| A | B | D | E | F | G | H | I | N | O | P | R | S | T | W
(click to show/hide expanded definition)
« Back to topA
Abatement — Reducing the degree or intensity of, or eliminating pollution, as a water pollution abatement program.
Acid Rain — Acid rain is a form of acid deposition in which sulphur dioxide and nitrogen oxides transform into acidic particles or vapors in the atmosphere over distances of hundreds to thousands of miles.
Acre — A measure of area equal to 43,560 square feet (4,046.87 square meters). One square mile equals 640 acres, and is also referred to as a Section.
Aquifer — A water-bearing stratum of permeable rock, sand, or gravel.
« Back to topB
Babble — To make a continuous low, murmuring sound, as flowing water.
Bacteria — Bacteria are single-celled organisms that are present everywhere and are mostly beneficial to human health. However, certain types of bacteria, when in large enough quantities, can cause human health problems.
Base Flow — (1) The flow that a perennially flowing stream reduces to during the dry season. It is supported by
groundwater seepage into the channel. (2) The fair-weather or sustained flow of streams; that part of stream
discharge not attributable to direct runoff from precipitation, snowmelt, or a spring. Discharge entering streams
channels as effluent from the groundwater reservoir. (3) The volume of flow in a stream channel that is not derived
from surface run-off. Base flow is characterized by los flow regime (frequency, magnitude, and duration daily,
seasonally, and yearly), by minimum low flow events and in context of the size and complexity of the stream and
Bedrock wells — A well that is drilled into the bedrock (ledge) through the sand, dirt, gravel, etc. that sits on top of that ledge. The well intersects fractures in the bedrock, and draws the water from there.
Buffer — An area of vegetation positioned between a waterbody or watercourse and nearby development. Buffers are valuable for slowing the flow of stormwater into adjacent water resources and for retention and filtering of Non-point Source Pollution.
« Back to topD
Disturbed area — (Geology) Area where vegetation, topsoil, or overburden has been removed, or where topsoil, spoil,
and processed waste has been placed.
Disturbed area. — All land areas that are stripped, graded, or grubbed at any time during the site preparation for, or construction of, a project unless the areas are returned to a condition with the same drainage patterns and vegetative cover type that existed prior to the disturbance. Both planting conducted to restore the previous cover type and restoration of any altered drainage patterns must occur within one year of disturbance.
"Same cover type" may include hydrologically improved cover type. For example, an area that was previously pasture may be replanted as forest.
"Disturbed area" does not include maintenance or redevelopment of an impervious area within the footprint of that impervious area, but does include new impervious areas. A natural or man-made waterbody is not considered a disturbed area.
Domestic water use — Water used normally for residential purposes
Drawdown — A lowering of the ground-water surface caused by pumping.
« Back to topE
Economic Valuation — In environmental and ecological fields, this is the estimation of an economic value for an ecosystem, a natural environment, or for some set of characteristics, processes, or functions of an ecosystem.
Ecosystem Services — Services and goods produced by ecosystem functioning and utilized by or otherwise promoting the existence and welfare of humans and human society. Some examples include water filtration by wetlands, oxygen production by vegetation, and fish nursury habita
Environmental Goods — Are typically non-marketed goods produced by ecosystems and ecosystems processes. Non-marketed goods means they are not openly sold or traded. Market price is the traditional economic indicator of value, therefore the value of environmental goods to consumers often cannot be found through traditional methods. It is more difficult to assign a value to goods such as clean air or water than to marketed goods such as a car, even though the environmental goods are highly valuable - even necessary for life - while the car may not be. This difficulty often results in the absence of any value at all for environmental goods, leading to an undervaluation of the ecosystems producing the goods. However, once the ecosystems and the goods they produce are lost, replacements are often more expensive, resulting in a net economic loss to society.
As an example, consider that water filtration and purification is a product of normal functioning in many ecosystems. Human-produced clean water (through purifications systems and in bottles) replaces the water no longer sufficiently cleaned by degraded ecosystems, but only at additional - and often greater - expense.
Environmental services — [need a definition.]
Environmental uses — The uses in the environment for a given element or component. Example water is an important and vital component of the environment.
Estuary — The area where a river meets the sea, where fresh and salt water meet.
Eutrophication — Eutrophication is a process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients that stimulate excessive plant growth (algae, periphyton attached algae, and nuisance plants weeds). 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.
Evapotranspiration — (1) The process by which plants take in water through their roots and then give it off
through the leaves as a by-product of respiration; the loss of water to the atmosphere from the earth’s surface by
evaporation and by transpiration through plants.
(2) The quantity of water transpired (given off), retained in plant
tissues, and evaporated from plant tissues and surrounding soil surfaces.
(3) The sum of Evaporation and
Transpiration from a unit land area.
(4) The combined processes by which water is transferred from the earth
surface to the atmosphere; evaporation of liquid or solid water plus transpiration from plants.
