Potomac Highlands Watershed School

Stream Cleaner Environmental Forum

Key Vocabulary


The term means “without oxygen” - water void of oxygen.  An anoxic event occurs when an area of water becomes completely depleted of oxygen below the surface.

Best management practice

A method used to prevent or reduce the pollution resulting from some activity. The term originated from rules and regulation in Section 208 of the Clean Water Act.

Civic responsibility

The responsibility of a citizen reflected in the actions and attitudes associated with democratic governance and social participation. Civic responsibility can include participation in government, church, and voluntary associations.  Actions of civic responsibility can be displayed in advocacy for various causes, such as political, economic, civil, environmental or quality of life issues.


The amount of a substance found in a certain volume of water - usually expressed as milligrams per liter (mg/L) or parts per million (ppm). 


General agreement among the members of a given group or community.

Cover Crop

Grass planted to keep rain from washing soil, nutrients and other pollution into streams, often used on farms and construction sites where top soil is exposed.

Dissolved oxygen

The amount of oxygen that is present in the water. It is measured in units of milligrams per liter (mg/L), or the milligrams of oxygen dissolved in a liter of water.


Community of organisms living in a particular environment and the physical elements in that environment with which they interact. An ecosystem can be as small as a field or as large as the ocean, depending on the scale of examination.

Hydrology Hydrology is the study of water; its movement on and under the ground and in the atmosphere, its distribution on the Earth, and its quality. . 
Hydrologic Cycle Also known as "Water Cycle."   Describes the continuous movement of water on and under the ground and in the atmosphere.  Nice illustration here.

Impervious Surface

A surface that water cannot penetrate.  Impervious surfaces include natural surfaces like solid rock, and man-made surfaces such as parking lots, buildings, and roads. 


The total amount of a substance that passes by some point in a certain amount of time - as in pounds per hour or tons per day. It is equal to the concentration times the total volume of water

Non point source

A pollution source that washed from the surface of the land.  A source of pollution that does not come from a pipe or defined point.  A pollution source not regulated by government agencies.


A chemical that plants and animals require for growth

Point source

A pollution source from a pipe or defined location regulated by government agencies.

Riparian Buffer

Areas along rivers and streams planted with tall grass and/or trees to help filter nutrients, sediments, and other pollutants from runoff as well as remove pollutants from groundwater.

Scientific Model

Mathematical tools used to understand large scale processes that can't be observed directly in their entirety.   The Chesapeake Bay Program uses mathematical models to simulate changes in the Bay ecosystem due to changes in population, land use, or pollution management.


Sediment is the product of erosion that washes soil particles into streams, rivers, and other bodies of water.  Poor land management practices, such as failing to stabilize construction sites, can greatly accelerate erosion.


A stakeholder is a person or a group with a legitimate interest in a project, organization, or government action. 


The way someone controls or manages something.  A good steward protects from harm.

Stream Flow

The water discharge in a stream or river channel.

Tributary A tributary is a stream or river that flows into a larger river.   Tributaries do not flow directly into estuaries, bays, or oceans. 

Tributary Strategy

River-specific cleanup plans in the Chesapeake Bay watershed.  Tributary Strategies detail the "on-the-ground" actions needed to reduce the amount of nutrients and sediment flowing into the Chesapeake Bay.  They are a framework that evolves over time to chart the most efficient and effective course to a clean Chesapeake Bay.


The area of land that drains to a stream, river, or body of water.