7 key public-domain water models

Bill's selection and precises of open source models

| comments? | William James | updated 2000-06-09 |

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  1. Introduction:

    Water quality modelling as a planning and management tool requires the package to be as comprehensive as possible so as to provide necessary decision support criteria for users. The likely problems with using continuous models such as SWMM and HSPF probably relate more to their ungainly user interface and generally unfriendly batch input approach. When these are replaced by graphical, knowledge-based decision support systems, most of the criticisms that these models are too complex disappear.

    Many software packages are available that address water quality issues to varying degrees. Brief descriptions follow of what I consider to be seven useful packages:

  2. SWMM

    The US EPA's Stormwater Management Model is a comprehensive mathematical model of urban runoff quantity and pollution processes in storm and combined sewer systems. First developed in 1971, the model has been regularly updated, with the last major revision, SWMM4, released in 1989. It is perhaps the best-known and most widely used of the several urban runoff quantity and quality models available in the public domain.

    All aspects of the urban hydrologic and quality cycles are simulated, including surface runoff, transport through the drainage network, storage and treatment, and receiving water effects. The package comprises service modules and four computational modules Including RUNOFF, TRANSPORT, Extended transport (EXTRAN) and STORAGE/TREATMENT.

    SWMM is both:

    1. a design model which undertakes detailed simulations of storm events, using relatively short time steps and as much catchment and drainage system detail as necessary, and
    2. a routine planning model, used for an overall assessment of the urban runoff problem and proposed abatement options. This mode is typified by continuous simulation for several years using long (e.g. hourly) time steps and minimum detail in the catchment scheme.

    Continuous simulation may also be used.

    Surface runoff hydrographs for individual subcatchments are generated by the RUNOFF module via an iterative solution of coupled continuity and Manning's equations, with infiltration represented by either Green-Ampt or Horton models. Simple routing of surface gutter/pipe routing via non-linear reservoir routing procedure is also available in RUNOFF.

    Water quality is handled In the RUNOFF, TRANSPORT and STORAGE/TREATMENT modules, however, WQM is not considered in the EXTRAN module.

    Real storm events are modelled on the basis of rainfall (hyetograph) and pollutant inputs and system (catchment, conveyance, storage/treatment, and receiving water) characterisation to predict responses in the form of flow and pollutant concentration (pollutographs).

    For a copy of SWMM, click here.

  3. HSPF

    Hydrological Simulation Program - FORTRAN (HSPF; Johanson et al., 1984; Donigian et al., 1984) is a comprehensive package for simulation of watershed hydrology and water quality for both conventional and toxic organic pollutants. HSPF integrates the watershed-scale ARM and NPS models into a basin-scale analysis framework that includes fate and transport in one-dimensional stream channels. It is the only comprehensive model of watershed hydrology and water quality that allows the integrated simulation of land and soil contaminant runoff processes with in-stream hydraulic and sediment-chemical Interactions.

    The result of this simulation is a time history of the runoff flow rate, sediment load, and nutrient and pesticide concentrations, along with a time history of water quantity and quality at any point in a watershed.

    HSPF simulates three sediment types (sand, silt, and clay) in addition to a single organic chemical and transformation products of that chemical. The transfer and reaction processes included are hydrolysis, oxidation, photolysis, biodegradation, volatilization, and sorption. Sorption is modelled as a first-order kinetic process in which the user must specify a desorption rate and an equilibrium partition coefficient for each of the three solids types. Resuspension and settling of silts and clays (cohesive solids) are defined in terms of shear stress at the sediment water interface. The capacity of the system to transport sand at a particular flow is calculated and re-suspension or settling is defined by the difference between the sand in suspension and the transport capacity. Calibration of the model requires data for each of the three solids types. Benthic exchange is modelled as sorption/desorption and deposition/scour with surficial benthic sediments. Underlying sediment and pore water are not modelled.

    Data needs for HSPF can be extensive. HSPF is a continuous simulation program and requires continuous data to drive the simulations. As a minimum, continuous rainfall records are required to drive the runoff model and additional records of evapotranspiration, temperature, and solar intensity are desirable. A large number of model parameters can be specified although default values are provided where reasonable values are available. HSPF is a general-purpose program and special attention has been paid to cases where input parameters are omitted. Option flags allow bypassing of whole sections of the program where data are not available.

