Active Topology Management

Product(s): WaterGEMS, HAMMER, StormCAD, CivilStorm, WaterCAD, SewerCAD, SewerGEMS, PondPack
Version(s): All
Area: Layout and Data Input


The purpose of this article is to explain active topology management in the OpenFlows products, for controlling which elements are enabled (present) in a particular scenario. Additional information on active topology management can be found by searching the Help documentation.


See bottom of article for a video demonstration.

In the analysis of the water or wastewater system, it may be helpful to assess future (or past) configurations of the system. This can include not only a change in data at a node, but also may include additional nodes and pipes that do not currently exist in the current system. For this reason, you may need to add elements to the existing model. However, when this is done the new elements are present in each scenario, even those that should depict only the existing elements. This is when you would use Active Topology management.

Due to the way that the data is stored in the database file, it is not possible to physically add or remove elements from one scenario with affecting all of them. Active Topology management enables you to create alternatives in which specific elements are present or not present. When the elements are inactive, they are not included in the network hydraulic calculations. Inactive elements are also not evaluated when displaying results, such as contour plots and profiles.

You can choose to either hide the inactive elements so that they disappear from scenarios where they aren't included or set the color so that the inactive elements are obvious in the drawing pane. The appearance of inactive elements is controlled in the Options dialog. See below for details.

Active Topology Alternative

The active or inactive status of an element is stored in the Active Topology Alternative. To open the Alternatives manager in CONNECT Edition, browse to the Home tab and choose Alternatives.

In V8i or V8 XM versions, browse to Analysis > Alternatives or click the Alternatives icon in the toolbar.

Expand the list of alternatives for Active Topology to view the available alternatives. There will be at least one active topology alternative available. To open the alternative, you can double-click on the alternative, or right-click it and select Open.

The dialog will include a tab for each element type. When you click on one of the tabs, a list of all of the elements of that type will be shown. There will be one editable column available: “Is Active?” If there is a checkmark for a given element, it means that the element is set as active in the alternative. If you uncheck the box, the element will be inactive.

If you make an element inactive in the model, this change applies to the Active Topology alternative associated with the scenario.

For the steps to create new scenarios and alternatives, see the Scenario and Alternative Management TechNote or the Help documentation in the program.

Selecting inactive elements in the model

There are a number of ways to make an element active or inactive. Besides making the changes directly to the active topology alternative, you can change the active topology settings in the Properties dialog or in the element FlexTables. In either of these, there is a field called “Is active?” You can make the element active or inactive by changing the value of this field. This method works well if there are a few elements you want to change.

However, if you want to change the active topology of a large number of elements, the Active Topology Selection tool can be useful. In CONNECT Edition, you can go to Home > Active Topology or Tools > Active Topology. In V8i, you can go to Tools > Active Topology Selection.

Note: Changing the active status using this tool only affects the Active Topology Alternative of the current scenario. If you want to change the active status for a different scenario other than the current one, you will need to change the active scenario first.

After selecting the Active Topology Selection tool, a Select toolbar will open.

Selecting elements with this can make them active or inactive. By default, the Add icon is selected. When this is selected, you can choose elements individually, drag a box around it with your mouse, or use the Query option in the toolbar. See below for details. When they are selected, they will appear red on the drawing pane.

Note: items that are already inactive will also appear in red.

When you click the green checkmark in the Select tool, the items will be made inactive for the active scenario.

You can also remove items using the Select toolbar, making them active again. If you select the Remove icon, when you select items in the drawing and select the green checkmark, the items will be active in the active scenario.

Active Topology by selection set, query and other selection methods

The Active Topology Selection tool also allows for more advanced methods of selecting items in the drawing. The “Select by Polygon” icon allows the user to draw a polygon on the drawing. Depending on whether the Add or Remove icon is selected, the elements within the polygon will be added or removed from active topology.

With the Query option, you can select elements in the model based on a preexisting selection set, a custom query, or from a number of standard queries.

Note: an alternative way to make elements active or inactive, is to filter the respective element FlexTable, then global edit the "is active" attribute.

The Find icon is helpful if you know which element you would like to make active or inactive, but do not know exactly where it is in the drawing. This will open a dialog where you can type the name of the element or choose from a list after selecting the icon in the upper right.

If you are selecting items and choose the wrong elements, you can choose the Clear icon on the right, which will clear all of the selections.

It is important to remember that changing the active topology status using this tool only affects the Active Topology alternative of the current scenario. If you want to change the active status for a different scenario other than the current one, you will need to change scenarios first.

Note: Selecting a node element to become Inactive will also select all adjacent pipes to become Inactive. This is because all pipes must end at an active node. See the following link for details: Error validating or computing model: "Pipe references deleted or inactive node".

Displaying Inactive Elements

Inactive elements are differentiated visually from Active ones in the main drawing pane. This is controlled in the Options menu found in the Tools pulldown. You can open this dialog by going to Files > Options (in CONNECT Edition) and Tools > Options (in V8i).

Find “Display inactive topology.” If this is checked, the inactive elements will appear in the drawing pane as the color identified to the right of the “Display inactive topology” item. If this item is not checked, the inactive elements will not be displayed in the drawing pane at all.

Inactive elements will appear in FlexTables but calculated values will be set to N/A. Inactive elements are also available for inclusion in selection sets. If you do not want inactive elements to be displayed in the FlexTables or reports, you can filter the column "Is Active?" to only elements with the entry "True" are included.


You can set up different active topology alternatives any number of ways. Different users may be more comfortable using one method over another. As you work with a model, you may end up using different methods for making certain elements active or inactive. Below are two possible instances.

The screenshots below use Example5.wtg as an example. The current scenario is "Original Data.” and the Active Topology alternative set as "Base Active Topology."

You now would like to model a future scenario in where additional elements are added to the north side of the model. In order to model this, you will need to create a new Active Topology alternative and a new scenario.

In Example5.wtg, a child scenario of the scenario Original Data has been created called “2002 New Subdivision.” A new child active topology alternative has been created called "New Subdivision." This child alternative has been assigned to the scenario in through the scenario properties. 

With the scenario "2002 New Subdivision," new elements were added to the model. They are active in the drawing pane.

Now change the scenario back to “Original Data.” Notice that the new elements are now inactive. This is because the default setting when is inactive when the alternative cannot be identified by the active scenario.

Active topology + Customer meter elements

When customer meters are attached to the pipes and you are making those pipes inactive using active topology, connected customer elements are still active in that case, which has been logged as a defect as of Connect Edition update 2, reference number is # 145793.

However, if there are other elements attached to pipe like hydrant it becomes inactive in the process along with the pipes, so it is just issue with the customer elements as of version and should be fixed in the future versions.


  • Select the inactive pipes, then run the “Find Associated Customer Meters” query.
  • Open customer meter FlexTable on that selection of customer meters, and global-edit to set Is Active false.


  • User notifications are generated when referenced pipes of customer elements become inactive
  • Right click on this error of customer meter, this should select all the related customer meters, right click in the drawing > Group Edit > Make the customer meters inactive.

 This should make the associated customer meters inactive as well.

See Also

How do I use and display Active Topology for elements on the ArcGIS/ArcMap platform?

Filter FlexTable to only show active elements

Scenario and Alternative Management

Elements seemingly changing to default settings, zero status, inactive