLWQA) - An international agreement signed by the United States and Canada in 1972 and updated in 1987. The agreement seeks to restore and maintain full beneficial uses of the Great Lakes System. Language committing the two nations to virtually eliminate the input of persistent toxic substances in order to protect human health and living aquatic resources was included when the agreement was updated in 1978. The philosophy adopted by the two governments is zero discharge of such substances.

Great Waters Program - This program was mandated by Title III of the 1990 Clean Air Act Amendments to assess the extent of atmospheric deposition of hazardous air pollutants to the Great Lakes and other designated waters. It includes setting up the Great Lakes Atmospheric Deposition Network and reporting the monitoring results from the network to investigate sources and deposition rates of air toxics, to find out what proportion of pollutants come from the atmosphere, and to evaluate any harmful effects to public health or the environment.

Groundwater - 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.

Groundwater 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.

Habitats - the sum total of all the living and non-living factors that surround and potentially influence an organism; a particular organism's environment; the places where plants and animals live.

Halophilic - organisms that thrive in environments with very high concentrations of salt.

Half-Life - The period of time necessary for one half of a substance introduced to a living system or ecosystem to be eliminated or disintegrated by natural processes.

Hazardous Air Pollutants (HAPs) - Any air pollutant listed as such in Title III of the 1990 Clean Air Act Amendments. These are chemicals that have the potential to cause serious health effects. HAPs are released by mobile sources and industrial sources. Also referred to as air toxics. 

Hazardous Waste - A waste which, because of its quantity, concentration, or characteristics, may be hazardous to human health or the environment when improperly treated, stored, transported, or disposed. Specific definitions of hazardous waste vary by statute or regulation.

Heavy Metals - Metallic elements with relatively high atomic weights that can contaminate groundwater and surface waters, wildlife, and food. Heavy metals have the potential to be toxic at relatively low concentrations. Examples include arsenic, cadmium, chromium, copper, lead, mercury, selenium, and zinc.

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.

Herbivore - An organism that consumes plant material..

Heterogeneity - an adjective used to describe an object or system consisting of multiple items having a large number of structural variations.

Hexachlorobenzene (HCB) - A critical pollutant once used as a pesticide for grain protection until banned by the U.S. in 1976. It is still produced as a byproduct during the manufacture of other chlorinated hydrocarbons. It is a persistent toxic substance and is found in the tissues of fish, animals, and humans from the Great Lakes Basin. Limited uses of HCB are still permitted.

Homeostatic - a system, either open or closed, that regulates its internal environment and tends to maintain a stable, constant condition.

Host - an organism that harbors or nourishes another organism.

HUC 6 - Six-digit Hydrologic Unit Code. Hydrologic Unit Codes are used for pinpointing the location of a body of water within the United States.

HUC 8 -  Eight-digit Hydrologic Unit Code. Hydrologic Unit Codes are used for pinpointing the location of a body of water within the United States.

Human Health Criteria - These are descriptive or numeric expressions that specify how much of a pollutant can be allowed in a water body and still allow for the protection of human health. See also water quality criteria. 

Hybrid - The offspring produced through interbreeding of two biological species; since hybrids are not fertile they are unable to reproduce. (Hybrids are difficult to document in marine mollusks).

Hydric Soils - Soils that are saturated, flooded, or ponded long enough during the growing season to develop anoxic conditions in the upper part of the soil profile. Field indicators of hydric soils can include a thick layer of decomposing plant material on the surface; the odor of rotten eggs (sulfur); and colors of bluish-gray, gray, black, with occasional contrasting brighter spots of color.

Hydrocarbons - A class of compounds that contain hydrogen and carbon. This group of compounds includes the naturally occurring hydrocarbons produced by plankton, as well as many petroleum-based products like gasoline and motor oil. Chlorinated hydrocarbons, a subclass of hydrocarbons, are human derived and generally toxic.

Hydrodynamics - the motion of water that generally corresponds to its capacity to do work such as transport sediments, erode soils, flush pore waters in sediments, fluctuate vertically, etc. Motions can vary within each of three flow types: primarily vertical, primarily bidirectional and horizontal, and primarily unidirectional and horizontal. Vertical fluxes are driven by evapotranspiration and precipitation. Bidirectional flows are driven by astronomic tides and wind-driven seiches. Unidirectional flows are down slope movement that occurs from seepage slopes and on floodplains.

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.

Hydrologic system - A group of interrelated surface and ground water bodies or forces within the same drainage basin.

Hydrology - the study of the cycle of water movement on, over and through the earth's surface; the science dealing with the properties, distribution, and circulation of water.

Hydroperiod - depth, duration, seasonality, and frequency of flooding.

Hydrophytic Vegetation - Plant life capable of growing in wet conditions, such as in water or in soil or other substrate that is periodically saturated with water. The presence of hydrophytic plants is one of the indicators used in wetland identification and delineation.

Hydrophyte - Aquatic plant.

Hydrostatic pressure - the pressure water exerts at any given point when a body of water is in a still motion.

Hydrozoa -  simple and compound polyps and jellyfishes including stinging corals and Portuguese man of war; of the class Hydrozoa (singular: hydrozoan).

Hypersaline - extremely saline, generally over 30 ppt salinity (average ocean water salinity).

Hypolimnion- Refers to the deepest, coldest, most dense layer of water in a stratified lake (layers of water differing in temperature and density).

Hypolithic - living on lower surface of rocks

Hyporheic - a region beneath and lateral to a stream bed, where there is mixing of shallow groundwater and surface waters.

Hypoxia - A condition or environment with very low oxygen levels.

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

Indicator species - A species whose status provides information on the overall health of the ecosystem and of other species in that ecosystem. Indicator species reflect the quality and changes in environmental conditions as well as aspects of community composition.

Indigenous - native

Indo-Pacific - The faunal province comprising the shallow waters of the Indian and tropical western Pacific Oceans.

Individual Permit - An Army Corps of Engineers permit that is issued following a case-by-case evaluation of an application to perform dredge or fill activities in the Waters of the U.S., including wetlands. 

Industrial Waste - Any liquid, gaseous, or solid waste resulting from any process of industry, manufacturing, trade, or business or from the development of any natural resource.

Infauna - plants that live in the sediment.

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

Inflow and Infiltration - The penetration of water from the soil into sewer or other pipes through defective joints or connections and/or the penetration of water through the ground surface into the subsurface soil.

Intake Credits - A process that allows a point source discharger to take into account the quality of its source water when determining its effluent limitation standards.

Integrated Atmospheric Deposition Network (IADN) -  A joint effort of the U.S. and Canada to measure atmospheric deposition of toxic material to the Great Lakes. It was mandated by the Great Lakes Water Quality Agreement. The network also fulfills the requirements of the Great Waters Program mandated by the 1990 Clean Air Act Amendments calling for a Great Lakes atmospheric deposition network. One master sampling station was installed at each of the Great Lakes by the end of 1991 to monitor for deposition of selected toxic pollutants, including mercury.

Integrated, multi-resource approach - Collaborative management (e.g., rehabilitation, protection) by individuals with expertise in all relevant fields of ecosystem resources with full recognition of the interdependence of such resources.

Integrated Pest Management (IPM) - A management system that uses all suitable techniques in an economical and ecologically-sound manner to reduce pest populations and maintain them at levels that do not have an economic impact, while minimizing danger to humans and the environment. 

