What is the difference between the "Elevation" and "Elevation (inlet/outlet invert)" fields in the properties of a reservoir?
The "Elevation" represents the water surface elevation (which establishes the hydraulic grade boundary condition) and the "Elevation (inlet/outlet invert)" represents the invert of the pipe that attaches the reservoir to the system. Pressure at the reservoir location is determined by the difference between these values.
The “Elevation (Inlet/Outlet Invert)” field is a transient-specific field (note that it is in the “Transient (Physical)” section of the properties) and so it only used during the transient simulation in HAMMER, and only considered in profiles in the Transient Results Viewer.
In an initial conditions profile of the system (View > Profiles), the “Elevation (Inlet/Outlet Invert)” field is not considered since it is transient-specific. (and hence, this field has no impact on a steady state or EPS in WaterGEMS and WaterCAD) The orange line always uses element “elevation” fields, and the blue line is the calculated hydraulic grade. For a reservoir, these two are always equal, so the initial conditions profile plots two equal points. Again, this is expected, because the “Elevation (Inlet/Outlet Invert)” fields is only for HAMMER, and not a required input field for a steady state/EPS. If it was, then all users of WaterCAD and WaterGEMS (which share the same file format) would need to enter both fields, else the profile would try to always plot the default of zero.
If you open the Transient Results Viewer and open a profile in the profiles tab, you will see that the physical elevation (green line) considers the “Elevation (Inlet/Outlet Invert)”.
General HAMMER V8i FAQ