• acid mine drainage (AMD)

    Acidic, heavymetals- laden stream contamination resulting from the drainage of water that contains acidic soils and tailings (residues) from the mining process. Usually associated with surface and underground coal mining.

  • acid rain

    A term in common use that implies the deposition of acid materials in wet precipitation (rain, snow, fog) as well as in the dry precipitation of dust and gases. One source is the combining of rain and sulphur dioxide emissions—a by-product of combustion of fossil fuels.

  • alkaline

    The “opposite” of acid, a solution or substance having a high concentration of (OH) ions that can buffer or neutralize an acid. An example of an alkaline substance is lime used to neutralize soil acidity on farm fields and lawns.

  • benthic macro-invertebrate

    Aquatic animals larger than ½ millimeter, without backbones, dwelling on or in the bottom of aquatic environments. Examples are clams, crayfish, and several types of aquatic insect larvae.

  • benthos

    Biota closely associated with the bottom of a water body.

  • Best Management Practice (BMP)

    A practice or combination of practices determined to be the most effective means of preventing or reducing the amount of pollution generated by nonpoint sources to a level compatible with water quality goals.

  • baseflow

    Sustained, low flow in a stream, primarily from groundwater discharge. Sometimes known as dry weather flow.

  • biological identity

    The condition of the biological communities (usually benthic macro-invertebrates and/or fish) of a waterbody based on a comparison to a reference that is a relatively undisturbed system and represents the best quality to be expected for the ecoregion.

  • biota

    All of the organisms, including animals, plants, fungi, and microbes, found in a given area.

  • buffer

    A solution resistant to pH changes, or whose chemical makeup tends to neutralize acids or bases without a change in pH. Surface waters and soils with chemical buffers are not as sensitive to acid deposition as those with poor buffering capacity.

  • channelization

    The artificial enlargement, straightening, or realignment of a stream channel.

  • detritus

    Disintegrated or broken up mineral or organic material in a water body.

  • dissolved oxygen

    Gaseous form of oxygen in solution with water, abbreviated as DO and measured as mg/L (milligrams per liter) or ppm (parts per million).

  • duff

    The organic layer on top of mineral soil consisting of fallen leaves and other decomposing vegetation. Thick layers of duff are often found on the floors of undisturbed forests.

  • eutrophication

    The process by which streams and other water bodies become enriched with dissolved nutrients, resulting in increased growth of algae and other microscopic plants.

  • embayment

    An indentation in the shoreline forming an open bay.

  • fall line

    A line roughly along Interstate 95 joining areas of relatively steep gradient on several rivers on Maryland’s western shore. The line marks the geographical area where each river descends from the hilly Piedmont to the flat and sandy Coastal Plain. It also marks the limit of upstream commercial navigation.

  • habitat

    The environment or specific surroundings where plants and animals live and grow.

  • Index of Biotic Integrity (IBI)

    A combination of measures, or metrics, that describe community structure, function and pollution sensitivity and are used to assess the health of an aquatic ecosystem.

  • impervious surface

    Hard, non-porous surfaces such as roads, parking lots, and rooftops that prevent precipitation from soaking into the ground, thus increasing surface runoff.

  • meander

    The winding of a stream channel.

  • migration corridors

    Narrow areas of habitat through which animals may travel to reach larger habitat areas.

  • nitrate

    The most biologically available form (NO3) of the nutrient, nitrogen; technically referred to as nitrate-nitrogen.

  • non-point source

    Pollution that does not originate from a definable point (e.g., soil or urban runoff).

  • nutrients

    Any chemical element or compound essential to life, including carbon, oxygen, nitrogen, phosphorus. When available in excess quantities, these function as pollutants by fueling abnormally high organic growth in waterbodies.

  • 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.

  • phosphorus

    An element that serves as a plant nutrient. Phosphorus is most easily used by plants in the form of orthophosphate (PO4).

  • point source discharge

    Pollutant discharge that originates from an identifiable point such as a pipe.

  • riffle

    A rocky, shallow, turbulent area of a stream or river where oxygen is physically introduced into the water.

  • riparian buffer

    A vegetated protective area next to a water body serving as a barrier against polluted runoff and a habitat corridor for terrestrial animals.

  • river basin

    The land area drained by a river and its tributaries.

  • sediment

    Mud, sand, silt, clay, and other debris from both organic and inorganic sources that is either suspended in or settles to the bottom of a water body.

  • stormwater

    Rainwater that reaches a stream or other water body as surface runoff without soaking into the ground. The water may enter the stream by direct runoff, or enter a system of channels and pipes designed to carry collected rainwater directly to a stream.

  • substrate

    Submerged mineral or vegetative surfaces used by biota for attachment, movement, or shelter. Stream substrates include gravel, cobble, boulder, roots, leaves, and limbs.

  • watershed

    The area of land from which rainfall (and/or snow melt) drains into a single point. Watersheds are sometimes referred to as drainage basins or drainage areas. Ridges of higher ground generally form the boundaries between watersheds. At these boundaries, rain falling on one side flows toward the low point of one watershed, while rain falling on the other side of the boundary flows toward the low point of a different watershed.

**This glossary was taken from “From the Mountains to the Sea: The State of Maryland’s Freshwater Streams” (Boward, Kazyak, Stranko, Hurd, & Prochaska 1999 – Marlyand Department of Natural Resources, with support from United States Environmental Protection Agency: National Health and Environmental Effects Research Laboratory: Atlantic Ecology Division and Region III: Environmental Services Division), which can be found here.