Interstate Waters -Rivers, lakes and other waters that flow across state or international boundaries. These include waters of the Great Lakes.

Interspersion - scattered or distributed at regular intervals.

Interstitial - microhabitat comprising space between particles of sand and gravel, associated with wet or submerged habitats.

Intertidal zone - The area of beach between the high and low tide waterlines.

Invertebrates - The classification for animals that do not have a backbone or internal skeleton. See also zooplankton and benthic invertebrates.

Iridescence - Colors of the rainbow in shifting hues and patterns.

Isomorphic - morphologically similar, having similar looking gametophyte and sporophyte phases of life history.

Isopod- One group of small to medium-sized crustaceans found in marine, freshwater and terrestrial habitats and as parasites.

Kelp - member of brown algal order Laminariales.

Lacey Act - This act, enforced by the U.S. Fish and Wildlife Service, is designed to control environmental releases of injurious fish and wildlife. This law includes species that threaten non-agricultural interests.

Lacustrine - pertaining to, produced by, or formed in a lake; living near lakes.

Lagoon - a body of shallow salt or brackish water separated from the deeper sea by a shallow or exposed sandbank, coral reef, or similar feature.

Lake Michigan Mass Balance Study -This mass balance research project, begun in 1994, is part of the Lake Michigan Lakewide Management Plan and is designed to develop a sound, scientific base of information that will guide future toxic pollutant load reduction and prevention activities.

Lakewide Management Plan (LaMP) - The binational programs called LaMPs provide a process for coordinating and prioritizing activities designed to reduce loadings of critical pollutants. The emphasis is on identifying the major sources of these pollutants and concentrating regulatory efforts where they will have the most impact. LaMPs are being developed for each of the Great Lakes.

Lampricide - a chemical which is designed to target the larvae of Lampreys in river systems before their recruitment as parasitic adults.

Larva (pl. larvae) - The immature, wingless form of many insects that hatches from the egg. The larva then transforms into a pupa, and then metamorphoses into the adult form.

Leachate -The contaminated liquid resulting from water seeping through a landfill or other materials. Chemicals such as fertilizer are leached from the soil when rainwater travels through the soil.

Lentic - Inhabiting still waters such as lakes, ponds or swamps; standing-water environments (e.g., lakes, wetlands, temporary pools).

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

Levels Reference Study - A report that suggested methods to alleviate the adverse consequences of fluctuating water levels in the Great Lakes-St. Lawrence River System. The Levels Reference Study Board, appointed by the International Joint Commission, completed the report in 1993 after an intensive public involvement process in the U.S. and Canada.

Life Cycle - A life cycle is a period involving one generation of an organism through means of reproduction, whether through asexual reproduction or sexual reproduction.

Limnology -The scientific study of freshwater, especially the history, geology, biology, physics, and chemistry of lakes.

Littoral - refers to the shallow water zone (less than 2 m deep) at the end of a water body, commonly seen in lakes or ponds; near the shore, intertidal

Littoral zone - area of a waterbody shallow enough for growth of rooted aquatic vegetation.

Load - An amount of water, sediment, nutrients, pollutants, heat, etc. that is introduced into a receiving water. Loading may be either of anthropogenic origin (pollutant loading) or natural (natural background loading).

Local Governmental Unit (LGU) -  A county board, joint county board, watershed management organization, watershed district or a township, or city.

Macrofauna - animals large enough to be seen with the naked eye, typically exceeding 1 mm in length or that will not pass through a 1 mm sieve.

Macroinvertebrate - animals without backbones that can be seen with the naked eye (caught with a 1 to 2 mm mesh net); includes insects, crayfish, snails, mussels, clams, fairy shrimp, etc.

Macrophytes - This term literally means large plant. Usually refers to rooted, seed-producing aquatic plants.

Marshes (marine and freshwater) - transitional habitats between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is covered by shallow water tidally or seasonally. Freshwater species are adapted to the short- and long-term water level fluctuations typical of freshwater ecosystems.

Mass Balance - A scientific approach that studies the sources, movement, and destination of any substance, for example a contaminant, that enters a lake system. A mass balance budget for a particular pollutant is the amount that enters a lake minus the amount that is tied-up in the sediment, broken down by chemical or biological processes, or removed by some other means. This should equal the amount that flows out of the lake system. This exercise enables scientists to assess the possible long-term effects of a pollutant and possible remediation actions. Also see Lake Michigan Mass Balance Study.

Mature - An individual that has reached the age for reproduction.

Maximum - most, highest (plural maxima).

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.

Mercury (Hg) - A heavy metal, mercury is a neurotoxin that is toxic if breathed or ingested at sufficiently high concentrations. Mercury is present naturally in the environment. It has commonly been used in a wide variety of applications including thermometers, fluorescent bulbs, mirrors, hide preservation, paints, for plastic coloring, in inks and stains, and in golf course pesticides. Because of its common use, mercury is released during garbage incineration. It is also released through the combustion of fuels such as coal and wood for energy production. Mercury readily bioaccumulates in all aquatic organisms, especially fish and shell fish and in humans and wildlife that consume fish. Many lakes in the Great Lakes region have fish consumption advisories due to high levels of mercury primarily caused by atmospheric deposition. Mercury is one of the nine critical pollutants. 

Mesohaline - Describing intermediate levels of salinity between freshwater and seawater, with a salinity range of 5-18 ppt.

Mesotrophic - A term used to describe a lake of moderate primary productivity. See also eutrophic and oligotrophic.

Metadata - data that describes or provides background information on other data.

Metamorphosis - The marked and rapid transformation of a larva into an adult that occurs in some animals.

Migratory - a creature that moves from one region to another when the seasons change.

Mixing Zone - A limited area or volume of water where initial dilution of a point source pollutant discharge takes place. The zone is extended to cover the secondary mixing in the surrounding waterbody. Numeric water quality criteria can be exceeded, but acutely toxic conditions are prevented from occurring in this zone.

Mollusca (Mollusk) - Soft-bodied, highly developed animals without a backbone and with an exterior or interior shell.

Molt / Molting - A process where crustaceans and insects shed their exoskeleton (external support). This is an important growth process, enabling the animal's body to expand.

Morphological - Related to the observable shape or anatomy of an organism.

Mudflat - bare, flat bottoms of lakes, rivers and ponds, or coastal waters, largely filled with organic deposits, freshly exposed by a lowering of the water level; a broad expanse of muddy substrate commonly occurring in estuaries and bays.

Multi-media Risk - The human health risk due to exposure to a pollutant through all pathways such as inhalation, ingestion, or skin contact.

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.

Mutagen -A substance that is known or suspected to cause mutations.

Mutation - A permanent change in the hereditary material involving a physical change in chromosomes or genes.

Nanoplankton - plankton from 2 to 20 microns in diameter that would pass through the mesh of a normal plankton net.

National Ambient Air Quality Standards (NAAQS) -  Standards that EPA sets under the Clean Air Act to protect public health with an adequate margin of safety (primary standards) and to protect the environment (secondary standards). These standards apply to sources that emit pollutants into the atmosphere. 

National Environmental Policy Act (NEPA) - A federal law passed in 1990 that promotes efforts to prevent or eliminate damage to the environment and biosphere and stimulates the health and welfare of people. It established a Council on Environmental Quality. It is comprised of two Titles: Title I - Declaration of National Environmental Policy; Title II - Council on Environmental Quality (42 U.S.C. 4321-4347).

