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Glossary

Absolute Date and Time
InfoWorks ICM simulations can run using absolute or relative dates and times. Absolute dates and times are real dates and times that fall within the range 01/02/1970 00:00 and 31/12/2037 23:59.
Acute impacts
Caused by high concentrations of pollutants for a short duration.
Advection (solution)
Solution to movement of sediments/ pollutants in the flow by assuming pollutants travel at the same speed and direction as the fluid.
Aesthetic Pollution
Usually refers to solid material washed into river banks which possess little environmental impact but is objectionable due to its visual impact.
Air entrainment
The process by which bubbles or pockets of air are caught within the fluid and transported with the flow.
Anaerobic process
A process carried out in the absence of air. Often results in biodegradable material being broken down into toxic pollutants (e.g. hydrogen sulphide or ammonium salts).
Ancillary structure
A structure within a sewerage system which is not a sewer. Ancillary structures include overflows, storage tanks and ponds, pumping stations, outfalls, sluice gates and flap valves.
ANTEC
Data which defines whether the depression storage on the catchment surface is full prior to a rainfall event.
Antecedent conditions
The wetness of a catchment before a rainfall event. There are two conditions, one representing the saturation of the ground as a whole, and one representing the wetness of the ground surface.(see ANTEC and UCWI).
Areal reduction factor
A factor applied to synthetic point rainfall depths or intensities to give values applicable to an area.
Asymptotic
A line is asymptotic to a particular curve if it continually approaches the curve but does not meet it within a finite distance.
Biochemical Oxygen Demand
Biochemical Oxygen Demand (BOD)is usually expressed as BOD5 20 which is the amount of dissolved oxygen (milligrams per litre of water) consumed by micro-biological actionwhen a water sample is inclubated in the dark over a 5-day period at 20C.
Boundary Shear Stress
The retarding force (usually friction) which is exerted at a solid boundary (e.g. pipe wall).
CARP
Comparative Acceptable River Pollution (procedure).
Catchment Runoff Data
Describes the initial state of subcatchment surfaces for the runoff model. Catchment Runoff Data is defined in a rainfall event.
Catchment Sediment Data
Describes the initial mass of sediment on the subcatchment surfaces for the Surface Pollutant Model. Catchment Sediment Data is defined in a rainfall event.
Chronic Impacts
Caused by prolonged exposure to low pollution concentration.
Chronomids
Midge larvae very common in moderately polluted water in the UK.
Chemical Oxygen Demand
Chemical Oxygen Demand (COD) is a measure of the amount of potassium dichromate needed to oxidise all the reducing material (often organic matter) in the water sample. COD is normally higher than BOD.
Combined Network
A sewer network which collects rainfall from impervious surfaces and foul water from domestic and industrial sources.
Combined Sewerage System
A sewerage system in which both foul sewage and storm water are carried in the same pipes (see separate system).
Consented Discharges
Discharges meeting the conditions imposed by the appropriate public authority for potentially polluting flow to a watercourse.
Consolidated Sediment
Sediment which has become impressed (squeezed)by the flow onto the pipe or channel bed. In normal flow conditions this material is effectively non-erodible.
Continuation Pipe
Usually refers to the pipe at a tank which continues towards the main outlet of the sewerage system.
Contributing Area
The area of the catchment which contributes storm runoff directly to a link or node in the sewerage system.
Critical Dilution Factor
The dilution factor of a receiving water such that inflows of pollutants can be assimilated.
CSO
Combined Sewer Overflow.
CSV
CSV is one implementation of a delimited text file, which uses a comma to separate values.
CSV files
Comma Separated Variable file format is a standard file format that can be imported and exported by many software packages. Many types of data can be imported and exported using csv format by InfoWorks ICM.
Current Active Window
The current Active Window in any Microsoft Windows application has a differently coloured title bar to all the other windows. In the default colour scheme, the active window title bar is blue, all other windows have a grey title bar.
Data Flags
You can apply user defined data flags to many parameters within InfoWorks to convey additional information about the parameter, such as the source or reliability of the data.
Database Data
The data stored in an standalone, workgroup or cloud database. This data can be shared by more than one user.
Database Items
Any item stored in the Database, such as a network.
Depression Storage
The depth of water retained on the ground surface in puddles or other depressions.
Design storm
A rainfall event of a given duration and return period. It is found by statistically manipulating past storm events to predict typical storm intensities.
Detention Tanks
Tanks constructed in a sewerage system to store temporarily a volume of water during peak flows (see off-line and on-line tanks).
Digital Converters
Equipment which translates data into a digital format suitable for transfer to a personal or mainframe computer.
