I am sure you ahev heard alot about the size of the image already. I think that is just a small portion to what hurts the image overall. The foreground has no real detail or depth. Just stark white in color. While the top is darker but still further away and even less detailed. I can see where your point of view was and the angle that you were trying to create but it doesn't create any mood. Even if the image was larger I do not think it would have scored very much more.
Not sure if you cropped it or just resized it. But I would have liked to seen it from a different angle. Amnd not so much of the river in the center of the photo. Maybe even up against that tree shooting at the fence line with the water coming through the middle. Just an example.
But do not get discouraged. Try and work on one thing in a photo at a time...composition....subject matter...point of view. Then slowly try and put them all together. In time you will improve.
I hope you're not discouraged by the results. This actually looks like a very good picture and if it were a larger size it would have scored much higher. Please keep playing!
You probably already got the gears about the size from the others, so I won't bring it up. I like the composition and the theme. The reflections in the water are a nice touch.
Personally, I always like to see an image that is close to the maximum allowed 640 pixels. Gives me a good overall sense for the photo. The upper middle portion of your shot seems most interesting, but again, I really wish it was larger.