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ADA - Association of Drainage Authorities

ADA is the membership organisation for water level management authorities in the United Kingdom, with over 230 members and associate members. ADA is recognised as the national representative for Internal Drainage Boards (IDBs) in England and Wales.

Click here for more information.


AFBI - Agri-Food and Biosciences Institue

The AFBI carries out high technology research and development, statutory, analytical, and diagnostic testing functions for DARD and other Government departments, public bodies and commercial companies.


AINA - Association of Inland Navigation Authorities

The industry body in the UK for owners and operators of navigable inland waterways.


ASSI - Area of Special Scientific Interest




BAP - Biodiversity Action Plan

A plan of action to conserve and enhance habitats or species. There is a UK BAP and Local BAPs that operate at the county level. IDBs are also committed to developing Biodiversity Action Plans.


BWB - British Waterways Board

The organisation was responsible for maintaining over 2,000 miles of this inland waterway network today so that people can use it for a wide range of leisure activities. As of 2 July 2012, the Government transferred inland waterways in England and Wales into a new charitable body, the Canal & River Trust. In Scotland, the management of canals remains within the public body, British Waterways, and is responsible to the Scottish Government.



CFMP - Catchment Flood Management Plan

Catchment Flood Management Plans are large-scale strategic plans for the integrated and sustainable management of flood risk in river catchments for the benefit of people and the developed and natural environment.


CIWEM - Chartered Institution of Water and Environmental Management

The Chartered Institution of Water and Environmental Management (CIWEM) is an independent professional body and a registered charity, advancing the science and practice of water and environmental management for a clean, green and sustainable world.


CPA - Common Agricultural Policy

A policy that regulates farming activities across the European Union, providing direct subsidies to farmers and land managers. A small part of these funds support rural development actions that mainly relate to agricultural activities, as well as forestry and environmental improvements on farmland.


CIS - Common Implementation Strategy

This strategy was agreed by the European Commission, Member States and Norway in 2001. The aim of the strategy is to provide support in the implementation of the Water Framework Directive, by developing a common understanding and guidance on key elements of the Directive.



Defra - Department for Environment, Food and Rural Affairs

Formed in June 2001, Defra is the government department responsible for environmental protection, food production and standards, agriculture, fisheries and rural communities in the United Kingdom. Defra is responsible for British Government policy in: agriculture, biodiversity, conservation, fisheries, chemicals and pesticides, flooding, inland waterways, water management and others.


DARD - Department of Agriculture and Rural Development

DARD aims to promote sustainable economic growth and the development of the countryside in Northern Ireland. The Department assists the competitive development of the agri-food, fishing and forestry sectors of the Northern Ireland economy, having regard for the need of the consumers, the welfare of animals and the conservation and enhancement of the environment.



EA - The Environment Agency

The Environment Agency is a British non-departmental public body of Defra and an Assembly Government Sponsored Body of the Welsh Government that serves England and Wales. The Environment Agency's stated purpose is, "to protect or enhance the environment, taken as a whole" so as to promote "the objective of achieving sustainable development" (taken from the Environment Act 1995, section 4). Protection of the environment relates to threats such as flood and pollution. The vision of the Agency is of "a rich, healthy and diverse environment for present and future generations".


EIA - Environmental Impact Assessment

The process by which the likely impacts of a project upon the environment are identified, collated, measured and assessed to determine their significance. The assessment helps to maximise positive effects and mitigate negative effects during project design.


EMAS - Eco-Management Audit Scheme

The Eco-Management and Audit Scheme (EMAS) is a voluntary environmental management instrument, which was developed in 1993 by the European Commission. It enables organisations to assess, manage and continuously improve their environmental performance. The scheme is globally applicable and open to all types of private and public organisations. In order to register with EMAS, organisations must meet the requirements of the EU EMAS-Regulation. Currently, more than 4,600 organisations and more than 7,900 sites are EMAS registered.


ELS - Entry Level Stewardship

With nearly 60% of England’s agricultural land now in Entry Level Stewardship, this is the basic underlying scheme open to all farmers and land managers in England. ELS agreements are for five years.The scheme provides you with a straight forward approach to delivering simple and effective environmental management across your whole farm, that complements your existing farming operation, and allows you to create your own practical environmental management programme.


EUWMA - European Union of Water Management Associations

EUWMA members are organizations in the EU member states representing organizations based on public law responsible for regional and local water management (flood protection, land drainage, water level management, irrigation). ADA is a member of EUWMA.

Click here for more information about EUWMA.



FRM - Flood Risk Management FWMA

Supersedes flood protection. Whilst including the use of flood defences, where appropriate, this approach recognises that ‘managed flooding’ is essential to sustain a good ecological status in a river and coastal systems.


FCERM - Flood and coastal risk management

(as stated above)


FEP - Farm Environment Plan

The Farm Environment Plan (FEP) is a structured survey of all environmental features on a farm. A FEP is a pre-requisite for Higher Level Stewardship (HLS). It identifies and assesses the condition of features of historical, wildlife, resource protection, access and landscape interest. It helps to determine the level of management that could be achieved through HLS and to consider the potential for creating environmental features and habitats, improving access, and managing land for flood management and natural resource protection.


FWMA - Flood and Water Management Act 2010

The Flood and Water Management Act (FWMA) was introduced on 8 April 2010 in England and Wales. It was intended to implement Sir Michael Pitt’s recommendations following the widespread flooding of 2007 when more than 55,000 homes and businesses were flooded. The flooding was largely caused by surface water runoff overloading drainage systems. The Act was also a response to the need to develop better resilience to climate change. The Act requires better management of flood risk, it creates safeguards against rises in surface water drainage charges and protects water supplies for consumers. It gives a new responsibility to the Environment Agency for developing a National Flood and Coastal Risk Management Strategy, and gives a new responsibility to local authorities, as Lead Local Flood Authorities (LLFA's), to co-ordinate flood risk management in their area.