Dilution and Fate Model
A model which accounts for the various factors which may influence the concentration of a contaminant while it is mixed and dispersed (e.g. reaeration, animal and plant uptake, deposition in sediments, etc.).
Dilution Model
Models the mixing and dispersion of a contaminant.
Diurnal Variation
(Usually related to dry weather flow) Represents the variation in flow or concentration over a daily cycle.
Domestic (foul) Inflow
Waste water from residential areas which includes all the outflow from sinks, toilets, washing machines, etc.
Dummy Pipe
A non-existent pipe included in the model to enable the hydraulics to be predicted more accurately.
Efficiency Factor
Factor introduced to predict the behaviour of overflow structures.
Ensemble
A population of simulations.
Environmental Quality Objective (EQO)
Water quality objectives relating to overflow spill frequency, duration and potency.
Environmental Quality Standards (EQS)
A defined maximum admissible concentration of a pollutant which varies according to the various uses of the waterway.
Eschericha Coli
A bacterium present in huge numbers in human and other animal faeces. Its presence in water is taken as irrefutable evidence of faecal contamination.
Eutrophication
Process of nutrient build-up in watercourse which encourages excessive plant growth which kills animal life by deprivation of oxygen.
Extreme Event
Single occurrence of an event which is likely to occur very infrequently (e.g. long drought or very serious storm, etc.).
Faecal Contamination
Water sample which has been exposed to human or animal excreta (faeces).
First foul flush
The initial associated discharge of active sediments and pollutants which is generally far higher than the average concentration.
Flow Regime
The typical variation of discharge of a waterway usually over an annual or seasonal period
Flow Survey (sewers)
Systemized analysis of the hydraulic behaviour of the network at a series of critical points in response to rainfall events. Ultrasonic flow gauges are usually used.
Foul Water
Domestic or industrial waste water which may be mixed with storm water.
Free-space Propagation (telemetry)
The transfer of data using the air as the transmission medium (e.g. radio waves).
Full results
The time-varying and summary results from a simulation.
Full run
A run that performs the full range of simulations including hydraulic simulations.
Gross Solids
Solids either floating, suspended or deposited which have a polluting effect on the receiving water. Often restricted to visible solids with one dimension greater than 25mm.
Gully Pot
A structure to permit the entry of surface runoff into the sewer system. It is usually fitted with a grating and a grit trap.
GUID
A Globally Unique IDentifier, or GUID, is an automatically generated identifier that is guaranteed to be unique across all on-premise systems. It is generated using a complex algorithm based on the date and time and the individual computer's network card ID. GUIDs take the form {629810C2-3F6B-11D3-9BF3-00600891B690} and you will see them in a number of places where uniqueness is essential.
GUIDs are also used for cloud database and consist of a string of 26 alphanumeric characters. For example - 01HXBXCDCMMB73D136S2WAY1G3. You will also see them in a number of places where uniqueness is essential.
Herbicides
Chemicals designed to kill plants either selectively or indiscriminately.
Hydraulic Capacity
The maximum flow a pipe of given dimensions, slope and roughness can carry (often quoted as pipe-full capacity which is less than the maximum capacity).
Hydraulic Performance
The flow conditions in a system usually as a response to a rainfall event.
Hydrogen Sulphide
Poisonous and highly corrosive gas which dissolves in water to form sulphuric acid.
Hydrograph
A series of values in numerical or graphical form of the flow rate, depth or level varying with time.
Hyetograph
A series of rainfall intensity values varying with time. Usually represented graphically by a block graph.
ICA
Describing the subject of Instrumentation, Control and Automation.
Impermeable surface
Surface which resists the infiltration of water (thus water landing on an impermeable surface will flow overland or evaporate).
Industrial Discharge
Outflow from an industrial unit which varies enormously depending on the processes carried out in the factory.
Infiltration flows (to sewers)
Groundwater which enters sewers by seepage through the ground.
Infiltration flows (to the ground)
Rainfall which soaks into the ground and does not form part of the immediate runoff.
Inflow Pollutograph
A series of values expressing the variation of a named pollutant with time as it flows into the system. This pollutograph is accompanied by a hydrograph.
Intensity/Duration/Frequency Relationship
A table or graph showing the way in which rainfall intensity at a particular location is related to storm duration and frequency of occurrence (return period).
Intercepting sewers
A sewer collecting discharge from one or more sewers. These are usually built to intercept outfalls which discharge directly into the sea or freshwater.
Intrinsically Safe (IS)
BS standard which, for sewers, indicates complete safety in operating the instrument in the presence of potentially explosive gases.
Land Use
The land use defines a set of typical values to be used by sub-catchments. For example, you may have different land uses representing residential, industrial or commercial catchments, and so on.