National Pollutant Discharge Elimination System (NPDES) -  Federal regulations that constitute the national program for issuing, modifying, revoking, re-issuing, terminating, monitoring, and enforcing permits and enforcing pretreatment requirements for point source discharges to surface waters under the Clean Water Act, Section 402.

Nationwide Permit (NWP) - A type of general permit issued by the Army Corps of Engineers allowing certain activities to take place in the Waters of the U.S. If certain conditions are met, the specified activities can take place without the need for an individual or regional permit.

Native - an animal or plant that lives or grows naturally in a certain region.

Native Transplant - native to a portion of the region but moved to a non-native area in the same region.

Naturalized species - An intentionally or unintentionally introduced species that has adapted to and reproduces successfully in its new environment. Some Great Lakes examples include the rainbow smelt, the alewife, and some salmon and trout species.

Navigable Waters - Navigable waters of the United States are waters subject to the ebb and flow of the tide and/or used to transport interstate or foreign commerce. A determination of navigability, once made, applies over the entire surface of the waterbody, and is not changed by later actions or events which impede or destroy navigable capacity. Also referred to as Waters of the U.S. 

Nearshore — nearshore waters beginning at the shoreline or the lakeward edge of the coastal wetlands and extending offshore to the deepest lakebed contour where the thermocline typically intersects with the lakebed in late summer or early fall. ???

Nekton ("Swimmers") - The nekton includes all aquatic animals that actively swim in the water column, such as fish or squid. The nekton is one of three divisions of aquatic life; the others are the plankton ("drifters") and the benthos ("bottom dwellers").

Nematode - unsegmented worms with elongated rounded body pointed at both ends; mostly free-living but some are parasitic.

Neurotoxin - A substance that is known or suspected to be poisonous to nerve tissue.

NGVD - National Geodetic Vertical Datum. 1. As corrected 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.

Niche - the relational position of an organism's species.

Nitrogen (N); Atomic Number: 7; Atomic Mass: 14.00amu. Nitrogen is found as a gas in nature and it is classified as a non-metal. It makes up over 75 percent of the air surrounding the Earth.

Nitrogen-fixation - incorporation of atmospheric nitrogen as a nitrogen source in the cells of certain bacteria and Cyanobacteria.

Nitrogen Oxides (NOx) - Pollutants that can be a component of smog and also can contribute to acid rain. One of the criteria pollutants regulated by the 1990 Clean Air Act Amendments. Sources include automobiles and industrial point sources.

Nocturnal - active at night.

No Net Loss - A federal and/or state policy to achieve no overall net loss of the nation's remaining wetlands base as defined by acreage and function and to restore and create wetlands where feasible, to increase the quality and quantity of the nation's wetland resource base.

No Observable Effect Concentration (NOEC) - For toxic substances, it is the highest tested concentration at which no adverse effects are observed in an aquatic organism at a specific time of observation.

Non-Chemical Stressors - Physical and biological factors that can impact water quality or ecosystem health. Examples include, heat, sediment, non-indigenous species.

Non indigenous - Not originating where it is found. Not native to the area.

Non-Indigenous Aquatic Nuisance Prevention and Control Act of 1990 - A federal law to prevent the unintentional introduction and dispersal of non-indigenous species into the waters of the U.S. The act mandates the establishment of: a national ballast water control program; the Aquatic Nuisance Species Task Force; initial research funding; technical assistance and education for federal and state agencies; state management plans; and grant programs to prevent, monitor, and control the spread of zebra mussels and other exotic species. It also provides for the establishment of regulations that control the introduction of and dispersal of these organisms. See also aquatic nuisance species.

Non-Indigenous / Non-Native Species - Those species found beyond their natural ranges or natural zone of potential dispersal. Also referred to as exotic species. See also aquatic nuisance species.

Nonpoint Source - See nonpoint source pollution.

Nonpoint Source Pollution (NPS) - Pollution where the sources cannot be traced to a single, distinct, identifiable point. Nonpoint source pollution can come from atmospheric deposition, erosion, and runoff from parking lots, farms, and streets.

Nonindigenous nuisance species - A nonindigenous species that threatens the diversity or abundance of native species or otherwise threatens ecosystem integrity or commercial, agricultural and/or recreational activities dependent on it.

Nuisance species - undesirable plants and animals, commonly exotic species.

Nutrients - Elements or compounds essential as raw materials for organism growth and development, such as carbon, nitrogen, and phosphorus.

Nutrient cycling - the transformation of nutrients from one chemical form to another by physical, chemical, and biological processes as they are transferred from one trophic level to another and returned to the abiotic environment.

Obligate - Restricted to a particular set of environmental conditions, without which an organism cannot survive.

Octachlorostyrene (OCS)  - A toxic substance and critical pollutant that is a by-product of high temperature industrial processes involving chlorine. Like dioxin, OCS is not produced intentionally. Release to the environment occurs in effluent from chlorine and gas production, aluminum smelting, and other metal production. OCS has been found in leachate from industrial landfills and fly ash from waste incinerators. 

Oligotrophic - Refers to an unproductive, nutrient poor lake that typically has very clear water. Lake Superior is classified as an ultra-oligotrophic lake.

Omnivore - consumes both plant and animal food, from trophic levels 1 and above.

One-hundred year flood - refers to the floodwater levels that would occur once in 100 years, or as a 1.0 percent probability per year.

Order - the taxonomic grouping between class and family.

Ordinary High Water Mark (OHW) - The elevation marking the highest water level which has been maintained for a sufficient time to leave evidence upon the landscape. Defined in Minnesota statutes as the boundary of protected waters. Generally, it is the point where the natural vegetation changes from predominately aquatic to upland species. For streams, the OHW is generally the top of the bank of the channel. The OHW is the elevation from which building and sewage setbacks are measured. OHWL means ordinary high water level.

Organic - containing carbon, but possibly also containing hydrogen, oxygen, chlorine, nitrogen, and other elements.

Organic material - anything that is living or was living; in soil it is usually made up of nuts, leaves, twigs, bark, etc.

Organic Chemicals - Nearly all of the millions of compounds that contain carbon atoms are organic chemicals. More than 90% of all known compounds are organic. The few carbon compounds that are not considered organic include carbon dioxide and bicarbonate. Hydrocarbons like methane are simple organic chemicals that contain only hydrogen and carbon. Other organic chemicals include most pesticides and chemicals based on benzene.

Osmotic stress - water stress due to differences in salinity between an organism and its aquatic environment.

Outfall - The location or structure where wastewater or drainage empties into the surface water from a sewer, drain, or other conduit.

Overstory - trees that tower above the surrounding canopy.

Overwinter - Survive the winter, hibernate.

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.

Ozone - A pollutant formed in the lower atmosphere by the reaction of nitrogen oxides and hydrocarbons in sunlight, commonly called smog, for which National Ambient Air Quality Standards have been established. Ozone is also found naturally in the upper atmosphere where it acts as a protective filter, screening out ultra-violet rays.

PAHs - See Polycyclic Aromatic Hydrocarbons.

Palustrine - nontidal wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens, and all such wetlands that occur in tidal areas where salinity due to ocean-derived salts is below 0.5%.

