I'm working on a fantasy setting and I had thought about the possibility of connecting two natural rivers (that flow in different directions, one to the west and one to the east) using an artificial canal. In this way, an attractive space would be created to place cities and turn it into an area of ​​tensions.

Of course, I realize that I have to work on the orography, since I have to justify two contrary flows that, at the same time, allow a channel.

What other details should I take into account for this approach to work?

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    $\begingroup$ Since we haven't a clue about the topo and foliage of that region, why you think it is a good idea to intersect the rivers, who owns them, did you gather surveys from the locals, obtain a permit, took care of the activists and journalists, befriended any rebel or gang to appease the riot(natives), etc , we can't decide for you but only provide some inspirations. $\endgroup$
    – user6760
    Feb 22 at 12:20
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    $\begingroup$ Are you expecting a free-flowing channel between the rivers? Is there an elevation change between the channels? $\endgroup$ Feb 22 at 19:11
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    $\begingroup$ I don't understand what you are asking. Artificial canals of this nature are common, and even natural ones exist. What is the "problem" you are facing? $\endgroup$
    – gerrit
    Feb 23 at 8:00
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    $\begingroup$ this is entirely plausible. Nearby rivers flowing in opposite directions is not common, but does occur (in fact, there are even a few confluences where the tributary joins flowing in the opposite direction to the major river), and canals between nearby rivers aren't remotely unusual. There's no reason the geography necessary for the former should interfere with the latter $\endgroup$
    – Tristan
    Feb 23 at 11:01
  • $\begingroup$ I can understand why you would want tension for your story, but why would one create something that would just cause tensions in real life? $\endgroup$
    – Michael
    Feb 23 at 14:58

7 Answers 7


There is at least one working example of what you have in mind: the canal connecting the Rhine basin with the Danube basin

The Rhine–Main–Danube Canal (German: Rhein-Main-Donau-Kanal; also called Main-Danube Canal, RMD Canal or Europa Canal), is a canal in Bavaria, Germany. Connecting the Main and the Danube rivers across the European Watershed, it runs from Bamberg via Nuremberg to Kelheim. The canal connects the North Sea and Atlantic Ocean to the Black Sea, providing a navigable artery between the Rhine delta (at Rotterdam in the Netherlands), and the Danube Delta in south-eastern Romania and south-western Ukraine (or Constanța, through the Danube–Black Sea Canal). The present canal was completed in 1992 and is 171 kilometres (106 mi) long.

Map of canal in context of rivers

You will need to have a way to pump water in the highest sections of the canal, because, as it happened for the early version of the real case one, it can easily run out of water which, for a waterway, is a curse.

You will also need to pay attention to the environmental consequences

The construction of canals involves ecological dangers. The Main-Danube Canal makes it possible for aquatic animals to spread from Western to Eastern Europe and vice versa. Invasive species often cause adverse impacts in the ecosystem of new habitats: competition with native species, lack of natural predators, introduction of diseases and parasites, etc. However, there is also the possibility that they will naturalize into the new ecosystem and their introduction lead to an enrichment of the resident wildlife.

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    $\begingroup$ also the Volga-Don Canal (previously an important portage): en.wikipedia.org/wiki/Volga%E2%80%93Don_Canal $\endgroup$
    – Tristan
    Feb 23 at 11:03
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    $\begingroup$ There was also this simple connection between the Lake Michigan watershed and the Mississippi watershed. (Shutdown in 1933 and replaced by a more extensive and complex system). $\endgroup$ Feb 23 at 15:21
  • $\begingroup$ You could in theory.. Have a canal from level to level basically a canyon, then acave lake at the mountains.. But it's a reservoir lake from which both rivers feed. $\endgroup$
    – Pica
    Mar 1 at 7:07

The biggest one is the water supply.

Connecting two natural (navigable) rivers is an entirely reasonable thing for a canal to do, and many canals do precisely that.

The problem is the high point in the middle, so unless you're going to pump water, you'll need to find a water supply that can provide water for the locks needed to get over the hump between.

  • $\begingroup$ If the continental divide is made out of granite.... +1 $\endgroup$
    – Mazura
    Feb 23 at 1:52
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    $\begingroup$ @Mazura, there are canals cut through granite in the UK, generally they weren't financially successful because of the sheer time and cost of construction $\endgroup$
    – Separatrix
    Feb 23 at 8:26
  • $\begingroup$ You just need wet enough hills with low enough cols for the canal to pass through. Then you can have pounds/reservoirs fed by the higher ground. I've mentioned a couple of examples near me in my answer, but another is the Leeds and Liverpool which crosses the Pennines, and is few by them. $\endgroup$
    – Chris H
    Feb 23 at 17:01

For a possible site of another such link, see the Traverse Gap. This would link the Mississippi to the Red River, which eventually flows into Hudson's Bay. This was an entry in XKCD's Dubious Islands cartoon.


