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DeniseS

Error 40254: Computed pool elevation is below minimum table value for reservoir

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Hello,

I've been using HEC-HMS for just about two years now and I'm still learning all of the details of it. I have a detention pond which is draining 1.76 acres onto a state highway. I have put in the Elevation-Area Table in the Paired Data. There is an outlet pipe (the only outlet) of 18"; it's inlet elevation is 1278.00. I'm assuming that is the very bottom of the detention pond, because in the drawing, contours are shown for this pond starting at 1279.00.  

When I run the 2-year Type II SCS Storm of 3.30 inches, the following error occurs and the process is aborted: "ERROR 40254: Computed pool elevation is below minimum table value for reservoir "Detention Pond".

There is also another error which follows the above error. It is ERROR 40261: Reservoir routing failed at simulation time "1 January 2000, 00:05:00" for reservoir "Detention Pond". 

Because I get an error relating to the time control specifications, is there not enough model time for the pool elevation to get high enough to prevent the first error from occurring?  Is that what is happening? Or is it something else?   This program can do so much and I'm still so very confused over half of it!! I need a one-on-one tutor to tell me, in layman's terms what all of the components are and what their methods are. :wacko:

Thanks for any advice!

Denise

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On 12/21/2016 at 0:15 PM, DeniseS said:

Because I get an error relating to the time control specifications, is there not enough model time for the pool elevation to get high enough to prevent the first error from occurring?  Is that what is happening? Or is it something else?   This program can do so much and I'm still so very confused over half of it!! I need a one-on-one tutor to tell me, in layman's terms what all of the components are and what their methods are. :wacko:

Thanks for any advice!

Denise

Denise,

In your Elevation-Area table, is your minimum elevation value 1278 or less?  It needs to be so HMS has enough information to route the flow through the detention basin since your outlet is at 1278.  So check your table and make sure the minimum elevation is 1278 or less.  If it is not, you should be able to manually change the value.

This may or may not solve your problem, but it's something you should look at.  There are lots of input parameters when defining a detention basin; it could be a problem with one of your other parameters also.

Chris

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Hi Chris,

I had 1278.00 as the very first elevation of my Elevation-Area Table, and the error was still occurring. I changed the routing method from Outflow Structures to Outflow Curve, and all of the simulations ran smoothly with no errors. There were warnings, but no errors.

I appreciate you taking the time to answer my question.

Denise

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