Glossary - letter A

Aarhus Convention
Convention signed in Aarhus, Denmark, on 25 June 1998 under the auspices of the UN Economic Commission for Europe (UNECE) dealing with access to information * , public participation * in the decision-making process and access to justice regarding environmental issues.
Source : According to the Ministry for the Environment and AFB.

Abstraction protection zone

Surface on which water seeps or streams to feed a water resource currently used for drinking water supply * or likely to be used in the future, whose protection is an important issue, and where soil management methods are important to achieve the quality objectives * set by the river basin * management plan * (SDAGE).

Source : According to Rhine-Meuse Water Agency.

Abstraction supply zones

Area * on which the water that soaks into the ground supplies the abstraction * for drinking water * .

Source : According to the Ministry for the Environment and the Ministry for the Agriculture.

Quantitative parameter * for describing a population * . The complete quantification of a fauna * or flora population * is usually impossible. By extension, it means a number of individuals in a given category: population, recruitment, stock, relative to a time or surface unit.
Source : According to Ifremer.

Accidental pollution
As opposed to "chronic pollution * ", it is a pollution characterized by unpredictability about: the time of the accident, the place of the accident, the type of pollutant * , the amount spilled, the circumstances of the accident, the consequences of the accident.
Source : According to Rhone-Mediterranean and Corsica Water Agency.

Acid rain
Anthropogenic air pollutant * which is dissolving in moist air and falling back in a liquid or solid form on plants, soils, water and minerals. It is called acid when its pH is less than 5.6. The main sources of these pollutants are: industry, thermal power stations, domestic heating and cars emitting sulphur dioxide and nitrogen oxides.
Source : According to Ifremer.

Act - see "Law"
Activated sludge

Biomass * of microorganisms * used for treating wastewater * from their pollutants * (mainly organic matter). Microorganisms are free, suspended in the wastewater, kept inside an aeration tank, and feed on the pollutants. Then, the separation of activated sludge * and water occurs in a clarifier: a part of the sludge is put back into the aeration tanks, while the other part (corresponding to the increase of stock) is discharged.

Source : According to FNDAE.

Activated sludge filter
Biological wastewater * treatment in which a mixture of wastewater and suspended organic matter is agitated and aerated. The activated sludge * is then separated from the treated wastewater * by secondary settling, and then returned to the aeration tank or eliminated in the form of residual sludge.
Source : According to CEN.

Active population
Population regrouping the employed (also called labour force) and unemployed people.
Source : According to INSEE.

Active substance
Molecule of natural or synthetic origin to which the pesticide effect is attributed.
Source : According to Ineris.

Adapted Global Biological Index
Index for assessing the biological quality of the water of a river through an analysis * of macro invertebrates, adapted to the specificities of large and deep rivers, where the IBGN protocol (Standardized Global Biological Index * ) may not always be strictly respected.
Source : According to AFB.

Additional monitoring

Control of surface waters * , as part of the water status monitoring programme * , listed in the Register of protected areas * : intakes of drinking water * intended for human consumption (more than 100 m3/day on the average), water bodies of species * habitat * and protection areas * (which are included in the operational monitoring * programme when they may not meet their environmental goals).

Source : According to AFB.

Administrative Basin Commission

Commission established in each basin * or group of basins * , chaired by the basin coordinator prefect * and composed of prefects of regions, prefects of departments (administrative divisions), heads of regional State centres in charge of environmental issues, the regional director for the environment who acts * as basin delegatee * and paymaster of the area * where the basin committee * has its home office, as well as the director of the water agency * . The Administrative Basin Commission assists the basin coordinator prefect in the exercise of his powers. It is especially consulted on the draft river basin management plan * , programme of measures * and master plan for flood * forecasting.

Source : According to the Ministry for the Environment and AFB.

Admissible/acceptable daily intake (ADI)
Amount of chemicals that a man or an animal can swallow per day, during his/its life, without any appreciable risk * to his/its health. Values are especially established for food additives and pesticide residues whose presence in food meets technical requirements or that are necessary for the protection of plants.
Source : According to Ademe.

