Welcome to the RAS Solution › Forums › HEC-RAS Help › Wrong flow through Storage Area connection

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  • February 27, 2015 at 11:42 am #5721
    Anonymous
    Guest

    I have a storage area connection connecting two storage areas. The connection is a combined weir and culvert. All the flow goes through the culvert, there is never flow over the weir.

    After running the model (unsteady) i compare the flow values reported in:
    1) Stage and flow hydrographs
    2) Storage area connection output. (Accessed by clicking the “View detailed output at XS, Culverts….” button in the main HEC-RAS window, and selecting Type = Storage Area Connection.

    For most SA connections the flow is the same (it should be). But for some SA connections the flow is completely different. Like + 50 % or – 50 %. The flow is equal for the first time steps but then the two results start gradually diverging. The HW and TW levels are the same in the

    I do compare the same time steps. There is no flow over the weir.

    Which, if any, of the outputs should I trust? The stage and flow hydrograph or the SA connection detailed output?

    Regards,
    Marulke

    February 27, 2015 at 7:43 pm #9159
    Lonnie A
    Participant

    The storage area flow hydrographs are net inflow and won’t match the storage area connector. The net inflow is the flow from the storage area connector + any flow assigned directly to the storage area minus flow leaving the storage area.

    February 28, 2015 at 11:59 am #9160
    Anonymous
    Guest

    Lonnie,
    this is not caused by a mix up between storage area and storage area connection.

    I have compared flows in several Storage Area Connections (not storage areas) by looking at:
    1) Stage and flow hydrographs for Storage Area Connection
    2) Storage area connection output. (Accessed by clicking the “View detailed output at XS, Culverts….” button in the main HEC-RAS window, and selecting Type = Storage Area Connection.

    In my opinion the flow reported in 1 and 2 above should be equal. Mostly they are. But for some connections there are periods where 1 and 2 show significantly different flow (for the same time steps).

    Suggestions?

    March 2, 2015 at 7:50 pm #9161
    Lonnie A
    Participant

    Marulke,
    I understand now what you were referring to. I looked at one of my older models I had available and also see differences between the DSS results and the table results. There were differences in both V4.1 and V5.0.
    Sorry I don’t have an answer as to why they are different. I’ll try and look into it some and if I find anything I’ll be sure to post back.
    Lonnie

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