Click here to view the Act.



GIS - Geographic Information System

GIS is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographical data.



HLS - Higher Level Stewardship

HLS aims to deliver significant environmental benefits in priority areas. It involves more complex environmental management requiring support and advice from our local advisers, to develop a comprehensive agreement that achieves a wide range of environmental benefits over a longer period of time. HLS agreements last for ten years.



ICE - Institution of Civil Engineers

The Institution of Civil Engineers (ICE) is a registered charity (no. 210252; no. SC038629 [Scotland]) that strives to promote and progress civil engineering. They believe that civil engineers are "at the heart of society, delivering sustainable development through knowledge, skills and professional expertise." The ICE was founded in 1818 by a small group of idealistic young men. We were granted a royal charter in 1828 where we declared that our aim was to "foster and promote the art and science of civil engineering".

Click here to learn more about ICE.


IDB - Internal Drainage Board

Internal Drainage Boards are an integral part of water level management in the UK. Each IDB is a local public authority established in areas of special drainage need in England and Wales. They have permissive powers to manage water levels within their respective drainage districts. They undertake works to reduce flood risk to people and property and manage water levels to meet local needs.

Click here to learn more.


IDD - Internal Drainage District

Drainage districts occur in England and Wales, varying in size from a few hundred acres to over 100,000 acres (400 km2), all in low lying areas of the country where flood risk management and land drainage are sensitive issues. Most drainage districts are administered by an Internal Drainage Board (IDB), which are single purpose local drainage authorities, dealing with the drainage and water level management of clean water only.







LLFA - Lead Local Flood Authorities

Sir Michael Pitt’s review of the flooding in 2007 stated that “the role of local authorities should be enhanced so that they take on responsibility for leading the co-ordination of flood risk management in their areas”. The Act provides for this through the new role of the lead local flood authority. As set out in the Government’s response to Sir Michael’s Review, the Act defines the lead local flood authority for an area as the unitary authority or the county council. This will avoid any delay or confusion about who is responsible, but in no way prevents partnership arrangements to make full use of all capabilities and experience locally. The Act enables lead local authorities to delegate flood or coastal erosion functions to another risk management authority by agreement.





NA - Natural England

Natural England is the non-departmental public body of the UK government responsible for ensuring that England's natural environment, including its land, flora and fauna, freshwater and marine environments, geology and soils, are protected and improved. It also has a responsibility to help people enjoy, understand and access the natural environment.


NFCDD - National Flood & Coastal Defence Database

Aims to be the definitive store for all data on flood and coastal defences, which is made available to all operating authorities.



OELS - Organic Entry Level Stewardship

The scheme (Natural England) provides you with a straight forward approach to delivering simple and effective environmental management across your whole farm, that complements your existing farming operation, and allows you to create your own practical environmental management programme. Organic Entry Level Stewardship (OELS) is open to all farmers, including those in the uplands, who manage all or part of their land organically, to deliver simple yet effective environmental management. OELS agreements are for 5 years.


Ofwat - Office of Water Services

Regulates water and sewrage providers in England and Wales.







RFCC - Regional Flood & Coastal Committee

The RFCC is a committee established by the Environment Agency under the Flood and Water Management Act 2010.

Click here for more about RFCCs.


RRC - River Restoration Centre

The River Restoration Centre (RRC) exists to promote, facilitate and support best practice in river, watercourse and floodplain management across the UK. It aims to provide a focal point for the exchange and dissemination of information and expertise relating to river restoration and enhancement. RRC is a non-profit making organisation which aims to offer impartial advice to enable practitioners and clients, to gain maximum benefit from current experiences in a variety of easily accessible ways. The RRC is not a project design or management consultancy. RRC became the successor body to the River Restoration Project on 1 April 1998.


RSPB - Royal Society for the Protection of Birds

The Royal Society for the Protection of Birds (RSPB) is a charitable organisation registered in England and Wales and in Scotland. It works to promote conservation and protection of birds and the wider environment through public awareness campaigns, petitions and through the operation of nature reserves throughout the United Kingdom.



SAC - Special Areas of Conservation

A site of European importance for habitats and/or species, designated in accordance with the EU Habitats Directive. A cSAC is a candidate site, but is afforded the same legal status as a SAC in England.


SEA - Strategic Environmental Assessment

The application of an environmental impact assessment process to the more strategic tiers of decision-making policies, plans and programmes. It is required in specific circumstances though EC Directive 2001/42/EC.


SPA - Special Protection Areas

A site of European importance for birds, designated in accordance with the EU Birds Directive. A pSPA is a proposed site, but is afforded the same status in UK policy terms as if confirmed.


SSSI - Site of Special Scientific Interest

Sites of Special Scientific Interest (SSSI) are the best examples of our natural heritage of wildlife habitats, geological features and landforms. An SSSI is an area that has been notified as being of special interest under the Wildlife and Countryside Act 1981.


SUDS - Sustainable Drainage Systems

A range of management practices, control structures and other facilities designed to accommodate the drainage of surface water from an urban area in a way that more closely resembles the run-off from a natural site.





UKTAG - UK Technical Advisory Group

Provides co-ordinated advice on technical aspects of the implementation of the EU Water Framework Directive in the UK.





WWMA - Wales Water Management Alliance

The three Internal Drainage Boards wholly or partly in Wales have formed the Wales Water Management Alliance to coordinate their activities and work alongside the proposed Single Body for Wales.


WFD - Water Framework Directive

Substantial piece of water legislation produced by the European Commission, with the aim of achieving sustainable management of water in the UK and the other Member States by 2015. The WFD sets out environmental objectives for water status based on ecological and chemical parameters, arrangements for river basin administration and planning, and a programme of measures in order to meet the objectives. The main aims of the Directive are to prevent further deterioration of, and promote enhancement of, the status (quality and quantity) of water bodies and related ecosystems. This includes the progressive reduction in the pollution of groundwater.

