SWMM Calculation Executive Summary

Note: If you are calculating the 2D Solver, the title will be 1D/2D Calculation Executive Summary and will include 2D results as noted below.

The Summary tab displays the following information, divided into categories:

Run Metrics
- Label: The label of the scenario just calculated.
- Flow Continuity Error: A metric that defines how well the computed inflows, outflows, and storage values balance out. The closer the value is to zero the better.
- Runoff Continuity Error: A metric that defines how well the incoming precipitation, catchment runon.
- Average Iterations Per Step: Average number of trials required to achieve convergence for each time step.
- Not Converging: Proportion of simulation time where convergence is not achieved.
- If the 2D solver was used, the following properties are included in the 1D-2D Volume Balance Report category:
  - Total System Volume (Initial): Initial volume of water in the model, a sum of both the 1D and 2D subsystems.
  - Total System Volume (Final):Total volume of water stored within the 1D network and 2D grid at the end of the simulation.
  - Total System Volume (Maximum): Largest total volume of water within the model, including both the 1D and 2D models.
  - Time of Maximum System Volume: Time at which the maximum total volume of water exists on both the 1D and 2D networks.
  - Total System Inflow Volume: Sum of all inflow volumes into both the 1D and 2D subnetworks.
  - Total System Infiltration Loss: Total volume of infiltration losses for both the 1D network and the 2D grid.
  - Total System Outflow Volume: Sum of all outflows from both the 1D and 2D subnetworks.
  - 1D-2D Volume Balance Error: The unaccounted volume that is lost to the 1D-2D model. Computed by subtracting Initial from the Final Volume, subtracting Inflows and Inputs from the Outflows and Losses, and subtracting the Rainfall on Grid. A positive value means water is lost from the 1D-2D system.
  - 1D-2D Volume Balance Error Percent: Ratio of the sum of final and outflow volume, to the sum of the initial and inflow volume in 1D and 2D.
- If the 2D solver was used, the following properties are included in the 1D-2D Volume Details category:
  - 2D Volume (Initial): Starting volume of water on the 2D grid.
  - 2D Volume (Final): Final volume of water on the 2D computational grid.
  - 2D Inflows: Sum of inflows onto the grid through 2D inflow points and flow lines.
  - Total 2D Inflow Volume: Sum of all inflows onto the grid from rainfall, coupled 1D elements, and 2D boundary elements.
  - 2D Infiltration Loss: Total volume of infiltration losses computed for the 2D grid.
  - Rainfall on Grid: Cumulative volume of precipitation onto the grid.
  - Outflow (2D Boundaries): Sum of grid outflows through any of its open 2D boundary conditions defined on the grid or 2D boundary lines.
  - Total 2D Outflow Volume: All flows exiting the 2D grid. Computed as a sum of 2D outflows through coupled 1D elements, 2D infiltration losses, and open 2D boundaries.
  - Net 2D Inflow: Net volume of rainfall on the grid, less the grid outflows through its 2D boundaries.
  - Total Volume of 1D-2D Exchange: The net volume exchanged between all the 1D-2D connections. A net positive value indicates more water was transferred from 1D to the grid.
  - Uncoupled 1D Inflow: Cumulative inflow into 1D subsystem via 1D nodes that are not coupled with the grid.
  - Uncoupled 1D Outflow: Net outflow through 1D subsystem outlets that are outside the grid.
  - Uncoupled 1D Overflow Losses: Net volume lost to the system due to overflow at 1D elements that are outside the grid.
  - 1D Infiltration Loss: Cumulative volume of infiltration within the 1D hydraulic network. A total volume lost to the system due to pond seepage.
  - Catchment Outflow Volume: Total volume which leaves catchments during the simulation.
  - Pond Volume (Initial): Total volume of water in all the ponds at the first time step.
  - Pond Volume (Final): Total volume of water in all the ponds at the end of the simulation.
  - Pond Total Outflow Volume: Net outflow volume that is computed with the flow rate at every reporting time step, for each pond.
  - 1D Volume (Initial): Initial volume within the 1D subsystem, reflecting initial depth and boundary conditions.
  - 1D Volume (Final): Volume of water within the 1D drainage network at the end of the simulation.
  - 1D Volume (Maximum): Peak volume stored within the 1D subsystem during the simulation.
  - Time of Maximum 1D Volume: Time at which the maximum stored volume within the 1D subsystem occurs.
  - 2D Volume (Maximum) Peak volume of water on the 2D grid during the simulation.
  - Time of Maximum 2D Volume: Time at which the maximum volume on the 2D grid occurs.
Routing Summary
- Dry Weather Inflow: The total volume of dry weather flow entering the system over the course of simulation.
- Wet Weather Inflow: The total volume of wet weather flow entering the system over the course of simulation.
