I'm 100% certain that's been edited. They obviously didn't like how the grass looked and they didn't want to crop the photo. So, they just stamped and painted in a little bit of water over the top of the grass and walla!
The Main point of the photo is the architecture, and the grass must have been distracting as it overlapped with the water. If you look a little bit to the left of that sharp transition, you'll see the top of the grass is a little grayed out, that's using the brush tool, with a grayish blue shade at about 25% opacity. It's very easy to edit a digital image, especially one of a game. It looks like a very quick thing they did right before releasing or uploading the photo.
Ha! Thats a photoshop job for sure. I actually think the water isnt even there in game, if you look at it closely, it looks a bit off all around, you can actually see near the far end a plant sticking through it. I think the entire water portion of the image was edited in
It's possible, but I don't think they would of wasted the time to create that pond. I think they simply edited the water to cover up the top of the grass. So they used the stamp tool, and then brushed over it to look nice, and by nice I mean the same as the rest of the water in game.