(5) The combined
evaporative-type processes, including evaporation, interception, and transpiration, usually applied to biological
systems. Evapotranspiration occurs through evaporation of water from the surface, evaporation from the capillary
fringe of the groundwater table, and the transpiration of groundwater by plants (Phreatophytes) whose roots tap
the capillary fringe of the groundwater table. The sum of evaporation plus transpiration.
« Back to topF
Fossil water — Water in underground strata that has accumulated over millions of years and is therefore not a renewable resource, unlike other ground water.
Fractured bedrock aquifer — An aquifer composed of solid rock, but where most water flows through cracks and
fractures in the rock instead of through pore spaces. Flow through fractured rock is typically relatively fast.
« Back to topG
GIS (Geographical Information System) — A computer information system that can input, store, manipulate, analyze,
and display geographically referenced (spatial) data to support the decision-making processes of an organization.
A map based on a database or databases. System plots locations of information on maps using latitude and
Ground water — (1) Generally, all subsurface water as distinct from Surface Water; specifically,
the part that is in the saturated zone of a defined aquifer.
(2) Water that flows or seeps downward and saturates
soil or rock, supplying springs and wells. The upper level of the saturate zone is called the Water Table.
stored underground in rock crevices and in the pores of geologic materials that make up the earth’s crust. Ground
water lies under the surface in the ground’s Zone of Saturation, and is also referred to as Phreatic Water.
« Back to topH
Hydrologic cycle — (1) The cycling of water from the atmosphere, onto and through the landscape and eventually
back into the atmosphere.
(2) The circuit of water movement from the atmosphere to the earth and return to the
atmosphere through various stages or processes such as precipitation, interception, runoff, infiltration, percolation,
storage, evaporation, and transportation. Also referred to as the Water Cycle and Hydrogeologic Cycle.
Hypoxia — Hypoxia means "low oxygen." In estuaries, lakes, and coastal waters low oxygen usually means a concentration of less than 2 parts per million. In many cases hypoxic waters do not have enough oxygen to support fish and other aquatic animals. Hypoxia can be caused by the presence of excess nutrients in water.
« Back to topI
Impervious area — The amount of impervious surface is a direct measure of the degree of urbanization, and it strongly affects both water quality in urban and suburban areas and replenishment of groundwater. Areas with more impervious, or nonporous, surfaces generate more runoff, which not only can contaminate and warm stream waters but also can degrade stream channels and banks. These changes have major impacts on the fish and wildlife that inhabit streams. In general, the impact on streams increases as the percentage of impervious surface in a watershed increases.
Infiltration — Infiltration is the process of water entering the soil. Often of concern is the infiltration rate - the rate at which water enters soil. This will be dependent on characteristics of the soil and use, vegetative cover, moisture content, and other factors.
Interception — In hydrology, the precipitation that is 'caught' or intercepted by the vegetation canopy covering the ground and not immediately available to surface and sub-surface processes.
« Back to topN
Nonpoint Source Pollution — Nonpoint source pollution (or NPS pollution) is a type of water pollution that does not originate from a specific place but instead from a variety of diffuse sources. Most NPS pollution comes from pollutants being washed into a waterbody by rainfall and snowmelt. There are many types of pollutants, both human-made and natural, that wash into our lakes, rivers, streams, wetlands, and coastal waters and percolated into our groundwater every year. Among these include excess sediment from stream bank erosion and improperly managed construction site, excess nutrients from fertilizer use and both excess nutrients and bacteria from livestock, pet waste and improperly working septic systems, and toxic chemicals such as oil, grease, and other motor vehicle fluids from road crossings, salt from winter ice melting, and herbicides and pesticides from residential and agricultural areas.
Nutrients — Nutrients are chemical elements and compounds found in the environment that plants and animals need to grow and survive. For water-quality investigations the various forms of nitrogen and phosphorus are the nutrients of interest. The forms include nitrate, nitrite, ammonia, organic nitrogen (in the form of plant material or other organic compounds), and phosphates (orthophosphate and others). Nitrate is the most common form of nitrogen and phosphates are the most common forms of phosphorus found in natural waters. High concentrations of nutrients in water bodies can potentially cause eutrophication and hypoxia.
« Back to topO
1. A systematic account of Existence.
2. (From philosophy) An explicit
formal specification of how to represent the objects, concepts
and other entities that are assumed to exist in some area of
interest and the relationships that hold among them.
For AI systems, what "exists" is that which can be
represented. When the knowledge about a domain is
represented in a declarative language, the set of objects
that can be represented is called the universe of discourse.
