bioaccumulation (bioconcentation) - A term used to describe a process that occurs when levels of toxic substances increase in an organism over time, due to continued exposure.

biodegradable - Capable of being broken down by living organisms into inorganic compounds.

biological diversity (biodiversity) -The variety of different species, the genetic variability of each species, and the variety of different ecosystems that they form.

biomagnification (biological magnification) - A cumulative increase in the concentrations of a persistent substance in successively higher levels of the food chain.

biota - Collectively, the plants, microorganisms, and animals of a certain area or region.

bog - A type of wetland that accumulates appreciable peat deposits. It depends primarily on precipitation for its water source and is usually acidic and rich in plant matter, with a conspicuous mat or living green moss.

boundary water - A river or lake that is part of the boundary between two or more countries or provinces that have rights to the water.

climate - Meteorological elements that characterize the average and extreme conditions of the atmosphere over a long period of time at any one place or region of the earth's surface.

climate change - The slow variations of climatic characteristics over time at a given place.

coliform bacteria - A group of bacteria used as an indicator of sanitary quality in water. Exposure to these organisms in drinking water causes diseases such as cholera.

combined sewers - A sewer that carries both sewage and storm water runoff.

condensation - The process by which a vapour becomes a liquid or solid; the opposite of evaporation. In meteorological usage, this term is applied only to the transformation from vapour to liquid.

conservation - The continuing protection and management of natural resources in accordance with principles that assure their optimum long-term economic and social benefits.

consumptive use - The difference between the total quantity of water withdrawn from a source for any use and the quantity of water returned to the source; e.g., the release of water into the atmosphere; the consumption of water by humans, animals, and plants; and the incorporation of water into the products of industrial or food processing.

contaminant - Any physical, chemical, biological, or radiological substance or matter that has an adverse affect on air, water, or soil.

cooling tower - A structure that helps remove heat from water used as a coolant; e.g., in electric power generating plants.

cubic metre per second (m³/s) - A unit expressing rate of discharge, typically used in measuring streamflow. One cubic metre per second is equal to the discharge in a stream of a cross section one metre wide and one metre deep, flowing with an average velocity of one metre per second.

dam - A structure of earth, rock, concrete, or other materials designed to retain water, creating a pond, lake, or reservoir.

delta - A fan-shaped alluvial deposit at a river mouth formed by the deposition of successive layers of sediment.

demand - The numerical expression of the desire for goods and services associated with an economic standard for acquiring them.

depletion - Loss of water from surface water reservoirs or groundwater aquifers at a rate greater than that of recharge.

dioxin - Any of a family of compounds known chemically as dibenzo-p-dioxins. Concern about them arises from their potential toxicity and contamination in commercial products.

discharge - In the simplest form, discharge means outflow of water. The use of this term is not restricted as to course or location, and it can be used to describe the flow of water from a pipe or from a drainage basin. Other words related to it are runoff, streamflow, and yield.

dissolved oxygen (DO) - The amount of oxygen freely available in water and necessary for aquatic life and the oxidation of organic materials.

dissolved solids (DS) - Very small pieces of organic and inorganic material contained in water. Excessive amounts make water unfit to drink or limit its use in industrial processes.

diversion - The transfer of water from a stream, lake, aquifer, or other source of water by a canal, pipe, well, or other conduit to another watercourse or to the land, as in the case of an irrigation system.

domestic use - The quantity of water used for household purposes such as washing, food preparation, and bathing.

drainage basin - See: Watershed.

dredgeate  - The material excavated from lake, river, or channel bottoms during dredging.

dredging - The removal of material from the bottom of water bodies using a scooping machine. This disturbs the ecosystem and causes silting that can kill aquatic life.

drought - A continuous and lengthy period during which no significant precipitation is recorded.

dry deposition - Emissions of sulphur and nitrogen oxides that, in the absence of water in the atmosphere (i.e., rain), settle to the ground as particulate matter.

dyke - An artificial embankment constructed to prevent flooding.

ecosystem - A system formed by the interaction of a group of organisms and their environment.

effluent - The sewage or industrial liquid waste that is released into natural water by sewage treatment plants, industry, or septic tanks.

