Water Planning Glossary


  • Algae: Simple, rootless plants that grow in bodies of water in relative proportion to the amounts of nutrients available. Blue-green algae are primitive algae, typically found in water high in phosphorus that form scum blooms that congregate at the water's surface. Diatoms are algae that have silica in their cell walls.
  • Algal Bloom: An unusual or excessive abundance of algae.
  • Aquifer: A geologic formation, group of formations, or part of a formation that contains sufficient saturated, permeable material to yield useful quantities of ground water to wells and springs.
  • Bacteria: Single celled organisms having no cellular nucleus. Pathogenic bacteria are capable of causing disease. Coliform bacteria are prolific in the intestines of warm blooded animals and are used as an indicator of fecal waste pollution.
  • Bankfull depth: The mean water depth that occurs during a bankfull stream flow event.
  • Bankfull width: The mean water width that occurs during a bankfull stream flow event.
  • Baseflow: Portions of stream discharge derived from natural sources, such as groundwater and large lakes and swamps situated outside the area of net rainfall that created local surface runoff; the sustained discharge that does not result from direct runoff or from stream regulations, water diversion, or other human activities.
  • Best Management Practices: Methods, measures or practices to prevent or reduce water pollution, including but not limited to, structural and nonstructural controls, operation and maintenance procedures, other requirements and scheduling and distribution of activities.
  • Bioengineering: An applied science that combines structural, biological, and ecological concepts and sediment and flood control.
  • Buffer: An area maintained in permanent vegetation and managed to reduce the impacts of adjacent land use.
  • Channelization: The practice of straightening a waterway to remove meanders and in order to increase the volume and/or rate of discharge. Sometimes concrete is used to line the sides and bottom of the channel.
  • Chlorophyll-a: The primary photosynthetic pigment in plants, used to measure the concentration of algae in lakes.
  • Clean Water Act: The Federal Water Pollution Control Act of 1948, amended beginning in 1956 to become the Federal Water Pollution Control Act of 1972. Congress passed the original Clean Water Act in 1972 and amended it with the Water Quality Act of 1987. The major impact of the 1987 amendments was to include a permitting process and requirements for municipal storm water discharges.
  • Community: An aggregation of living organisms having mutual relationships among themselves and to their environment.
  • Cone of Depression: The depression of the water table or potentiometric surface caused by pumping from a well, wellfield, or surface water body within its area of influence.
  • Detention basin: Impoundments constructed to retain storm water for extended periods of time and allow for the retention of pollutants in the pond through deposition of sediments and attached pollutants.
  • Ecoregion: An environmental area characterized by a specific land use, soil type, land surface form and natural vegetation.
  • Ecosystem: The system formed by the interaction of a community of organisms with their environment.
  • Ecosystem Management: The careful and skillful use of ecological, economic, social, and managerial principles in managing ecosystems to produce, restore, or sustain ecosystem integrity and desired uses, products, and services over the long term.
  • Environment: All the biotic and abiotic factors of a site.
  • Ephemeral Stream: A stream or portion of a stream that flows only in direct response to precipitation. It receives little or no water from springs and no long-continued supply from melting snow or other sources. Its channel is at all times above the water table. The term may be arbitrarily restricted to streams which do not flow continuously during periods of one month.
  • Erosion: The wearing away of land surface by water or wind which occurs naturally from weather or runoff, but is often intensified by human activities.
  • Eutrophic: Habitats, particularly soils and water, that are rich in nutrients and plant growth. Eutrophic waters generally have high sedimentation at their bottoms. The lower levels of eutrophic waters have very low levels of dissolved oxygen.
  • Eutrophication: The aging process by which lakes are fertilized with nutrients. Natural eutrophication changes the character of a lake very gradually. Cultural eutrophication is the accelerated aging of a lake resulting from human activities.
  • Evapotranspiration: The total loss of water to the atmosphere by evaporation from land and water surface and by transpiration from plants.
  • Exotic or Invasive Species: An organism that is out of its naturally occurring range and environment, and occupying the habitat of native species.
  • Filter Strip: A linear strip of land maintained to slow the velocity of runoff and filter sediment.
  • Floodplain: That portion of a stream valley adjacent to the channel that is built by sediments of the stream and covered with water when the stream overflows its banks at flood stage. Also, the nearly level land situated on either side of a channel that is subject to overflow flooding.
  • Forest: A descriptive classification of land type predominated by trees and woody vegetation and characterized by high structural diversity, greater than 25 percent canopy shading, and by the significant accumulation of organic duff on the soil surface.