    HSPF produces a time history of the runoff flow rate, sediment load, and nutrient and pesticide concentrations, along with a time history of water quantity and quality at any point In a watershed. Simulation results can be processed through a frequency and duration analysis routine that produces output compatible with conventional toxicological measures (e.g., 96-hour LC50).

    Limitations of HSPF include the assumption that the 'Stanford Watershed Model" is appropriate for the area being modelled. Further, the in-stream model assumes that the receiving water body is well-mixed with width and depth and is thus limited to well-mixed rivers and reservoirs. Application of this methodology generally requires a team effort because of its comprehensive nature.

    HSPF and the earlier models from which it was developed have been extensively applied in a wide variety of hydrologic and water quality studies (Barnwell and Johanson, 1981; Barnwell and Kittle, 1984) including pesticide runoff model testing (Lorber and Mulkey, 1981), aquatic fate and transport model testing (Mulkey et al., 1986; Schnoor et al., 1987), analyses of agricultural best management practices (Donigian et al., 1983; Bicknell et al., 1984) and as part of pesticide exposure assessments in surface waters. An application of HSPF in a screening methodology for pesticide review is described by Donigian et al. (1986). The Stream Transport and Agricultural Runoff for Exposure Assessment Methodology (STREAM) applies the HSPF program to various test watersheds for five major crops in four agricultural regions in the United States, defines a 'representative' watershed based on regional conditions and an extrapolation of the calibration for the test watershed, and performs a sensitivity analysis on key pesticide parameters to generate cumulative frequency distributions of pesticide loads and concentrations in each region. The resulting methodology requires the user to evaluate only the crops and regions of interest, the pesticide application rate, and three pesticide parameters - the partition coefficient, the sediment decay rate, and the solution decay rate.

    For a copy of HSPF, click here.

  4. QUAL2E

    The Enhanced Stream Water Quality Model QUAL2E and QUAL2EUNCAS (Brown and Barnwell, 1987) permits simulation of several water quality constituents in a branching stream system using a finite difference solution to the one-dimensional advective-dispersive mass transport and reaction equation. The conceptual representation of a stream used in the QUAL2E formulation is a stream reach that has been divided into a number of subreaches or computational elements equivalent to finite differences. For each computational element, a hydrologic balance in terms of flow (Q), a heat balance in terms of temperature (T). and a materials balance in terms of concentration (C) is written. Both advective and dispersive transport are considered in the materials balance. Mass can be gained or lost from the element by transport processes, external sources and sinks (e.g., waste discharges or withdrawals) or by internal sources and sinks (e.g., benthic sources or biological transformations).

    The equation is solved for the steady-flow, steady state condition in a classical implicit backward difference method. The specific equations and solution technique are described in detail in the QUAL2E computer program documentation.

    The QUAL series of computer programs has a long history in water quality management. The foundation upon which the series is built was laid by the Texas Water Development Board (TWDB) in the late 1960s. In the early 1970s, EPA began a program to provide water quality models for major river basins and specified that QUAL-I be used as the basis for developing new, more advanced, basin-specific models. Many versions of the QUAL-II model emerged from this effort. One in particular was further improved in the mid- 1970s for the Southeast Michigan Council of Governments (SEMCOG), the area-wide wastewater planning agency for the Detroit metropolitan area. Because of its flexibility and thorough documentation, the SEMCOG version of QUAL-II, known as QUAL-11/ SEMCOG received widespread use, especially in wasteload allocation studies. In the late 1970's, the National Council of the Paper Industry for Air and Stream Improvement (NCASI) undertook a thorough review, testing and documentation project covering a variety of water quality models, including QUAL-II/SEMCOG. Changes resulting from this review were incorporated in the program and the model was renamed QUAL-II/NCASI. NCASI and other groups, such as the U. S. Geological Survey (USGS) tested the revised program on several intensively sampled rivers across the United States. Recently, the model has seen several European applications in England, Greece, Belgium and Spain. Other applications of QUAL-II range from South America to the Far East, including South Korea, the People's Republic of China, and Thailand. A number of applications and ongoing work with the QUAL2E model are described by Barnwell, Brown and Whittemore (1987).

    Prototype representation in QUAL2E consists of dividing a stream into a network of "Headwaters', "Reaches', and 'Junctions.' The fundamental reason for subdividing sections of stream into 'Reaches" is that QUAL2E assumes that some 26 physical, chemical and biological properties (model input parameters or coefficients) are constant along a "Reach.' The question that must be addressed in order to define a "Reach' is what constitutes "significant' change in these model inputs - 'significant' in the sense of their impact on simulation results, not necessarily in the sense of change in the inputs themselves.

