I’m using HEC-RAS to assess several sluice gate configurations over a wide range of flow rates. The default in the model is to calculate orifice flow with head referencing the invert of the orifice instead of the center of the opening. With the head referenced to the invert of the orifice a significant discontinuity results between weir and orifice flow through the gate. The gate is inline and discharges into a channel downstream, but the channel is relatively steep, and the backwater effects are not significant over the majority of the analyzed flow rates. My preference is to reference head to the centerline of the orifice to provide a smoother transition between the weir and orifice stage-discharge curves, but am looking for some advice/confirmation before going against the default as well as the guidance provided with the Application Guide examples provided in Chapters 12, 15, 18, 21 and 23. Thanks.