Parasite - An organism that lives on or within a body and takes its nourishment from the host without giving any benefit.

Part 70 Permit - A federal regulation that defines the requirements for permitting facilities for air emissions. States with federally-approved permit programs administer the permitting of facilities within their state. 

Particulates - Very small separate particles composed of organic or inorganic matter.

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 (ppb) - The number of parts of a substance per billion parts of another substance into which it is combined. Often expressed as micrograms per liter for water and micrograms/kilogram for fish and sediments.

Parts per Million (ppm) - The number of parts of a substance per million parts of another substance into which it is combined. Often expressed as milligrams/liter water or milligrams/kilogram for fish tissue and sediments.

Parts per Thousand (ppt) - The number of parts of a substance per thousands parts of another substance into which it is combined. Often expressed as grams/liter of water or grams/kilogram for fish tissue and sediments.

Pathogen - A disease-causing microorganism or agent.

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.

Pelagic - Refers to fish and animals that live in the open sea, away from the bottom.

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.

Perennial - Persisting for several years, sometimes dying back to a perennial crown during the winter and initiating new growth each spring.

Periphyton - Microscopic plants or algae that are firmly attached to solid surfaces under water such as rocks, logs, pilings and other structures. Algae that grow attached to surfaces such as rocks or larger plants.

Permeability - A measure of the ease with which water penetrates a material; 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 impermeable material, such as clay, don't allow water to flow freely.

Persistent Toxic Substance - A toxic pollutant that remains in the environment for a substantial period of time, potentially causing injury to ecosystem health.Any substance that can cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological or reproductive malfunctions or physical deformities in any organism or its offspring, or which can become poisonous after concentration in the food chain or in combination with other substances; that has a half-life in water greater than eight weeks; where half-life means the time required for the concentration of a substance to diminish to one-half of its original value in a lake or other water body.

pH - A numeric value that indicates relative acidity and alkalinity on a scale of 1 to 14. A pH of 7.0 is neutral, higher values indicate increasing alkalinity; lower values indicate increasing acidity.

Phenotypic - Of or relating to the observable characteristics of an individual.

Phosphorous (P) - Atomic Number: 15; Atomic Mass: 30.97amu. Phosphorus is a very reactive element and is classified as a non-metal. Plants and animals need phosphorus to survive. Phosphorus is often the limiting nutrient in freshwater systems.

Phosphorous Enrichment - The adding of excessive phosphorous into a freshwater or marine ecosystem.

Photophilic - Light-loving. Refers to organisms that thrive in bright sunlight.

Phylum - primary taxonomic grouping, division

Physiographic setting — the location in a landscape, such as stream headwater locations, valley bottom depression, and coastal position, similar to geomorphic setting.

Physiography - a description of the surface features of the Earth, with an emphasis on the mode or origin*.*

Phytoplankton - Algae that grow suspended in the water column or open waters of a lake. A type of plant plankton, such as algae, that is the basic food source in many aquatic and marine ecosystems.

Piscivore - fish eater.

Planktivore - plankton eater.

Plankton - drifting organisms. The plankton includes all aquatic organisms that are carried passively in the water currents.A term used to describe bacteria, tiny plants (phytoplankton) and animals (zooplankton) that live in the water column of lakes.

Pleistocene - from two million to 11 thousand years ago, extensive glaciation of the northern hemisphere.

Pneumatophores - specialized roots formed by several species of plants occurring in frequently inundated habitats. The root is erect and protrudes above the soil surface.

Point Source - See point source pollution.

Point Source Pollution - Pollution from a distinct, identifiable source, such as a pipe, smokestack, or exhaust.

Pollutant - Chemicals or refuse material released into the atmosphere or water or onto the land.

Pollution Prevention (P2) - Eliminating or reducing at the source the use, generation, or release of toxic pollutants. Methods of reducing pollution include, but are not limited to, industrial process modification, inventory control measures, feedstock substitutions, various housekeeping and management practices, and improved efficiency of machinery. Federal versions of this term are often referred to as source reduction.

Pollution Prevention Act of 1990 - A federal law that establishes a national policy of pollution prevention, and requires the EPA to develop and implement a strategy to promote source reduction. This act declares as national policy that pollution prevention is the preferred approach to environmental protection.

Polychlorinated Biphenyls (PCBs) - One of the nine critical pollutants, PCBs are a group of over 200 nonflammable compounds formerly used in heating and cooling equipment, electrical insulation, hydraulic and lubricating fluids, and various inks, adhesives, and paints. These compounds are highly toxic to aquatic life, persist in the environment for long periods of time, and are bioaccumulative. PCBs are suspected carcinogens, and are linked to infant development problems. Fish from some lakes and streams throughout the Great Lakes region contain measurable amounts of PCBs. See also Fish Consumption Advisory. 

Polycyclic Aromatic Hydrocarbons (PAHs) - A family of organic chemicals based on the chemical structure of benzene which result from incomplete combustion of organic chemicals and are associated with grease and other components derived from petroleum byproducts. Some examples of the many PAH compounds include; benz(a)anthracene, beno(b)fluoranthene, benzo(a)pyrene, chrysene, phenanthrene, and pyrene.

Population - a collection of individuals of one species or mixed species making up the residents of a particular area.

Potable Water - water of a quality suitable for drinking.

Prechlorination - The addition of chlorine at the headworks of a treatment plant prior to other treatment processes.

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

Predator - An organism that captures or preys upon another organism for its food; a predaceous organism.

Pretreatment - Partial wastewater treatment required for some industries. Pretreatment removes some types of industrial pollutants before the wastewater is discharged to a municipal wastewater treatment plant.

Primary Productivity - The amount of production of living organic material through photosynthesis by plants, including algae, measured over a period of time.

Primary Treatment - The first step in wastewater treatment in which most of the debris and solids are removed mechanically.

Priority Pollutants - Pollutants identified in certain federal and state regulations. Priority pollutants have different definitions in air, water, and waste programs.

Propagules - a structure (such as a cutting, a seed, or a spore) from which a new plant can grow.

Protozoa - single-celled animals.

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.

Purple Loosestrife - A wetland plant from Eurasia that quickly invades water bodies, including the Great Lakes, forming dense stands unsuitable as cover, food, or nesting sites for fish, amphibians, waterfowl and wildlife. Imported as an ornamental plant, it spread quickly across North America along roads, canals and drainage ditches. Research on the use of European beetles that attack only purple loosestrife shows promise for biological control in North America.

Quagga Mussel - A close cousin to the zebra mussel, this exotic mussel was brought into the Great Lakes in the ballast water of transoceanic ships and is expected to have impacts similar to those of the zebra mussel. Although some evidence suggests that it prefers the deeper waters of the Great Lakes, it has, like the zebra mussel, quickly infested inland river systems. The name quagga comes from an extinct member of the zebra family.

Quality assurance/quality control plan - a detailed plan that describes the means of data collection, handling, formatting, storage, and public accessibility for a project.

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.

Receiving Waters - Rivers, streams, lakes, or any body of water into which wastewater is discharged.

Rebar - also called reinforcing bar; a steel rod with ridges for use in reinforced concrete.

Redox potential - oxygen-reduction potential, often used to quantify the degree of electrochemical reduction of wetland soils under anoxic conditions.

Red Tide - A reddish discoloration of coastal surface waters due to concentrations of certain toxin-producing algae.

