WaterGEMS CONNECT provides the user with a unique and flexible tool to evaluate a water distribution system and identify the most critical elements.

There are two general types of criticality analysis:

1. Pipe/Segment study in which each selected pipe or system segment is isolated and the effect of the effect of that shutdown is analyzed.
2. Valve study in which each valve is treated as inoperable and open and the effect on a shutdown in the segment containing that valve is analyzed.

Criticality Analysis can be started by picking Analysis > Criticality from the ribbon.

The user can shut down individual segments of the system and the results on system performance are determined. Rather than having to do this through the scenario manager, the user will be able to simulate a set of outages in a single run. This set can vary from a single element to each possible segment in a large system.

WaterGEMS CONNECT reports a variety of indicators for each outage during a criticality analysis. Depending on the type of run, criticality analysis can report the flow shortfall, volume shortfall or pressure shortfall in the distribution system for each segment outage.

Before being able to conduct a criticality analysis, WaterGEMS CONNECT must identify the segments to be removed from service. Once the options have been set in a Criticality Studies level of the Segmentation and Criticality manager, the user decides which scenario is to be used for the analysis and sets the rules for use of valving in the options tab.

In order to use criticality analysis, the user must make several decisions on the way that WaterGEMS CONNECT performs the analysis. Each of those is described below.

Segments vs. Individual Pipes

When a distribution system outage occurs, the portion of the system that is taken out of service is referred to as a “segment”. A “segment” or “Network segment” is the smallest portion of a distribution system that can be isolated by valving.

The user must decide which elements will be used to identify segments. This is done under the options tab under criticality studies. See the Segmentation section in the documentation for procedural details.

There are two general approaches to isolating portions of the system. The more correct way is to place all the isolating valves on pipe elements. In this way WaterGEMS CONNECT can accurately identify which system elements are out of service during an outage. In some cases however, the user does not have sufficient data on the location of isolating valves. In this case, WaterGEMS CONNECT assumes that each pipe element can be isolated and each distribution segment consists of a single pipe (not including the nodes at each end). The user identifies if isolating valves are to be used in the analysis by checking the box next to “Consider Valves?” on the Options tab of the Criticality Studies level. (Related to this is the ability of the user to identify if a valve is to be considered the boundary of a segment all of the time, only when it is closed in the selected scenario, or never.)

The figure below shows the segments that are identified if “Consider valves?” is checked. Note that the various colors assigned to elements by the program are not representative of any network attribute but are only used to differentiate adjacent segments.

The figure below shows the segments that are identified when the “Consider valves?” box is unchecked.

The user then picks the scenario to be used in the analysis by clicking New and picking the scenario from the list of available scenarios. Depending on the scenario selected, the criticality analysis will be either a steady state or extended period simulation and will use or not use pressure dependent demands (PDD). (If a fire flow analysis scenario is selected, it is treated as a steady state and if a water quality scenario is selected, it is treated as an EPS.)

In the scenario picker dialog, you can select one of two study types. The default is “Critical Pipes/Segments”. The second option is “Critical Valves”. In order to use the critical valves study type, you must use valves in your model, either control valves or isolation valves (recommended). You can create a study of each type (Pipes/Segments or Valves) for the same scenario but you cannot create more than one study type for a single scenario. i.e. You cannot create two “Critical Pipes/Segments” studies for the scenario “Base”. You can create one “Critical Pipes/Segments” study and one “Critical Valves” study.

Once the scenario has been selected for segmentation, the user can then decide if segments should be identified for the entire network or a subset of the network in the tab called “Segmentation scope”. If the scope of the segmentation analysis is a Subset of the system, an ellipse (…) button becomes available. By clicking this button, the user can decide on the elements to include using boxes, queries, polygons, or picking individual elements. Including any element in the Segmentation Scope means that the segment containing that element will be included in the segmentation and subsequent criticality analysis. Boundary elements between segments are not used if they are included in the Segmentation Scope. When done, the user right clicks and returns to segmentation scope. With the name of the scenario highlighted, clicking the GO arrow will start the segmentation. To delete the list of elements from the Segmentation Scope selection, pick the ellipse button and then pick the Clear button (last one on right).