EPANET++ is a free web application for modeling water distribution networks, an extension of EPANET.

Scenario manager

How scenarios and alternatives work

In Basic mode, alternatives are hidden and automatic, and all new scenarios are children of the Base scenario.

With Basic mode off, a complex inheritance tree is available, and alternatives can be shared among scenarios. But the default behavior of edits when a new alternative association is needed (in the absence of proactive user management) is to create an alternative named like the current scenario, which gives each scenario its unique set of alternatives.

Properties and settings belong to alternatives categories that appear as columns of the scenarios and alternatives table and as management options in Scenario manager.

Overrides are created in scenarios, but they really belong to the respective alternatives associated with the scenario; so a scenario is like a window to its alternatives. Associations of alternatives to scenarios are managed in the second pane of the Scenario manager or in the Scenarios table in the bottom pane. Creating a new scenario creates no alternatives; the new scenario uses its parent's alternatives until overrides are created that need new alternatives. When overrides are created in a scenario, they are stored in their respective alternative for the scenario; if the scenario has no such alternative, a new alternative is created using the name of the scenario.

Example: You create a "Figure: Node and link IDs" scenario and edit a Text to say "Node and Link IDs." When you create the scenario, no alternatives are created. But at the moment you save the Text, a Text alternative called "Figure: Node and link IDs" is created with the override for the Text value. In Basic mode, you see this as simply an override in the scenario itself.

Copy properties copies only overrides. In any scenario other than Base, it copies only the overrides the asset has in that scenario.

How to manage scenarios

• Choose Scenarios or an alternatives category in the list at the top to show its tree.
• Create a child of the selected item with Add child. Add base adds another Base, which starts as a copy of Base as it is now; later edits to Base do not change it. A new child is named after its parent; type a name to rename it. Copy copies the selected alternative. Merge upward moves the overrides of the selected alternative into an alternative above it, chosen by name, and the selected alternative then inherits them; it first names any value an alternative it skips also overrides, which is not changed. To copy a scenario, use Copy scenario in the Scenarios menu, in Basic mode; it copies the scenario's overrides, with the alternatives that hold them. Add base and Copy scenario each create alternatives: Add base creates a Base alternative for the new Base in each category that holds values, and Copy scenario creates a new alternative, named like the copy, for each alternative that holds the scenario's overrides.
• Drag an item onto another to make it a child of that item. A scenario moved to a new parent inherits from it everything it has not overridden; what it has overridden does not change. Drag an item between two items to reorder them.
• Click an item to select it. Press F2 or choose Rename to rename the selected item. Renaming a scenario asks whether to rename the alternatives that carry its name; in Basic mode they are renamed with it, without asking. Double-click a scenario or press Enter to make it current. Click the arrow beside an item or press Left or Right to collapse or expand it. Right-click an item for the same commands as the buttons.
• Press Delete or click the minus button to delete the selected item. An item in use is not deleted, and the message names what uses it. Deleting a scenario with Basic mode off keeps the alternatives it uses. Deleting a scenario with Basic mode on also deletes each of its alternatives that no other scenario uses.
• To make a scenario use another alternative, including Base, choose it in the scenario's row of the second pane of the Scenario manager or the Scenarios table. An override made in a shared alternative changes every scenario that uses it.

What a scenario is for

Scenarios save many designs, views, or situations in the same project, such as average day, maximum day, peak hour, a report presentation figure, a main out of service, or a proposed replacement. The network is drawn once, in the Base scenario. Every other scenario holds only its overrides, the values that differ from the scenario it inherits from, and reads everything else from that scenario. An edit to Base therefore reaches every scenario that has not overridden that value.

A new project starts with six ready-made scenarios: 1. Flow test: Static, 2. Flow test: Mid, 3. Flow test: Max, 4. Average Day, 5. Max Day, and 6. Peak hour. They are ordinary scenarios that can be renamed, edited, and deleted. Each starts with one override, its demand multiplier: 1 for the flow tests and Average Day, 2 for Max Day, and 3 for Peak hour. The multipliers are placeholders to be replaced with values for the system being modeled. A project opened from a file, including each example, or imported from an EPANET file has Base alone.

Fire flow is checked with the Fire flow analysis, which tests every junction or the selected junctions. Max Day is the scenario normally open when it is run.

The open scenario

The Scenario button in the status strip below the map names the open scenario and counts its overrides, as in Scenario: Base | No. of overrides: 0. Click it, or choose Water, Scenarios, to switch scenarios or to add, copy, rename, or delete one. Each scenario in the list shows its number of overrides in parentheses, and a check mark is at the open one. The Scenario manager row opens the tree of scenarios and alternatives. It is dimmed while Basic mode is checked.

The drawing, the labels, Properties, Tables, and the results all belong to the open scenario, and the page solves the open scenario only. Scenario comparison, described in its own entry, solves the others from copies. The open scenario is saved with the project.

