Terms You Should Know About Water Conservation

Water Drop


A subsurface formation of rock, glacial material, or other deposits which are capable of storing and yielding water to a well or spring.


Restoration and stabilization techniques that use plants, often native species, to mimic natural functions and benefits.


The use of vegetation (usually grasses or wetland plants) to filter and treat storm water runoff as it is conveyed through an open channel.

Biological diversity

Multiple species of organisms living together in balance with their environment and with each other.


The use of vegetation in retention areas designed to allow infiltration of runoff into the ground. The plants provide additional pollutant removal and filtering functions while infiltration allows the temperature of the runoff to be cooled.


Abandoned or underutilized properties where development is complicated by real or perceived contamination.

Buffer zone

A designated transitional area around a stream, lake, or wetland left in a natural, usually vegetated state so as to protect the water body from runoff pollution. Development is often restricted or prohibited in a buffer zone.

Catch basin

An inlet to a storm or combined sewer equipped with a sediment sump, and sometimes a hood, on its outlet pipe to the sewer. Catch basins can collect some of the sediment and debris washed off the streets, and help to provide a water seal against the venting of sewer gases. Catch basins should be cleaned out regularly to function properly.

Channel erosion

The widening, deepening (called channel scour), and upstream cutting of a stream channel caused by moderate and extreme flow events. Channel erosion is one way that a stream reacts to changes in flow patterns.

Chemical water quality

The quality of a water body determined using chemical rather than physical or biological parameters and methods.

Conservation Design

A type of site design that incorporates conservation measures such as on-site tree preservation, preserving natural areas and open space.


A semi-enclosed coastal water body such as a bay, mouth of a river, salt marsh, or lagoon, where freshwater and saltwater mix. These waters support a rich and diverse ecology.


A process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients that stimulate excessive plant growth. This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die.

Filter Strip

Grassed strips situated along roads or parking areas that remove pollutants from runoff as it passes through, allowing some infiltration, and reductions of velocity.


Can be either a natural feature or statistically derived area adjacent to a stream or river where water from the stream or river overflows its banks at some frequency during extreme storm events.


Water that flows below the ground surface through saturated soil, glacial deposits, or rock.


The science addressing the properties, distribution, and circulation of water across the landscape, through the ground, and in the atmosphere.

Impervious surface

A surface that cannot be penetrated by water such as pavement, rock, or a rooftop and thereby prevents infiltration and generates runoff.


The process or rate at which water percolates from the land surface into the ground.

Measurable goal

A numerical, achievable target or objective selected by a municipality, project manager, or the community that guides and measures the success of the selection, design, and operation or maintenance of a storm water management measure.

National Pollutant Discharge Elimination System (NPDES)

A provision of the Clean Water Act that prohibits discharge of pollutants into waters of the United States unless a special permit is issued by the EPA, a state, or (where delegated) a tribal government or an Indian reservation.

Natural buffer

A variable width area maintained with natural vegetation between a pollutant source and a water body that provides natural filtration and other forms of protection.


The point of discharge from a river, pipe, drain, etc. to a receiving body of water.

Polluted runoff

Rainwater or snow melt that picks up pollutants and debris as it runs off roads, highways, parking lots, lawns, , and other land-use activities that can generate pollutants.

Porous pavement and pavers

Porous pavement often appears the same as traditional asphalt or concrete but is manufactured without "fine" materials, and instead incorporates void spaces that allow for infiltration. Runoff is thereby infiltrated directly into the soil and receives some water quality treatment.


Water from rainfall, snow melt, or otherwise discharged that flows across the ground surface instead of infiltrating the ground.

Sanitary sewer system

Underground pipes that carry only domestic or industrial waste water to a sewage treatment plant or receiving water.


A solid-liquid separation process utilizing gravitational settling to remove soil or rock particles from the water column.

Storm sewer system

A system of pipes and channels that carry storm water runoff from the surfaces of building, paved surfaces, and the land to discharge areas.

Storm water

Water derived from a storm event or conveyed through a storm sewer system.

Surface water

Water that flows across the land surface, in channels, or is contained in depressions on the land surface (e.g. runoff, ponds, lakes, rivers, and streams).

Urban (metropolitan) runoff

Runoff derived from urban or suburban land-use that is distinguished from agricultural or industrial runoff sources.

Water (hydrologic) cycle

The flow and distribution of water from the sky, to the Earth's surface, through various routes on or in the Earth, and back to the atmosphere. The main components are precipitation, infiltration, surface runoff, channel and depression storage, and groundwater.


The land area, or catchment, that contributes water to a specific water body. All the rain or snow that falls within this area flows to the water bodies as surface runoff, in tributary streams, or as groundwater.

Sources: Natural Resources Defense Council