Maxima/wxMaxima and partial differential equations

Jan 2020
I have two partial differential equations (Saint Venant equations) and another equations like this:

B(h)*diff(h, t, 1)+A(h)*diff(v, t, 1)+v*diff(A(h), t, 1) = 0;
diff(v, t, 1)+a*v*diff(v,x, 1)+g*diff(h, x, 1)-(So-Sf)=0;
h= c²/g;
A(h)= 1/2*(B(h)+bottom*h;
B(h)= bottom + 2*M*h;

This is not yet complete definition but, when it is, how I can solve PDEs symbolic way, so B(h) is replaced with bottom + 2*M*h, h is replaced with c²/g etc?

I'm new with wxMaxima and another mathematical softwares and I haven't found any good examples for this problem.