Click here to view the Water Framework Directive document.


WLM - Water level management

Water level management is the general term for any human actions that are used to alter the phyasical levels of watercourses in order to help manage the area's drainage. Actions may include: dredging, use of pumping stations, excavation of banks etc.


WLMP - Water Level Management Plan

A document setting out water level management objectives in a defined floodplain area, very often a SSSI.










The deliberate removal of water from a water body, either surface or groundwater.


Alien species

Any non-native species (plant or animal). Several of these nonnative species are invasive and have been causing serious problems to the aquatic and riverine ecology and environment.


Appropriate assessment

A step in the decision-making process for plans and projects required under Regulation 48 of The Conservation (Natural Habitats, &c.) Regulations, 1994. The purpose of the appropriate assessment is to determine whether it can be concluded that proposals would not adversely affect the integrity of a European conservation site.



An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose. In a more restricted use, aqueduct (occasionally water bridge) applies to any bridge or viaduct that transports water—instead of a path, road or railway—across a gap.



An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology.



An aquitard is a zone within the earth that restricts the flow of groundwater from one aquifer to another. An aquitard can sometimes, if completely impermeable, be called an aquiclude or aquifuge. Aquitards comprise layers of either clay or non-porous rock with low hydraulic conductivity.


Artificial water body

Is a body of surface water created by human activity. It is known as a heavily modified water body if, as a result of physical alterations by human activity, it is changed substantially in character as designated by an individual Member State and in accordance with the provisions of Annex II of the Water Framework Directive.




The back-ditch (or borrow, soak or soke dyke) is a channel created when a flood embankment or seawall is built, with the material for the flood defence structure being won from the adjacent land to leave the channel.



Describes the part of the watercourse which is above normal water level and that will hold flood flows.


Base flow

Natural discharge of groundwater from an aquifer, via springs and seepages, to rivers. It is baseflow that sustains the low flow of surface steams and rivers during prolonged dry weather.



Biodiversity is the degree of variation of life forms within a given species, ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate.


Biological element

A collective term for a particular characteristic group of animals or plants present in an aquatic ecosystem (e.g. phytoplankton; benthic invertebrates; phytobenthos; macrophytes; macroalgae; angiosperms; fish).


Biological indicator

A parameter that can be monitored to estimate the value of a biological quality element. Indicators may include the presence or absence of a particularly sensitive species.


Birds Directive

In 1979, the European Community adopted Council Directive 79/409/EEC on the conservation of wild birds. The Directive provides a framework for the conservation and management of wild birds in Europe.

Click here fore more information about the Birds Directive.



A borehole is the generalised term for any narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water.


Borrow dyke

See Back-ditch.


Brackish water

Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers.




Canals are man-made channels for water. There are two types of canal: waterways (used for transport by boats), and aqueducts (used for the conveyance and delivery of potable water for human consumption).


Canal & River Trust

The Canal & River Trust brings together over 2,000 miles of historic canals, rivers and docks, three important waterways museums, the national waterways collection and national waterway archives.

Click here to find out more about the Canal & River Trust.


Capillary action

Capillary action, or capillarity, is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity.


Capital schemes

A capital scheme is a project-based investment of capital (e.g. IDBs use capital schemes to build new pumping stations). [see also 'Revenue Schemes']



The area from which precipitation contributes to the flow from a river or lake. For rivers and lakes this includes tributaries and the areas they drain.



The bed or course of a river, stream, or canal.


Channel capacity

The size of the river channel cross-section to banfull level expressed as the cross-sectional area in square metres.


Channel deepening

Much like channel widening, this technique is typically used to lower the bed of a river to reduce local flood levels (as it increases the channel capacity). Also undertaken to lower normal river or dich levels to facilitate agricultural practices by increasing the depth of the outfall from piped field drains into field ditches. This can result it higher biodiversity of the channel.


Channel widening

Much like the channel deepening technique, channel widening is typically used to widen a river to reduce local flood levels (as it increases the channel capacity). This can result it higher biodiversity of the channel.


Climate Change Act 2008

An Act to set a target for the year 2050 for the reduction of targeted greenhouse gas emissions; to provide for a system of carbon budgeting; to establish a Committee on Climate Change; to confer powers to establish trading schemes for the purpose of limiting greenhouse gas emissions or encouraging activities that reduce such emissions or remove greenhouse gas from the atmosphere; to make provision about adaptation to climate change; to confer powers to make schemes for providing financial incentives to produce less domestic waste and to recycle more of what is produced; to make provision about the collection of household waste; to confer powers to make provision about charging for single use carrier bags; to amend the provisions of the Energy Act 2004 about renewable transport fuel obligations; to make provision about carbon emissions reduction targets; to make other provision about climate change; and for connected purposes.

Click here to view the Act


Competent authority

Any Minister, Government department, public or statutory undertaker, public body of any description or person holding a public office, that makes a decision affecting a European Site. For WLMPs, this includes local authorities, Internal Drainage Boards and the Environment Agency.



Conservation is an ethic of resource use, allocation, and protection. Its primary focus is upon maintaining the health of the natural world its, fisheries, habitats, and biological diversity. Secondary focus is on materials conservation and energy conservation, which are important to protecting the natural world.


Conservation objectives

Objectives that need to be achieved to maintain or restore to favourable conservation condition the features for which a Site of Special Scientific Interest (SSSI) or European site was designated. Each set of conservation objectives is accompanied by site-specific attributes that help define favourable condition (commonly referred to as favourable condition tables).


Conservation of Habitats and Species Regulations 2010

These Regulations make provision for a purpose mentioned in section 2(2) of the European Communities Act 1972 and it appears to the Secretary of State and to the Welsh Ministers that it is expedient for any reference in these Regulations to an Annex to Council Directive92/43/EEC (on the conservation of natural habitats and of wild fauna and flora) to be construed as a reference to that Annex as amended from time to time.