environment - All of the external factors, conditions, and influences that affect an organism or a community.

environmental assessment - The critical appraisal of the likely effects of a proposed project, activity, or policy on the environment, both positive and negative.

environmental monitoring - The process of checking, observing, or keeping track of something for a specified period of time or at specified intervals.

erosion - The wearing down or washing away of the soil and land surface by the action of water, wind, or ice.

estuary - Regions of interaction between rivers and nearshore ocean waters, where tidal action and river flow create a mixing of fresh water and saltwater. These areas may include bays, mouths of rivers, salt marshes, and lagoons. These brackish water ecosystems shelter and feed marine life, birds, and wildlife.

eutrophic lake - Shallow, murky bodies of water that have excessive concentrations of plant nutrients causing excessive algal production.

eutrophication - The natural process by which lakes and ponds become enriched with dissolved nutrients, resulting in increased growth of algae and other microscopic plants.

evaporation - The process by which a liquid changes to a vapour.

evapotranspiration - The loss of water from a land area through evaporation from the soil and through plant transpiration.

fen - A type of wetland that accumulates peat deposits. Fens are less acidic than bogs, deriving most of their water from groundwater rich in calcium and magnesium.

flood - The temporary inundation of normally dry land areas resulting from the overflowing of the natural or artificial confines of a river or other body of water.

flood damage - The economic loss caused by floods, including damage by inundation, erosion, and/or sediment deposition. Damages also include emergency costs and business or financial losses. Evaluation may be based on the cost of replacing, repairing, or rehabilitating; the comparative change in market or sales value; or the change in the income or production caused by flooding.

flood forecasting - Prediction of stage, discharge, time of occurrence, and duration of a flood, especially of peak discharge at a specified point on a stream, resulting from precipitation and/or snowmelt.

flood fringe - The portion of the floodplain where water depths are shallow and velocities are low.

flood peak - The highest magnitude of the stage of discharge attained by a flood. Also called peak stage or peak discharge.

floodplain - Any normally dry land area that is susceptible to being inundated by water from any natural source. This area is usually low land adjacent to a stream or lake.

floodproofing - Any combination of structural and nonstructural additions, changes, or adjustments to structures that reduce or eliminate flood damage.

floodway - The channel of a river or stream and those parts of the adjacent floodplain adjoining the channel that are required to carry and discharge the base flood.

flow - The rate of water discharged from a source; expressed in volume with respect to time, e.g., m³/s.

flow augmentation - The addition of water to a stream, especially to meet instream flow needs.

food chain - A sequence of organisms, each of which uses the next, lower member of the sequence as a food source.

food web - The complex intermeshing of individual food chains in an ecosystem.

fresh water - Water that generally contains less than 1000 milligrams per litre of dissolved solids such as salts, metals, nutrients, etc.

glacier - A huge mass of ice, formed on land by the compaction and re-crystallization of snow, that moves very slowly downslope or outward due to its own weight.

greenhouse effect - The warming of the earth's atmosphere caused by a build-up of carbon dioxide or other trace gases; it is believed by many scientists that this build-up allows light from the sun's rays to heat the earth but prevents a counterbalancing loss of heat.

groundwater - The supply of fresh water found beneath the earth's surface (usually in aquifers) that is often used for supplying wells and springs.

groundwater recharge - The inflow to an aquifer.

habitat - The native environment where a plant or animal naturally grows or lives.

hazardous waste - Waste that poses a risk to human health or the environment and requires special disposal techniques to make it harmless or less dangerous.

hydroelectricity - Electric energy produced by water-powered turbine generators.

hydrologic cycle - The constant circulation of water from the sea, through the atmosphere, to the land, and back to the sea by over-land, underground, and atmospheric routes.

hydrology - The science of waters of the earth; water's properties, circulation, principles, and distribution.

infiltration - The movement of water into soil or porous rock. Infiltration occurs as water flows through the larger pores of rock or between soil particles under the influence of gravity, or as a gradual wetting of small particles by capillary action.

inflow - The entry of extraneous rainwater into a sewer system from sources other than infiltration, such as basement drains, sewer holes, storm drains, and street washing.