  • Habitat: A place where the physical and biological elements of ecosystems provide a suitable environment and the food, cover, and space resources needed for plant and animal livelihood.
  • Headwaters: The uppermost reaches of a stream or river.
  • Hydrogeology: The science dealing with the relationship of subsurface water and geologic materials.
  • Hydrologic Function: The capacity of a stream to move or to store water, bedload material, and suspended sediment. Stream gradient, the resultant stream power and size of material are critical factors.
  • Hydrology: The study of the properties, distribution, circulation, and effects of water on the earth's surface, soil, and atmosphere.
  • Hypoxia: An oxygen depleted area caused by excessive nitrogen and phosphorus in the freshwater supply to the ocean. Hypoxia can cause stress or death in the bottom dwelling organisms that can't move out of the hypoxia zone. Often called the "dead zone," the hypoxic zone is located along the Louisiana-Texas coast in which water near the bottom of the Gulf of Mexico contains less than 2 parts per million of dissolved oxygen.
  • Impervious Surface: Ground cover that does not allow, or minimally allows, for infiltration of water (e.g., roofs, parking lots, roads) and which increases the volume and speed of runoff after a rainfall.
  • Impoundment: Any lake, reservoir, pond or other containment of surface water occupying a bed or depression in the earth's surface and having a discernible shoreline.
  • Infiltration: Movement of surface water into the soil.
  • Intermittent Stream: A defined channel in which surface water is absent during a portion of the year.

  • Karst: An area of irregular limestone in which erosion has produced fissures, sinkholes, underground streams, and caverns.
  • Large Woody Debris: A term used to describe logs, tree boles, rootwads, and limbs that are in, on, or near a stream channel.
  • Littoral: Of, relating to, or existing on a shore.
  • Loading: The total amount of material (sediment, nutrients and oxygen-demanding material) brought into a lake by inflowing streams, runoff, direct discharge through pipes, groundwater, the air (aerial or atmospheric load) and other sources over a specific period of time (often annually).
  • Macrophyte: Rooted or free-floating large aquatic plants that are found in wetlands, lakes and streams.
  • Meander: A circuitous winding or bend in the river.
  • Mesotrophic: Lake condition in which nutrient levels are between eutrophic and oligotrophic levels. A mesotrophic lake has fairly good water quality and may be used for recreational activities.
  • National Pollutant Discharge Elimination System (NPDES): Created in 1972 under the Clean Water Act to authorize discharges to local receiving waters only pursuant to government permits, in an effort to reduce point source pollutants.
  • Nationwide Urban Runoff Program (NURP): An U.S. EPA program aimed at characterizing the composition of storm water runoff and its impacts upon receiving waters and assessing best management practices. The program was undertaken in 28 U.S. cities in the early 1980s.
  • Native Species: A naturally occurring organism that is within its range and normal environment.
  • Nonpoint Source: Nutrient and pollution sources not discharged from a single point, e.g. runoff from agricultural fields, feedlots or urban streets.
  • Nutrient: Elements or compounds essential to growth and development of living things (e.g., nitrogen, potassium, phosphorus).
  • Nutrient Cycling: The path of an element through the ecosystem, including its assimilation by organisms and its release in a reusable inorganic form.
  • Oligotrophic: A soil or water body having a very low nutrient content. In soils this may be due to the paucity of nutrients in the parent rock. Alternatively, excessive leaching can result in oligotrophic soils. Oligotrophic water bodies are unable to sustain active aquatic flora and fauna communities.
  • Parts Per Million (ppm): A common basis of reporting water analysis. One part per million (ppm) equals one pound per million pounds of water. Part per billion: one pound per billion pounds of water.
  • Perennial Streams: A defined channel containing surface water throughout an average rainfall year.
  • Point Source: Originating from a discrete identifiable source or conveyance.
  • Pollution: The process of contaminating air, water and land with impurities to a level that is undesirable and results in a decrease in usefulness of the environment for beneficial purposes.
  • Polychlorinated biphenyls (PCBs):
  • A group of at least 50 widely used compounds containing chlorine. PCBs can accumulate in food chains and are thought likely to produce a variety of harmful side effects, particularly during the reproductive cycle of plants and animals. Many are non biodegradable.
  • Pool: Deeper areas of a stream with slow-moving water, often used by larger fish for cover.
  • Potable Water: Drinking water. Water whose chemical constituents do not exceed the limits set forth in State water quality standards.
  • Potentiometric Surface: A surface which represents the pressure head in a confined aquifer and is defined by the levels to which water will rise in a well in the confined aquifer, that fully penetrates the aquifer.