Penetration of a substance * through a barrier for exchange with the organism.
Source : According to BRGM.


Relative significance of the cost of public water supply and sanitation * services (production, conveyance and distribution of drinking water * ; collection, conveyance and treatment of wastewater * ) in the available income of consumers. This criterion is to be taken into account, e.g. when defining an overall price policy for public water supply and sanitation * services.

Source : According to the Ministry for the Environment.

Agenda 21
Action Plan for the 21st century focusing on sustainable development * . Agenda 21 was adopted by the countries signatories of the Rio de Janeiro Declaration * in June 1992. Its main functions are to alleviate poverty and social exclusion, to produce sustainable goods and services and to protect the environment.
Source : According to Rhine-Meuse Water Agency.


In the technical sense, an urbanized area * equipped with a community sanitation * system consisting of one or several wastewater * collecting systems * (sewers * ) and one or more wastewater treatment plants * , forming a coherent sewerage * system. Under the meaning of the Urban Waste * Water Treatment Directive * , an area where the population * and/or economic activities are sufficiently concentrated to make it possible to collect urban wastewater * for delivery to a wastewater treatment * system or final discharge * point. The general code of local governments plans to designate such an urban agglomeration as a sewerage agglomeration.

Source : According to Adour-Garonne Water Agency and Ministry for the Environment.

Aggregation bias
Bias induced during an investigation, when the numbers of users of several sites are added while the overall improvement of environmental quality will not bring the same benefits at each site.
Source : According to Kenneth McConnell (economist).

Agri-environmental grants
Financial accompanying measure, achieved within the framework of the agro environmental and climatic measures (MAEC), offered to farmers to encourage them to turn to an agriculture being more environment-friendly. This financial aid has to be approved by a regional committee, and its payment implies acting in accordance with a precise mission statement, in relation with the performed changes. Its amount is estimated through the calculation of the additional costs, or by the loss of income caused by the agro environmental practices.
Source : According to Alpes-de-Haute-Provence Chamber of Agriculture.

Agri-environmental measure
Measure for taking greater account of the environment (water protection, etc) in agricultural practices, by encouraging: (i) farmers to limit the use * of fertilizers and pesticides; (ii) the destocking of livestock to mitigate pollution * by cattle effluent * ; (iii) farmers to adopt practices that improve the environmental quality of rural areas * or the maintenance of abandoned lands; (iv) setting aside farmlands over 20 years for ecological purposes; the launching of Sustainable Development * Plans (SDPs) on an experimental basis in 1993, to globalize agri-environmental aid and other development assistance. Agri-environmental measures (AEMs) result in aid or compensation granted to farmers, using farming practices respectful of the environment, in the form of a contractual agreement between the State, the EEC and the farmers for a 5 to 10 year period (or 20 years even).
Source : According to the Ministry for the Environment and AFB.


Young fish * living on its yolk reserves or having not yet acquired its adult form.

Source : according to Larousse dictionary.

Algal bloom

Intense and unusual growth of algae.

Source : According to Ifremer.

Alien species

Any live specimen of a species * , subspecies or lower taxon of animals, plants, fungi or micro- organisms introduced outside its natural range; it includes any part, gametes, seeds, eggs or propagules of such species, as well as any hybrids, varieties or breeds that might survive and subsequently reproduce.

Source : according to to European Commission.

A substance * (very often a protein) alien to the human body and that can cause an allergy when it enters it (possible ways: ingestion, injection, inhalation...). Seafood (crustaceans * , but also molluscs, often seashells and even fish * , often scombridae and Gadidae) contain allergens to which some consumers are sensitive. There might be cross-reactivity between some allergens.
Source : According to Ifremer.

Allis shad

Fish * species * belonging to the Clupeidae family (such as sardine and herring). The allis shad are among the anadromous species (i.e. which swim up rivers to spawn in the middle part of the rivers). As such, their populations * have paid a heavy price to river development (dams * without fish pass facilities, extraction * of gravel changing the spawning * , etc). Their presence is therefore a good indicator of the status of a river development. Two species of allis shad are present (and exploited) in French waters: the allis shad (Alosa Alosa) and twaite shad (Alosa fallax).

