Wikipedia Traffic for the SWMM versus EPANET Articles

Subject:  Wikipedia Traffic for the SWMM versus EPANET Articles

Wikipedia has one article for EPANET and three articles for SWMM 5 (two are redirected to the Stormwater Management Model Main Article).  The statistics for the last three years (data before 2007 is unavailable) show an average of 28 visitors per day to SWMM and 16 per day to EPANET).  The search name has switched from the word SWMM to Stormwater Management Model starting in 2009.

Steps to take and rules for Cloning Datasets in InfoSWMM and InfoSewer

Note: Steps to take and rules for Cloning Datasets in InfoSWMM and InfoSewer

Before cloning an active dataset, the user should switch to the Base Scenario.  This saves the active datasets and allows the user to clone the dataset with all edits. 

This is a brief description of how datasets are created and saved. 

·         Any data the user changes are only changed in the Active data sets while the user is working in a given scenario. 

·         The modified data are not saved into the selected custom data sets until the user selects different data sets—either by selecting a new scenario or by using the Edit Active Scenario command. 

If the user changes to a new scenario that shares some of the same data sets (e.g. same pipe, valve and pump data sets), the data in these common data sets are still not updated (saved) by changing scenarios.  The user has to actually select a different custom data set of the same type to get the data to update in the custom data set (e.g. the user must select a different pipe set to get the modified pipe data to save into the selected pipe set).  Once created, a dataset is not updated (saved) until it is no longer in use by the active scenario. 

In addition, there is a fundamental difference in between BASE dataset and other dataset(s). 

·         The other dataset(s) must be explicitly created first before they can be used. 

·         BASE dataset will "never" exist until it is switched off from the active scenario. 

·         It gets implicitly created at the first time when it is released from the active scenario.  That is why BASE dataset is never found in a "new" project which has only a base scenario.

How to Make an Internal Outfall into an External Outfall when you have more than one link connected to an Outfall in InfoSWMM

Subject:  How to Make an Internal Outfall into an External Outfall when you have more than one link connected to an Outfall

    Step 1:  Identify the Problem "ERROR 141: Outfall J-561 has more than 1 inlet link or an outlet link." Means you have an outfall node in the middle of your model.

Step 2:  Make a new outfall.

Step 3:  Make the new Outfall  have the same invert as the old outfall 

Step 4:  Convert the older outfall  to a Junction using the Pick Axe and the Convert Type tool

Step 5:  Make a new Link connecting the old and the new Outfall

Step 6:  Convert the new Link to an  Outlet Type using the Convert Type Tool.

Step 7:  Set up the parameters for the new Outlet Link

Step 8:  For those outfalls that DO have more than one link you need to make a new Outfall.

You should be able to run the model now

WARNING 04: minimum elevation drop used for Conduit - What Does this Message Mean in SWMM 5?

Subject:  WARNING 04: minimum elevation drop used for Conduit  - What Does this Message Mean?

This message means that the elevation drop across the link  is less than the minimum allowable drop or (0.001 /3.048 meters)

Elevation1 = Link Offset Upstream + Upstream Node Invert

Elevation2 = Link Offset Downstream + Downstream Node Invert

Internally Elevation1 – Elevation2 should be greater than 0.001 /3.048 meters.  If it is not then SWMM 5 or InfoSWMM will use the minimum drop or0.001 /3.048 meters

It simply is a rule that does not allow flat slopes as the flat slopes mean no normal flow calculations. You should not have to worry about this warningmessage.

Here is an example of a conduit in which the rule is applied.  The rule is applied to link U-104 because it is flat and has no slope.

