l/l subroutine

We have been trying to use the I/I option with SWMM4.4 that uses the F3 and F4 cards and the H5 card. It just does not seem to be working out as we always get a message of error stating the the time step in the F3 card (TSTEP) is not the same as THISTO (even if it is indeed the same). THISTO is 5 minutes and we input the same in the F3 card. If somebody at CDM is listening to this or Dr. Huber, we would like to hear from you and get a little bit more of information that what is in the documentation. We tried to read between the lines and tried many different things but we did not succeed after a full day to even get the thing working. An example showing a file that does indeed work with the E1 card and the F3, F4 and H5 would be useful. We badly need some help on this as we are running out of time (and money...)

Also, it is not clear how the H5 cards are used. Do we have one for each subcatchments where we want to have the moderately fast or slow response hydrographs to be calculated ? If so, how is the model told where to input the computed hydrograph if the NGTO is not specified in the H5 card ? Is there a limit on the number of H5 cards ?

Thank you for any help that would come for this topic.

Gilles,

Regarding your first problem, the program checks for an exact equality between THISTO and TSTEP. This could be the problem (we should build in some slight tolerance for round-off errors.) The value of TSTEP is input in hours (as pointed out by Ron). Try inputting your time step values in units of hours, on line B3. This may give the same round-off for both numbers when they are converted to seconds in the program. And be sure to enter exactly the same hourly value for 5 minutes. That is, 5 minutes = 1/12 hour = 0.0833 hr. Don't use 0.083 on one line and 0.0833 on another line. In fact, use 0.0833333 on both lines to maximize the precision.

The RUNOFF.DOC file contains a working example along with the only documentation for this routine, unless CDM has something tucked away somewhere.

Regarding the H5 lines, yes, you need to insert H5 lines for any subcatchment for which you want to use this option. The computed l/I hydrograph enters the inlet defined by NGTO on the corresponding H1 line. The H1 and H5 lines are entered as pairs; don't enter all the H1 lines followed by all the H5 lines.

Only one H5 line can be entered for any one H1 line. You include an H5 line for any subcatchment that you desire (only one). You do not have to include an H5 line unless you want to. The limit on the number of H5 lines is the number of H1 lines.

Let us know if any of this helps.
Wayne