    Mass transport in the QUAL2E computer program is handled in a relatively simple manner. There seems to be some confusion about QUAL2E's transport capabilities as it is sometimes called a "dynamic' model. However, in all of the computer programs in the QUAL series, there is an explicit assumption of steady flow; the only time-varying forcing functions are the climatologic variables that primarily affect temperature and algal growth. A more proper term for this capability is diurnal, indicating variation over a 24-hour period. The forcing function used for estimating transport is the streamflow rate, which, as mentioned above, is assumed to be constant. Stream velocity, cross-sectional area, and depth are computed from streamflow.

    One of the most important considerations in determining the assimilative capacity of a stream is Its ability to maintain an adequate dissolved oxygen concentration. The QUAL2E computer program includes the major interactions of the nutrient cycles, algal production, benthic and carbonaceous oxygen demand, atmospheric reaeration, and their effect on the dissolved oxygen balance In addition, the computer program includes a heat balance for the computation of temperature and mass balances for conservative minerals, coliform bacteria, and nonconservative constituents such as radioactive substances. Chlorophyll 'a' is modelled as the indicator of planktonic algae biomass in QUAL2E.

    The nitrogen cycle is composed of four compartments: Organic nitrogen, Ammonia nitrogen, Nitrite nitrogen, and Nitrate nitrogen. The phosphorus cycle is similar to, but simpler than, the nitrogen cycle, having only two compartments. Ultimate carbonaceous biochemical oxygen demand (BOD) is modelled as a first-order degradation process in QUAL2E, which also takes into account removal by settling and does not affect the oxygen balance. QUAL2E will convert the traditional 5-day BOD values to ultimate BOD for internal calculations. The processes discussed above represent the primary Internal sinks of dissolved oxygen in the QUAL2E computer program. The major source of dissolved oxygen, in addition to that supplied from algal photosynthesis, is atmospheric reaeration.

    An uncertainty analysis is available in QUAL2EUNCAS. A major problem faced by the user when working with a complex model such as QUAL2E is model calibration and determination of the most efficient plan for collection of calibration data. This problem can be addressed by application of principles of uncertainty analysis. These strategies have been applied to QUAL2E and the resulting computer program is named QUAL2E-UNCAS. Three uncertainty analysis techniques are employed in QUAL2E-UNCAS: sensitivity analysis, first order error analysis, and monte carlo simulation. The computer program uses pre- and post-processing algorithms to select the input variables and/or parameters to be altered without the user having to manually restructure the input data set and to store and manipulate only the output of Interest. The modeler is free to select the important variables and locations in the stream network where uncertainty effects are desired.

    QUAL2E requires some degree of modeling sophistication and expertise on the part of a user. The user must supply more than 100 individual inputs, some of which require considerable judgement to estimate. The uncertainty analysis procedures incorporated in the computer program serve both to guide the user in the calibration process as well as to provide information about the uncertainty associated with calibrated model.

    For a copy of QUAL2E, click here.

  5. WASP

    Water Quality Analysis Simulation Program, WASP (Ambrose et al., 1987) is a generalized framework for modeling contaminant fate and transport in surface waters. WASP5 is the latest of a series of WASP programs (DI Toro et al., 1983; Ambrose, et al., 1983; Connolly and Winfield, 1984, Ambrose et al., 1986). Based on the flexible compartment modeling approach, WASP can be applied in one, two, or three dimensions. WASP is designed to permit easy substitution of user-written routines into the program structure. Problems that have been studied using the WASP framework include biochemical oxygen demand and dissolved oxygen dynamics, nutrients and eutrophication, bacterial contamination, and organic chemical and heavy metal contamination.

    Two WASP models are provided: the toxics WASP model, TOXI, combines a kinetic structure adapted from EXAMS2 (Burns and Cline, 1985) with the WASP transport structure and simple sediment balance algorithms to predict dissolved and sorbed chemical concentrations in the bed and overlying waters. The dissolved oxygen/ eutrophication WASP model EUTRO combines a kinetic structure adapted from the Potomac Eutrophication Model (Thomann and Fitzpatrick, 1982) with the WASP transport structure to predict DO and phytoplankton dynamics affected by nutrients and organic material.

