I have a storage area (SA) at the US end of a reach. Inflow is provided by a lateral inflow hydrograph. There are two downstream connections from the SA:
1) Storage Area connection controlled by a weir
2) River reach (ordinary CS, no inline or lateral structure)
I am running unsteady, mixed flow, mode, but the flow is constant throughout the simulation.
I compare the water surface elevations at three locations in the SA:
1) The most US cross section for the river reach.
2) Stage hydrograph for the SA
3) Stage hydrograph for the SA connection
2 and 3 above are the same for all time steps (profiles), and for the first time step identical to the set initial elevation.
The problem is that the water level in 1 is completely different, about 60 cm (2 ft) too high at the first time step, and departing more and more (several meters) as time goes. (Flow, and everything else is kept constant.)
The difference is not caused by the velocity head. I have checked the reach connectivity – looks OK. No error messages for the first profiles – after a while the model blows up.
I have tried very short time steps and various other options, but there is no agreement between the two water levels calculated for the same SA.
Is it a problem to have a SA with two outlets as I have used?
Grateful for any suggestions.
Marulke