Yes, that is a willow. Grow crazy fast. I have large (30 feet tall) willow trees all around my pond that I would like to cut down but the wife won't let me. If it was further out in your pond and provided a little bit of cover for your fish I would say leave it for a while but being almost completely out of the water I would cut it down. I have been told that a willow tree can suck up 100 gallons of water a day.