How to Determine if your model is Unstable in SWMM 5 or InfoSWMM

Subject:  How to Determine if your model is Unstable in SWMM 5 or InfoSWMM

SWMM 5 and InfoSWMM has a good output feature in the RPT file that tells you the list of links with the highest flow instability during the simulation.  If you look at the link flow with the highest instability value and it looks okay to you then it usually means the rest of your model output is stable.  The index is the number of flow turns for the link during the simulation.  A flow turn occurs when

We call DQ the difference between the New and Old flow,

The value of DQ is greater than 0.001 cfs (we do not want to count small perturbations),

The sign difference between the new DQ and the Old DQ is negative.   In other words we want to count those oscillations in which the DQ value was negative and is now positive or was positive and is now negative. We don't count then when the flow is monotonically increasing or decreasing in the link.

For example, the Link U-104 below has a large number of Flow Turns but a plot of the link flow shows the Flow Turns to mainly unimportant.

The relationship between the rainfall, total losses from the previous area, evaporation and infiltration only rate for SWMM 5

Subject:  The relationship between the rainfall, total losses from the previous area, evaporation and infiltration only rate.

The total loss from a subcatchment pervious area is the sum of the evaporation + infiltration loss.  Typically the evaporation rate is much less than the infiltration rate. SWMM 5 now has too options – evaporation during only dry periods or evaporation during both wet and dry periods.

Figure 1:  An example network that shows the relationship between the rainfall, total losses from the previous area, evaporation and infiltration only rate. 

Figure 2:  The same model with the Evaporation during only Dry Periods turned on

Making your inactive elements active in different alternative scenarios in InfoSWMM

Subject:  Making your inactive elements active in different alternative scenarios in InfoSWMM

Step 1:  Open up the Facility Manager and turn off Apply to Active Facility Only, click on Map Selection and then finally the +Add button

Step 2:  Select those elements you want to add to the Facililty (they are yellow in this case)

Step 3:  Save and then Close the Facility Manager Dialog

Step 4:  The Objects should be active now.

Step 5:  Run the Model and check if they are being used in the RPT file.

Step 6:  You can also run the Compare Scenario Command to see the different alternative models use a different set of outfalls.

Risk Assessment Manager in InfoSWMM

Subject:  Risk Assessment Manager in InfoSWMM

If you can get the Risk Assessment Manager than you can do a flooding extent based on the Maximum Head or just the Flooded Nodes.

What are the Units for the five St. Venant Flow Terms in SWMM 5 and InfoSWMM?

Subject:  What are the Units for the five St. Venant Flow Terms in SWMM 5 and InfoSWMM?

The new flow (Q) calculated at during each iteration of time step as

(1)        Q for the new iteration = (Q at the Old Time Step – DQ2 + DQ3 + DQ4 ) /   ( 1.0 + DQ1 + DQ5)

In which DQ2, DQ3 and DQ4 all have units of flow (note internally SWMM 5 has units of CFS and the flows are converted to the user units in the output file, graphs and tables of SWMM 5).  

The equations and units for DQ2, DQ3 and DQ4 are:

(2)        Units of DQ2 = DT * GRAVITY * aWtd * ( H2 – H1) / Length = second * feet/second^2 * feet^2  * feet / feet = feet^3/second = CFS

(3)        Units of DQ3 = 2 * Velocity * ( aMid – aOld) * Sigma = feet/second * feet^2 = feet^3/second = CFS

(4)        Units of DQ4 = DT * Velocity * Velocity * ( aMid – aOld) * Sigma / Length = second * feet/second * feet/second * feet^2 / feet = feet^3/second = CFS

The equations and units for DQ1 and DQ5 are:

(5)        Units of DQ1 = DT * GRAVITY * (n/PHI)^2  * Velocity / Hydraulic Radius^1.333 = second * feet/second^2 * second^2 * feet^1/3 * feet/second / feet^1.33 = Dimensionless

(6)        Units of DQ5 = K * Q / Area / 2 / Length * DT = feet^3/second * 1/feet^2 * 1/feet * second = Dimensionless

The five components calculated at the each time step and at each iteration during a time step and together predict the new Link Flow (Q) in SWMM 5.  The value of the different components can be seen over time in Figure 1 and as a component percentage in Figure 2 and 3.

Figure 1:  The Five St. Venant Components over time.

