Dear EFDC users, Good day!I would like to simulate a constant water level. I made a model with constant inflow and outflow during the simulation time. I expected the model to result in a constant water level, but the water level was time-variable. What should I do to simulate a constant water level? I guess the initial and boundary conditions should be fixed, but how can I do it? Thanks in advance. Sincerely,Minjeong

test.zip

If you want to maintain a constant water level, I would recommend using an open boundary rather than a flow boundary.

I have no water level data for an open boundary. How can I maintain a constant water level using a flow boundary?

You can maintain a constant flow by using the same inflow and outflow BC. Please note that inflow should have positive values whereas outflow is negative values.

Dear Mizu, I tried the same inflow (1cms) and outflow (-1cms) BC, but I couldn’t maintain a constant water level. The simulated water level is attached here and the model was attached to the first post. I don’t know what made this variation of water level. The model is a simple rectangle one with a constantly decreasing bathymetry.

Based on the plot you provided, it appears the water levels are effectively constant. The variations you are showing are within the range of numerical precision for the model when using a 2-time level solution and single precision executable. You may see improved numerical stability in your model if you switch to the 3-time level solution, and it may also improve further if you use the double precision executable. Using the two together should yield very stable results numerically. A more conservative time step could also help maintain a perfectly (numerically) constant water level.