This is old hat to many photographers, but the use of shutter speed to freeze flowing water is something worth understanding even at the risk of repeating what might be obvious.Water in motion can make striking images. Our eyes naturally blend the motion of falling water drops and make water falls / rapids into silky ribbons of water even when they are actually individual droplets of water. A camera can freeze that motion, or allow it to flow, it all depends on the shutter speed.
The accompanying shot of the water wheel was shot at 1/50 of a second. This allowed the water to move a short distance during the exposure and blurring, but not forming a long smooth silky fall. In this case, I wanted the water to show motion, to make the shot feel like it's in motion, but I wanted the spokes of the wheel to be relatively sharp, nearly frozen in time. That's what I was seeing when I looked at the scene and that shutter speed (on a tripod, BTW) was just right.