Source : According to Ifremer.

Alluvial forest
A regularly or exceptionally flooded forest ecosystem * . It is a wooded strip along a watercourse * whose width is greater than 10 metres. In areas * flooded during 150 to 200 days per year, the alluvial forest is composed of permanent vegetation consisting of softwood and dominated by willows, alders. A hardwood forest, consisting of ash and elm trees, settles in the highest areas, flooded at least 50 days per year. These forest habitats * are home to the newt, European beaver, the otter and many birds. Most of these habitats are of community interest.
Source : According to Poitou-Charentes Regional Council.

Alluvial plain
Generic term generally used to designate the area * built at the bottom of a valley by the deposit of alluvium * of a stream. In a broad sense, it includes different environments and associated zones: riverbed, floodplain * , open space, water dependent areas, etc.
Source : According to Rhone-Mediterranean and Corsica Water Agency.

Alluvial sheet
Volume of groundwater * contained in alluvial soils, usually unconfined and often in relation with a watercourse * .
Source : According to BRGM.

Alluvial wetland

Located in the valley bottoms of rivers, an area * including riverine habitats * (islets * , shingle beaches, river banks * , etc) and alluvial water-dependent areas * (flood * -prone meadows, peat bogs, oxbows, riparian * forests, alluvial forests * , water dependent areas, etc) and wetland * headwaters (including peatlands). Alluvial wetlands are biodiversity * reservoirs and often habitats for the breeding or resting of many protected animal species * . Their more or less long-term storage capacity prevents flood * risk * by reducing the intensity of floods and replenishes the flow * at low-flow * . Most of them are involved in recharging groundwater * and cleaning * wastewater * . Wetlands have high landscape value. Through their many functions, they participate in the quantitative and qualitative management of water resources.

Source : According to AFB.

All materials (pebbles, gravel, sand) deposited by running water * in floodplains * , especially during floods * .
Source : According to AFB.

Change in the status of an aquatic environment or a river system causing degradation. Alterations are defined by their nature (physical, ionic, organic, toxic, biological, etc.) and their effect (eutrophication * , asphyxia, poisoning, change in populations * , etc). In most cases these alterations are due to human activities, but they can also be natural.
Source : According to the Ministry of Sustainable Development.

Vertical elevation of a place or object relative to a basic level. Altitude is also a value that expresses a difference between a given point and an average level. On land, this level is usually the sea * level (or "zero level"). Specifically, the altitude of the body of water * is considered as average for natural water bodies and as normal operating level or normal water retention * level (NR) for man-made water bodies. The normal level, as well as the average level, is defined as the usual level of the water line of the body of water. Unless levelling, the elevation of the water line or elevation of the water body * is that of the closest altimeter indication obtained on site (landmark, etc.) or on a 1:25,000 map. The altitude is indicated by using the applicable local benchmark (French Surveying and Levelling or NGF), accurate to the metre. It can exceed 1,000 metres for water bodies in the mountains but can also be negative for stations located in areas * below sea level.
Source : According to AFB.

Altruistic value
Value corresponding to the willingness to preserve an environmental good that people of the current generation can enjoy.
Source : According to the Ministry for the Environment.

Services provided free of charge by nature or the environment to individuals, associated with notions of comfort, convenience, pleasure and knowledge related to a location. For example, the fact of living on the edge of an urban park * or staying in a rural area * brings benefits in terms of landscape quality, quietness, microclimate, etc.
Source : According to Rhone-Mediterranean and Corsica Water Agency.


Vertebrate * animal that has the characteristic of starting its life in the water. At birth, an amphibian breathes through its gills, like a fish * . As an adult he now has lungs through which he can breathe freely, but he continues to absorb most of the oxygen he needs through the skin.

Source : according to Aquitaine Wildlife Observatory (AWO).


