How A River Cares for Others

When you fly over any continent on our planet and stare down at the shapes and lines, you see streams of all sizes meandering all over the place. You see ecosystems flourishing along them—you really see how crucial rivers are to plants and animals. And you see how streams tie into the landforms, for, indeed, the rivers have shaped and are shaping the planet itself. You start to see there is no talking about the planet without including the rivers. That’s a lot of care on the part of the river. And it gets even more basic than that.

The rivers are a key link in the dynamics of the planet itself—in its entire functioning as one whole entity—because our planet depends on the water cycle for the distribution and freshening of the most crucial ingredient for any living world: a life-friendly solvent.

Brian Koberlein neatly summarized a recent Arxiv article by William Bains, Janusz J. Petkowski, Sara Seager:

“A life-friendly solvent must dissolve some molecules but not all; they must be able to play a role in the metabolism of living things; a wide range of complex organic molecules must be able to survive in the solvent; and it must commonly exist on certain rocky worlds for billions of years.

On Earth that solvent is water (H₂O). Water dissolves some molecules into solution, giving organisms access to a range of materials. Since it is a liquid, water also makes it easy for complex molecules to mix together and interact. Terrestrial life isn’t possible without the solvent and fluid properties of water.”

To distribute this key ingredient, the river of course flows. That’s the river’s first and, I would argue, foremost characteristic of a river. It’s how it starts. And it’s the river’s most obvious job: returning our planet’s solvent fluid to the ocean from whence it came. And flow is also the river’s one and only source of power.

Now, water spread out on the earth’s surface in large, thin sheets also flows toward the sea—but not very surely or efficiently. How convenient, then, that as the river water falls, pulled by an invisible attraction AKA as gravity, that gravitational force is converted to a kinetic force that gives the river velocity and an ability to carry sediment. And then that force is converted to a friction force that allows the river to literally “channel” its energy. That is to say, the river uses its power to build itself a bankfull channel with boundaries that define a width and depth that are exactly perfect for the weather, geography, and geology of its environment. Building itself is the river’s life’s work (that’s the technical physics term for what the river’s doing here). Now the water can flow to the sea a lot more quickly.

Whenever something, like a river, uses power to do work, it converts some of its energy into entropy (thanks to the justly famous, always inviolable Second Law of Thermodynamics!). You can see that famous truth for yourself when you look at a river because it embodies some of that entropy in its sinuosity. And as it meanders, it carves out a valley. Now, when the river experiences flows greater than its channel can handle, as it inevitably will, the river water can spill out into the width of that valley.  That greater width allows the water to SLOW. DOWN. This is how a river keeps itself safe. It floods. And this is also how a river cares for its neighbors. In fact, it’s how the river BUILDS the neighborhood. For when the floodwaters slow down out there in the valley, the water loses its ability to carry so much sediment and therefore drops dirt, organic material, and seeds into a nice even layer across the valley. The river builds a floodplain. And as you see from your airplane window, that lush strip alongside the river is one of the most beloved, richest,  most life-giving ecosystems on the planet.

Reverse-engineering this contribution to the world, you see that the river can only care for its neighbors when it floods its banks and flows onto a floodplain. And it can only build and access its floodplain if its own channel is healthy. If the channel boundaries are weak, eventually the river will start down-cutting into its own foundation. Deeper and deeper it will go until it can’t reach the floodplain anymore. Then that riparian ecosystem converts to something drier. Plants and animals can’t reach the water easily. Many die.

So, all a river needs to do to care for others is to be itself. This is the easiest and most pleasant thing for a river to do. It requires no sacrifice or suffering.

The only way it can go wrong is if something interferes with the river’s “integrity”—that’s a hydrology term for when the river has the right channel dimensions to “carry its burden.” That’s also a hydrology term albeit a little dark sounding. It just means that the river can carry its sediment load—the bits and pieces of the world that the river has encountered in its journey. Some of those it has picked up, some were dumped into it. Either way, it carries these experiences, shapes them, sets them down, maybe picks them up later, and in this way builds itself to be exactly as is best for it and the world around it.

What interferes with a river’s ability to be itself?

• Dams or diversions that block or change the amount of its flow. The river feels weak or completely stuck.
• Anything that weakens a river’s boundaries whether that’s building on the banks, trampling down the bank, erasing bank vegetation so the soil erodes, digging down into the riverbed, dumping extra material onto the riverbed, or changing the slope in any way. This causes the river to eat away at its edges. And then it can’t do its life’s work. It feels both ragged and clogged.
• And most of all: disconnecting a river from its floodplain. Berms of all kinds are the worst offenders. We want to live on a floodplain, but trying to make it safe enough to live on is dangerous for the river and for us. The river eats away at its internal boundaries—down into its very foundation. It isolates more and more. The active erosion may be largely out of sight, but you can see the neighbors suffering too because now the river isn’t creating something beautiful out in the world. It can’t. It’s lost its safety and its ability to contribute

So here’s the takeaway.

• Rivers are the most supportive and therefore, you could say, caring thing on our planet, right there alongside the atmosphere in terms of its care for others.
• If you want to care like a river, you must tend to your own flow and your personal boundaries. And you must spill out of yourself regularly. It’s a vulnerable state. It not only builds the world around you but also relies on that world to absorb you when you’re extra, to give you space to spread out and slow down and drop your load. It’s a win-win. Truly a reciprocal relationship.

You can’t care like a river and be isolated. Neither can you let your boundaries be impinged on at all. Not even a little. But don’t worry. It’s not selfish because, don’t forget, those boundaries, those riverbanks, are the thing that you can’t tear your eyes from when you’re up in that airplane with that bird’s-eye view. They are gorgeous and life giving to everyone, including to you.