ERROR 171: has invalid or out of sequence data while using the SWMM engine

Product(s): SewerGEMS, CivilStorm
Version(s): 10.XX.XX.XX, 08.11.XX.XX
Area: Layout and Data Input


I am getting ERROR 171: <Pump/Channel Curve Name> has invalid or out of sequence data while using the SWMM engine.  Why is this and how do I fix it?


When analyzing using SWMM Solver, user notification of "The SWMM Engine failed during calculation. Go to the Report Tab on the Calculation Summary Report which can be accessed via Analysis > Summary." appears.

In calculation summary ERROR 171 appears.

For Pump Curve

Look at the pump curve referenced in the message and make sure that all the flow values are in increasing order and that all the head values are in decreasing order. If you have head values that are the same somewhere in your curve please make sure that you vary those values by a small increment or you will receive the same message. For example, if you have a head value that is 120 ft. and your next value is also 120 ft. make the first value 120.01 ft. and the second value 120.00 ft.

Note: If even after adjusting the head values you can see the same value (E.g. after changing 120 ft to 120.01 ft you are still seeing 120 ft), then change the display precision by right clicking the column name and selecting "Units and Formatting". Then change the display precision to "2" to view up to 2 decimal places. You can set this display precision as required.

This will ensure that you have still have decreasing head values while having little to no variation in head.

For Channel Curve

This error can occur in case an irregular closed section is defined as a catalog section. When defining an irregular section a depth vs. width curve needs to be defined. As in the case of a pump curve, repetition of values in the "Elevation (Relative)" field will lead to this error. For a cross-section, there cant be multiple widths for a single elevation value. So while defining the channel curve, care should be taken that there is no repetition of elevation values. Check the channel curve for such discrepancies and correct them wherever applicable.

While changing the elevation values you can check for the display precision if the changes in elevation are minuscule.

See Also

Changing the display precision (decimal places) for an attribute

ERROR 119: invalid cross section for Link <link_name> while using the SWMM engine

Error computing model using Explicit solver: ERROR 173: Time Series (element label)_Inflow_Ts has its data out of sequence