inorganic - Matter other than plant or animal and not containing a combination of carbon, hydrogen, and oxygen, as in living things.

instream use - Uses of water within the stream channel, e.g., fish and other aquatic life, recreation, navigation, and hydroelectric power production.

integrated resource planning - The management of two or more resources in the same general area; commonly includes water, soil, timber, grazing land, fish, wildlife, and recreation.

interbasin transfer - The diversion of water from one drainage basin to one or more other drainage basins.

irrigation - The controlled application of water to cropland, hayland, and/or pasture to supplement that supplied through nature.

jökulhlaup - Destructive flood that occurs as the result of the rapid ablation of ice by volcanic activity beneath the ice of a large glacier.

kilowatt (kW) - A unit of electrical power equal to 1000 watts or 1.341 horsepower.

kilowatt hour (kWh) - One kilowatt of power applied for one hour.

lagoon - (1) A shallow pond where sunlight, bacterial action, and oxygen work to purify wastewater. (2) A shallow body of water, often separated from the sea by coral reefs or sandbars.

lake - Any inland body of standing water, usually fresh water, larger than a pool or pond; a body of water filling a depression in the earth's surface.

leaching - The removal of soluble organic and inorganic substances from the topsoil downward by the action of percolating water.

litre - The basic unit of measurement for volume in the metric system; equal to 61.025 cubic inches or 1.0567 liquid quarts.

marsh - A type of wetland that does not accumulate appreciable peat deposits and is dominated by herbaceous vegetation. Marshes may be either fresh water or saltwater and tidal or non-tidal.

megawatt - A unit of electricity equivalent to 1000 kilowatts.

model - A simulation, by descriptive, statistical, or other means, of a process or project that is difficult or impossible to observe directly.

NAPLs - Nonaqueous phase liquids; i.e., chemical solvents such as trichloroethylene (TCE) or carbon tetrachloride – often toxic. Many of the most problematic NAPLs are DNAPLs – dense nonaqueous phase liquids.

natural flow  - The flow of a stream as it would be if unaltered by upstream diversion, storage, import, export, or change in upstream consumptive use caused by development.

navigable waters - Traditionally, waters sufficiently deep and wide for navigation by all, or specific sizes of, vessels.

non-renewable resources - Natural resources that can be used up completely or else used up to such a degree that it is economically impractical to obtain any more of them; e.g., coal, crude oil, and metal ores.

nutrient - As a pollutant, any element or compound, such as phosphorus or nitrogen, that fuels abnormally high organic growth in aquatic ecosystems (e.g., eutrophication of a lake).

oligotrophic lake - Deep, clear lakes with low nutrient supplies. They contain little organic matter and have a high dissolved oxygen level.

organic - (1) Referring to or derived from living organisms. (2) In chemistry, any compound containing carbon.

organism  - A living thing.

parts per million (PPM) - The number of "parts" by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations. Large concentrations are expressed in percentages.

pathogenic microorganisms - Microorganisms that can cause disease in other organisms or in humans, animals, and plants.

percolation - The movement of water downward through the subsurface to the zone of saturation.

permafrost - Perennially frozen layer in the soil, found in alpine, arctic, and antarctic regions.

pesticide - A substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. Also, any substance or mixture of substances intended to regulate plant or leaf growth. Pesticides can accumulate in the food chain and/or contaminate the environment if misused.

pH - An expression of both acidity and alkalinity on a scale of 0 to 14, with 7 representing neutrality; numbers less than 7 indicate increasing acidity and numbers greater than 7 indicate increasing alkalinity.

photosynthesis - The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll, using sunlight as an energy source.

phytoplankton - Usually microscopic aquatic plants, sometimes consisting of only one cell.

plankton - Tiny plants and animals that live in water.

polychlorinated biphenyls (PCBs) - A group of chemicals found in industrial wastes.

pond - A small natural body of standing fresh water filling a surface depression, usually smaller than a lake.

precipitation  - Water falling, in a liquid or solid state, from the atmosphere to a land or water surface.

rain - Water falling to earth in drops that have been condensed from moisture in the atmosphere.

