open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello, everybody, I am a beginner at TELEMAC 2D.
I am simulating a large dam 20km and 185 m water depth, with intake as SOURCE TERMS and my boundary conditions, are:
Nodes: 207788
Elements: 404899
For now steady state
I filled the reservoir
I have several prescribed Q (see figure 1).
In the beginning, I used prescribed H located 500 m downstream, but I realizes that overtopping is not very common and I decided to erase BC downstream, (figure 2).
So until now, I have checked my simulations changing WATER DISCHARGE OF SOURCES when I increased the negative value of this term the water level is decreasing, as expected.
In my mesh, I tried to cut my domain but in any case, the real situation is nobody knows when the overtopping occurs, and right now the water is store with the dam as a big wall, but I don't know how to check my simulations.
On the other hands, I was wondering about different numerical parameters and I would like to have some advice about it:
I check dam-break case and Malpasset case and the used solver were solver=1,7 and I used solver= 2. Where can I find information about what is better solved for my case?
and about the type of advection will be better for my case.
Thank you very much
In attach
1. Information about results
2. Figures
3. Cas file