Magnitude/Duration/Frequency
See Intensity/Duration/Frequency
Micro-biological
The biological processes concerning micro-organisms such as bacteria, viruses and protozoa.
Minor timestep
Timestep inserted between run timesteps as a result of timestep halving carried out to allow convergence.
Model Group
The model data and results in the cloud or on-premise database are organised into a flexible hierarchy; within the hierarchy the database items are grouped into manageable units. The top level of the database hierarchy is the Model Group. Each database contains one or more model groups. You may also create additional levels in the database hierarchy by defining subsidiary model groups within a top-level model group.
Multiplexer-analog
Instrumentation unit which sends/receives signals from a logic controller to an instrument.
Native Units
The default units used within InfoWorks ICM. These are metric units and are used to carry out all underlying calculations within InfoWorks.
Non-visual object
A database object which is associated with a network object but is not displayed in the Explorer window.
Normal loading
Quantity of discharge which is only exceeded on rare occasions.
Observed run
A run that performs the runoff only aspect of one or more simulations; hydraulic simulations are not included in an observed run.
Off-line Tank
Detention tank which is off the normal path of flow in a network but which comes into operation at large flows.
On-line Tank
A detention tank which forms part of the normal flow path in a sewerage system.
Oracle Database
A database stored and managed on an Oracle database server.
Over-designed systems
Systems which are able to deal efficiently with rare events.
Overflow Efficiency Factor
Factor which gives a measure of how effective the overflow design is at operating at its chosen setting for removal of gross solids.
Overflow setting
This is usually expressed as a multiple of dry weather flow and is the discharge which will just cause the overflow to operate.
Overflow Spill Rate
The rate of discharge from an overflow.
Oxidisable Material
Material which can be oxidised either naturally (biodegradable) or in the presence of powerful oxidising agents.
Oxygen Sag
The rate of uptake of dissolved oxygen by pollutants whilst allowing for the reoxygeneration of the waterway.
Particulate Fraction
Separate particles of a range of sizes (usually fine or coarse).
Pathogens
Micro-organisms which infect animals or plants with a disease.
Peakedness
A measure of the sharpness of a rainfall profile, that is the ratio of the maximum to the mean intensity. Percentile peakedness is the profile that has the specified percentage of storms of a given return period with peakedness less than or equal to it.
Peaking Factor
The multiple of dry weather flow which occurs at the same time as rainfall.
Pervious Surface
A type of ground surface which allows infiltration of water although some surface runoff may still occur
Photosynthesis
The process by which plants convert solar energy to complex substances from carbon dioxide and water. Oxygen is a by-product of this process.
Pollutant Concentration Profile
Pollutant concentration, duration and frequency.
Pollutant Graph
Graphical representation of pollution concentration or mass against time.
Pollution Index
A Pollution Index, or Pollution Index Definition, describes the water quality characteristics of the subcatchment surface. It does the same job as a Runoff Surface does for runoff. There is only one Pollution Index for each Land Use.
Pollutograph
Graphical representation of pollution concentration or mass against time.
Population Equivalent
Usually used to describe commercial or industrial pollutant inflows in terms of the number of people who would produce a similar quantity of pollutants (usually calculated only for BOD and never refers to toxic substances).
Potency
Pollutants attached to sediment by a fixed ratio (kg pollutant/kg sediment).
Potency Factor
Multiplier factor used to express a pollutants potency in terms of each particulate fraction.
Profiles
A profile is a series of time-varying data values applicable to a particular measurement point. You can have more than one profile associated with a sub-event. For example, if you have three rainfall gauges measuring rainfall intensities during one sub-event, you will have three profiles.
QIN Files
Files used to represent the discharge from inflows to the sewerage network.
Quality Objectives (rivers)
Defined standards which must be met. An acceptable failure rate to meet these objections is usually specified.
Rainfall Hyetograph
A series of values of rainfall intensity varying with time. Sometimes called a rainfall profile.
Reach (river)
A stretch of river usually between easily definable points where the river characteristics are similar.
Reaeration Coefficient
Coefficient used to account for the depth, velocity of flow which may influence reaeration (e.g. weirs).
Receiving Waters
Water which receives (intermittent) flow from an overflow structure.
Rehabilitation Works
Upgrading of existing system.
Relative Date and Time
InfoWorks ICM simulations can run using absolute or relative dates and times. Relative dates and times use the date/time format to hold a value that is not valid in real life but represents a point within a 31 day time range beginning at zero. Values that are valid for relative dates and times fall within the range 00/00/0000 00:00 and 30/00/0000 23:59.