Reference condition - set of selected measurements or conditions to which a restoration project will be compared, may be relatively pristine or very degraded.

Reference site - a site that is representative of the expected ecological conditions and integrity of other sites of the same type and region.

Regime - a regular pattern of occurrence or action.

Regional Permit -A type of general permit that may be issued by a division or district engineer (Army Corps of Engineers), after compliance with other procedures, for activities in navigable waters of the U.S. or wetlands. Related Program - Section 404, 33 CFR

Regulation - Rules that outline specific procedures developed by federal or state agencies which are used to implement laws.

Remedial Action Plan (RAP) - These are federally-mandated local plans designed to restore environmental quality to Areas of Concern on the Great Lakes (there were initially 43 in the U.S. and Canada). The Areas of Concern were identified for their persistent pollution problems. Remedial Action Plans were called for by a protocol added to the Great Lakes Water Quality Agreement in 1987.

Reservoir - An artificially created pond, lake or other space used for storage, regulation or control of water. May be permanent or temporary. 2. a storage space.

Residence Time - The time required for a water body to exchange its entire volume of water. Lake Superior takes about 173 to 191 years to flush its entire volume. The other Great Lakes have much smaller residence times. This is an important factor used in determining the residence time of toxic pollutants in the lake. Also referred to as flushing time.

Resource Conservation and Recovery Act (RCRA) - A federal law that established a comprehensive cradle to grave system for regulating hazardous waste.

Restoration - the process of reestablishing a self-sustaining habitat that in time may come to closely resemble a natural condition in terms of structure and function.

Restoration monitoring - the systematic collection and analysis of data that provides information useful for measuring restoration project performance at a variety of scales (locally, regionally, and nationally).

Resuspension - a renewed suspension of insoluble particles after they have been precipitated.

Retention - 1. That part of precipitation falling on a drainage area which does not escape as a stream flow, during a given period. 2. The storage of stormwater to prevent it from leaving the development site. May be permanent or temporary. 3. to retain or hold.

Rhizomes - A form of reproduction where a plant grows an underground offshoot from its roots or stems those surfaces and grows into a new plant at a different location; somewhat elongate usually horizontal subterranean plant stem that is often thickened by deposits of reserve food material, produces shoots above and roots below, and is distinguished from a true root in possessing buds, nodes, and usually scale-like leaves.

Riffle - A shallow area of a stream in which water flows rapidly over a rocky or gravelly stream bed.

Riparian - a form of wetland transition comprised of multiple habitats and located between permanently saturated wetland and upland habitats. These areas exhibit vegetation or physical characteristics reflective of permanent surface of subsurface water influence. Lands along, adjacent to, or contiguous with perennially and intermittently flowing rivers and streams, glacial potholes, and the shores of lakes and reservoirs with stable water levels are typically riparian areas. Excluded are such sites as ephemeral streams or washes that do not exhibit the presence of vegetation dependent upon free water in the soil.

Riparian Area - Vegetated ecosystems found along any stream or river. These areas characteristically have a high water table and are subject to periodic flooding and influence from the adjacent water body.

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.

Riprap - Rock or other large material that is placed to protect streambanks or lakeshores from erosion due to runoff or wave action.

Risk Assessment - A complex process by which scientists determine the harm that a substance, activity, lifestyle, or natural phenomenon can inflict on human health or the environment. The process involves analyzing scientific data to describe the form, dimension, and characteristics of risk. Assessments are usually predictive estimates of how risky a particular situation is. See also risk management, ecological risk assessment comparative risk analysis.

Risk Management - The process by which risk assessment results are used with other information to make regulatory decisions. Risk management asks, What shall we do about this risk? See also risk assessment and ecological risk assessment.

Risk Reduction - Anything, such as education, regulation, or remediation, that reduces the adverse effects of exposure to risks from a substance, activity, lifestyle, or natural phenomenon.

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

Rivers and Harbors Act of 1899 - A federal statute that allows the Army Corps of Engineers to regulate the creation of obstructions and filling of navigable waters of the U.S. (33 U.S.C 401-413).

Riverine - Relating to, formed by, or resembling a river.

Riverine forests - forests found along sluggish streams, drainage depressions, and in large alluvial floodplains. Although associated with deepwater swamps in the southeastern United States, riverine forests are found throughout the United States and are not subject to prolonged flooding.

River Watch - A citizen-based volunteer water monitoring, education and outreach program sponsored by the EPA. The primary emphasis of the program is to work with secondary school teachers and students to incorporate River Watch concepts into existing course curricula.

Rock bottom - all wetlands and deepwater habitats with substrates having an areal cover of stones, boulders, or bedrock 75% or greater, and vegetative cover of less than 30%.

Rocky shoreline - extensive littoral habitats on wave-exposed coasts, the substrate is composed of boulders, rocks, or cobble.

Rubble - A dense accumulation of broken shells, coral fragments, and stones on the sea or lake bottom.

Ruffe - See Eurasian ruffe.

Rule -See Regulation.

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.

Salinity - the concentration of dissolved salts in a body of water, commonly expressed as parts per thousand.

Salmonid - A member of the family Salmonidae, which includes salmon, trout and whitefish..

Sampling designs - the procedure for selecting samples from a population and the subsequent statistical analysis.

SAV - Any Submerged Aquatic Vegetation, i.e., vascular aquatic plants that are rooted in the bottom sediments and grow no higher than the surface of the water, such as eelgrass or redhead grass. Freshwater species are adapted to the short- and long-term water level fluctuations typical of freshwater ecosystems.

Scavenger - An animal that feeds on refuse or dead and decaying animal and plant material.

Science Advisory Board (SAB) - A binational advisory group that provides advice on the adequacy of Great Lakes science and research to the International Joint Commission and the Water Quality Board. The board is responsible for developing recommendations on all matters related to research and the development of scientific knowledge pertinent to the identification, evaluation, and resolution of current and anticipated problems related to Great Lake water quality. 

Scientific Name - name agreed to by taxonomists internationally, usually the scientific name is given by the discoverer, but sometime organisms are renamed based on new knowledge of their genetic relationships to other organisms. Properly, the scientific name includes the genus name and species name, both in italics, e.g., humans are Homo sapiens.

Sea Lamprey -An exotic, eel-like animal that attaches to fish with a sucking disk and sharp teeth. A native of the Atlantic Ocean, the lamprey made its way into all the Great Lakes following the opening of the Welland Canal in 1829 and its deepening in the 1900s. By the 1930s, sea lamprey were found in all of the Great Lakes. During the 1940s and 1950s, lamprey caused the collapse of lake trout, whitefish, and chub populations in all the Great Lakes with the exception of Lake Superior. It has been estimated that one sea lamprey can kill up to 40 pounds of lake trout during its lifespan. See also Sea Lamprey Control Program.

Sea Lamprey Control Program - The U.S. Fish and Wildlife Service and the Department of Fisheries and Oceans in Canada work together, under the direction of the Great Lakes Fishery Commission, to minimize sea lamprey populations in the Great Lakes. Lamprey are controlled by applying a selective toxicant, TFM, to streams during the lampreys most vulnerable life stage. Other control techniques include barriers, pheromone release, and sterilization of male lamprey.

Seasonality - the change in natural cycles over time, such as lunar cycles and flooding cycles; changes from one season to the next.

