Cool looking clouds.
The lake looks like it's largely at default settings (aside from the water shader settings), so I wouldn't expect much oddness. But it looks like it just might be an issue with low geometry subdivision on the lake disc. I've seen some similar issues causing radial patterns before and it may be related.
I also note your index of refraction is extremely high. This is one setting you generally don't want to change since 1.33 is a realistic real-world setting. Other values will work of course, but may create strange effects.
By the way in the future it would be better just to post the .tgd as an attachment rather than pasting it into the post window.
- Oshyan