    WASP input and output linkages also have been provided to other stand-alone models. Flows and volumes predicted by the link-node hydrodynamic model DYNHYD can be read and used by WASP. Loading files from PRZM and HSPF can be reformatted and read by WASP. Toxicant concentrations predicted by TOXI can be read and used by both the WASP Food Chain Model and the fish bioaccumulation model FGETS.

    A body of water is represented in WASP as a series of computational elements or segments. Environmental properties and chemical concentrations are modelled as spatially constant within segments. Segment volumes and type (surface water, subsurface water, surface benthic, subsurface benthic) must be specified, along with hydraulic coefficients for riverine networks.

    Structurally, the WASP program includes six mechanisms for describing transport. These 'transport fields' consist of advection and dispersion in the water column; advection and dispersion in the pore water; settling, re-suspension, and sedimentation of up to three classes of solids; and evaporation or precipitation. To describe advection within WASP, each inflow or circulation pattern requires specification of the fraction routed through relevant water column segments and the time history of the corresponding flow. Dispersion requires specification of cross-sectional areas between model segments, characteristic mixing lengths, and the time history of the corresponding dispersion coefficient. For each state variable (termed 'system' In WASP), the user must specify loads, boundary concentrations, and initial concentrations. The dissolved fractions of each variable also must be specified for each segment. Only dissolved concentrations are transported by pore water and only particulate concentrations are transported by solids.

    Each variable is advected and dispersed among water segments, and exchanged with surficial benthic segments by diffusive mixing. Sorbed or particulate fractions may settle through water column segments and deposit to or erode from surficial benthic segments. Within the bed, dissolved variables may migrate downward or upward through percolation and pore water diffusion. Sorbed variables may migrate downward or upward through net sedimentation or erosion.

    For a copy of WASP, click here.

  6. SLAMM

    The Source Loading and Management Model (SLAMM) was developed to assist water and land resources planners in evaluating the effects of alternative control practices and development characteristics on urban runoff quality and quantity. SLAMM only evaluates runoff characteristics at the source areas In the watershed and at the discharge outfall; it does not directly evaluate receiving water responses.

    However, earlier versions of SLAMM have been used in conjunction with receiving water models (HSPF) to examine the ultimate effects of urban runoff (Ontario Ministry of the Environment 1986).

    SLAMM is different from other urban runoff models. Beside examining land development practices and many source area and outfall control practices, it contains two major areas of improvements. These are corrected algorithms for the washoff of street dirt and the incorporation of small storm hydrology. Without these corrections, it is not possible to appropriately predict the outfall responses associated with source area controls and development practices.

    SLAMM continually develops mass balances for both particulate and dissolved pollutants and runoff flow volumes for different development and rain characteristics. It was designed to give relatively simple answers (pollutant mass discharges and control measure costs for a very large variety of potential conditions). It is therefore used as a planning tool, such as to generate information needed to make planning level decisions, while not generating superfluous information unnecessary for these planning decisions. It is recognized that many stormwater models are available that can generate predicted outfall conditions with great resolution, but this information is of little value to planners and substantially increases the data 'gathering and computational costs.

    SLAMM predicts urban runoff discharge parameters (total storm runoff flow volume, flow-weighted pollutant concentrations, and total storm pollutant yields) for many individual storms and for the study period. It does not predict these parameters for periods within individual storms. Stormwater management decisions are most appropriately based on long-term conditions and not on rapidly varying conditions. As examples, stormwater effects are mostly associated with the long-term discharges of pollutants that accumulate in the receiving water sediments (Pitt and Bozeman 1982) or in increased flows that destroy habitats and increase channel erosion (Pitt and Bissonnette 1984).

    Very few studies investigating problems in urban runoff receiving waters have found significant urban runoff quality effects associated with individual events (Heaney et al. 1980). Water quality standards (especially for heavy metals and bacteria) may be violated during most rains at outfalls, but the durations of the violations are usually short and only occur for small percentages of the year (EPA 1983). A model capable of accurately estimating rapidly changing conditions within an individual storm would be very large and require greater knowledge than is currently available. SLAMM was developed to supply the type of information most needed to make management decisions, balanced against current urban runoff knowledge, costs of obtaining program Input Information, and costs of running the program. If receiving water response information is also needed, the output from SLAMM can be used in specific receiving water models for the pollutants of concern.

