Given how small seems the exhibit, how large proportion of it is occupied by a pond, and how easily climbable would be the fences for many mammals, I guess if it was tought for some kind of turtle?
Could this may be just the former pond for the Lilford crane? That all seems really strange as I belive that's too small for a duck species and don't have space for a turtle species. So it could be just a pond for local wild life?
No, it's still there. But now it's fully grown-in and looks very different. It's a micro habitat for local insects with according educational displays and insect hotels next to it.