I'm modeling a detention basin in HEC-HMS using the reservoir function. The reservoir has two drainage sub-basins flowing into it. There are three culverts and a spillway acting as the outlet structure. I've entered the reservoir data in the elevation-storage format. For the tailwater conditions I've entered an elevation-discharge rating curve.
The problem I'm having is that when I run the simulation I get several errors which say "ERROR 40243: Could not compute water elevation for reservoir". The simulation will then keep on computing for about five minutes and then finish and give results. The results it calculates seem reasonable but I question their accuracy since I'm getting this error message and the program is obviously having trouble computing the simulation. Also the water elevation in the reservoir never reaches the spillway elevation so the outlet culverts seem adequtely sized.