Thursday, May 26, 2016

Error message of "Start Date must be after Lookback Date"

I have noticed a few comments asking about the error message "Simulation Start Date must be after Lookback Date".

In the screenshot below, I set a start date of 20May2016 and a lookback date of 23May2016.  Note that the Start Date is at the top and the Lookback Date is one row below.

In my test, HEC-ResSim does not allow the simulation to go forward.  Instead, it gives me an error message when I press "OK".

To solve this, make sure that the lookback date is at a date prior to the start date.

Incorrect Dates:

Corrected Dates with Lookback Date prior to Start Date:

Thursday, May 19, 2016

Additional error fixing in HEC-ResSim

This post will cover two additional error messages that can occur in the development of an HEC-ResSim model.  Special thanks to Logan Osgood-Jacobs of the Seattle District of the Corps of Engineers for supplying these screenshots.

Error 1:  Ghost Nodes

Ghost nodes, or nodes that you did not intend to include in the model, seem to periodically occur in the development of ResSim models.  I have gotten these when I have had to edit the watershed configuration and then perform an update to the reservoir network.  However, I believe that others have gotten ghost nodes in the initial development of the model.

So, how do you tell if you have a ghost node?  The most direct way is getting an error message similar to the one below when you compute your simulation.

This error message is indicating an issue with Node 81.  In the Reservoir Network Module, go to Reports > Advanced > Node List.  The report is shown below.  There is a node named, "Node 81".  Not having a ~E indicates that there is a problem.  Simply delete this node, go to the Simulation Module and "Replace from base" and re-simulate.  This should take care of the problem.  

Error 2: Physical Data Tables not Increasing

Typically, HEC-ResSim will give you an error message as you are inputting physical data into the model if your data are not increasing.  However, Logan got this error message during the simulation.  She had copied the physical data table from a spreadsheet to the ResSim model.  It appears that ResSim did not provide an error message at that time and, instead, provided an error message during the simulation.  This error was fixed by ensuring that the values in the table were increasing.