Methodical review allowing both to identify and quantify the different components of water, but also to evaluate its characteristics and state, according to specific criteria. This review is based on the following of specific protocols adapted to the various controlled parameters * .

Source : according to IOWater.

Analysis laboratory

Organization in charge of carrying out analyses or coordinating analyses made by subcontractors. The laboratories are stakeholders which generally act * as providers under contracts (procurement). They produce data * according to the specifications attached to the order * .

Source : According to the Ministry for the Environment.

Analyzed fraction

Component of the substrate * /medium to be analyzed. Three broad categories of analyzed fractions were defined by the National Service for Water Data * and Reference-dataset Management (Sandre): (i) rough or full substrate (e.g. the "untreated water * " fraction analyzed from the "water" substrate); (ii) partial fractions (as classified by part of the same medium, e.g. for sediments: particles <2 mm, particles <63 µm, <20 etc); (iii) the organic fractions (as classified by part of same organism, e.g. for fish: liver, scales... or mangrove, root system, floating root, etc). so-called systematic fractions, i.e. a system classification (e.g. cyprinidae>

Source : According to AFB and IOWater.

Describes a set of intersecting channels in a wide floodplain * , or a delta, well endowed with all kinds of distributaries and cut-offs separated by shoals. The term, borrowed from the medical language, is used in hydrology * only as an adjective: we indeed speak of an anastomosed river
Source : According to AFB.

Annual average residence time
Time needed to complete the theoretical water renewal of a body of water * , on average, over a calendar year. The residence time of water, expressed in days, can be calculated by the following formula: total capacity / annual discharge * of rivers that feed the body of water.
Source : According to AFB.

Annual flow
Average flow * over a year: it is most often obtained by adding the average daily water flows of the year and by dividing the result by the number of days in the year.
Source : According to the Ministry for the Environment and AFB.

Annual mean flow
Average flow * over a year: it is most often obtained by adding the average daily flows of the year and by dividing the result by the number of days in the year.
Source : According to AFB.

Anthropocentric value
Value that can be instrumental and overlaps the concept of economic utilization or non-utilization value * , or can be intrinsic and express the value of non-human species * for themselves, but always with a subjective perspective because human beings define it (anthropogenic conception of the intrinsic value * ).
Source : According to Foundation for Research on Biodiversity.

All activities related to marine plant cultivation and breeding of marine animals. The words "aquiculture" and even "mariculture" once used are regarded as obsolete synonyms. We distinguish inland aquaculture, which means all fish * farming activities in freshwater and marine aquaculture, which means all sea * farming activities in sea water. There are four types: shellfish * culture (shellfish breeding)), pisciculture (fish farming), the breeding of crustaceans * and seaweed (algae culture).
Source : According to Ifremer.

Aquatic corridor
Corresponds to the continuum or ecological continuity * formed by a watercourse * , its water-dependent areas * and tributaries from their headwaters to the sea * . This network enables the movement of aquatic and semi-aquatic species * (otter, beaver) necessary for the colonization of their habitat * and the completion of their life cycle. It also helps to maintain the good physical functioning of rivers to transport sediment and convey fluid flows * in the system. These mechanisms are essential to the creation of aquatic habitats of good hydro-morphological quality (alternations of flow facies * ) and necessary for the self-purifying function of the watercourse. At the regional level, the aquatic corridor appears uniformly (rivers). At the local level, it consists of many habitats: alluvial benches, floodplains * , ox-bows, sills * , pools.
Source : According to AFB.

Aquatic ecosystem

Specific ecosystem * of aquatic environments generally described by the living beings that are part of it, the nature of the bed * and river banks * , the characteristics of the catchment area * , the hydraulic regime, and the physical-chemical characteristics of water.

Source : According to the Ministry for the Environment.

Aquatic insect

Articulated invertebrate animal which have the characteristic of breathing through trachea. Some insects have become aquatic (representing 3% of insects) but have retained this aerial breathing.

Source : according to INRA.

