Watershed Glossary

Watershed Glossary

Benthic - Referring to bottom-dwelling aquatic organisms.

Bioaccumulation - The increase in the concentration of a chemical in an organism that resides in an environment contaminated by low concentrations of various organic compounds.

Biological magnification - The increase in the concentration of a heavy metal (i.e., mercury) or organic contaminants (i.e., chlorinated hydrocarbons-CBCs) in organisms as a result of their consumption with in a food chain/web.

Biological Diversity - Describes attributes of species richness, genetic variation, and complexity within an ecosystem.

Buffer Zones - In general, an area used to separate conflicting uses. In relation to riparian and watershed management areas, its a zone that can be maintained to minimize impacts to the local water resource (i.e., vegetative buffer strips along a creek).

Channelization - Navigation or flood control projects that widen, deepen, or straighten streams, canals, or rivers. Environmental consequences associated with channelization include bank erosion, increased sedimentation and flooding, and decreased biomass.

Conservation Tillage - Any sequence of tillage that reduces loss of water or soil relative to conventional tillage.

Discharge - Volume of water flowing past a point in a water system for a specific time interval.

Ecosystem - A biological community and the local, surrounding non-biological factors associated with it

Erosion - Process of wearing away of a surface by physical means (water, wind, ice).

Eutrophication - Addition of excessive nutrients (usually nitrates or phosphates) to a body of water, leading to overgrowth of aquatic plants.

Frequency - Stable rivers can accommodate natural levels of water resulting from typical storms. However, with increased runoff water entering the system from surrounding areas with impervious roadways and surfaces lacking vegetation, water levels quickly rise to less manageable levels. High water levels, with greater than normal velocities can accelerate the rate of bank erosion, increase sediment load, and displace aquatic species of plants and animals.


Hydrologic cycle - The flows and stocks of water in the ecosphere including the processes of precipitation, evaporation, transpiration, condensation, and surface and subsurface runoff.

Impervious - Description of a material that prevents passage of a fluid (i.e., asphalt surfaces)

Infiltration - Downward entry of water into the soil profile

Interception - Capture of precipitation by surfaces and structures (i.e., vegetation)

Macrophytes - Large rooted or floating aquatic plants.

Methylation - The process by which an element (commonly a metal) is joined with a methyl group (CH4). For example, methyl mercury is produced from an atom of mercury bonded to a methyl group. This compound is produced in the natural environment chiefly by bacteria following contamination of ionic, inorganic forms of mercury. This new compound then becomes absorbed by various organisms, moves up levels of a food chain, and increases its concentration with each level.

Oxides - Gases containing (for our purposes) either nitrogen or sulfur combined with oxygen. The most common oxides contributing to pollution include nitrogen dioxide (NO2) and sulfur dioxide (SO2). Both types of gases are major air pollution contributors. Sources of pollution from oxides typically include smokestacks, exhaust, and sulfur-containing compounds.

Percolation - Downward movement of water within the soil profile.


Phytoplankton - Microscopic plants, such as algae, suspended in aquatic environments.

Riparian - Type of wetland transition zone between upland habitats and aquatic habitats. Lush vegetation along a stream is usually associated with a riparian area.

Runoff - The portion of storm water or snow melt that enters a water system instead of entering the ground through infiltration.

Sedimentation - Soil particles, clay, sand, or other materials settle out of a fluid suspension into the bottom of a body of water. Human caused earth-moving activities such as agriculture and construction greatly increase sediment load.

Slope - The degree of deviation of a surface from the horizontal plane, usually measured in a percent, degrees or numerical ratio.

Species Richness - A measure of the number of species in relation to the total number of individuals in a particular community.

Substrate - In terms of river/stream characteristics, substrate usually refers to both inorganic and organic particles on the stream bed. Examples of substrates include: bedrock, boulder, cobble, gravel, silt, sand, detritus, muck, and artificial.

Tillage - Mechanical manipulation of soil, usually associated with agriculture in terms of crop production.

Trophic Level - All the members of an ecological community that are the same number of food-chain steps from the primary source of energy.

Turbidity - A measure of the amount of suspended material (sediment) in water based on the relative ability of light to penetrate the water's surface. This cloudiness of water due to excess sediment, is an extremely important factor in maintaining aquatic diversity. Many sensitive organisms, especially fish, require relatively clear water conditions for reproducing and finding prey. Some organisms, like shell-fish are filter-feeders and continually filter the water in the environment. These organisms can become choked by sediment and eventually die in heavily turbid waters.

Watershed - The area of land that drains into a stream or lake, synonymous with drainage basin.