Dear Anne :

The key items to remember is that at the approach cross section (at the cross section upstream of the bridge opening upstream face cross section), the water surface elevation is assumed to be level (the same value) across the cross section. However, the velocity through each of the openings is different. This gets translated upstream to the approach cross section. The sum of the water surface elevation and velocity head is the total energy head (EGL). Hence, this is why you are seeing different EGLs at the 3 bridge openings. You can easily explain this in your report.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com