There hasn't been a waterfall per se at Dry Falls in central Washington for at least 10,000 years. But when there was a falls there, it would have been spectacular: 400 feet high, 3½ miles wide and ten times as powerful as all the world's current rivers combined.
It's widely accepted that during the last ice age, a glacial dam blocked rivers, resulting in a giant lake over what is now Missoula, Montana. The dam broke at least a dozen times, releasing a torrent of water hundreds of feet deep, racing across Idaho and eastern Washington at speeds of more than 60 miles an hour.
During these cataclysmic floods, Dry Falls would have been quite wet for a few days. Standing on the bluff at one side of the Lower Grand Coulee, it's obvious tremendous force was needed to carve something so wide and so deep. But it's also hard to get and communicate a sense of the scale.
From the rim, I spotted a hiker down below. I didn't know it was a hiker at first. All I saw was a bright red dot. I could only tell it was a person after I spotted it moving. There were some dots on the water, too — Canada geese. I only spotted them after seeing their wake in what was otherwise a perfect reflection on the lake.
Even with those experiences, it was still hard for me to comprehend that I was looking at something that was once a 3½ mile waterfall. It would be even more difficult for someone trying to get that sense of scale from a photograph.
This is the same reason that the Grand Canyon experience is so much different in person and in print. When you're standing on the rim in Arizona, your eye wanders, looking for clues to help you gauge the canyon's width and depth. Photographs tend to compress the perspective and they present only the context clues the photographer wants you to see.
Dry Falls is gorgeous even without the story, but I wanted to create an image that at least tried to show how big the place really is. When that is your goal, there are a few photographic tools you can use to communicate scale.
Include a person or wildlife
One way to illustrate the scale of a sweeping landscape is to include an element that has a recognizable size. Even without any other clues, you can generally tell how large a person is. Or a deer. Or a bird. Including something with a recognizable size provides an important clue to help your viewer figure out how big the scene is. They can judge the size of the full scene in the context of the size of the subject they know.
For a variety of reasons, I don't typically photograph people, so I looked for another subject to provide a sense of scale. I watched several flocks of gulls fly up the canyon and got the idea to use them.
A few people on the rim walked by me, a bit puzzled that I was trying to photograph something as boring and abundant as "sea gulls," but I continued trying. Several groups flew overhead; others flew along the rim of the opposite side, too small to show up in the image. Finally, I got one flock that flew up the middle of the canyon. I think the birds are just large enough to be visible in the image and small enough to communicate how large Dry Falls is.
Even without a person or animal, there are ways to communicate the size of your scene. One involves making use of diminishing perspective. When you look down railroad tracks, the rails seem to get closer together. The rails, of course, are always the same distance apart, but your brain interprets the converging lines as demonstrating distance.
You don't always need something as obvious as railroad tracks. You can accomplish something similar by using a composition that shows what is close and far away.
The image at the bottom of this post is also of Dry Falls and demonstrates this idea. At the bottom of the image you see a channel of water coming from the lake. Especially with the opposite cliff reflecting in the lake, the channel looks huge compared to the other channels and to the passages between the grassy islands and the other side.
The lake itself, Dry Falls Lake, looks many, many times larger than Green Lake in the background. In reality, it is bigger, but the size differences are exaggerated in this perspective.
(And as a bonus, if you look really close just above the rim at the right side of the image, you may see some white dots; they are gulls.)
This type of composition, which works best with a close foreground captured with a wide angle lens, can help communicate how vast a scene is, even if the viewer doesn't know the actual size of any object in it.
Rivers work very well for these types of compositions. In general, rivers have a relatively steady width, so with some distance, their banks seem to converge, just like the railroad tracks. If the river winds around in an "S" pattern, it's even better. Our eyes tend to follow those patterns and interpret that path as a great distance.
You don't always need scale
While the sense of scale really helped my Dry Falls images, you don't always need to demonstrate the scale of your subjects. Some of my most interesting photographs are of small rocks or tiny gorges that I photographed in such a way that it is impossible to tell how big they are.
Sometimes a little mystery makes an image more interesting. Other times, the scale is the subject.