Tributary Area to a Node in InfoSWMM

Note:  Tributary Area to a Node in InfoSWMM

Here are the steps you neeed to take to calculate the tributary area of a node in InfoSWMM:

Step 1:  Use the DB Editor to get the total area in your model using the Data Statistics Tool.




Step 2:  Use the Process options in InfoSWMM to ONLY simulate surface runoff and flow routing.



Step 3. Copy the Node name and Total Inflow Volume from the Juntion Summary Output Table to Excel



Step 4:  Find the Total Wet Weather Flow during the simulation from the Wet Weather Inflow Row in the Flow Continuity Table.

Dry Weather Inflow   0.000  0.000
Wet Weather Inflow  0.782   0.255

Step 5. Make a new column in Excel to calculate the tributary area.

The Tributary Area of a Node = Total Inflow Volume / Total Wet Weather Flow * Total Subcatchment Area from Step 1.

You will now have the tributary area for each node.  You can verify this number = the total tributary area at the outfalls should equal the Total Subcatchment Area from Step 1.

		Maximum	Maximum
		Lateral	Total	Time	of	Lateral	Total	Tributary
		Inflow	Inflow	Occurrence	Volume	Inflow	Inflow	Area
Node	Type	CFS	CFS	days	hr:min	10^6 gal	10^6 gal	acres
P001	JUNCTION	5.54	10.86	0	2:27	0.1	0.255	14.74
P005	JUNCTION	2.14	7.42	0	2:26	0.039	0.155	8.96
P009	JUNCTION	5.78	5.78	0	2:25	0.106	0.106	6.13
P011	JUNCTION	0.7	0.7	0	2:34	0.01	0.01	0.58
OUTLET	OUTFALL	0	10.84	0	2:28	0	0.255	14.74

How to add a volume variable to SWMM 5

Subject:  How to add a volume variable to SWMM 5


The purpose of this email is to explain how to add another print variable to the DOS version of SWMM 5 so that it can saved in a table in the text output file (after you recompile the modified C code).  The changes have no impact on the SWMM 5 GUI or the SWMM 5 DLL engine.

It is relatively simple five step procedure:

Step 1:  Add a new variable LINK_VOLUME at the end of the link variables in enums.h This is much easier if you just add a report variable that already is part of the link or node structure in objects.h  Your only restriction is that is should be added before the water quality variables.
 // increase by 1 the value of Max  Results in enums.h 
#define MAX_LINK_RESULTS 7    

enum LinkResultType {
      LINK_FLOW,              // flow rate
      LINK_DEPTH,             // flow depth
      LINK_VELOCITY,          // flow velocity
      LINK_FROUDE,            // Froude number
      LINK_CAPACITY,          // ratio of depth to full depth
      LINK_VOLUME, // current volume of the conduit - august 2007
      LINK_QUAL};             // concentration of each pollutant 

Step 2:  Add the report index for LINK_VOLUME to procedure output_open in ouput.c

k = LINK_VOLUME; 
fwrite(&k, sizeof(int), 1, Fout.file);
for (j=0; j<nPolluts; j++)

Step 3: Save the link new volume to the binary output file in procedure link_get_results in link.c.  The new volume of the link has already been saved in the already existing variable newVolume in the Link Structure.

x[LINK_CAPACITY] = (float)c;
x[LINK_VOLUME]   = (float)Link[j].newVolume;

Step 4. Modify report.c to include the new report variable in procedure report_links

fprintf(Frpt.file, "\n  %11s %8s  %9.3f %9.3f %9.3f %9.1f %9.1f",                          theDate, theTime, LinkResults[LINK_FLOW], LinkResults[LINK_VELOCITY], LinkResults[LINK_DEPTH]  LinkResults[LINK_CAPACITY]* 100.0,LinkResults[LINK_VOLUME]);

Step 5.  Modify procedure report_LinkHeader in report.c to show the new variable volume:

fprintf(Frpt.file,
"\n                             Flow  Velocity     Depth   Percent      Volume");
"); 

Rain Barrel LID Summary

Subject:  Rain Barrel LID Summary

Rain Barrel LID Summary

Rain Barrel LID Fluxes in SWMM 5.0.021

Subject:  Rain Barrel LID Fluxes in SWMM 5.0.021

The fluxes are limited in a Rain Barrel Low Impact Development (LID) control in SWMM 5.  The fluxes only include (Figure 1 and Figure 2):

1.      Total Inflow,
2.      Surface Outflow,
3.      Drain Outflow and
4.      Final Storage

The fluxes are also listed in the LID Performance Summary Table in the output text file.