Aquatic mammal

Set of aquatic vertebrate * animals which have the characteristic of being viviparous: the female lets the young grow in its belly, from which they get out alive. Marine mammals living in the oceans * (cetaceans), as well as various freshwater species * , such as the European otter, are aquatic mammals. Their mode of operation depends on the aquatic ecosystem * where they live.

Source : according to Loire-Bretagne Water Agency.


Continuous or discontinuous geological formation, containing temporary or permanent water that can be mobilized. It consists of permeable rock (porous or fractured formation) able to provide water naturally or though exploitation (drainage * , pumping).

Source : According to BRGM.

Aquifer system
Several aquifers * that constitute a hydro-geological unit. Its hydrodynamic characteristics give it a hydraulic quasi-independence (non-propagation of effects outside its limits). As such, it is an entity * for managing the groundwater * it contains.
Source : According to the Ministry for the Environment and AFB.

Area for flood storage purpose

Natural or agricultural floodplain * (not currently urbanized), that can be extended to floods * whose occurrence is higher than the hundred-year flood * , as part of a hydrogeomorphical approach. When local stakes require it (level of hazards * , areas * considered important, etc), floodplains * , which, at the date of approval of the river basin * management plan * (SDAGE), are classified "to be urbanized" but are not yet highly urbanized, may be considered, for their part not yet urbanized, as areas for flood storage purpose.

Source : According to Rhine-Meuse Water Agency.

Article 5 report

According to the Water Framework Directive * (WFD), it means analyzing the whole basin * or group of basins * , focusing on three aspects: characteristics of the basin or group of basins, impacts * of human activities on water status and economic analysis * of water use * . The assessment especially aims to prepare later the master plan for water development and management * (SDAGE) and the programme of measures * by assessing the risk * of not achieving the environmental objectives * for water bodies. The first assessments were adopted by the basin committees * and approved by the basin coordinator prefects * in 2004. They were updated in 2013 to prepare for the 2nd cycle management (2016-2021).

Source : According to the Ministry for the Environment and AFB.

Artificial water body
A body of surface water created by human activities in an area * that was previously dry. It can be for instance an artificial lake * or canal * . These water bodies are designated by the same criteria as heavily modified water bodies and must achieve the same objectives (good ecological potential * and good chemical status * ), set out by the Water Framework Directive * 2000/60/EC.
Source : According to the Ministry for the Environment and AFB.

Assessment data
Data resulting from an assessment.
Source : According to AFB.

Assessment operation
Set of observations of samples * taken and/or analyses made during one or more days at a control point * , for assessing a quality element * .
Source : According to AFB.

Assessment process
Implementation of a sequence of operations for assessing the status of water qualify on an assessment site * according to one or more quality elements * over a given period and in accordance with a given assessment profile.
Source : According to AFB.

Assessment site

Place on a water body * regrouping control points * where control operations * are carried out over a given period to determine the quality of aquatic environments. The assessment site is the entity * that gathers all relevant components required for a complete assessment of water status. For example, the assessment site can be: a station measuring the quality of surface water for bodies of water, the station measuring the quality of surface water in streams, the monitoring point for littoral * waters, the well for groundwater * quality.

Source : According to AFB.

Assigned flow

According to the Water Act * of 1992, "when hydraulic development works, other than those conceded or authorized and intended or resulting in the regulation of the flow * of a non-State owned watercourse * or for increasing its flow during low-flow * periods, all or part of the artificial discharge * can be assigned, by declaration * of public utility * , to some uses * on a section of this watercourse and for a fixed period".

Source : According to the Ministry for the Environment and AFB.

Associated groundwater

A groundwater * sheet neighbouring a stream and whose hydraulic properties are closely related to those of the stream. The exploitation of such a sheet leads to a decrease in the low-flow * of the river, either because the groundwater sheet * provides less water to the stream, or because the river begins to feed the sheet.

Source : According to BRGM.

Associated station
Differs depending on the type of the measuring station. For a twin-gauge station, the station associated with the "mother" station is the daughter station and vice versa. For a virtual station, the associated stations are those used to reconstruct the flow * rate.
Source : According to SCHAPI.