Click here to view the Regulations


Countryside and Rights of Way Act 2000

An Act to make new provision for public access to the countryside; to amend the law relating to public rights of way; to enable traffic regulation orders to be made for the purpose of conserving an area’s natural beauty; to make provision with respect to the driving of mechanically propelled vehicles elsewhere than on roads; to amend the law relating to nature conservation and the protection of wildlife; to make further provision with respect to areas of outstanding natural beauty; and for connected purposes.

Click here to view the Act


Crest gate

See Floodgate.


Cross compliance

A form of conditionality by which, farmers in receipt of public subsidies are required to comply with all legislation affecting their businesses, including European Union environmental legislation. The requirements of cross compliance are: i) an obligation to maintain agricultural land in Good Agricultural and Environmental Condition and ii) an obligation to comply with specified Statutory Management Requirements according to European Union legislation, for example the Nitrates Directive, Groundwater Directive.



A sewer or drain crossing under a road or embankment.




A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations.


Delineation (of water bodies)

Identifying the type and defining the boundary of a water body for rivers, lakes, transitional and coastal waters and groundwater under the Water Framework Directive.



A river delta is landform that is formed at the mouth or at the source of a river, where the river flows into an ocean, sea, estuary, lake, or reservoir. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river.


Detention basin

A detention basin is a stormwater management facility installed on, or adjacent to, tributaries of rivers, streams, lakes or bays that is designed to protect against flooding and, in some cases, downstream erosion by storing water for a limited period of a time. In its basic form, a detention basin is used to manage water quantity while having a limited effectiveness in protecting water quality, unless it includes a permanent pool feature.


Diffuse source pollution

Pollution which originates from various activities, and which cannot be traced to a single source and originates from a spatially extensive land use (e.g. agriculture, settlements, transport, industry).


Dike (or Dyke)

A man-made embankment, ditch or watercourse constructed to prevent flooding (or to keep out the sea). Also see Spur Dyke, Borrow Dyke and Soak/Soke Dyke.


Discharge (pollution)

The release of polluting substances from individual point or diffuse sources directly or indirectly into water bodies.


Discharge (river)

The volume of flow of water or fluid per unit. It is usually expressed in cumecs (cubic metres per second).


Drainage rates

All properties within a drainage district are deemed to derive benefit from the activities of an IDB. Every property is therefore subject to a drainage rate paid annually to the IDB.

Contact ADA if you would like to know more about drainage rates.



Dredging is an excavation activity or operation usually carried out at least partly underwater, in fresh water areas (or shallow seas) with the purpose of gathering up bottom sediments and disposing of them at a different location. Dredging is also used purely for clearing waterways (which could be seen when a river is over occupied by weeds/vegitation).


Drinking Water Protected Areas

Bodies of water that are used or could be used in the future for the abstraction of water intended for human consumption.



A drought is an extended period of months or years when a region notes a deficiency in its water supply whether surface or underground water. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region. Although droughts can persist for several years, even a short, intense drought can cause significant damage and harm the local economy.

Click here to learn more about the concept of drought (external site: Environment Agency).


Drum flail

Used for cutting scrub and other woody vegetation to ground level. Also see Flail mower.


Dry valley

A valley in which the waters of the stream/river that originally cut the valley now flow below the present land surface as groundwater. The groundwater flow direction may no longer parallel that of the former stream.


Dyke (or Dike)

A man-made embankment, ditch or watercourse constructed to prevent flooding (or to keep out the sea). Also see Spur Dyke, Borrow Dyke and Soak/Soke Dyke.



Ecological potential

The status of a heavily modified water body measured against the maximum ecological quality it could achieve given the constraints imposed upon it by those heavily modified characteristics necessary for its use.


Ecological status

Ecological status applies to surface water bodies and is based on the following quality elements: biological quality, general chemical and physico-chemical quality, water quality with respect to specific pollutants (synthetic and non synthetic), and hydromorphological quality. There are five classes of ecological status (high, good, moderate, poor or bad). Ecological status and chemical status together define the overall surface water status of a water.



The branch of biology dealing with the relations and interactions between organisms and their environment, including other organisms.



An ecosystem is a community of living organisms (plants, animals and microbes) in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system. Ecosystems come in various sizes but usually encompass specific, limited spaces (although it is sometimes said that the entire planet is an ecosystem). Ecosystems are defined by the network of interactions among organisms, and between organisms and their environment. They are linked together through nutrient cycle and energy flow.


Effective rainfall

The proportion of rainfall that is available for run-off and groundwater recharge after satisfying actual evaporation and any soil moisture deficit.



Effluent is an outflowing of water (or gas) from a natural body of water, or from a human-made structure.


Effluent river conditions

A reach of a river is effluent with respect to groundwater if the river gains water from the underlying aquifer.


Environmental Impact Assessment (Land Drainage Improvement Works) Regulations 1999

The Minister of Agriculture, Fisheries and Food and the Secretary of State for Wales, acting jointly, being Ministers designatedfor the purposes of section 2(2) of the European Communities Act 1972 in relation to measures relating to the requirement for an assessment of the impact on the environment of projects likely to have significant effects on the environment, in exercise of the powers conferred on them by the said section 2(2) and of all other powers enabling them in that behalf, hereby make the following Regulations:

Click here to view the Regulations


Ephemeral stream

An ephemeral stream is one that remains dry during some of the year. Flow can result from a rising water table intersecting the stream-bed or from periods of surface flow.



An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea.


European site

A site that has been designated as a site of international nature conservation importance, either as a Special Protection Area (SPA) or a Special Area of Conservation (SAC). In England, this also includes a candidate Special Area of Conservation (cSAC) and Ramsar sites.



Eutrophication is the ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system. can be human-caused or natural. Untreated sewage effluent and agricultural run-off carrying fertilizers are examples of human-caused eutrophication. However, it also occurs naturally in situations where nutrients accumulate (e.g. depositional environments), or where they flow into systems on an ephemeral basis.