Where overrides show

On the map, an asset that has an override in the open scenario is ringed in amber, and an asset that inherits an override from a parent scenario or alternative is ringed with a dashed gray line. For demand, diameter, roughness, minor (local) loss coefficient, and length, a ring appears only while Settings, Symbology, Node labels or Link labels shows that value on the map; an override of any other property always has its ring. In Tables, a cell that holds a value set by the open scenario is amber, and its tip names the alternative that holds it, as in Physical alt.: Larger main. Show scenarios, in the cell menu of a table, lists every asset once for each scenario.

Each row of Properties that a scenario can override has a mark at its left. A solid dot means the open scenario overrides the value; click it to clear the override. A hollow dot means the value is inherited; click it to make the value shown an override. A triangle means scenarios below this one override the value; click it to clear their overrides, after a confirmation. Beneath an overridden row is the inherited value it replaces, as in Base scenario: 18. The Settings box has the solid dot and the triangle only, because typing a value there is what makes an override.

To hide the rings, clear Show override markers on the map in Settings, Page, or choose Map, Clean map. Both are kept in this browser, not in the project. Tables marks overrides either way.

Making and clearing overrides

With a scenario other than Base open, an edit to a value that scenarios can override is stored as an override in the open scenario, however it is made: typing in Properties, editing a cell in Tables, Replace in Find and replace, dragging a node or entering its coordinates, Morph (the new type is the override), or Paste properties to selection. A setting typed in the Settings box is stored as an override when scenarios can override that setting. Base is not changed. In Base, the same edits change the network itself and reach every scenario that has not overridden the value.

Delete acts differently. In a scenario, Delete does not remove an asset that exists in Base. It makes the asset inactive in the open scenario, and for a node also its pipes, and a message states this. The asset is still in the drawing and in the other scenarios. An asset drawn while a scenario is open is inactive in Base and active in that scenario, and Delete in that scenario removes it. Deleting an asset in Base also deletes its overrides in every scenario, after a question that counts them. Customers and Shapes belong to no scenario and are deleted outright.

The Override manager row of the Scenarios list opens a list of every override of the open scenario by category, each beside the inherited value it replaces. A time series graph on the map that the scenario opened, moved, or changed is a row of its own. Check rows and click Clear selected overrides, click Clear override in one row, or click Clear all overrides. Each value then returns to the inherited value, and Undo reverses it. Select an ID in the list to go to the asset on the map. The dot in Properties and the Clear override row in the cell menu of Tables clear one override at a time.

What a scenario can and cannot override

Properties	Every property of a node or link except those listed below, including its position, whether it is active, and its type (Morph). A Text can override its words, position, size, alignment, bold, angle, and whether it is shown. A custom property can always be overridden. The properties are held in the categories Physical, Demand, Active topology, Initial settings, Constituent, Fire flow, Energy cost, Custom properties, Text, Presentation, and Calculation.
Settings	The settings saved with the project, except those listed below: the calculation options (for example the demand multiplier, total run time, hydraulic time step, and friction method), the default demand pattern, the values given to new assets, and the presentation settings (sizes, colors, labels, contours, the map view, and the time series graphs on the map).
The same in every scenario	The ID, Description, and Tag of an asset; the end nodes and bends of a link; Customers and Shapes; the units and the coordinate system; and the contents of the Libraries (patterns, curves, pipe types, fittings lists, controls, and rules). An edit to any of these changes every scenario. A scenario can point an asset at a different curve, pipe type, fittings list, or pattern, but cannot change what is in them.

Example on Net1

Open the Net1 example. Choose Water, Scenarios, New scenario…, type Larger main, and click OK. Select Pipe 10 on the map and enter 24 for Diameter in Properties; Base has 18 in., shown beneath the field as Base scenario: 18. Choose Base in the Scenarios list, choose New scenario… again, type Max day, and enter 1.8 for Demand multiplier in Settings, Calculation, Hydraulics. Then choose Water, Reports, Scenario comparison.

Scenario	No. of overrides	Demand multiplier	Lowest pressure	Highest velocity
Base	0	1	108 psi at N32, 14:00	2.76 ft/sec at L11, 16:00
Larger main	1	1	109 psi at N32, 14:00	2.87 ft/sec at L11, 16:00
Max day	1	1.8	15.78 psi at N32, 9:00	3.49 ft/sec at L10, 9:00

The total run time is 24:00 in all three, so each lowest pressure and highest velocity is the extreme over the day, at the time shown. The larger main raises the lowest pressure by about 1 psi. A multiplier of 1.8 lowers it to 15.78 psi at 9:00, and the highest velocity moves to Pipe 10. Each scenario holds one override, and Base keeps its values.

Points to note

• An override equal to the inherited value is still an override. It is counted, and Override manager marks it (same).
• Basic mode is a setting for this browser, not for the project. It is disabled for a project whose scenarios and alternatives it cannot show. Alternatives and the Scenario manager are described under How scenarios and alternatives work and How to manage scenarios, at the top of this entry.
• Undo keeps 20 steps. Each step restores the scenarios and the open scenario along with the drawing, so adding, renaming, and deleting a scenario can be undone.
• Exporting an EPANET file writes the open scenario only, with the values and node positions that scenario reads. The scenarios themselves are recorded in the project file only.