I agree, it's really beautiful. What first catches my attention is the gradual lightening of the stream from dark to almost irridescent where the stream meets the larger body.
The repetition of the light on the top of the rocks and then repeated on the sand to the left of the stream comes next. That small area of light in the sand keeps the left side from throwing everything off balance.
Finally, I am always drawn to color that has this type of more limited, pastel type palette. Pretty much dark lavenders and subdued pinks except for that lemony yellow that threads through the sky. If you imagine the image without that yellow it still has wonderful graphic elements but not the same "punch".
Maybe like you point out it is the simplicity. Earth, sky and water at their most basic, almost primordial.