Favourable condition

A Site of Special Scientific Interest (SSSI) is in 'favourable condition' when the conservation objectives for the site are being achieved. Natural England monitors a range of attributes, related to the ecological requirements of the site’s interest features, in order to make this assessment. Where an SSSI is also a European site, this assessment is an important indicator of the contribution the site makes to the favourable conservation status of the habitats and species it supports.


Favourable conservation status

The condition in which a natural habitat or species listed in the Annexes of the Habitats Directive or Birds Directive is capable of sustaining itself in the long term across its natural range.



A fen is one of the four main types of wetland, and is usually fed by mineral-rich surface water or groundwater. Fens are characterised by their water chemistry, which is neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients. They are usually dominated by grasses and sedges, and typically have brown mosses.



Fjord type estuaries are formed in deeply eroded valleys formed by glaciers. These U-shaped estuaries typically have steep sides, rock bottoms, and underwater sills contoured by glacial movement. 


Flail mower

A flail mower is a type of power take-off (PTO) driven implement that can attach to the three-point hitches found on the rear of most tractors. This type of mower is best used to provide a rough cut to taller grass, as seen on banks of watercourses.



A high water level along a river channel (or on a coast) that leads to inundation of land which is not normally submerged. River floods which involve inundation of the floodplain can be caused by prolonged/intense precipitation, collapse/burst of dams (natural or caused by man), blocked river channel causing river water to exceed bank level and spill into surrounding land, and other ways.


Flood and Water Management Act 2010

An Act to make provision about water, including provision about the management of risks in connection with flooding and coastal erosion.

Click here to view the Act


Flood barriers

A flood barrier is a specific type of floodgate, designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier.


Flood channel

Usually purpose-built channels designed to convey flood flows across a flood plain in an additional route to the natural channel. Can be used to take flood flows away from built-up areas where widening the channel may not be possible.


Flood storage area

An artificial structure designed to store floodwater in order to mitigate flooding downstream. This storage can be on-line, where all water flows through the storage area and impounding is controlled by a dam and sluice structure, or off-line, where flow diverted from the river is controlled by a weir or sluice.



Floodgates are adjustable gates used to control water flow in flood barriers, reservoir, river, stream, or levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in sluices and canals, or they may be designed to stop water flow entirely as part of a levee or storm surge system. Since most of these devices operate by controlling the water surface elevation being stored or routed, they are also known as crest gates.



An area through which watercourses run and over which floodwater naturally extends. The extent and depth of flooding over a floodplain will vary and depend on the severity of the flood.


Floods Directive

The purpose of the European Union Directive on flooding (2007/60/EC) is to establish a framework for the assessment and management of flood risks aiming at the reduction of the adverse consequences on human health, the environment, cultural heritage and economic activity associated with floods in the Community. It requires member states to undertake flood risk assessments, flood risk mapping and produce flood risk management plans.

Click here for more information about the Floods Directive.



Good chemical status (groundwater)

Means the concentrations of pollutants in the groundwater body do not exceed the criteria set out in Article 3 of the Groundwater Daughter Directive (2006/118/EC).


Good chemical status (surface waters)

Means that concentrations of chemicals in the water body do not exceed the environmental standards specified in the Environmental Quality Standards Directive 2008/105/EC. These chemicals include Priority Substances, Priority Hazardous Substances and eight other pollutants carried over from the Dangerous Substance Daughter Directives.


Good ecological potential

Those surface waters which are identified as Heavily Modified Water Bodies and Artificial Water Bodies must achieve ‘good ecological potential’ (good potential is a recognition that changes to morphology may make good ecological status very difficult to meet). In the first cycle of river basin planning good potential may be defined in relation to the mitigation measures required to achieve it.


Good ecological status

The objective for a surface water body to have biological, structural and chemical characteristics similar to those expected under nearly undisturbed conditions.


Good quantitative status (groundwater)

Means the level of groundwater in the groundwater body meets the criteria set out in Annex V (2.1.2) of the Water Framework Directive.



Groundwater is water located beneath the earth's surface in soil pore spaces and in the fractures of rock formations. Typically, groundwater is thought of as liquid water flowing through shallow aquifers, but technically it can also include soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water.


Groundwater Directive

This new directive establishes a regime which sets underground water quality standards and introduces measures to prevent or limit inputs of pollutants into groundwater. The directive establishes quality criteria that takes account local characteristics and allows for further improvements to be made based on monitoring data and new scientific knowledge. The directive thus represents a proportionate and scientifically sound response to the requirements of the Water Framework Directive (WFD) as it relates to assessments on chemical status of groundwater and the identification and reversal of significant and sustained upward trends in pollutant concentrations.

Click here for more information about the Groundwater Directive.


Groundwater flooding

Groundwater flooding is the emergence of groundwater at the ground surface or the rising of groundwater into man-made ground, through natural processes, under conditions where the 'normal' range of groundwater levels and groundwater flows are exceeded.


Groundwater rebound

Rising groundwater levels resulting from a reduction in abstraction rates following a period of high abstraction which kept groundwater levels artificially low.


Groundwater recharge

Inflow of water to a groundwater body from the surface. Infiltration of precipitation and its movement to the water table is one form of natural recharge.


Groundwater table

See Water table.




A habitat (which is Latin for "it inhabits") is an ecological or environmental area that is inhabited by a particular species of animal, plant, or other type of organism. It is the natural environment in which an organism lives, or the physical environment that surrounds (influences and is utilized by) a species population.


Habitats Directive

The 1992 European Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora. This requires Member States to introduce measures to protect species listed in the Annexes. The 169 habitats listed in Annex I of the Directive and the 623 species listed in Annex II are to be protected by means of a network of sites – Special Areas of Conservation (SACs). These sites, along with Special Protection Areas (SPAs) classified under the Birds Directive, form a network of protected areas known as Natura 2000.