Figure 2:  The relative magnitude of the St Venant terms over time for the same for the same link as in Figure 1.

Figure 3:  The relative magnitude of the St Venant terms over time for the same for the same link as in Figure 1 shown in an area chart normalized to 100 percent.  Normally the DQ1 and DQ2 terms balance each other except for backwater conditions or reverse flow in which the terms DQ3 and DQ4 can dominate.

How to use SWMM 5 DOS to make an Output Table in the RPT file

Subject:   How to use SWMM 5 DOS to make an Output Table in the RPT file

You can make tables of the node,  link  and  Subcatchment output data in SWMM 5 if you use the DOS SWMM 5 program but not the Windows DLL.   Step 1 is to create the DOS batch file, Step 2 is to select the nodes, links and subcatchments, Step 3 is to run the batch file and Step 4 is to view the RPT tables or extract the data to Excel.  You can do this directly in the InfoSWMM and H2OMAP SWMM graphical user interfaces by using Run Manager, Step 5 to select the nodes, links and subcatchments andStep 6 to view the tables in the browser.

Step 1.   Make a Batch File to call the DOS SWMM 5

swmm5.exe Example1.inp  D:\swmm5.0.022\bob.rpt

pause

Step 2.  Add the nodes,  links and  subcatchments tables you want to generate in the RPT file

[REPORT]

CONTROLS         NO

LINKS                 ALL

NODES               ALL

SUBCATCHMENTS ALL

Step 3.  Run the Batch file

Step 4.  Extract the Tables from the RPT File of SWMM 5

  <<< Node 17 >>>

  ---------------------------------------------------------------------------------

                           Inflow  Flooding     Depth      Head       TSS      Lead

  Date        Time            CFS       CFS      feet      feet      MG/L      UG/L

  ---------------------------------------------------------------------------------

  JAN-01-1998 01:00:00      0.000     0.000     0.000   980.000     0.000     0.000

  JAN-01-1998 02:00:00      5.910     0.000     0.608   980.608    26.065     5.213

  JAN-01-1998 03:00:00     11.935     0.000     0.887   980.887    22.826     4.565

  JAN-01-1998 04:00:00     18.291     0.000     1.143   981.143    21.176     4.235

  JAN-01-1998 05:00:00     12.640     0.000     0.916   980.916    22.426     4.485

  JAN-01-1998 06:00:00      3.925     0.000     0.493   980.493    27.578     5.516

  JAN-01-1998 07:00:00      0.388     0.000     0.161   980.161    38.134     7.627

  JAN-01-1998 08:00:00      0.067     0.000     0.071   980.071    26.937     5.387

  JAN-01-1998 09:00:00      0.029     0.000     0.048   980.048     1.878     0.376

Step 5.  InfoSWMM and H2OMAP SWMM dialog for selecting nodes, links and subcatchments for generating a detailed RPT filetable.

Step 6.  Sample InfoSWMM and H2OMAP SWMM RPT Tables if Report Options is used.

How is RHO computed for a Link in SWMM 5?

Subject:  How is RHO computed for a Link in SWMM 5?

SWMM 5 uses a sliding metric to calculate the cross sectional area and hydraulic radius used in the simulation for the link dynamic flow.  The area and hydraulic radius used moves from the Upstream End of the Link to the Midpoint of the Link based on the Froude number and a few other considerations (see Figure 1 for the other considerations).

The area and hydraulic radius used as a function of the Froude Number:

1.   Upstream cross sectional area and upstream hydraulic radius is used when the Froude Number > 1

2.   Midpoint sectional area and hydraulic radius is used then the Froude Number is < 0.5

3.   An area and hydraulic radius between the upstream and midpoint sections is used then the Froude Number is between 0.5 and 1

Figure 1:  How to compute RHO based on the Froude Number.

Figure 2:  The computed value of the Froude Number and the value of RHO over time.

Figure 3: Relationship between the upstream area, midpoint area and the actual area used during the simulation.