Respirometry
Method for determining toxicity and estimating BOD by measuring bacterial respiration when exposed to a sample.
Return Period
The average period between occurrences of an event greater than or equal to a given value.
Reverse Flow
Flow in the opposite direction to that which normally occurs.
River Impact Model (RIM)
River model capable of modelling the impact of pollution downstream.
SAAR
Standard Average Annual Rainfall (from 1916-1950).
SaaS
Software as a service.
SAMPROC
Program provided with a timeseries data set for adjusting UCWI.
Sediment Fraction
Particulate matter of a given range of sizes/density.
Self-cleansing (velocity)
Flow velocity which is able to remove sediments which have settled in pipes (usually taken to be about 1.75m/s in the UK).
Separate System
A sewerage system in which foul sewage and storm water are conveyed in separate pipes (partially separate system is a part separate and part combined system).
Shear Stress
Retarding force produced by successive layers of a substance being shifted laterally over each other. It is highest at a solid boundary.
Shield's Curve
A plot of Shield's entrainment function against the particle Reynolds number. The position a sediment fraction has on the curve in given flow conditions allows the prediction of whether the particle will be transported by the flow.
Simulation model
The representation of specific conditions over a set time period by a computer model.
SMP
Sewerage Management Planning.
Soil Moisture Deficit (SMD)
A measure of soil wetness, calculated by the Meteorological Office in the UK, to indicate the capacity of the soil to absorb rainfall.
Spill Event
An isolatable period when an overflow discharges to a watercourse.
Spill Frequency
The number of spill events over a given period.
SQL Server Database
A database stored and managed under Microsoft SQL Server.
SSD file
Sewerage system data file. A file used by the WALLRUS suite of programs to describe the sewerage system.
Storage Layer
Pipe sediments which are non-erodible.
Storm Sewage
A mixture of storm runoff and foul sewage in a combined system.
Storm Tanks
Storage tanks designed to hold most of the stormwater in either sewers or treatment works such that downstream flooding or incomplete treatment respectively is minimised.
SUCWI
Standard Urban Catchment Wetness Index (see UCWI).
Sulphide Problems
Usually corrosion problems, particularly in concrete pipes in hot climates (see hydrogen sulphide).
Surface Runoff Rate
The rate of flow over the ground surface from where the rainfall loads to its entry into the sewerage system.
Surface Washoff
The process of whereby the rainfall runoff carries surface sediments into the sewer network.
Suspended Solids (SS)
Particulate matter carried in suspension by flow.
Synthetic Rainfall
Rainfall depths or intensities derived from rainfall statistics and not representing an individual real rainstorm.
Synthetic Rainfall Series
A design rainfall series derived from the annual time-series.
Telemetry Control Systems
System of transfer of information, usually including remote sites, often with real-time control capabilities.
Thiessen Polygon
Given a number of points within an area (nodes for example), Thiessen Polygons are used to completely divide up the area so that, for each point, there is a polygon whose boundaries define the area that is closer to that point than to any other point.
Timeseries Rainfall
A continuous record of individual events generated artificially by the analysis of past events which include the randomness in the variations in the timing and magnitude of rainfall events.
Transitory Data
Transitory Data is stored in your Local Root directory and includes local copies of checked out networks, locally stored results, and other temporary files.
Transportable Data
Data stored in a Transportable Database. Transportable Databases are portable and should be used for transferring data between databases of any format.
Transportable Database
Transportable Databases store copies of some or all the data from an InfoWorks database for transfer purposes.
Tree object
A database object which appears as an icon in the Explorer window.
Tubificial Worms
Genus of common worms found in rivers.
Turbidity
A factor describing the cloudiness of water.
TVD
Time Varying Data
UCWI
Urban Catchment Wetness Index - describes the wetness of the catchment at the start of a rainstorm.
Version controlled item
Version controlled items have an extra level of management within the database. Changes to these items can be committed to create a series of versions of the same item. You can also create branches from any version. Only the differences between versions are stored in the database. Version controlled items can be locked to prevent accidental deletion.
Water Quality Standards
Legal standards set by the European Community directives enforced by member states (by the National Rivers Authority in the UK).
WRc
Water Research Centre.
User Units
Units used for display purposes. The display units are set up on the Units Page of the Options Dialog. InfoWorks converts the displayed values into InfoWorks Native Units for storage and calculation.
Unique Database Identifier
A unique GUID is used to give a unique ID to every new on-premise database that you create. This ID is then used when creating sub-directories for database data in both the Local Root and Remote Root directories.
Unique Identifier
A unique ID is given to every new cloud database that you create. This ID is then used when creating sub-directories for database data in local folders.
UPM
Urban Pollution Management.

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