Click here for more information about the Habitats Directive.


Heavily Modified Water Body

A surface water body that does not achieve good ecological status because of substantial changes to its physical character resulting from physical alterations caused by human use, and which has been designated, in accordance with criteria specified in the Water Framework Directive, as ‘heavily modified’.



Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants.[1] Selective herbicides kill specific targets, while leaving the desired crop relatively unharmed.


High ecological status

Is a state, in a surface water body, where the values of the hydromorphological, physico-chemical, and biological quality elements correspond to conditions undisturbed by anthropogenic activities.


Highland carrier

Watercourses that convey drainage water coming from higher in the catchment across or around a lower, drained area of land and having little or no connection with the drainage network of that drained area.


Hydraulic conductivity

Hydraulic conductivity is a property of vascular plants, soil or rock, that describes the ease with which water can move through pore spaces or fractures.



The study of aquifers. Also see Aquifers.



The study of the movement, distribution, and quality of water on Earth.



Impact Assessment

A tool to enable the Environment Agency to weigh and present the evidence on the positive and negative effects of a plan. For example information on the estimated cost and benefit of proposing actual measures.


Improvement measures

Measures intended to improve the status of water bodies or the condition of protected areas.



Infiltration is the process by which water on the ground surface enters the soil. Infiltration is governed by two forces: gravity and capillary action. While smaller pores offer greater resistance to gravity, very small pores pull water through capillary action in addition to and even against the force of gravity.


Infiltration rate

Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimeters per hour. The rate decreases as the soil becomes saturated. If the precipitation rate exceeds the infiltration rate, runoff will usually occur unless there is some physical barrier.


Influent stream

An influent stream or river is one that loses flow to ground water, i.e., a stream that replenishes ground water reservoirs by percolation through its porous bed. Since influent streams tend to lose substantial amounts of their water, they are usually of an ephemeral nature.


Integrity of a European site

Integrity is defined as the coherence of a site’s ecological structure and function, across its whole area, which enables it to sustain the habitat, complex of habitats and/or the levels of populations of the species for which it was classified.


Internal Drainage Boards (Finance) Regulations 1992

Financial Regulations for Internal Drainage Boards in England & Wales.

Click here to view Regulations



Irrigation is the artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing weed growing in grain fields and helping in preventing soil consolidation.



ISO14000 is the international standards on environmental management. ISO14000 is a family of standards related to environmental management that exists to help organizations (a) minimize how their operations (processes etc.) negatively affect the environment (i.e. cause adverse changes to air, water, or land); (b) comply with applicable laws, regulations, and other environmentally oriented requirements, and (c) continually improve in the above.

The requirements of ISO 14000 are an integral part of the European Union's environmental management scheme EMAS (Eco-Management Audit Scheme). EMAS's structure and material requirements are more demanding, foremost concerning performance improvement, legal compliance and reporting duties.



There are currently no words beginning with 'J' in ADA's glossary.



There are currently no words beginning with 'K' in ADA's glossary.



Land Drainage Act 1991

An Act to consolidate the enactments relating to Internal Drainage Boards, and to the functions of such boards and of local authorities in relation to land drainage, with amendments to give effect to recommendations of the Law Commission.

Click here to view more information about the Land Drainage Act 1991.


Land Drainage Act 1994

An Act to amend the Land Drainage Act 1991 in relation to the functions of Internal Drainage Boards and local authorities.

Click here to view more information about the Land Drainage Act 1994.



Taken from the French word 'levée' (meaning 'to raise'), a levee is is an elongated naturally occurring ridge, or artificially constructed fill or wall, which regulates water levels. It is usually earthen and often parallel to the course of a river in its floodplain or along low-lying coastlines.



The transfer of material, dissolved or particulate, associated with a flow of water.



Main River

Watercourses defined on a ‘Main River Map’ designated by Defra. The Environment Agency has permissive powers to carry out flood defence works, maintenance and operational activities for Main River.



A term used to describe the part of the watercourse where the water level is normally positioned.



A marsh is a type of wetland that is dominated by herbaceous rather than woody plant species. Marshes can often be found at the edges of lakes and streams, where they form a transition between the aquatic and terrestrial ecosystems. They are often dominated by grasses, rushes or reeds.



This term is used in the Water Framework Directive to mean an action that will be taken on the ground to help achieve Water Framework Directive objectives.



The act of making a condition or consequence less severe. (For example: 'Mitigation measures for Water Voles')



Describes the physical form and condition of a water body, for example the width, depth and perimeter of a river channel, the structure and condition of the riverbed and bank.



Mudflats or mud flats, also known as tidal flats, are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and marine animal detritus.



Natura 2000

The network of protected areas – Special Areas of Conservation (SACs) and Special Protection Areas (SPAs) – established respectively under the Habitats Directive and the Birds Directive.


Natural Environment and Rural Communities Act 2006

An Act to make provision about bodies concerned with the natural environment and rural communities; to make provision in connection with wildlife, sites of special scientific interest, National Parks and the Broads; to amend the law relating to rights of way; to make provision as to the Inland Waterways Amenity Advisory Council; to provide for flexible administrative arrangements in connection with functions relating to the environment and rural affairs and certain other functions; and for connected purposes.

Click here to view the Act


No deterioration (in water body status)

None of the quality elements used in the classification of water body status deteriorates to the extent that the overall status is reduced.


No deterioration measures

Measures intended to prevent deterioration in water body status.


Non-native species

See Alien species.



Operating authority

A body with powers to undertake management of flood risk, coastal erosion risk and water level management. This includes the Environment Agency, local authorities and Internal Drainage Boards.


Ordinary watercourses

All rivers, streams, ditches, drains, cuts, dykes, sluices, sewers (other than public sewers) and passages through which water flows but which do not form part of a 'Main River'. Also see Main River.




