Mission and Intent

The SWMM Knowledge Base is intended to function as an online learning resource for users of the public domain EPA SWMM program. It consists of digitally curated content from the SWMM-USERS list server, organized in an easily readable format. Fully searchable, the SWMM Knowledge Base provides a high signal-to-noise ratio, and promotes content discoverability through related topic suggestions.

Together with the open access Journal of Water Management Modeling, the annual International Conference on Water Management Modeling, and the SWMM-USERS list server, the SWMM Knowledge Base rounds out a group of high quality resources that supports, promotes and encourages development of SWMM by the EPA and the user community.

The SWMM Knowledge Base continuously solicits feedback from the community in making the presentation and content as accessible and useful as possible. Please send any comments and questions to staff at info@openswmm.org. The SWMM Knowledge Base is hosted and moderated by the staff of CHI.

SWMM-USERS list server

The SWMM-USERS list server is an email-based forum for users of the public-domain US EPA SWMM program to share ideas and ask questions on issues related to water management modeling with SWMM. Subscription is free, and subscribers receive all the email that is sent to the list and can in turn send email to the list. The list is carefully monitored to discourage off-topic posts, and discussions are archived in the SWMM Knowledge Base.

Subscribing to SWMM-USERS

To subscribe to the SWMM-USERS list server, either create an OPEN SWMM account and complete your profile, or email a subscription request to the list server.

Subscribing via OpenSWMM

Create an OPEN SWMM account, complete your profile, agree to the terms and conditions and you will be subscribed to the SWMM-USERS list server. It is important to ensure your OPEN SWMM account is created using the email address you would like the SWMM-USERS list server to use.

Subscribing by email

Send an email to listserv@listserv.uoguelph.ca. Do not put anything in the subject line and, in the body of the message, insert the following line (don't include the square brackets).

SUBSCRIBE SWMM-USERS [your first name] [your last name]

Ensure there is no other text included in the body of the message. For example,


It is important to subscribe to the list from the email account that you wish to use for SWMM-USERS communications (the "reply to" email address is used by the list server). Also, if you are changing or terminating an email address, please remember to unsubscribe from that address before you close it.

Before being subscribed you will receive an email asking you to complete your profile and agree to the conditions for subscribing (posted below).

Microsoft's fraud detection check warning message

In the past few months a number of folks have been seeing the following warning attached to emails they have sent to the SWMM-USERS list server:

[ This sender failed our fraud detection checks and may not be who they appear to be. Learn about spoofing at http://aka.ms/LearnAboutSpoofing ]

As far as we know, only the sender of the email will receive the warning, and only if their email is managed by Microsoft. It is a warning attached by your email server to the email coming from SWMM-USERS. The list server forwards email “on behalf of” yourself, and we believe Microsoft’s security system considers it suspect that the email is coming from the list server but says its coming from your organization’s email domain. Other list server members that share your email domain may also get the warning, but we don’t think anyone else will.

While phishing is a significant security concern for anyone with an email account, and we can’t guarantee that there won’t be a phishing scheme perpetrated through the list server, these warning messages are not necessarily something to be concerned about and hopefully will not be a permanent thing.

By not allowing attachments, images or link masking, SWMM-USERS content is relatively safe, but remember that there is always a risk in following external links. Make sure you recognize the domain and check that it is spelled correctly. The spoofing link in the warning message above provides additional information about protecting yourself.

Unsubscribing from SWMM-USERS

To stop receiving emails from the list, either uncheck the terms and conditions part of your profile (click your account button in the upper right corner of this page and choose Edit Profile) or send the following email (with NO other text and no brackets) to listserv@listserv.uoguelph.ca from your registered email address:


Conditions for subscribing

We endeavor to keep the SWMM-USERS list server and it's archive thoroughly professional, focused on encouraging the wise use of the public domain EPA SWMM software, and free of commercialism and extraneous issues.

This technical list has an extraordinary signal-to-noise ratio, which we wish to protect. Before being subscribed, you will be asked to agree to the following 4 simple conditions:

  1. I agree to not promote a commercial product or service on the list.
  2. I acknowledge that discussion should focus on the wise use of the public-domain EPA SWMM program.
  3. I have read and will abide by the guidelines for posting (see Guidelines for posting below).
  4. I agree to have my postings archived in the SWMM Knowledgebase (see Digital curation below).

Contravening these conditions may result in your membership being rescinded, at least until such time as the problem can be resolved. In addition, please note that your membership may be automatically deleted if the list server interprets your post as spam. If this happens to you, please contact us at info@openswmm.org.

Let us know if you have any questions or problems. We feel confident that you will enjoy being a member of this helpful, professional and dedicated group.

Guidelines for posting

The SWMM Knowledge Base and SWMM-USERs listserver differs from other online forums in that all posts are sent to all member's professional email inbox. While this proactive approach encourages a timely response, subscribers have higher standards and expect to receive only a specific type of information from specific people.

As such, all posts must support the official business of the list, which is the wise use of public-domain EPA SWMM. Do not post anything unless you are certain that it is appropriate for the list. If you aren't sure, email us at info@openswmm.org first - especially if it could be construed as an advertisement or blatant promotion. Announcements for related conferences or job opportunities are permitted if limited to a single line plus a URL pointing the reader to more information.

This is a professional, technical environment: postings should be attributable and conform to professional standards and ethics. Please include your name, affiliation, professional/academic status, city and country (and nothing else) in your signature.

