  We show that in two dimensions the incompressible Euler equations can be
re-expressed in terms of an abelian gauge theory with a Chern-Simons term. The
magnetic field corresponds to fluid vorticity and the electric field is the
product of the vorticity and the gradient of the stream function. This picture
can be extended to active scalar models, including the surface
quasi-geostrophic equation. We examine the theory in the presence of a boundary
and show that the Noether charge algebra is a Kac-Moody algebra. We argue that
this symmetry is associated with the nodal lines of zero magnetic field.