    SLAMM was conceived in the mid 1970s mostly as a data reduction tool for use In early street cleaning projects (Pitt 1979). Special field studies were designed and conducted in conjunction with many separate field projects to obtain necessary Information (mostly source area sheetflow characterization and control measure performance information). After substantial work with the initial versions of the 'model", It was decided that a needed management tool (at the decision making or planning level) could be developed. SLAMM was therefore expanded to enable other management practices (located at source areas and at the outfall) to be evaluated. A preliminary description of SLAMM was included in the Castro Valley Nationwide Urban Runofr Program (NURP) report (Pitt and Shawley 1982), but it was not until the other NURP projects and recent field studies conducted by Pitt (1987) were completed that a more comprehensive version of the model could to be finished and tested.

    SLAMM requires information concerning the urban runoff controls to be evaluated and the development characteristics of the study area. SLAMM can evaluate the effects of a number of different stormwater control practices on runoff quality and quantity, including:

    1. wet detention basins
    2. porous pavement
    3. infiltration devices
    4. street cleaning
    5. catchbasin cleaning
    6. grass swales
    7. roof runoff disconnections
    8. paved parking and storage area runoff disconnections

    The modeling procedures used to evaluate these stormwater controls are based on many past research projects (Pitt 1985 and 1987). However, if improperly designed, constructed, or maintained, the controls could have little benefit. SLAMM requires specific information concerning each practice to be evaluated. As an example, grass swale evaluations require the effective infiltration rate in the swale, the drainage density, and the swale width. Wet detention basin evaluations require information concerning the area and cross-sectional shape of the basin and the sizes and types of outlet structures. There are also many development features of an area that affect runoff and that must be known, including:

    1. areas of each source type in the watershed
    2. effective SCS soil type
    3. building density
    4. land use
    5. presence of alleys
    6. roof pitch
    7. pavement texture
    8. traffic density

    Of these features, the areas of the separate sources (such as roof area, street area, landscaped area, etc.) are the most important and should be obtained from aerial photographs. Building density, land use, and alley information can also be obtained from aerial photographs. SCS native soil types can be obtained from soil maps, but native soils have little hydraulic resemblance to typically highly disturbed and compacted urban soils. Specific infiltration tests should therefore be conducted in an area to obtain an estimate of the actual hydraulic responses of the urban soils of interest.

    Inventory surveys of the neighbourhoods to be evaluated should be conducted to determine roof and paved area connections and the type of drainage system. Other site information that can be obtained from site surveys include roof pitches, pavement textures, and traffic densities. If the model is to be used for future developments, these characteristics can be estimated from current developments or from the site plans.

    Rain information for the period of study is also needed. Because SLAMM only evaluates complete storm conditions, detailed rain data is not needed. Only rain start and end dates (and times) and total rain depths are needed for each event. Typically, study periods containing 10 to 100 rains are used in each evaluation. SLAMM currently does not evaluate snowmelt or baseflow conditions. Like any urban runoff model, SLAMM must also be calibrated and verified for local conditions. Needed calibration files describe the runoff responses and the sheetflow runoff qualities for the different source areas.

    The principal outputs are statistical information on quantity and quality of runoff (and overflow in combined drainage and sewerage systems which are common in US cities) and pollutographs for selected individual events.



    Cornell Mixing Zone Expert System (CORMIX) can be used for the analysis, computation, design of aqueous toxic or conventional pollutant discharges into diverse waterbodies. Major emphasis is on computation of plume geometry and dilution characteristics within a receiving water's initial mixing zone so that compliance with regulatory constraints can be judged. It also computes discharge plume behavior at larger distances.

    CORMIX, Version 2.10, combines:

      CORMIX1 - for submerged single point discharges;
      CORMIX2 - for submerged multiport diffuser discharges; and
      CORMIX3 - for buoyant surface discharges,

    into a single comprehensive system for modeling diverse types of aquatic pollutant discharge into all types of receiving water bodies streams, rivers, lakes, reservoirs, estuaries, coastal waters). Version 2.10 also includes a FAST-CORMIX option that provides fast data entry mode for experienced users.

    Notes from CEAM-USERS Digest 133:

    The person responsible (as at 970701) for distribution of CORMIX is
    located at:

      Center for Exposure Assessment Modeling (CEAM)
      U.S. Environmental Protection Agency (U.S. EPA)
      Office of Research and Development (ORD)
      National Exposure Research Laboratory - Ecosystems Research Division
      960 College Station Road
      Athens, Georgia (GA) 30605-2700 USA
      email: ceam@epamail.epa.gov

    Users can send questions and/or requests for technical assistance to the CEAM address.

