Nor Any Drop to Drink: Watching Water in Badlands National Park
Work for one day in the visitor center at Badlands National Park, and someone is sure to ask, “Why is it called that?” The term “badlands” is a translation from the Lakota “mako sica” and the French fur traders’ “les mauvaises terres à traverser”—which is to say, “bad lands to travel across.” The rugged terrain is part of the problem, of course, as is the harsh climate. Winters can see the mercury plummet to well below zero, while summer temperatures can reach triple digits (in Fahrenheit, of course). Winds over fifty miles per hour can occur at any time of year, and the starkness of the prairie affords little shelter from the gusts.
But I often think that the lack of potable water in the badlands is what really made this area earn its name. For most park visitors or area residents today, this poses little challenge. We turn on the tap and out comes safe, clear drinking water. Hikers fill up bottles before venturing out on the trails. Backpackers on overnight trips often limit the length of their stay based on the amount of water they can carry: foot travelers should bring along a minimum of a gallon per person per day, and in the heat of summer planning on two gallons per person per day is prudent. That water weighs a lot, at a little more than eight pounds per gallon. Even an overnight trip in mild conditions adds nearly seventeen pounds to a hiker’s load.
Still, we have it easy today. Imagine traveling through this landscape on foot or horseback a hundred years ago, before piped water made having a drink as easy as turning a faucet handle. Suddenly the lack of water is a potentially life-threatening problem. The badlands we see today were carved out by the White River, visible in the valley just a few miles distant, but don’t be fooled: the water in the White River is not fit for consumption. On one day in May 1982, the White River’s total sediment load at a sampling point near Oacoma, SD, was measured at a mind-boggling 1,640,000 tons. Minute clay particles eroded from the badlands formations remain defiantly suspended in the water. They’d clog a backpacking filter before you could get anything drinkable out of it.
I went out for a four-mile wander on the Castle and Medicine Root trails yesterday afternoon, taking advantage of a sunny, windless, fifty-degree day. I found water, water everywhere—always a remarkable sight in this semiarid place that gets eighteen inches of precipitation in a good year. (2012 was not a good year, with only about twelve and a half inches.) Snowdrifts in shady hollows, the last vestiges of a winter storm two weeks ago, dripped water that turned badlands clays into boot-sucking mud traps and ran off in opaque streams.
I spent a long time watching the behavior of the water on the landscape, fascinated anew by how the interaction of water with sediment is so scalable. You can see the same processes in a tiny runoff stream in the badlands as you see in a mighty river. Let’s take a look.
Whether it’s in the smallest rivulet or the most roaring creek, fast-moving water packs a strong punch. It abrades the surfaces it passes over and alongside, and picks up particles of sediment. Depending on how steeply the stream is falling and how fast it’s running, it may roll cobbles or even boulders. Lazy, meandering rivers with a gentle gradient can usually only carry finer sediment.
When a stream slows down, it can no longer carry the larger particles of sediment in its current load. These settle out and are deposited. This happens when a big river flows into a lake or ocean. It may also happens when a little rill flows into a larger, more placid channel (as in the two images above), or when a rivulet that has been making its way over a dry surface hits a break in slope and flattens out (below).
Compare these images with NASA photos showing the Yellow River (Huang He) Delta …
… and the vast inland Okavango Delta in Botswana.
Want to see sediment tumbling along in a runoff channel? Watch the grains of sand move from left to right in this video. Recognize that the water is moving a lot faster than the sand is. Since each grain of sand isn’t suspended in the water but is instead being rolled and bumped along the bottom, it has to contend with friction. When a bubble passes by, you’ll see how much faster the water is traveling.
Notice, too, how much the miniature braided stream in the video (just ten inches across) resembles this braided river in Alaska:
What I love most about watching water on the landscape is that you can see it in action wherever you go. The patterns you observe in one place—even if it’s very small-scale, like the little badlands runoff channels—closely resemble those that occur elsewhere.