  • Recharge: The replenishment of ground water through the infiltration of rainfall and other surface waters.
  • Recharge Area/Zone: An area (or zone) that, due to its pervious ground cover, karst topography, or permeability, contributes to the state of recharge.
  • Retention: The prevention of direct discharge of stormwater runoff into receiving waters; examples include systems which discharge through percolation, exfiltration, and evaporation processes and which generally have residence times less than three days.
  • Retention Time: The length of time water, nutrient, or other chemical substances remain in a lake.
  • Riffle: Shallow section of a stream or river with rapid current and a surface broken by gravel, rubble, or boulders.
  • Riparian: Pertaining to anything connected with or immediately adjacent to the banks of a stream or other body of water.
  • Riparian Forest Buffer: An area of trees, usually accompanied by shrubs and other vegetation, adjacent to a body of water and managed to maintain the integrity of stream channels and shorelines to 1) reduce the impact of upland sources of pollution by trapping, filtering, and converting sediments, nutrients, and other chemicals, and 2) supply food, cover, and thermal protection to fish and other wildlife.
  • Riprap: Stones of varying size used to dissipate energy or stabilize a soil surface.
  • Runoff: Surface water (usually rainfall) that is not evaporated, transpired, used, or absorbed into the ground water system, and thus flows to a surface water body.
  • Scour: Local removal of material from a streambed by flowing water.
  • Secchi Disk: A device used to measure the depth of light penetration in water.
  • Sediment: Fragmented material that originated from weathering rocks and decomposing organic material that is transported by, suspended in, and eventually deposited in the streambed.
  • Sheetflow: A flow process associated with water movement on sloping ground surfaces that is not channelized or concentrated.
  • Storm water: Water that results from storm (usually rainfall) event.
  • Stream: A perennial or intermittent watercourse having a defined channel (excluding man-made ditches) which contains flow from surface and groundwater sources during at least 50 percent of an average rainfall year.
  • Stream Discharge: Quantity of stream flow per unit of time. Stream discharge is calculated by multiplying stream velocity (V) by stream cross-sectional area (A) so that Q=VA, where Q = discharge (m3/second); V = velocity (m/s); and A = cross section (m2).
  • Stream Order: A numerical system (ranking from headwaters to river terminus) used to designate the relative position of a stream or stream segment in a drainage basin.
  • Streambank: The portion of the channel cross-section that restricts lateral movement of water at normal water levels.
  • Swale: A natural depression or wide shallow ditch used to temporarily store, route, or filter runoff.
  • Trophic State Index (TSI): The trophic state index was developed in 1977 to provide a convenient measure of water quality. The scale is 1 to 100 and uses the three parameters of total phosphorus, chlorophyll a and Secchi disk depth to categorize lake water quality.
  • Trophic Status: The level of growth or productivity of a lake as measured by phosphorus content, algae abundance, and depth of light penetration.
  • Turbidity: Murkiness or cloudiness of water, indicating the presence of suspended sediments, dissolved solids, natural or man-made chemicals, algae, etc.


  • Water Budget: The movement of water into and out of a lake as described by a balance equation in which the change in storage of water equals the rate of inflow from all sources minus the rate of loss.
  • Water Quality: A state of lake water represented by a combination of productivity, chemistry, cleanliness and recreational potential.
  • Watershed: 1) An area of land that drains into a particular river or body of water; usually divided by topography. 2) The total area of land above a given point on a waterway that contributes surface runoff water to the flow at that point; a drainage basin or a major subdivision of a drainage basin.
  • Wetlands: Low-lying areas inundated or saturated by water at a frequency and duration sufficient to support wetland vegetation (e.g. wetlands include such areas as swamps, marshes and wet meadows). Wetlands remove pollutants through a series of chemical, physical and biological mechanisms.


  • Zoning: The practice of dividing land into regions or parcels pertaining to its use or activities within it.