Secchi Disk Depth (SDD) - An estimate of the transparency of a lake, obtained by lowering a small (20 cm) disk into the water until it is no longer visible and noting the depth at which it disappears from view. Oligotrophic lakes are typically more transparent (and have a larger Secchi depth) than more productive, or eutrophic lakes.

Secondary Treatment - The second step in most publicly-owned treatment systems, where bacteria consume the organic parts of the waste.

Section 10 - Refers to federal statute Section 10 of the Rivers and Harbors Act of 1899.

Section 118 -  A term used to refer to federal regulation Section 118 of the Clean Water Act that identifies program requirements for the Great Lakes. 

Section 305 (b) - A report required by the Clean Water Act on the status of fishable, swimmable waters. The states submit a biennial report to the EPA, which compiles the reports into a report to Congress. 

Section 319 - A term used to refer to federal regulation Section 319 of the Clean Water Act that identifies the program requirement for nonpoint source management programs. 

Section 401 -  A term used to refer to federal regulation Section 401 of the Clean Water Act that requires water quality certification by the appropriate state agency. Under 401, no federal permit to discharge pollutants into the waters of the U.S. is valid unless the state where the discharge occurs grants or waives its right to certify that the permit will not violate the state water quality standards. A federal agency cannot issue a permit when the state has denied water quality certification. 

Section 402 - A term used to refer to federal regulation Section 402 of the Clean Water Act that identifies permit requirements for point source discharge, known as the National Pollutant Discharge Elimination System. 

Section 404 -  A term used to refer to federal regulation Section 404 of the Clean Water Act that outlines permit requirement for dredging and other filling activities in waters of the U.S.. This is the primary federal law that regulates activities affecting wetlands. The Section 404 program is administered by the Army Corps of Engineers in accordance with the EPA. 

Section 6217 - A federal regulation that is a part of the Coastal Zone Act Reauthorization Amendments of 1990 entitled, Protecting Coastal Waters. This provision requires states with Coastal Zone Management Programs that have received federal approval under Section 306 of the Coastal Zone Management Act, to develop and implement Coastal Nonpoint Pollution Control Programs. These programs are to be used to control sources of nonpoint pollution which impact coastal water quality. 

Sediments - Soil particles that are or were at one time suspended in and carried by water as a result of erosion and/or resuspension. The particles are deposited in areas where the water flow is slowed such as in harbors, wetlands, and lakes.

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.

Seiche - Seiches are lakewide displacements of water that are wind-induced. Water pushed by the wind can pile up on shore causing noticeable increases in water depth. When the wind is reduced the water mass continues to slosh back and forth like water in a bathtub.

Senescence - the life stage in a plant or plant part (such as a leaf) from full maturity to death, also applies to winter dormancy

Sequencing - A term used in wetlands regulations to define a process that involves avoiding, minimizing and mitigating impacts. 

Sessile - permanently attached or established, not free to move about.

Shorelands - Refers to lands located 1000 feet from the ordinary high water level of a lake, pond, or flowage and 300 feet from a river, stream or the landward extent of floodplains.

Silica - A white or colorless crystalline compound, SiO2, occurring abundantly as quartz, sand, flint, agate, and many other minerals and used to manufacture a wide variety of materials, especially glass and concrete.

Siliceous - Relating to or containing or resembling silica.

Site-Specific Criteria - Water quality criteria that have been developed to be specifically appropriate to the water quality characteristics and/or species composition at a particular location (e.g., NPDES permitted discharges).

Socioeconomic monitoring - tracking of key indicators that characterize the economic and social state of a human community.

Soft bottom - loose, unconsolidated substrate characterized by fine to coarse-grained sediment.

Soft shoreline - sand beaches and muddy shores; stretches of land covered by loose material, exposed to and shaped by waves and/or wind.

Soil and Water Conservation Districts (SWCDs) -  Local county units of government that assist landowners with implementation of soil and water conservation measures and practices. 

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".

Source Reduction -A term that means reducing pollution at its source. It includes management systems, technologies, and other practices which reduce or eliminate the amount of any hazardous substance, pollutant, or contaminant entering any waste stream or otherwise released into the environment prior to recycling, treatment, or disposal. The term includes equipment or technology modifications, reformulation or redesign of products, substitution of raw materials and improvements in housekeeping, maintenance, training or inventory control. See also Pollution Prevention.

Spawning - A form of sexual reproduction where microscopic eggs and sperm are discharged into the water column.
 

Special Designation - Part of a Lakewide Management Program or Binational Program, wherein governments are encouraged to make special designations which: favor zero discharge of human made toxins and protect and enhance the unique character and pristine nature of the lake basin. The U.S. policy on special designation includes enhanced anti-degradation approaches (including best available technology) for new or proposed expansions to facilities. 

Splash zone - the water line; The area where waves of ocean or lake strike the support members of offshore platforms and installations.???

Sporadic - recurring in scattered and irregular or unpredictable instances.

State of the Lakes Ecosystem Conference (SOLEC) - A conference sponsored by Environment Canada and EPA, held in 1994, to review and make available information on the state of the chemical, physical, and biological integrity of the Great Lakes Basin Ecosystem. A major purpose of the conference was to cooperate in implementing the Great Lakes Water Quality Agreement by supporting better decision-making through improved availability of information on the condition of the living components of the system and the stresses which affect them.

Statistical protocol - a method of analyzing a collection of observed values in order to make an inference about one or more characteristic of a population or unit.

Statute -An enactment of the legislative body of a government that is formally expressed and documented as a law.

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).

Stewardship - The careful and responsible management of ecosystem resources entrusted to humans in the interest of achieving and protecting ecosystem integrity for its intrinsic value and/or for the benefit of current and future generations.

Stocked - Populating a body of water with fish reared in hatcheries.

Storm Water - Rainwater runoff, snow melt runoff, surface water runoff and discharges that are collected by storm sewers. 

Strands - a diffuse freshwater stream flowing through a shallow vegetated depression on a gentle slope.

Stratification - The formation of separate layers (of temperature, plant, or animal life) in a lake or reservoir. Each layer has similar characteristics such as all water in the layer has the same temperature.

Stratified random sampling - a population is divided into subgroups that are homogeneous. Random samples are then taken within each subgroup, assuring that key subgroups within a population are sampled, particularly those in the minority. This type of sampling can be done for populations or for areas.

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.

Stressor - Any chemical, physical, or biological entity that can induce adverse effects on individuals, populations, communities, or ecosystems.

Structural habitat characteristics - characteristics that define the physical composition of a habitat, the functions an ecosystem can perform are often dependent upon its structure.

Subaerial - Pertaining to land regions just above water level (ie, under air).

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.

Subspecies - A geographically defined group of populations comprising individuals which differ in certain characters from other such subdivisions of the species.

Substratum - A layer that lies underneath another; The underlying cause or basis of something

Subtidal - The zone of the shoreline that is below low tide and is always covered by water.???

Sulfur Dioxide (SO₂₎ - A chemical compound that when emitted to the atmosphere is considered to be a major component of acid rain. One of the criteria pollutants regulated by the 1990 Clean Air Act Amendments, SO2 is emitted mainly by anthropogenic sources. Sources include industrial point sources, such as coal fired electric utilities.

Sunsetting - A process to restrict, phase out, and eventually ban the manufacture, generation, use, storage, discharge, and disposal of a persistent toxic substance.