- Groundwater Inflow: The total volume of groundwater flow entering the system over the course of simulation.
- RDII Inflow: The total volume of RDII flow entering the system over the course of simulation.
- External Inflow: The total volume of flow that enters system via Inflows interface files.
- External Outflow: The total volume of flow that exits the system to outflows interface file.
- Overflow Losses: The total flow volume that exits the system as flooding or overflow.
- Evaporation Losses: The total volume of flow that exits the system via evaporation.
- Exfiltration Losses: The total flow volume that exits the system via exfiltration at storage units.
- Stored Volume (Initial): The total volume of flow stored at the start of simulation.
- Stored Volume (Final): The total volume flow stored at the end of simulation.
- Flow Continuity Error: A metric that defines how well the computed inflows, outflows, and storage values balance out. The closer the value is to zero the better.
System Statistics
- Time Step (Minimum) - The minimum time step required to achieve convergence, when variable time steps are allowed.
- Time Step (Average) - The average time step required to achieve convergence, when variable time steps are allowed.
- Time Step (Maximum) - The maximum time step required to achieve convergence, when variable time steps are allowed.
- Steady State - Proportion of simulation time where steady state computations are performed.
- Average Iterations Per Step - Average number of trial required to achieve convergence for each time step.
- Not Converging - Proportion of simulation time where convergence is not achieved.
- If the 2D solver was used, the following properties are included in the System Stats (2D) category:
  - Total Elapsed Time: Total run time to execute 2D calculations.
  - Total CPU Time: Sum of execution times on each CPU.
  - CPU Usage: The utilization ratio of Total CPU Time to Total Elapsed Time. Limited by the number of CPU cores and logical processors available.
Process Models
- Rainfall\Runoff? - Specifies if Rainfall\Runoff analysis was performed during the simulation.
- RDII? - Specifies if a RDII analysis was performed during the simulation.
- Snowmelt? - Specifies if a snowmelt analysis was performed during the simulation.
- Groundwater? - Specifies if a groundwater analysis was performed during the simulation.
- Flow Routing? - Specifies if a flow routing analysis was performed during the simulation.
- Water Quality? - Specifies if a water quality analysis was performed during the simulation.
- If the 2D solver was used, the following properties are included in the Process Models (2D) category:
  - 2D Grid?: Indicates if 2D calculations were part of the last simulation.
  - Rainfall on Grid?: Indicates if precipitation was modeled as falling directly on the grid.
  - 2D Infiltration?: Infiltration losses were computed for the 2D grid area.
Analysis Options
- Infiltration Method - The infiltration method used by the EPA SWMM runoff method during the simulation.
- Flow Routing Method - The routing method used by the SWMM engine during the simulation.
- Start Date - The date which the simulation began.
- Start Time - The time on the Start Date which the simulation began.
- Stop Date - The date which the simulation ended.
- Stop Time - The time on the Stop Date which the simulation ended.
- Duration - The length of time over which the simulation ran.
- Start Dry Time - The number of days with no rainfall prior to the start of the simulation. This value is used to compute an initial buildup of pollutant load on the surface of subcatchments.
- Output Increment - The time step which results are reported for the simulation.
- Hydrologic Increment - The time step length used to compute runoff from subcatchments during periods of rainfall, or when ponded water still remains on the surface, or when LID controls are still infiltrating or evaporating runoff.
- Dry Step - The time step length used for runoff computations (consisting essentially of pollutant buildup) during periods when there is no rainfall, no ponded water, and LID controls are dry. This must be greater or equal to the Wet Weather time step.
- Route Step - The time step length used for routing flows and water quality constituents through the conveyance system.
- Has Variable Time Step? - Is true if an internally computed variable time step was used at each routing time period.
- Allows Ponding? - Excess water was allowed to collect atop nodes and be re-introduced into the system as conditions permit. In order for ponding to actually occur at a particular node.
- Maximum Trials - The maximum allowable iterations for each time step to achieve convergence.
- Head Tolerance - When the difference in computed head at each node between successive trials is below this value the flow solution for the current time step is assumed to have converged.
- Threads <Count> - The number of threads used in the simulation.