We can describe the ontology of a program by defining a set of
representational terms. Definitions associate the names of
entities in the universe of discourse (e.g. classes,
relations, functions or other objects) with human-readable
text describing what the names mean, and formal axioms that
constrain the interpretation and well-formed use of these
terms. Formally, an ontology is the statement of a logical
A set of agents that share the same ontology will be able to
communicate about a domain of discourse without necessarily
operating on a globally shared theory. We say that an agent
commits to an ontology if its observable actions are
consistent with the definitions in the ontology. The idea of
ontological commitment is based on the Knowledge-Level
3. The hierarchical structuring of
knowledge about things by subcategorising them according to
their essential (or at least relevant and/or cognitive)
qualities. See subject index. This is an extension of the
previous senses of "ontology" (above) which has become common
in discussions about the difficulty of maintaining subject
Overdraft — (1) A condition that occurs in a ground water basin when pumping exceeds recharge over an extended
period of time.
(2) That quantity of water pumped in excess of the safe yield; the act of overdrawing a water supply
or aquifer in amounts greater than replenishment. Also, the sustained extraction of ground water from an aquifer
at a rate greater than the recharge rate of the aquifer, resulting in a drop in the level of the water table. Also see
Ground Water Overdraft and Ground Water Mining.
« Back to topP
Private systems. — [need definition.]
« Back to topR
Recharge (Hydrologic) — (1) The downward movement of water through soil to groundwater.
(2) The process by
which water is added to the Zone of Saturation.
(3) The introduction of surface or ground water to groundwater
storage such as an aquifer. Recharge or replenishment of groundwater supplies consists of three (3) types:
 Natural Recharge which consists of precipitation or other natural surface flows making their way into
 Artificial or Induced Recharge which includes actions by man specifically designed to increase supplies
in a groundwater reservoirs through various methods such as water spreading (flooding), ditches, and
pumping techniques; and
 Incidental Recharge which consists of actions, such as irrigation and water diversion, which add to
groundwater supplies but are intended for other purposes.
Remote Sensing — The measurement or acquisition of information of some property of an object or phenomenon by
a recording device that is not in physical or intimate contact with the object or phenomenon under study. Also, the
utilization at a distance (as from aircraft, spacecraft, satellites, or ships) of any device and its attendant display for
gathering information pertinent to the environment, such as measurements of force fields, electromagnetic
radiation, infrared sensing, land use, water bodies, etc. Such systems typically employ devices such as cameras,
lasers, radio frequency receivers, radar systems, infrared detectors, sonar seismographs, gravimeters,
magnetometers, and scintillation counters.
Retention — That part of the precipitation falling on a drainage area that does not escape as a surface streamflow,
during a given period.
Runoff — Water flowing over or just beneath the land surface, following the natural contour or slope of the land, and not confined by a channel such as a permanent or temporary stream.
« Back to topS
Safe Water — Water that does not contain harmful bacteria, toxic materials, or chemicals, and is considered safe for drinking even if it may have taste, odor, color, and certain mineral problems.
Seacoast Area — For this Website, includes the Coastal watersheds from the Kennebunk River in Maine south and west to and including the Cocheco River in New Hampshire- for details, see the watershed map (hot link)
Sediment — Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. Excess sediment in a water body is one of the most prolific sources of nonpoint source pollution in the Seacoast area.
Seston — All material, both organic and inorganic, suspended in a waterway.
Solution channels — Tubular or planar channel formed by solution in carbonate-rock terrains, usually along joints
and bedding planes.
Surface water — The term surface water refers to water that comes from our rivers, streams, creeks, lakes, and reservoirs. The main uses of surface water include drinking-water and other public uses, irrigation uses, and for use by the thermoelectric-power industry to cool electicity-generating equipment.
Surficial aquifers — Are the uppermost saturated zone, typically an unconfined aquifer, of mappable extent. We further restrict the definition to include important water-supply aquifers that are the most likely to be degraded by human activities.
« Back to topT
Total Economic Value — In ecosystem service valuation, the total economic value of an ecosystem or the service considered. This is the sub of the values of all uses (and non-uses) of that ecosystem or service.
Toxic chemicals — Chemicals that can have toxic effects on the public or environment above listed quantities.
« Back to topW
Wastewater treatment — A facility designed to receive the wastewater from domestic sources and to remove
materials that damage water quality and threaten public health and safety when discharged into receiving streams
or bodies of water. The substances removed are classified into four basic areas:
 greases and fats;
 solids from human waste and other sources;
 dissolved pollutants from human waste and decomposition products; and
 dangerous microorganisms.
Most facilities employ a combination of mechanical removal steps and bacterial decomposition to achieve the
desired results. Chlorine is often added to discharges from the plants to reduce the danger of spreading disease by
the release of pathogenic bacteria.
Water cycle — please see the definition for hydrologic cycle
Water availability — The total amount of water available from a water supply or source.
Water budget — A summation of inputs, outputs, and net changes to a particular water resource system over a fixed period. (Also, water balance model).
Water supply — The basic origin of a water, either a surface source (such as a lake, river, or reservoir) or a subsurface source (such as a well). After treatment and pumping via pipe lines, the treated and pumped water becomes a water supply.
Water utilities — [need a definition.]
« Back to top