  ***********************
  LID Performance Summary
  ***********************


  ----------------------------------------------------------------------------------------------------------
                                   Total      Evap     Infil   Surface    Drain      Init.     Final     Pcnt.
                                  Inflow      Loss      Loss   Outflow   Outflow   Storage   Storage     Error
  Subcatchment      LID Control       in        in        in        in        in        in        in
  -----------------------------------------------------------------------------------------------------------
  S1                RainBarrels    110.95      0.00      0.00     62.95     28.15      0.00     23.11    -2.94

Figure 1. Flux Pathways for a Rain Barrel LID

Figure 2. Rain Barrel LID Fluxes

Rain Barrel LID Drain Outflow in SWMM 5.0.021

Subject:  Rain Barrel LID Drain Outflow in SWMM 5.0.021

 The drain outflow in a Rain Barrel LID is defined by the user defined drain coefficient and drain exponent and the simulation storage depth  The storage outflow does not occur until it has been dry for at least the drain delay time in hours.

Figure 1.  Storage Outflow or Drain Outflow for a Rain Barrel LID

Figure 2. You can see the effect of the Drain Delay in the output file for LID Simulation.

Rain Barrel LID Storage Depth in SWMM 5.0.021

Subject:  Rain Barrel LID Storage Depth in SWMM 5.0.021

The storage depth in a Rain Barrel LID is limited by the user defined maximum rain barrel height in inches or millimeters.  A rain barrel is one of the new LID features in SWMM 5.0.021

Figure 1.  Storage Depth in a Rain Barrel LID

Link and Node Basics in SWMM 5

Subject:  Link and Node Basics in SWMM 5

Figure 1. Link and Node Basics in SWMM 5

What are Hours Above Full Normal Flow in SWMM 5?

Subject:  What is Hours Above Full Normal Flow in SWMM 5?

The Conduit Surcharge Summary Table in the Status Report or Report text file of a drainage system model provides detailed insights into the performance of various pipes (or conduits) in the system. One of the critical columns in this table is "Hours above Full Normal Flow," which represents the total number of hours the flow in a given conduit was above the reference full flow.

Hours above Full Normal Flow:

This parameter indicates the duration for which the flow in the conduit exceeded the 'Full Normal Flow.' Full Normal Flow refers to the maximum flow that can pass through a conduit under normal (gravity) conditions, as calculated by Manning's equation.

However, the flow in the conduit can surpass the Full Normal Flow even when the conduit isn't entirely full. This situation can occur when the head difference across the conduit is high enough.

Head Difference:

The head difference is the difference in water surface elevations at the upstream and downstream ends of a conduit. Essentially, it's the drop in water level from one end of the conduit to the other. This head difference is the driving force for the flow of water in gravity-fed systems. The higher the head difference, the greater the force pushing water through the conduit, which can result in flows exceeding the Full Normal Flow.

Capacity or d/D:

The capacity of the conduit, also represented by the ratio d/D, is a measure of how full the pipe is. In this ratio, 'd' stands for the depth of flow in the conduit, while 'D' denotes the diameter of the conduit. This ratio varies from 0 to 1, where 0 signifies an empty conduit, and 1 represents a fully filled conduit.

Understanding these parameters allows engineers and system designers to monitor the system's performance and identify potential issues. For instance, frequent or prolonged periods of flow above the Full Normal Flow might suggest that a conduit is undersized for the flow it is receiving, indicating a need for system upgrades or management changes.

Figure 1.  Hours above Normal Flow in SWMM 5 Links

Figure 2. Flow versus Full Flow in SWMM 5

Storage Maximum Outflow Includes the Reverse Flow in SWMM 5

Note:  Storage Maximum Outflow Includes Reverse Flow in SWMM 5

The SWMM 5 text output file has a Storage Volume Summary Table.  The Maximum Outflow from a storage node includes ALL of the outflow from the Storage node including both downstream link flow and reverse flow into the upstream links of the storage node.  You need to look at all of the flow out of a Storage node to find out how the maximum flow was computed during the simulation.

Figure 1.  Storage Volume Summary Table

Figure 2:  Total Flow Out of A Storage Node includes Reverse Flow.

EPS and Steady State Variables in GM, FM and Pumps of InfoSewer v7

Subject:  EPS and Steady State Variables in GM, FM and Pumps of InfoSewer v7

Figure 1:  InfoSewer Output Variables

Area Types in SWMM 5 for Links with Offsets

Subject:  Area Types in SWMM 5 for Links with Offsets

 There are six types of link flow in SWMM 5:

1.   Dry Conduit at both Ends
2.   Upstream End is Dry
3.   Downstream End is Dry
4.   Subcritical Flow
5.   SuperCritical Flow
6.   Free Fall at Upstream End
7.   Free Fall at Downstream End

Figure 1.  Six types of Link Area Allocation

Figure 2.  Example Link Area Type in SWMM 5

Cloud Movement

Source:  http://www.atlanticvortex.com/EN/FAQ.htm

Force Main Friction Loss in SWMM 5

Subject:  Force Main Friction Loss in SWMM 5

You can model Force Mains in SWMM 5 using either Darcy Weisbach or Hazen Williams as the full pipe friction loss method (see Figure 1 for the internal defintion of full flow).   No matter which method you use for full flow the  program will use Manning’s equation to calculate the loss in the link when the link is not full (see Figure 2 for the equations used for calculating the friction loss – variable dq1 in SWMM 5).  Force Main Friction Loss in SWMM 5.

