In case you hadn't noticed it yet, the most remarkable thing about the waterfalls in the Columbia River Gorge may not even be the waterfalls themselves, but the seemingly iridescent green blanket of moss that covers everything in sight. I've photographed plenty of waterfalls before, but none that look quite like these. I was tempted to turn down the green in post-processing or no one would believe this was real. But it really is this green!
Whenever I photograph flowing water, I try to render it in an impressionistic way, using a long shutter speed of somewhere between half a second and five seconds. To accomplish this during daylight hours, you must use a combination of low ISO setting, relatively small aperture (high f-stop number), and even add a neutral density to further reduce the amount of light entering the lens.