Collection of geographical maps. The National Service for Water Data * and Reference-dataset Management (Sandre), in particular, provides geo-referenced data (e.g. water bodies, measuring stations, river basin * areas * such as BD Carthage, regulatory zoning, etc) via an online service, known as Atlas, on the Sandre website.

Source : According to AFB and IOWater.

Atlas of flooded areas
Mapping of the surface area * flooded by a significant high water level * that allows keeping record of the largest floods * .
Source : According to Rhine-Meuse Water Agency.

Atlas of floodplains
Mapping of the surface area * that would be flooded by high water levels * modelled for each frequency * (10-year to 100-year floods * ) or determination by a hydro-geomorphologic method of homogeneous spatial units modelled for different types of floods * . The Atlas * of floodplains * thus represent potential flood-prone areas having (or not) been flooded by a known high water level.
Source : According to Rhine-Meuse Water Agency.


What is proper to a living organism or an object. An attribute (or properties) is information * that characterizes an entity * (or object). For example, the object "Wastewater * treatment plant" is characterized by properties including its size, type, etc. Data * dictionaries established by the National Service for Water Data and Reference-dataset Management (Sandre) include entities characterized by attributes. An attribute can be physically translated into a field of a database * .

Source : According to AFB and IOWater.

Auction system
Issue related to the valuation of a good/property in a contingent valuation, which can be considered in different ways. The first of them corresponds to a system of increasing or decreasing successive bids. Example: we propose an amount to the individual and, according to his response (acceptance or rejection), we propose a second amount (higher or lower), then a third amount, and so on. The criticisms made to this mechanism are for the most part linked to the fact that responses are highly dependent on the first offer.
Source : According to Robert Cameron Mitchell (economist).

An administrative police act * that authorizes an activity or development (abstraction * , discharge * , work, etc) by laying out the conditions for business or implementation and allowing the administration to closely monitor it. Please refer in particular to "procedure" and "nomenclature * " decrees * that set out the thresholds at which a declaration * or authorization procedure is used. The authorization involves establishing a document on the impact * on aquatic environments and groundwater * .
Source : According to the Ministry for the Environment and AFB.

Authorization or declaration subject to the Environmental Code
This term includes declarations * and authorizations * related to the Water Law * , declarations and authorizations related to Classified Facilities for Environmental Protection (ICPE), authorizations for Inert Waste * Storage Facilities (ISDI), etc. However, according to the principle of independence of the regulations, this term does not include authorizations or declarations under another code, the Urban Planning Code in particular.
Source : According to Rhine-Meuse Water Agency.

Available groundwater resource
Long-term average annual total recharge * rate of the groundwater * body to which is subtracted the long-term annual flow * rate required to achieve the ecological quality objectives * for associated surface waters * , established in Article 4, in order * to avoid any significant diminution in the ecological status * of such waters and to avoid any significant damage to associated terrestrial ecosystems * .
Source : According to the Ministry of Ecology.

Average annual rainfall
Average rainfall over a year: it is obtained mostly by adding the average daily rainfalls of the year and dividing the result by the number of days in the year.
Source : According to AFB.

Average depth
Average water depth in metres. The average depth of a body of water * is calculated by dividing the volume by the surface area * , both determined at the average elevation * for a natural body of water, and at the normal operating elevation for an artificial body of water.
Source : According to AFB.

Average elevation
Usual average altitude * of the water line of a natural body of water * . The average elevation is calculated by regularly measuring the height of the water line of the water body * using a scale, indexed on the geographic levelling in force or any other technical means (probe, sounding line or other) and on a given period (calendar year or other period). For lack of regular measurements, especially for smaller water bodies, the height of the water line, that was found when delimiting the surface hydrography * of an object in the Carthage database * , is sometimes used.
Source : According to AFB.

Avoided-cost method
Method for estimating the costs to be incurred should the studied environmental good be absent. For example, the disappearance of a wetland * for flood * control would result in an increased flood * risk * and therefore an increase in the damage caused.
Source : According to the Ministry for the Environment.