Peat is an accumulation of partially decayed vegetation. Bogs are the most important source of peat,[2] but other less common wetland types also deposit peat, including fens.


Phreatiz zone

The position at which the groundwater is at atmospheric pressure (found below the water table line).


Physical alterations

Modifications of the hydromorphology of a water body by human activity.



Any substance liable to cause pollution. Also see Silt and Siltation.



The direct or indirect introduction, as a result of human activity, of substances or heat into the air, water or land which: (i) may be harmful to human health or the quality of aquatic ecosystems or terrestrial ecosystems directly depending on aquatic ecosystems; (ii) result in damage to material property; or (iii) impair or interfere with amenities and other legitimate uses of the environment.



The ratio of the volume of the interstices to the total volume of rock expressed as a fraction.



Precipitation is any product of the condensation of atmospheric water vapor that falls under gravity (typically in the form of rain, hail, snow, sleet and mist.



The act of obtaining equipment, materials, or supplies. (For example: 'IDB Procurement Policies')



A collective term for the various structures that plants use to reproduce. It applies to seeds and spores, and parts of a plant that serve as means of vegetative reproduction, such as corms, rhizomes, tubers and turions.


Protection of Badgers Act 1992

An Act to consolidate the Badgers Act 1973, the Badgers Act 1991 and the Badgers (Further Protection) Act 1991.

Click here to view the Act


Pumping station

Pumping stations are facilities including pumps and equipment for pumping fluids from one place to another. They are used for a variety of infrastructure systems, such as the supply of water to canals, the drainage of low-lying land, and the removal of sewage to processing sites. A pumping station is, by definition, an integral part of a pumped-storage hydroelectricity installation.



Quality element

A feature of an aquatic ecosystem that can be described as a number for the purposes of calculating an ecological quality ratio, such as the concentration of a pollutant; the number of species of a type of plant.


Quantitative status (groundwater)

An expression of the degree to which a body of groundwater is affected by direct and indirect abstractions. If this complies with Directive requirements the status is good.



Ramsar site

An area of land, normally already identified as a SSSI, whose wetlands qualities, habitats or species, are recognised as being of international importance through classification as a Ramsar site under the Ramsar Convention.



The quantity of water that is added to a groundwater reservoir from areally distributed sources such as the direct infiltration of rainfall or leakage from an adjacent formation or from a watercourse crossing the aquifer. Often measured in mm.


Refugia Bank

A [channel or river] bank left to grow naturally with no human interference/maintenance. (Opposite: see 'Working Bank')



A reservoir (from French 'réservoir' meaning 'storehouse'), artificial lake or impoundment from a dam is used to store water. Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete. The term reservoir may also be used to describe naturally occurring underground reservoirs such as those beneath an oil or water well.


Risk assessment

The analysis that predicts the likelihood that a water body is at significant risk of failing to achieve one or more of the Water Framework Directive objectives.


River bank

See Bank.


River basin

It means the area of land from which all surface water run-off flows, through a sequence of streams, rivers and lakes into the sea at a single river mouth, estuary or delta.


River basin district

A river basin or several river basin districts, together with associated coastal waters.


River Trusts

Charities and organisations set up to assist in the conservation, protection and improvement of rivers and associated environments.



Runoff (also know as surface runoff) is the water flow that occurs when the soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle, and the primary agent in water erosion.



Salmon & Freshwater Fisheries Act 1975

An Act to consolidate the Salmon and Freshwater Fisheries Act 1923 and certain other enactments relating to salmon and freshwater fisheries, and to repeal certain obsolete enactments relating to such fisheries.

Click here to view the Act


Salt marsh

A salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic (salt-tolerant) plants such as herbs, grasses, or low shrubs.


Schedule 1 species

A Schedule to the Wildlife and Countryside Act 1981 that lists birds for which the offences of intentionally killing, injuring, or taking these birds, their eggs or nests is the subject of special penalties. There are also offences of disturbing these birds at their nests, or their dependent young.


Schedule 5 animals

The Wildlife and Countryside Act 1981 makes it an offence (subject to exceptions) to intentionally kill, injure, or take, possess, or trade in any wild animal listed in Schedule 5, and prohibits interference with places used for shelter or protection, or intentionally disturbing animals occupying such places. The Act also prohibits certain methods of killing, injuring, or taking wild animals.


Schedule 8 plants

The Wildlife and Countryside Act 1981 makes it an offence (subject to exceptions) to pick, uproot, trade in, or possess (for the purposes of trade) any wild plant listed in Schedule 8, and prohibits the unauthorised, intentional uprooting of such plants.


Sediment pollution

See Siltation.



See Wastewater.


Significant effect

Where a plan or project is likely to affect a European site, it is necessary to decide whether or not it would have a significant effect. If there is any doubt, the operating authority must consult Natural England.



Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment (also known as suspended load) in a surface water body. It may also exist as soil deposited at the bottom of a water body.



Siltation is the pollution of water by fine particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments, and to the increased accumulation (temporary or permanent) of fine sediments on bottoms where they are undesirable. Siltation is most often caused by soil erosion or sediment spill.



A sluice is a water channel controlled at its head by a gate. There are many types of sluice gates: flap sluice, vertical rising sluice, radial sluice, rising sector sluice, needle sluice


Soak (or soke) dyke

See Back-ditch.


Spur dykes

These typically man-made hydraulic structures are situated to protect against erosion. They are typically placed in alluvial rivers perpendicular, or at an angle, to the bank of the channel or the revetment, and are used widely along coastlines. There are two common types of spur dykes, permeable and impermeable, depending on the materials used to construct them.



Individuals or groups that are or could become interested in, involved in or affected by our policies and activities.