Superfund - See Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).

Supralittoral region - an area above the high tide mark or ordinary high water mark receiving splashing from waves.

Surface Water - All water above the surface of the ground including, but not limited to lakes, ponds, reservoirs, artificial impoundments, streams, rivers, springs, seeps, and wetlands.

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 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.

Sustainable community - A community where the natural environment and its human inhabitants interrelate in a manner that maintains ecosystem integrity and provides a high quality of life for humans.

Sustainable development - Development that meets the needs of the present without compromising the ability of future generations to meet their own needs and respects the limits imposed by the capacity of an ecosystem to absorb the impact of human activities.

Sustainable use (of resources) - Consumption or employment of a resource which, all other factors being equal, does not cause depletion that harms the resource or constitutes a threat to ecosystem integrity.

Symbiosis - To live together; a condition in which two animals, two plants, or a plant and an animal live in partnership. The relationship can be that of commensalism, where one organism benefits from activities of the other; parasitism, where one organism lives on another to the detriment of its host; or mutualism, where both organisms benefit from the association.

Sympatric - occurring in the same or overlapping geographical areas.

Taxon - A term used to denote any group or rank in the classification of organisms, e.g., class, order, family. (pl. Taxa)

Taxonomy - a classification of organisms into groups based on similarities of structure or origin etc.

Terrestrial - Living or growing on land or in the soil.

Tertiary Treatment - The advanced cleaning of wastewater that goes beyond secondary treatment. This process removes nutrients such as phosphorus and nitrogen and most biological oxygen demand and suspended solids.

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.

Thermal Stratification - The layering of warmer waters over colder waters that can occur in lakes, usually in the summertime. This layering occurs because as surface waters are warmed they become less dense than the underlying colder waters.

Thermocline - zone in water where the temperature changes drastically; a horizontal region in a thermally stratified body of water than separates warmer oxygen-rich surface water from cold oxygen-poor deep water.

Thermophilic - an organism that thrives at relatively high temperatures, between 45 and 80 °C.

Tidal - Involving the periodic variation in the surface level of the oceans and of bays, gulfs, inlets, and estuaries, caused by gravitational attraction of the moon and sun.

Tidal freshwater - Freshwater (0-0.5 ppt) that is tidally influenced.

Tidal system - The systems involving the periodic variation in the surface level of the oceans and of bays, gulfs, inlets, and estuaries, caused by gravitational attraction of the moon and sun.

Tide - the rhythmic, alternate rise and fall of the surface (or water level) of the ocean, and connected bodies of water, occurring twice a day over most of the earth, resulting from the gravitational attraction of the moon, and to a lesser degree, the sun.

Time series - an ordered sequence of values of a certain variable that are equally spaced over time.

Time series analysis - looking for patterns such as seasonal variations or impacts of events in data sets whose measurements are collected at equally spaced intervals over time.

Topography - the general configuration of a land surface or any part of the earth's surface, including its relief and the position of its natural and man-made features.

Total Maximum Daily Load (TMDL) - TMDLs are set by regulators to allocate the maximum amount of a pollutant that may be introduced into a water body and still assure attainment and maintenance of water quality standards. 

Toxaphene - One of the nine critical pollutants, toxaphene is an insecticide that was developed as a substitute for DDT. Its use is now restricted in the U.S. and Canada. Toxaphene has been detected in wildlife as far north as the Arctic and levels in Lake Superior appear to be increasing in fish and sediments. 

Toxicant - A poison: any substance that causes injury or illness or death of a living organism.

Toxic Pollutant - A substance or combination of substances, including disease-causing agents, which may cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions (including reproductive malfunctions), or physical deformation in organisms or their offspring. Also refers to those substances listed under Section 307(a) of the Clean Water Act. 

Toxic Substances - See Toxic Pollutants.

Toxic Substances Management in the Great Lakes Basin Through the Permitting Process Agreement - An binational agreement entered into by the environmental administrators of the Great Lakes States in 1986 requiring that Best Available Control Technology be installed wherever possible on all new and existing sources of persistent air toxic pollutants which impact the Great Lakes. This agreement is pursuant to implementing the governors Great Lakes Toxic Substances Control Agreement.

Toxicity - The inherent potential of a substance to cause adverse effects in a living organism. See acute toxicity and chronic toxicity.

Toxicity Test - A procedure that measures the degree of effect caused by a chemical or effluent, by exposing living test organisms to the substance. See also acute toxicity and chronic toxicity.

Trace Minerals - Nutrients essential to the body but found in very small amounts. Trace minerals include iron zinc, selenium, fluoride, molybdenum, copper, and manganese.

Transient - passing through or by a place with only a brief stay or sojourn.

Translucent -Allowing light to pass through, but not transparent.

Transmission - the act of sending through or across, infection: an incident in which an infectious disease is transmitted.

Transmittance - the fraction of radiant energy that passes through a substance

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. See Evapotranspiration.

Trophic - refers to food, nutrition, or growth state.

Trophic level - a group of organisms united by obtaining their energy from the same part of the food web of a biological community.

Tropical - Refers to an area or climate that is frost-free and has temperatures high enough to support year-round plant growth if enough moisture is present.

Unconsolidated - loosely arranged.

Understory - trees and tall bushes that are completely submerged under the canopy.

U.S. Ballast Water Management Regulation - Mandatory regulations, enforced cooperatively by the U.S. and Canadian Coast Guards, that prohibit a commercial trans-oceanic vessel from importing ballast water having salinity values less than 30 parts per thousand into the Great Lakes in an effort aimed at preventing further introductions of harmful freshwater exotic species.

United States Code (USC) - An abbreviation used to identify federal statutes. It is used when referring to a specific code section(s). For example, the Clean Water Act is 33 U.S.C. 1251-1387.

Variance - A mechanism or provision that allows modification to or waiver of requirements or standards.

Variant - Any unnamed variation within a species, variety, forma specialis or physiolgic race.

Vertebrates - Animals with a backbone.

Vertical mixing - Up/down mixing in water, either via a vertical ocean current, by upwelling along a coast, by turnover (breakdown of thermal stratification) or by artificial means.

Vestigial - Describing a characteristic which has receded from a useful structure in an ancestral form, and has little or no current use.

Virtual Elimination - A term that refers to the elimination of inputs and discharges of persistent toxic substances with the end goal being their elimination from the Great Lakes Ecosystem. Because it is not practical to completely remove persistent toxic substances, especially from contaminated sediments, the qualifier virtual is appropriate. It may not be possible to achieve total elimination from the Great Lakes System for some persistent toxic substances produced by natural processes and/or by the release of toxins from contaminated sediments. Because of these impediments, virtual elimination is seen by many as a more realistic objective than zero discharge. See also Zero Discharge.

Virtual Elimination Pilot Project - A federal project undertaken by the EPA in response to the Great Lakes Water Quality Agreement, that has as its goal the virtual elimination of persistent bioaccumulative chemicals of concern from the Great Lakes Basin. 

Virtual Elimination Strategy - A binational report produced by the Virtual Elimination Task Force for the International Joint Commission that outlines a conceptual framework to achieve the virtual elimination of persistent toxic substances from the Great Lakes Basin. 

Virtual Elimination Task Force - A binational organization established by the International Joint Commission to address specific virtual elimination issues in the Great Lakes ecosystem.