    The user list for announcements is: CEAM-USERS@valley.rtpnc.epa.gov

    Release of CORMIX Technical Report (June 1997)

    The Oregon Graduate Institute--the technical support center for CORMIX users--through the U.S. EPA Center for Exposure Assessment Modeling (CEAM) announces the availability of the technical report titled "CORMIX3: An Expert System for Mixing Zone Analysis and Prediction of Buoyant Surface Discharges" by Gilbert R. Jones, Jonathan D. Nash, and Gerhard H.Jirka. This report, by the DeFrees Hydraulics Laboratory of Cornell University, documents the technical background of CORMIX3. The report is available as both an Adobe Acrobat 3.0 (pdf) and Postscript file at Uniform Resource Locator (URL):


    Users can down load the documentation free of charge after completing a short registration form. For questions, information, and technical support concerning CORMIX model and/or program content, application, and/or theory, contact Dr. Robert Doneker for assistance at:

      Department of Environmental Science and Engineering
      Oregon Graduate Institute
      P.O. Box 91000
      Portland, OR 97291-1000
      Telephone: Voice: 503/690-4053
      Fax: 503/690-1273
      E-mail: doneker@ese.ogi.edu

    For a copy of CORMIX and its documentation, click here



    EPANET is a computer program that performs extended period simulation of hydraulic and water quality behavior within pressurized pipe networks. A network can consist of pipes, nodes (pipe junctions), pumps, valves and storage tanks or reservoirs. EPANET tracks the flow of water in each pipe, the pressure at each node, the height of water in each tank, and the concentration of a substance throughout the network during a multi-time period simulation. In addition to substance concentrations, water age and source tracing can also be simulated.

    EPANET is designed to be a tool for improving our understanding of the movement and fate of drinking water constituents within distribution systems. The water quality module of EPANET is equipped to model such phenomena as reactions within the bulk flow, reactions at the pipe wall, and mass transport between the bulk flow and pipe wall. As we gain more experience and knowledge of water quality behavior within distribution systems we intend to update and refine EPANET to reflect this progress.

    Another feature of EPANET is its coordinated approach to modeling network hydraulics and water quality. The program can compute a simultaneous solution for both conditions together. Alternatively it can compute only network hydraulics and save these results to a file, or use a previously saved hydraulics file to drive a water quality simulation.

    The water quality module of EPANET can track the growth or decay of a substance by reaction as it travels through a distribution system. Reaction can occur both within the bulk flow and with material along the pipe wall. Bulk fluid reactions can also occur within tanks. EPANET models both types of reactions using first order kinetics. The bulk reaction is defined through a bulk reaction rate constant (Kb) while a wall reaction rate constant (Kw) is associated with the wall reaction. Different values for Kb can be used for different pipes and tanks in the network and the same holds true for Kw. Kb has units of 1/days while Kw has units of ft/day (or m/day). These coefficients are positive for growth reactions and negative for decay reactions.

    EPANET views a water distribution network as a collection of links connected together at their endpoints called nodes. Links and nodes are identified with ID numbers and can be arranged in any fashion.

    EPANET can be used for many different kinds of applications in distribution system analysis. Sampling program design, hydraulic model calibration, chlorine residual analysis, and consumer exposure assessment are some examples. EPANET can help assess alternative management strategies for improving water quality throughout a system. These would include:

    • altering source utilization within multiple source systems,
    • altering pumping and tank filling/emptying schedules,
    • use of satellite treatment, such as re-chlorination at storage tanks,
    • targeted pipe cleaning and replacement.

    The EPANET package contains two program modules. One is a network simulator that runs under DOS, receiving its input from a file and writing its output to another file. The user must use external programs to edit the input file and view or print the output file. (An optional DOS shell program is provided that interactively edits EPANET input, runs the simulator, and views or prints its output according to selections made from a menu). The second module is a program that allows one to edit EPANET input data, run the simulator, and graphically display its results in a variety of ways on a map of the network. Thus there are two different ways to run EPANET -- under DOS or under Windows. We believe that for most situations the visualization power of the Windows version is an essential aid in trying to comprehend the results of running EPANET and recommend that this mode be used if your computer hardware and software can support it.

    This Windows version of EPANET provides an integrated environment for editing network input data, running hydraulic and water quality simulations, and viewing the results in a variety of formats. These include color-coded network maps, data tables, and time series graphs.