I think I would try modeling the second opening two ways: 1 - use the d/s dimensions at both ends, 2 - use the u/s dimensions at both ends. Then compare the results. If they show outlet control in both cases, then it may not matter which you use (use the configuration that gives the higher headwater if they are not the same). If inlet control, then the true u/s opening should probably be used. Either way, I would lean towards using the configuration that gives the most conservative headwater elevation.

Mike
perkins@nwrservices.com