You could easily create a running water effect that you assign to a layer in the material (to display it on top of the stone material) or you create a copy of the mesh and use the water material for that.
But it depends on how close you get, from a meter away it will look realistic enough (especially with some post processing). But if you want to be really close (like 10cm), then you have to either use complex particles or some fluid-system (like the one from nVidia). In either case, it’s not going to be worth the effort if it’s just for archviz and the waterwall is just a small part of the architecture - and not the main focus of it.
But that’s just my opinion of course, generally you can do a lot with smoke and mirror, generally people won’t care if the whole presentation looks coherent in quality and “feel”.