Another example of a canal between two different rivers:

The Casiquiare river (Spanish pronunciation: [kasiˈkjaɾe]) is a distributary of the upper Orinoco flowing southward into the Rio Negro, in Venezuela, South America. As such, it forms a unique natural canal between the Orinoco and Amazon river systems. It is the world's largest river of the kind that links two major river systems, a so-called bifurcation. The area forms a water divide, more dramatically at regional flood stage.


So this is an example of a natural river or canal connecting two different river basins. If there can be natural connections between two different river drainage basin there can be artificial ones - man made canals.

I can imagine a landscape where two rivers run. One runs from north to south, and one from south to north, and they almost meet. But there is a region of higher land running east to west between them.

So both rivers turn toward the east when they come to the higher lands and run to the east parallel to each other. Many streams from the higher ground flow down to the northern river and the southern river. After a distance the arrangement of higher and lower ground cases both to turn away, the northern river turning back to the north and the southern river turning back to the south, and they reach the sea shore very far from each other.

But the higher ground running east-west between the two rivers is not highest at its center. Instead it is more like a double ridge with lower ground in between the higher ground to north and south. And of course there are streams and lakes between the two higher parallel ridges.

And there is a place where the main watercourse in the valley has in the past eroded the northern ridge to flow north into the northern river, but the land has risen a little to block that gap. And the same thing also happened to the southern ridge near there once, but that gap is also now blocked by risen land. So the central river now continues to flow on for some distance.

And people come and see those two low parts of the parallel ridges, and dam the central river to make a lake where the water level will rise. And they dig out in the two former gaps that the central river once flowed through digging canals leading toward from where the lake will rise to the northern river and the southern river.

And eventually the man-made lake will overflow into the two canals leading to the northern river and the southern river, creating a watercourse between the northern river which turns north and flows north for a long distance and the southern river that turns south and flows south for a long distance.

And maybe the difference in water levels is not too great and maybe the flow from the man-made lake will be slow and gentle enough that boats will be able to row or sail up it easily and won't have to be towed. Or maybe it will be steeper and boats will have to be towed up stream to the lake before being carried downstream by the flow to the other river. And maybe the flow of water will be so steep and fast that locks will be needed to raise and lower boats on journey from one river to another one.

Maybe the canals will be so narrow and shallow that only tiny river barges can use them, or maybe the canals will be so wide and deep that seagoing ships will be able to use them.

And of course the directions of the rivers can be rotated to fit in with any already established geography.

And it is possible that some writers might describe the geography only briefly, while other might go into great detail and think of several different stories which can be told where details of the canal operation are the basis of the stories.


It's quite common - even my closest canal, the Kennet and Avon does this. It links the Bristol Channel (river Severn) to London and the south east coast of the UK. The Avon is fed by the Cotswold range of hill, and the Kennet drain the Wiltshire downs, but is a tributary of the Thames, which is fed by the Cotswolds. It's worth reading the history of the K&A on Wikipedia, as that shows you how more local improvements led to a case for building the missing link. It also hints at a potential role for canals in times of conflict.

Kennet and Avon canal map

Map from Wikipedia

The Wilts and Berks canal more directly linked the Thames to the Avon, illustrating how both rivers can drain the same hilly area, with the canal using locks to get over low points in the hills (high points in its route). But this canal is no longer continuous.

If you have a look at a topographic map (this one is the area I discuss above) it becomes clearer.

Another example worthy of mention for your setting is the later Caledonian Canal Which crosses Scotland using mainly lochs (lakes) and limited construction. The UK lends itself to systems like you imagine, as it's fairly long and narrow; in many places with only one major unavoidable range of hills on a coast-to-coast route.

One thing you would have to consider is that it takes a significant level of cooperation to build it in the first place.


Welcome to Chicago

The Chicago Sanitary and Ship Canal does what you are asking, to go with the other examples presented here. In particular, it connects the Chicago River to the Des Plaines River, reversing the normal flow in the main stem and south fork of the Chicago River to flow towards the canal instead of into Lake Michigan.


A different thing but the same idea: the Diolkis of Corinth was a road used to carry boats from one side of the Isthmus of Corinth to the other. This had a large city, but Corinth was also built for defence at the narrowest point, which could be handy if you had neighbours like Sparta to the south. I would have thought it was an obvious plot device if I had read this in a fantasy novel, but it was real.


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