Rivers!!

Starting a new miniseries now that it's full-on summer..."Rivers!!" Like the kayaker here, I get all excited about this part of the hydrologic cycle. More than just a bunch of water flowing downhill, rivers are part of the physical and social landscape in both deep and metaphorical ways. So let's fall in, get immersed, and revere them over the next 5 brief posts!




Part 2 in "Rivers!!" They're defined as large natural streams of water, but seem like more than that. To me, they are all about movement, a visual marker of time passing before my eyes, with notes of cleansing, and undertones of things being washed away. Actually, that's just what they do hydrologically speaking. Tugged by gravity, water moves down the river bed, pulling anything that's loose along with it. The more water there is and the faster it moves, the bigger the things (mainly soil and rocks) it can move along with it. Movement: the water moves the fastest, and the clay--silt--sand--gravel--stones--cobbles--and finally boulders all trail along behind it--with clay making the most progress downstream over a year's time, and boulders the least. They even have a term for water and movement; it's cubic feet per second, and that's how river size and flow are described in the world of hydrologists and boaters. See, it's the passage of time right before your eyes! Each sand grain and pebble moving ever so slightly from one minute to the next--like a look into the fourth dimension!

Part 3: Here's a cool picture for a hot day! Iceland is home to lots of young, ambitious rivers with big jobs to do. That's because they have huge volumes of glacial debris to move down the road. Notice how different this river looks compared to the last post of glassy water with its orderly streambank and scattering of cobbles under the surface?...There's a basic rule of thumb here: the shape of a river is a product of its bedload and its water, bedload being exactly what it sounds like. When there is more rock, sand and gravel to move than there is water to move it, you get a braided channel like this one. The water picks some pieces up, loses its head of stream and drops them nearby, making it hard for things to get organized into well-engineered, deeper channels where fast moving water can really move the bedload. "A mile wide and an inch deep" was coined to describe the Plate River in Colorado---whether it's Iceland or the Rocky Mountains, the same forces are at work!

Part 4: Here on the San Juan River, the last rays of sun highlight the canyon rim. Rivers don't just move rocks and water, they carve landscapes. All that excavation and transport of rocks, sand and silt has consequences, The river moves a load. The base of the cliff gets undercut, the cliff slides, and the river has another load of material to cart off. Meanwhile, things just got steeper at the top of the slide, so with the next big storm, that part slides, the cliff band fractures and falls and the canyon gets a little bit wider. Wash, rinse and repeat, over and over for a few million years, and you might end up with a Grand Canyon cut deep into the bedrock of the Colorado Plateau. Or another kind of masterpiece sculpted from a different sort of landscape.


Part 5. I'm realizing this miniseries is too short to do rivers justice--they're just so multi-faceted. This one will have to stick to the physical side of things; stay tuned for the up-coming "Rivers and Riparian" miniseries for some of the rest. And what is the key ingredient in a river? The water, of course. Defined as a large natural stream, what constitutes a river in the arid west would be a creek, stream or brook in the mesic eastern US. In the workings of a watershed, the land catches rain and snow, and what doesn't sink in runs off the land into little drainages which come together, constantly growing with the addition of each new one, until it's big enough to be considered a river in the regional scheme of things. Moving water downhill, another quarter turn in the water cycle: the ultimate function of the river. About as glamorous as the sewer pipe heading out of your house--at least that's how we treat them sometimes. Or as magnificent as the strings section in an orchestra if we open our eyes to the bigger picture.





Part 6: The wrap-up. Rivers!--an exciting sounding word for a rousing subject, they've made plenty a writer wax poetic. I myself am looking forward to an overnight journey down a quiet passage on the Colorado River tomorrow. I'll be in the midst of all of this hydrology: the constant sound of flowing water, the slippery stones and pools of sediment, the world passing by on either side, the abundance of cold water captured by the high Rocky Mountains and routed through this arid landscape, all the suspended sediment that pours in from every side drainage....are you getting the picture? In more technical terms I'll try to be mindful that the river is one stage in the hydrologic cycle; that there are really several other, less obvious stages that will be going on around me what with evaporation, transpiration, cloud formation, and possibly a shower or two--they're calling for a slight chance of thunderstorms tomorrow. And as I stagger from the boat over slick cobbles and up the bank, I might reflect on the bedload to water balance and wonder how far those rocks have come on their journeys downstream. We'll be speculating on how far the flow has dropped since the epic snowmelt this spring- it was running over 30,000 cubic feet per second back in June. Like the picture, I'll try to see beyond the here and now of water, river bed, and river bank to the recent and distant past of variable flows, floods and low water. The slow and measured journeys of the different sized rocks and gravels. The expanse of land in the watershed--the land that caught and released this water.

A hydrology montage for the Yuba River showing part of a hydrograph above and some of the watershed below

Which all reminds me that I met a holy man near the San Juan River a few months back. He said he can't float a river, wouldn't be appropriate. Instead he goes down to the shore and makes offerings to it. And, he let slip that the San Juan is a male river, but the Colorado? Now that's a female. So I'll be keeping an eye out for those womanly qualities too!


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