In lieu of specifics on the error number, I recommend that you look over your input. Make sure that your numbers are entered correctly then confirm that the stage, storage and discharge curve cover your expected discharge form the basin.

I believe I have found the cause of the error.
In my Elevation-area function for the reservoir, the storage is defined down to a certain elevation (an elevation below that of the "initial elevation" setting of the reservoir). When I attempt to run it I am getting the following error:

ERROR: Error in computing storage-outflow for Upper Lake
Function: ReservoirCapacity; Error number: 11

However, when I delete the Elevation-Area data below the "initial elevation" setting of the reservoir, the model runs fine. Any idea what could be causing this? Obviously, the program should allow storage to be defined below the "initial elevation" right?

Any insight is greatly appreciated.