Subsidence is the motion of a surface (usually, the Earth's surface) as it shifts downward relative to a datum such as sea-level. Groundwater-related subsidence is the subsidence (or the sinking) of land resulting from groundwater extraction, and a major problem in the developing world as major metropolises swell without adequate regulation and enforcement, as well as a being a common problem in the developed world. One estimate has 80% of serious land subsidence problems associated with the excessive extraction of groundwater, making it a growing problem throughout the world.



A natural process of change in plant communities. In the case of drainage channels, it is usually the change from a very open channel immediately after vegetation or silt clearance to a more vegetated channel. Channel management can effectively arrest or reverse this succession in order to maintain required standards of flood conveyance or storage capacity.


Surface runoff

See Runoff.



Telemetry systems

Telemetry is a technology that allows data measurements to be made at a distance. The word is derived from Greek roots: tele = remote, and metron = measure. These systems are commonly used within water level management.


Tidal flat

See Mudflat.



Describes the shape, profile and features of the surface of the land.


Transitional water

A Water Framework Directive term for waters that are intermediate between fresh and marine water. Transitional waters include estuaries and saline lagoons.



The means by which the Water Framework Directive requires surface water bodies to be differentiated according to their physical and physico-chemical characteristics.



Unconfined aquifer

A partially saturated aquifer which contains a water table which is free to fluctuate vertically under atmospheric pressure in response to discharge or recharge. Also see Aquifer.


Unsaturated zone

See Vadose zone.



Vadose zone

Also termed the 'unsaturated zone', is the part of Earth between the land surface and the top of the phreatic zone, i.e. the position at which the groundwater (the water in the soil's pores) is at atmospheric pressure. Hence the vadose zone extends from the top of the ground surface to the water table.



Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in metres per second (m/s or ms−1). This can be used to measure how fast a stretch of river, stream or any other watercourse flows.




Warping is a technique where rivers cover adjacent land with silt by natural or artificial flooding. The purpose of warping is to spread the rich nutrients of the silt across agricultural land to improve crop growing. This silt, stirred up in river esturaries, comes up with every tide. A good tide full of silt could deposit about 1 penny thickness on the land. However, this technique is now rarely practiced, as after the spreading of the silt, the land could be out of action for up to five years (expensive lost for farmers).



Usually an area of floodplain surrounded by artificial banks that, in a flood event, fills with water and provides temporary storage of flood water and flows.



It is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations. In the most common usage, it refers to the municipal wastewater that contains a broad spectrum of contaminants resulting from the mixing of wastewater from homes, businesses, industrial areas and often storm drains, especially in older sewer systems. Municipal wastewater is usually treated in a combined sewer, sanitary sewer, effluent sewer or septic tank. Sewage is a sbsequent of wastewater.


Water body

A discrete and significant element of surface water such as a river, lake or reservoir, or a distinct volume of groundwater within an aquifer.


Water Environment (Water Framework Directive) (England and Wales) Regulations 2003

The Secretary of State and the National Assembly for Wales, acting respectively in relation to river basin districts that are wholly in England and river basin districts that are wholly in Wales, and jointly in relation to river basin districts that are partly in England and partly in Wales, being designated for the purposes of section 2(2) of the European Communities Act 1972 in relation to matters relating to water resources, in exercise of the powers conferred upon them by that section, hereby make the following Regulations:

Click here to view Regulations


Water management

Water management is the activity of planning, developing, distributing and managing the optimum use of water resources. In an ideal world, water management planning has regard to all the competing demands for water and seeks to allocate water on an equitable basis to satisfy all uses and demands. This is rarely possible in practice.


Water resources

Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water.


Water table

A water table is the underground surface below which the ground is wholly saturated with water. The water table fluctuates both with the seasons and from year to year because it is affected by climatic variations and by the amount of precipitation used by vegetation. It also is affected by withdrawing excessive amounts of water from wells or by recharging them artificially. If fully saturated, water tables can exceed the ground surface.


Water well

A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers.



A watercourse is any flowing body of water. These include rivers, streams, anabranches, and so forth.



Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind and gravity.



A weir is a barrier across a river designed to alter the flow characteristics. In most cases, weirs take the form of a barrier, smaller than most conventional dams, across a river that causes water to pool behind the structure (not unlike a dam) and allows water to flow over the top. Weirs are commonly used to alter the flow regime of the river, prevent flooding, measure discharge and help render a river navigable. Weirs allow hydrologists and engineers a simple method of measuring the volumetric flow rate in small to medium-sized streams or in industrial discharge locations.



See Water well.



A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on characteristics that distinguish it as a distinct ecosystem. The primary factor that distinguishes wetlands is the characteristic vegetation that is adapted to its unique soil conditions: Wetlands are made up primarily of hydric soil, which supports aquatic plants. The Ramsar Convention defines wetlands as: “An area of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt including areas of marine water, the depth of which at low tide does not exceed 6m.”


Wildlife and Countryside Act 1981

An Act to repeal and re-enact with amendments the Protection of Birds Acts 1954 to 1967 and the Conservation of Wild Creatures and Wild Plants Act 1975; to prohibit certain methods of killing or taking wild animals; to amend the law relating to protection of certain mammals; to restrict the introduction of certain animals and plants; to amend the Endangered Species (Import and Export) Act 1976; to amend the law relating to nature conservation, the countryside and National Parks and to make provision with respect to the Countryside Commission; to amend the law relating to public rights of way; and for connected purposes.

Click here for more information about the Wildlife and Countryside Act 1981.


Wildlife and Countryside (Amendment) Act 1991

An Act to amend sections 5 and 11 of the Wildlife and Countryside Act 1981 so as to make it an offence knowingly to cause or permit to be done certain acts mentioned in those sections.

Click here to view ammendments


Working Bank

A [channel or river] bank maintained through cutting of vegetation, re-profiling etc. (Opposite: see 'Refugia Bank')



There are currently no words beginning with 'X' in ADA's glossary.




The volume of water pumped or discharged from a borehole, well or spring.



There are currently no words beginning with 'Z' in ADA's glossary.