Time steps

Hi SWMMers,

I'm having trouble with the time steps. They seems to work only with time intervals of 1 hour or more. The example #3 has a time step of 30 hours, is it correct? The example #2 doesn't run, like the first does. Has anyone tried to model a little system and want to share it, to help myself or anyone else? It is better if is based on dynamic Wave and Metric units.

Regards

Giovanni Di Conza
giovanni_diconza@LIBERO.IT

I've just started doing some testing of the Beta SWMM5 and the only computational problem I've come with in the limited time that I've had with it is,

1. Inputting rainfall records thru TIME SERIES, the model is not correctly reading the rainfall time series as continuous rainfall. Rather, it is reading the rainfall as "spikes" at each of the time increments read. This seems to happen whether continuous or incremental records are read in. This of course results in nonsense multiple spikes in the hydrographs generated for each subcatchment and routed thru the system.

Noel S. Atkisson, P.E.
n.atkisson@dannembaum.com

I just wanted to clarify some issues raised by the last two SWMM 5 beta posters:

1. Neither we at EPA and CDM, nor many other testers have had any problem with setting the computational time steps in SWMM 5 or in running the example data sets. The routing time step in Example 3 of the beta test package is 30 seconds, not 30 hours. Giovanni, if you could be more precise about your problem, send it in to swmmqa@epa.gov and we'll try to debug it.

2. Rainfall time series are read correctly as continuous values, over the time interval specified for the Rain Gage to which the time series belongs. That is, if Rain Gage RG1 has a time interval of 15 minutes and uses time series TS1, then each value entered for TS1 applies over a 15 minute interval. We have tested many rainfall-runoff examples (under US units) and everything is working as it should. (There is a bug in the conversion factor for metric rainfall units of mm/hr to feet/sec). What might be confusing is that the graph displayed in the Time Series Editor shows the time series as point values connected by straight lines, rather than a "step" function as one would expect for rainfall. This is strictly a display issue, and we'll try to find some way to make things look clearer. Noel, if you think you have a data set that's giving nonsensical results, then please send it in to swmmqa@epa.gov so we can check it out.

As I write this the first batch of SWMM 5 bugs are being posted to our web site. We are encouraged so far by the number of people who have taken the time to check things out and we expect more will do so as they find the time and as the robustness of the beta version improves. Thanks for your feedback.

Lewis Rossman
rossman.lewis@epa.gov

Dear Giovanni,

Like other European SWMMers, I think you may experience some troubles with international settings. SWMM5 now is a Full Win32 application. For this reason you should look at *.inp example files (using a text editor) and set up your "International Settings" (in Control Panel) in order to fit SWMM requirements.

Regards,

Gabriele Freni
freni@idra.unipa.it