Virulent - Infectious; having the ability to cause disease.

Viviparous - producing living young instead of eggs from within the body in the manner of nearly all mammals, many reptiles, and a few fishes; germinating while still attached to the parent plant.

Volatile Organic Compounds (VOCs) - Organic chemicals that evaporate readily into the atmosphere, providing a path for transport through the environment.

Voluntary PCB Phasedown Program - A federal program initiated by EPA Region 5 requesting electric utilities in the Great Lakes Basin to voluntarily remove from service all electrical equipment containing PCBs at levels greater than 500 parts per million.

Wasteload Allocation (WLA) - The portion of a receiving water's total maximum daily load that is allocated to one of its existing or future point sources of pollution. WLAs constitute a type of water-quality-based effluent limitation. 

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

Wastewater Treatment Plant (WWTP) - A facility that receives sewage and stormwater from collection structures, then uses various levels of treatment to "purify" the water. Most modern publicly-owned treatment works in larger municipalities provide primary treatment, secondary treatment, tertiary treatment, and disinfection techniques to kill disease-producing organisms. 

Water Column - a conceptual volume of water extending from the water surface down to, but not including the substrate, found in marine, estuarine, river, and lacustrine systems.

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

Water Quality Advisory Board - A binational advisory group to the International Joint Commission to assist in evaluating progress by Canada and the U.S. in accomplishing the Great Lakes Water Quality Agreement goals and to make recommendations regarding the development and implementation of programs.
Water Quality Agreement of 1987 -A binational agreement that amends the Great Lakes Water Quality Agreement of 1978.

Water Quality Criteria -Numeric or narrative expressions that specify concentrations of water constituents (such as toxic chemicals or heavy metals) which, if not exceeded, are expected to support an ecosystem suitable for protecting life in water and life dependent on water for its existence. States incorporate water quality criteria into their water quality standards to protect public health or welfare, enhance the quality of water, and serve the purposes of the Clean Water Act.

Water Quality Standard -A water quality standard defines the water quality goals of a water body, or thereof, by designating the use or uses to be made of the water, by setting water quality criteria necessary to protect the uses, and by preventing degradation of water quality through anti-degradation provisions. States adopt water quality standards to protect public health or welfare, enhance the quality of water, and serve the purposes of the Clean Water Act.

Waters of the State - A term used by various states in their statutes and regulations that refers to all water bodies regulated by the state. They include streams, lakes, ponds, marshes, watercourses, waterways, wells, springs, reservoirs, aquifers, irrigation systems, drainage systems and all other bodies or accumulations of water, surface or underground, natural or artificial, public or private, which are contained within, flow through, or border upon the state or any portion thereof.

Waters of the United States - A term used in federal regulations that defines all water bodies regulated as waters of the U.S. It includes: (1) All waters which may be susceptible to use in interstate or foreign commerce; (2) All interstate waters including interstate wetlands; (3) All other waters such as intrastate lakes rivers, streams ( including intermittent streams), mud flats, sandflats, wetlands, sloughs, prairie potholes, wet meadows, playa lakes, or natural ponds, the use, degradation or destruction of which could affect interstate or foreign commerce including any such waters; (4) All impoundments of waters otherwise defined as waters of the United States; (5) Tributaries of waters identified in this section; (6) The territorial seas; (7) Wetlands adjacent to waters (other than waters that are themselves wetlands) identified in this section. 

Watershed - The drainage basin or area in which surface water drains toward a lake, stream, or river at a lower elevation. A ridge of high land dividing two areas that are drained by different river systems. 2. The region draining into a river, river system, or other body of water. 3. A critical point that marks a division or a change of course; a turning point.

Water Table -The upper surface of the groundwater or that level below which the soil is saturated with water; 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.

Weir - a fence or wattle built across a stream to catch or retain fish.

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.

Wet Deposition -The deposition of pollutants from the atmosphere that occurs during precipitation events. Acid rain is one form of wet deposition. Wet deposition is calculated by multiplying precipitation amounts by the pollutant concentration. Wet deposition rates are often very different than dry deposition rates.

Wetland Mitigation - A regulatory requirement to replace or enhance wetland areas destroyed or impacted by proposed land disturbances with artificially created or restored wetlands.

Wetlands - The lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. Wetlands must have a predominance of hydric soils; be inundated or saturated by surface water or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation. This is a legal definition and controversy still exists among scientists and policy makers as to how many of these characteristics must be present in order for an area to be defined as a wetland.

Whole Effluent Toxicity Test (WET) - The total toxic effect of a complex effluent measured directly by a toxicity test. 

Wildlife Criteria - Water quality criteria designed to protect wildlife. These are surface water concentrations of toxic substances that will cause no significant reduction in the viability or usefulness (in a commercial or recreational sense) of a population of animals that use the waters of the Great Lakes System as a drinking and/or foraging source over several generations.

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

Young-of-the-year - juveniles during the period from the last larval stage to adulthood, or one year of age, whichever comes sooner.

Zebra Mussel - An exotic species originally introduced into the Great Lakes via the ballast water of transoceanic ships. This small bivalve mussel poses a multibillion dollar threat to industrial, agricultural, and municipal water supplies across North America by clogging water intake pipes. It can also have impacts on fisheries, native freshwater mussels, and natural ecosystems. By moving along contiguous waters of the Great Lakes, attached to ships, barges and recreational boats, this Eurasian native has rapidly spread throughout the Mississippi River Basin and many of its major tributaries such as the Ohio River. Free-swimming larvae are also spread by river currents. Boater education campaigns focus on preventing further spread of this species.

Zero Discharge - Zero discharge refers to halting all inputs from all human sources and pathways to prevent any opportunity for persistent toxic substances to enter the environment from human activity. To completely prevent such releases, the manufacture, use, transport, and disposal of these substances would have to stop. The Binational Program has designated nine toxic substances (critical pollutants) to be part of the Zero Discharge Demonstration Program for the Lake Superior Basin. These substances are chlordane, dieldrin, dichloro-diphenyl-trichloro-ethane (DDT and its metabolites such as DDE), hexachlorobenzene (HCB), mercury, octachlorostryrene (OCS), polychlorinated biphenyls (PCBs), 2, 3, 7, 8 tetrachlorodibenzo-p-dioxin (TCDD), and toxaphene.

Zero Discharge Demonstration Program - This international program is in response to the recommendation by the International Joint Commission that Lake Superior be designated a zero discharge demonstration zone where no point source discharge of any persistent bioaccumulative toxic substance be permitted. Nine persistent toxic substances (critical pollutants) have been designated as critical for the program. The first priority of the program is the goal of achieving zero discharge of the nine substances from point sources. To completely prevent such releases, the manufacture, use, transport, and disposal of these substances must stop. This objective is to be met by: pollution prevention; enhanced controls and regulations, and; protection through special designations of all or part of the basin

Zonation - a state or condition that is marked with bands of color, texture, or different species.

Zone of Initial Dilution (ZID) -The region of initial mixing surrounding or adjacent to the end of an outfall pipe or diffuser. The ZID may not be larger than allowed by mixing zone restrictions in applicable water quality standards.

Zooplankton - Small, mostly microscopic animals that swim or float freely in open water. Zooplankton eat algae, detritus, and other zooplankton and in turn are eaten by fish.