Figure 1.  How the full pipe condition is defined in SWMM 5

Figure 2:  Friction equations used in SWMM 5 for a Force Main.

Figure 3:  Regions of Friction loss equations in SWMM 5.

Capacity Limited Links in SWMM 5

Subject: Capacity Limited Links in SWMM 5

The table in the text report file of SWMM 5 called “Conduit Surcharge Summary” has a column entitled “Hours Capacity Limited” Here is how a link is defined as Capacity Limited in SWMM 5. Two factors have to be present:

1. The upstream end of the link has to be full and

2. The HGL Slope has to be greater than the Slope of the Link

What is the Area of a Node in SWMM 5?

Subject: What is the Area of a Node in SWMM 5?

The minimum area of a node is the default area of the node, which is the user defined minimum surface area or 12.566 square feet if the user does not define the surface area of the node. The surface area of a node is usually the half of the surface area of all of the connecting conduits but if the link is dry then the sum of all of the surface areas may be less than the default surface area. If you look at a scatter plot of the area versus the depth then you will see that it always has the minimum surface area.

What is Node Convergence in SWMM 5?

Subject: What is Node Convergence in SWMM 5?

If a link has converged within two iterations then the hydraulic computations will be bypassed for the link in new iterations. A link is deemed converged if BOTH the upstream and downstream node depth has converged between successive iterations as long as two iterations have occurred during the time step. The nodes are considered converged if the depths between successive iterations is less than the stop tolerance of the program (the default stop tolerance is 0.005 feet). The new node depths are ALWAYS computed for each iteration but the links connected to the converged nodes may bypass computations and save on simulation time. Note: If the nodes ever become non converged after 2 iterations then the link flows will be computed.

What is Link Bypass in SWMM 5?

Subject: What is Link Bypass in SWMM 5?

If a link has converged within two iterations then the hydraulic computations will be bypassed for new iterations. A link is deemed converged if BOTH the upstream and downstream nodes depth has converged between successive iterations as long as two iterations have occurred during the time step. This is simulation savings step as it my eliminate up to 75 percent of the computational time in a SWMM 5 simulation. The image below shows that for some links the flow in the link is converged within 2 iterations whereas for others it may take 3 or 4 iterations. Overall, 37 percent of the link computations are bypassed during the simulation of this particular hydraulic network.

Time Step Critical Elements in SWMM 5

Subject: Time Step Critical Elements in SWMM 5

The time step critical elements in the SWMM 5 report text output file tells you which elements were controlling the time step during the simulation. If no element was controlling the time step then the program will just use the maximum time step. For example, if the maximum time step was 10 seconds and the average time step was 9.8 then only a few time steps were set by a link or node that needed a smaller than maximum time step (Figure 1). If the maximum time step for the same simulation was 30 seconds then many links and nodes will set the time step (Figure 2).

Figure 1. Most of the time the simulation used the maximum time step of 10 seconds so only a few links were time step critical.

Figure 2. Most of the time the simulation used less than the maximum time step of 30 seconds so many links were time step critical.

Pump Power Usage in SWMM 5

Subject: Pump Power Usage in SWMM 5

The pumping summary table (Figure 1) includes a column that tells the user how much power was consumed by the pump in kilowatts by the head loss or head gain of the water flowing through the pump. The power usage equations are shown in Figure 2.

Figure 1. Pump Summary Table in SWMM 5.0.021

Figure 2. Pump Power Equations in SWMM in which dt is the time step.

Non Linear Term in the Saint Venant Equation of SWMM 5

Non Linear Term in the Saint Venant Equation of SWMM 5The flow equation has six components that have to be in balance at each time step:

1. The unsteady flow term or dQ/dt

2. The friction loss term (normally based on Manning's equation except for full force mains),

3. The bed slope term or dz/dx

4. The water surface slope term or dy/dx,

5. The non linear term or d(Q^2/A)/dx and

6. The entrance, exit and other loss terms.

All of these terms have to add up to zero at each time step. If the water surface slope becomes zero or negative then the only way the equation can be balanced is for the flow to decrease. If the spike is due to a change in the downstream head versus the upstream head then typically you will a dip in the flow graph as the water surface slope term becomes flat or negative, followed by a rise in the flow as the upstream head increases versus the downstream head.

You get more than the normal flow based on the head difference because in addition to the head difference you also get a push from the non linear terms or dq3 and dq4 in this graph.

If you use the Keep Inertial term option then you use all 5 terms at all times, if you use the Dampen option you use all five terms until the Froude number of the link greater than 1 and then you do not use terms dq3 and dq4, if you use the Ignore option then the dq3 and dq4 terms are not used at all for the calculation of the flow in the link.