receiving waters - A river, ocean, stream, or other watercourse into which wastewater or treated effluent is discharged.

recharge - The processes involved in the addition of water to the zone of saturation; also the amount of water added.

recyclable - Refers to such products as paper, glass, plastic, used oil, and metals that can be reprocessed instead of being disposed of as waste.

renewable resource  - Natural resource (e.g., tree biomass, fresh water, fish) whose supply can essentially never be exhausted, usually because it is continuously produced.

reservoir  - A pond, lake, or basin (natural or artificial) that stores, regulates, or controls water.

resource - A person, thing, or action needed for living or to improve the quality of life.

river  - A natural stream of water of substantial volume.

river basin - A term used to designate the area drained by a river and its tributaries.

runoff  - The amount of precipitation appearing in surface streams, rivers, and lakes; 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.

saltwater intrusion  - The invasion of fresh surface water or groundwater by saltwater.

sanitary sewers  - Underground pipes that carry off only domestic or industrial waste, not storm water.

sediment  - Fragmented organic or inorganic material derived from the weathering of soil, alluvial, and rock materials; removed by erosion and transported by water, wind, ice, and gravity.

sedimentation  - The deposition of sediment from a state of suspension in water or air.

seiche  - A periodic oscillation, or standing wave, in an enclosed water body the physical dimensions of which determine how frequently the water level changes.

septic tank  - Tank used to hold domestic wastes when a sewer line is not available to carry them to a treatment plant; part of a rural on-site sewage treatment system.

sewage - The waste and wastewater produced by residential and commercial establishments and discharged into sewers.

sewage system  - Pipelines or conduits, pumping stations, force mains, and all other structures, devices, and facilities used for collecting or conducting wastes to a point for treatment or disposal.

sewer - A channel or conduit that carries wastewater and storm water runoff from the source to a treatment plant or receiving stream.

sewerage  - The entire system of sewage collection, treatment, and disposal.

silt  - Fine particles of sand or rock that can be picked up by the air or water and deposited as sediment.

sludge  - A semi-solid residue from any of a number of air or water treatment processes.

solvent  - Substances (usually liquid) capable of dissolving or dispersing one or more other substances.

spoils - Dirt or rock that has been removed from its original location, destroying the composition of the soil in the process, as with strip-mining or dredging.

spring  - An area where groundwater flows naturally onto the land surface.

storm sewer  - A system of pipes (separate from sanitary sewers) that carry only water runoff from building and land surfaces.

stream  - Any body of running water moving under gravity flow through clearly defined natural channels to progressively lower levels.

streamflow  - The discharge that occurs in a natural channel. Although the term "discharge" can be applied to the flow of a canal, the word "streamflow" uniquely describes the discharge in a surface stream. The term "streamflow" is more general than the term "runoff", as streamflow may be applied to discharge whether or not it is affected by diversion or regulation.

surface water  - All water naturally open to the atmosphere (rivers, lakes, reservoirs, streams, impoundments, seas, estuaries, etc.); also refers to springs, wells, or other collectors that are directly influenced by surface water.

suspended solids (SS)  - Defined in waste management, these are small particles of solid pollutants that resist separation by conventional methods. Suspended solids (along with biological oxygen demand) are a measurement of water quality and an indicator of treatment plant efficiency.

sustainable development - Development that ensures that the use of resources and the environment today does not restrict their use by future generations.

swamp - A type of wetland that is dominated by woody vegetation and does not accumulate appreciable peat deposits. Swamps may be fresh water or saltwater and tidal or nontidal.

temperature - The degree of hotness or coldness.

thermal pollution  - The impairment of water quality through temperature increase; usually occurs as a result of industrial cooling water discharges.

toxic - Harmful to living organisms.

transpiration  - The process by which water absorbed by plants, usually through the roots, is evaporated into the atmosphere from the plant surface, principally from the leaves.

tributary - A stream that contributes its water to another stream or body of water.

tsunami  - A Japanese term that has been adopted to describe a large seismically generated sea wave capable of considerable destruction in certain coastal areas, especially where sub-marine earthquakes occur.

turbidity  - Cloudiness caused by the presence of suspended solids in water; an indicator of water quality.