The grid tab is displayed if the 2D solver was used as the active solver and 2D results are available.

Grid Summary
- <General> Category
  - ID: Unique identifier assigned to this element.
  - Label: Descriptive label for this element.
  - Notes: Additional information about this element.
- Results Category
  - Time (Flood Arrival): The time when the depth first exceeds the calculation option Minimum Flood Arrival Depth on Grid.
  - Flooded Area (Final): The extent of flooding on the grid at the end of the simulation.
- Results (Maximum Values) Category
  - Flood Hazard: The flood hazard value computed with the maximum depth.

The Nodes tab displays statistic attributes for the following node types: Manhole, Catch Basin, Cross Section, Headwall, Outfall, Transition, Wet Well, Pressure Junction and Pond.

Node Depths: When the Node Depths category is selected, the Nodes tab displays a table displaying the following:
- ID - The unique element ID.
- Label - The element's label.
- Element Type - The type of element.
- Depth (Maximum) - The maximum computed flow depth that occurs at this element over the course of the simulation.
- Time to Maximum Depth - The time at which the maximum depth occurs.
- Depth (Average) - The average depth that happens at the node over the course of the simulation.
- Hydraulic Grade (Maximum) - The maximum hydraulic grade that occurs at the element over the course of the simulation.
- Time to Maximum Hydraulic Grade - Time when maximum hydraulic grade occurs.
Node Inflows: When the Node Inflows category is selected, the Nodes tab displays a table displaying the following:
- ID - The unique element ID.
- Label - The element's label.
- Element Type - The type of element.
- Local Inflow (Maximum) - The maximum amount of flow injected into system at the node.
- Time to Maximum Local Inflow - The time at which the maximum local inflow occurs.
- Local Inflow (Total Volume) - The total volume of flow injected locally at the node over the course of the simulation.
- Flow (Total In Maximum) - The maximum inflow that occurs during the simulation. This flow is the sum of all incoming piped flow, and flow injected into the system at the node.
- Time To Maximum Inflow - Time when the maximum inflow occurs.

The Links tab will display statistic attributes for all the conduits, channels and pressure pipes in the model.

