This is a Terragen 2 render. Original size 1200 x 900. Terrain is from a DEM file of Grand Canyon west, a bit modified and displaced in X axis with a redirect shader. Vegetation is from XFRog libraries. Water transparency is a new feature, currently in development, and only in alpha test versions. TG2 is also going multithreaded in next public release, so rendertimes are drastically reduced.
Thanks for comments and helpful criticism !