Don't post to the list under someone else's email or if you are not a bona fide member. Don't make unsubstantiated accusations, aspersions, sweeping claims or characterize the intent of others. Don't make an unpleasant gripe, or broadcast a criticism of a product or service that cannot be responded to in the spirit of these guidelines.

For privacy, security and brevity, images and attachments are not permitted and will be removed by the server when sending emails to the list. If you wish to include data sets or SWMM model files, paste the data or input file (in part or in whole) into the body of your email. Simplifying your model to the minimum necessary helps control the size of the email everybody receives.

In most cases, reply to the whole list so that future users of EPA SWMM can benefit from the archived knowledge. To make the archive more useful, please limit discussion to one topic per posting thread, and relate the subject heading precisely to the content.

Remember that the folks participating in the list discussions are busy professionals. Ensure you do your homework before posting a question, as the subject may already be covered. Read the SWMM reference documentation, work through the SWMM applications manual, download and review the example models, search the SWMM Knowledge Base and consider taking a training course.

If you are annoyed by a posting, email that person privately. Remember to be kind, the sender just made a mistake as we all do. If you can't resolve the issue email us at info@openswmm.org.

General posting etiquette

  • Be patient with inexperienced list users.
  • Be especially polite, as readers cannot tell whether you are joking.
  • Don't use capital letters: this can be interpreted as SHOUTING.
  • Don't echo back long messages and don't edit quoted messages to change their meaning.
  • Never send negative messages. Don't be terse. Consider using the phone instead.
  • Never send a message when you are angry or upset.
  • Don't react to a flame, but post a brief apology for unintended impact or unacceptable use.
  • Give senders the benefit of the doubt.
  • Review your message before posting it (always Think before Send).
  • And, finally, enjoy the list's benefits and share your enjoyment by being pleasant.

Digital curation

To enhance the effectiveness of the SWMM Knowledge Base as a resource for those interested in learning the application of EPA SWMM, SWMM-USERS content is subject to automatic processing, and may be subject to manual processing before inclusion in the SWMM Knowledge Base. This processing is intended to improve the readability, specificity and succinctness of discussion threads and the effectiveness of the search engine.

Automatic processing

The following processing of SWMM-USERS content is automatically performed by the server:

  • Grouping of emails into discussion topics/threads
  • Removal of salutations and signatures for brevity
  • Removal of quoted messages to avoid redundancy
  • Redaction of email addresses for privacy
  • Detection and formatting of paragraphs
  • Detection and formatting of numbered lists
  • Detection and formatting of code snippets and tabular data

Manual processing

There may also be some manual editing performed, strictly limited to:

  • Correcting mistakes made by the automatic processing, such as incorrectly removed content or incorrect formatting
  • Merging or splitting of threads to follow the one topic per thread guideline
  • Renaming of threads to better match the subject matter
  • Spelling and/or grammatical corrections to enhance readability

In all cases, the original, largely unprocessed email is available for viewing (email addresses are still redacted). If you find errors or omissions caused by processing, or poorly formatted content, please email info@openswmm.org and we will try to address it immediately.


Deprecation helps improve the signal to noise ratio of the SWMM Knowledge Base and involves the demoting of content that either does not conform to the posting standards of the SWMM-USERs list server, or was of a time sensitive nature and is no longer useful to current readers. Deprecated posts are still available, but are not displayed by default. As a result, search results become more useful to those interested in learning about the application of EPA SWMM. In each case, the reason for deprecation is given. Reasons may include:

Duplicate posting

Occasionally two identical or almost identical posts are made. This may be due to bugs in the SWMM-USERS list server software, or due to inadvertent double posts by users. In these cases, one of the posts is deprecated.

Dated information of no historical interest

Some posts pertain to announcements of long-past events (such as meetings, surveys, etc.) and are thus of little value to current readers. Other time sensitive information may not be deprecated due to historical interest (such as discussion of older SWMM features or bugs).

Not relevant to the use of EPA SWMM - pertains to commercial software

Questions and answers that are specific to the use of commercial modeling software (either SWMM "shells" or alternative modeling software) are sometimes posted in error to the SWMM-USERS list server and are deprecated here.

Not relevant to the use of EPA SWMM - pertains to other software

Similarly, discussions that are strictly about other non-commercial software packages (e.g. HEC-RAS, HEC-HMS, etc.) are also discouraged on SWMM-USERS and deprecated here.

Does not meaningfully add to the discussion or knowledge base

This reason applies to a number of types of deprecated posts. Examples include: one line posts expressing thanks (deprecated for brevity), inadvertent posts that were meant to be sent directly to an individual, apologies for these inadvertent posts, posts on topics outside of the intent of the SWMM-USERS list server, posts that do not inform the discussion topic and routine reminders of posting standards.

If you feel a post has been deprecated in error or there is content that should be deprecated, please email info@openswmm.org and we will try to address it immediately.

Hot topics

Threads listed in the hot topics section on the home page are automatically selected by the server based on the largest number of contributors within the last 12 months.


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The use of this website is subject to the following terms of use:

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Terms of use

The OPEN SWMM website is made available without barriers to all who could benefit from it. The SWMM Knowledge Base content on this site can be downloaded, printed, copied, distributed, and linked-to, provided full attribution to both the SWMM Knowledge Base and the author is given. SWMM Knowledge Base content may not be re-published, either online or in print, in part or in whole, without prior written consent of both CHI and the authors involved.