Link Flows - When the Link Flows category is selected, the Links tab displays a table displaying the following:
- ID - The unique element ID.
- Label - The element's label.
- Element Type - The type of element.
- Flow (Maximum) - Maximum flow that occurs in link over the course of simulation.
- Time (Maximum Flow) - Time (measured from the start of simulation) when the Flow (Maximum) occurs in this link.
- Velocity (Maximum Calculated) - In conduits, this value is the maximum average velocity that occurs during the simulation. In pressure pipes, this value is the maximum actual velocity that occurs during the simulation. In gutters, this value is the maximum velocity computed during the simulation under the assumption of a uniform depth of bypass flow.
- Time (Maximum Calculated Velocity) - The time (measured from the start of the simulation) when the Velocity (Maximum) occurs in the link.
- Flow (Maximum)/Full Flow - The ratio of the max flow that occurs in the link to the full flow of the current link.
- Depth (Maximum)/Rise - The ratio of maximum calculated flow depth in the link, to constructed rise of the link.
- Adjusted Length/ Actual Length - The ratio of the adjusted length of the link to its actual length. This will be a value greater than one if length was increased during the simulation to help the solution to converge.
Flow Classification - When the Flow Classification category is selected, the Links tab displays a table displaying the following:
- ID - The unique element ID.
- Label - The element's label.
- Element Type - The type of element.
- Time (Dry) / Time (Simulation) - The fraction of the total simulation time that the current link spends completely dry.
- Time (Upstream Dry) / Time (Simulation) - The fraction of the total simulation time that the upstream of the current link spends dry.
- Time (Downstream Dry) / Time (Simulation) - The fraction of the total simulation time that the downstream of the current link spends dry.
- Time (Subcritical) / Time (Simulation) - The fraction of the overall simulation time that flow regime in the current conduit is subcritical.
- Time (Supercritical) / Time (Simulation) - The fraction of the total simulation time that flow regime in the current conduit is supercritical.
- Time (Upstream Critical) / Time (Simulation) - The fraction of the total simulation time the link spends with upstream critical depth.
- Time (Downstream Critical) / Time (Simulation) - The fraction of the total simulation time the link spends with downstream critical depth.
- Time (Normal Depth) / Time (Simulation) - The fraction of time where the flow in the link is governed by Normal Depth.
- Time (Inlet Control) / Time (Simulation) - The fraction of total simulation time that the culvert spends under inlet control.

The Catchments tab shows the following statistics for all catchments in the model:

ID - The unique element ID.
Label - The element's label.
Element Type - The type of element.
Precipitation (Total) - The total calculated precipitation depth that falls on the catchment over the course of the simulation.
Runon (Total) - The total depth that flows onto this catchment from other catchments or outfalls over the course of the simulation.
Evaporation (Total) - The total volume of flow that evaporates off of the catchment over the course of the simulation.
Infiltration (Total) - The total volume of flow that infiltrates into the catchment over the course of the simulation.
Volume (Total Runoff) - Total volume of the runoff hydrograph.
Flow (Maximum) - Maximum flow that occurs in element over the course of simulation.
Time (Maximum Flow) - Time (measured from the start of simulation) when the Flow (Maximum) occurs in this link.
Runoff Coefficient (Calculated) - The ratio of the total runoff depth to the sum of the total precipitation and runon depths.

The Storage tab shows various statistics for all Wet Wells and Ponds in the model. The following attributes are displayed:

ID - The unique element ID.
Label - The element's label.
Element Type - The type of element.
Volume (Average) - The average stored flow volume over the course of the simulation.
Percent Full (Average) - The ratio of the average stored flow volume to full volume of the current storage unit.
Evaporation Loss - The ratio of the volume of evaporation loss to the total cumulative flow volume stored over the course of the simulation.
Exfiltration Loss - The ratio of the volume which exits the storage unit via exfiltration to the total cumulative flow volume stored over the course of the simulation.
Storage (Maximum) - The maximum volume of flow that is stored at one time over the course of the simulation.
Percent Full (Maximum) - The ratio of the maximum stored flow volume to full volume of the current storage unit.
Time to Maximum Storage - Time when the maximum storage level is reached.
Flow (Out to Links Maximum) - The maximum flow that exits to bounding links over the course of the simulation.

The Pumps tab displays the following statistics for all Pumps (regular and variable speed) in the model:

ID - The unique element ID.
Label - The element's label.
Element Type - The type of element.
Utilized - Fraction of total simulation time which the pump is turned on.
Number of Start-Ups - The number of time during the simulation in which the pump turns on.
Flow (Minimum Pumped) - The minimum flow pumped over the course of the simulation.
Flow (Average) - The average of the flow pumped over the course of the simulation.
Flow (Maximum) - The maximum flow supplied by the pump over the course of the simulation.
Volume (Pumped) - The total volume of flow supplied by the pump over the course of the simulation.
Power Usage - The total energy utilized by the pump over the course of the simulation.
Time Below Pump Curve - The fraction of the time utilized the pump operates below its pump curve.
Time Above Pump Curve - The fraction of the time utilized the pump operates above its pump curve.