Dear all,
I have problems with running surface runoff and pipe flow simulations separately. I.e., I run first a (long term) runoff calculation and yield a runoff, i.e. .rof-file. In a second step, I run a pipe flow simulation for certain shorter periods. For this I use the runoff file (Options --> Files --> Use File) and turn off the runoff simulation. I always start the pipe flow simulation under dry weather conditions.
There are no problems so far as the start & end dates and times are the same for both the runoff and pipe flow simulation (apart from obtaining slightly different results compared to the case when running runoff and pipe flow simultaneously for which I do not have an explanation as start conditions should be the same).
However, if the simulation period of the pipe flow simulation is much shorter and the start date of the pipe flow simulation is considerably later than that of the runoff simulation, the pipe flow simulation does not work. I.e., there is no additional pipe flow under wet weather conditions.
Does anyone have an explanation and/ or a solution for this issue? And does anyone have an idea why one get slightly different if the simulations are run separately or simultaneously? I would be very grateful for an answer.
Best regards. Christoph
Replies
Dear Bob,
Thank you very much for the answer!
Christoph
Hello Christoph,
Sorry for the delay in answering but the simple answer is that the runoff interface file lacks a date and is just a list of runoff values. It is structured by the number of hydrology time steps. For example, if you save a file that has 0 to 1000 steps in one simulation and use the same file one simulation week later in another simulation your runoff flows are still read but the flows are off by one week. There is a workaround for you - save your runoff to an outfall and then save the outfall flows to an OUTFLOWS file followed by the use of the OUTFLOWS file as an INFLOWS file in a subsequent run. The OUTFLOWS file does have the date and time. I hope this helps for your continuous simulations.
SWMM5 Interface File
Hostivice - lokalita SADOVA - sanitary&storm sewer system
120 - reporting time step in sec
1 - number of constituents as listed below:
FLOW LPS
2 - number of nodes as listed below:
2
4
Node Year Mon Day Hr Min Sec FLOW
2 1983 08 12 00 00 00 0.000000
4 1983 08 12 00 00 00 0.000000
2 1983 08 12 00 02 00 0.000000
4 1983 08 12 00 02 00 2.500000
from the SWMM5 help file
The interface file can be used to save the results generated from a simulation run. If runoff is not affected in future runs, the user can request that SWMM use this interface file to supply runoff results without having to repeat the calculations again.
Dear Bob,
Thank you Bob for your reply and your willingness to help me.
In the meanwhile I made a simple model for demonstration/ testing. I run both hydrology and hydraulics together and separate. The combined simulation works and also the separate if the calculation periods for both simulations are the same. The separate simulation still does not work if the pipe routing simulation is shorter than the runoff simulation.
In general I cannot abstain from running both parts separately due to computational demands and because I want the hydrological Simulation to be continuous.
I attached an example with rain data, runoff file, the model in 4 versions & corresponding results:
...runoff is the model calculating only runoff
...runoff_pipeflow runs hyydrology and hydraulics together
...pipeflow_long runs only hydraulics over the same period as the simulated surface runoff
...pipeflow_short runs only hydraulics over a specific shorter period
I would appreciate very much if you could have a look on this since I really do not have an idea.
I am looking Forward Hearing from you. Best wishes.
Christoph
I don't think there is an issue but in the meantime can you not run both hydrology and hydraulics together while we investigate.