Minecraft aqueduct

I like your idea here, I haven't seen many aqueducts built before, but one thing you should definitely think of doing is varying your building materials. You've only used one type of block (sandstone?), and although you have some lovely arches, varying block types will give more definition and more visual interest to the structure. Borders done in a different block, or details in the larger patches of sandstone area could spice up your structure a bit more. Looking at some photos of aqueducts (if you haven't already) could help here, too.
Another thing you might consider is scaling it up slightly, in order to be able to add more details and to give your larger arches more of a smooth curve. I'm not sure if you're in creative or survival, though, so I have no idea how difficult resizing/rescaling would be.
Happy building! <img src="e.deviantart.net/emoticons/s/s…" width="15" height="15" alt="" title=" (Smile)"/>