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My favorite fact about raindrop paths/watersheds is that they determine most of the political boundary between Argentina and Chile. If the rain at a point ultim

My favorite fact about raindrop paths/watersheds is that they determine most of the political boundary between Argentina and Chile. If the rain at a point ultimately flows to the Pacific Ocean, that point is in Chile; if it flows to the Atlantic Ocean, it is in Argentina. This is article 1 of the original boundary treaty [0] from the 19th century. The treaty was made before the Andes were fully explored, and so it doesn't handle some interesting edges cases like the Southern Patagonian Ice Field. The field has the property that when rain falls there, it freezes and goes nowhere! [0] https://en.wikipedia.org/wiki/Boundary_Treaty_of_1881_between_Chile_and_Argentina https://en.wikipedia.org/wiki/Boundary_Treaty_of_1881_betwee... [1] https://en.wikipedia.org/wiki/Southern_Patagonian_Ice_Field https://en.wikipedia.org/wiki/Southern_Patagonian_Ice_Field

dredmorbius 2y ago
Watersheds and rivers are often key determinants of pre-industrial borders, if only because they served (variously) as obstacles (wide, fast rivers) and facilitators (narrow / slow) to navigation. Until the development of steam-driven railroads and internal-combustion-driven vehicles, if you wanted to move any considerable quantity of goods or people, your best option was a ship over either a (reasonably) calm sea, or inland rivers, lakes, and canals. Ice ran a close second, and ice roads remain vital transport routes in Siberia and Alaska. Where run over rivers and lakes, those tend to be (near) level terrain, and frictional losses are minimised. China built over 1,000 km of canals 1,000 to 2,000 years ago. Inland travel within England and Great Britain was revolutionised by the development of canals. The US opened up its interior with the Erie Canal, on which a single mule could haul an 80-foot barge laden with 40 tonnes of goods or people. Not only was the travel efficient (in terms of motive power and drovers) but it was comfortable. A four-foot-deep ditch (the Erie Canal) was immune to the rutting and mud of a road, and though the speed of travel was low, in a matter of a few days people could travel in great comfort across New York from the Hudson to Lake Erie and from there to points inland via the Great Lakes, Chicago, and Mississippi / Missouri / Ohio / Red, and other, rivers. I'd realised the political boundaries aspect looking at a map of European watersheds created by Robert Szucs: <https://www.seattlepi.com/local/science/article/Viral-maps-show-all-U-S-Europe-river-basins-in-10159099.php https://www.seattlepi.com/local/science/article/Viral-maps-s...> (Europe is in the carousel at the top, third image, isolated here: <https://s.hdnux.com/photos/54/21/22/11605137/3/960x0.webp https://s.hdnux.com/photos/54/21/22/11605137/3/960x0.webp>) It's not that national borders are specifically identified as watersheds, but in large part you can patch together current state boundaries out of watersheds and rivers, or find internal divisions (e.g., UK counties, German states, French provinces) out of watersheds. In regions in which borders were more arbitrarily assigned, as with the inland US, Middle East (o hai Sykes-Picot), and Africa, the artificiality of imposed borders is highly evident, though regional affiliations become clearer. South American countries are, as you note, more closely aligned with watersheds. It's also more evident why the north-eastern region of South America is so politically divided: it's largely composed of non-contiguous watersheds which have become their own polities. <https://s.hdnux.com/photos/54/21/22/11605136/4/960x0.webp https://s.hdnux.com/photos/54/21/22/11605136/4/960x0.webp>
- thaumasiotes 2y ago
  > obstacles (wide, fast rivers) and facilitators (narrow / slow) to navigation Wide rivers are slow. Narrow rivers are fast. That is the nature of fluid dynamics. Wide rivers are obstacles to movement on the land and facilitators of movement on the water; narrow rivers are worse at both of those things.
  - dredmorbius 2y ago
    I could have been clearer that both descriptions were meant to be or statements. Fast rivers or wide rivers are challenging, the former as they're inherently treacherous, the latter as they're difficult to bridge. Narrow rivers can be bridged. Slow rivers can be traversed by boats, ships, barges, etc. Yes, wide rivers tend to be slow, and narrow rivers tend to be fast, all else constant, but all else is rarely constant such that there are narrow slow rivers and wide fast / treacherous ones.
jmilloy 2y ago
I think borders based on watersheds make so much more sense than those on rivers, both of which are common.
- NegativeLatency 2y ago
  Either seem better than arbitrary lines
  - deleted 2y ago
    [deleted]
- emmelaich 2y ago
  Harder to find though.
  - londons_explore 2y ago
    The big bit of a river is easy to find, sure. But up near the source where it splits into thousands of small tributaries which move and change a lot? That's a recipe for boundary disputes. Whereas a watershed rarely changes far, even on geological timescales.
jajko 2y ago
Even glaciers flow, otherwise they would over time become as thick as cloud layer that provides that rain drop or snow flake. Its just that speed of flow is... glacial. 1 year on glacier, once snow is compressed into ice which takes few years, is represented by maybe 1-2m layer in European Alps. Thats why glaciers have crevasses - they bend as valleys flow (or over some hard bottom bumps that weren't grinded flat yet), and it cracks at those bends. Just like say chocolate on surface of cold Snickers bar if you try same bending
brazzy 2y ago
And there was a man named Francisco Moreno who explored the area and was able to use his knowledge to resolve border disputes about some of those edge cases in favor of Argentina, making him something of a national hero. Argentina's most famous glacier is named after him: https://en.wikipedia.org/wiki/Perito_Moreno_Glacier https://en.wikipedia.org/wiki/Perito_Moreno_Glacier
gus_massa 2y ago
It was later amended to consider the top of the mountains that define the watersheds. Watersheds are difficult to determine and may change from time to time. Mountaintops are easier to determine and more permanent.
deleted 2y ago
[deleted]

dredmorbius 2y ago

Watersheds and rivers are often key determinants of pre-industrial borders, if only because they served (variously) as obstacles (wide, fast rivers) and facilitators (narrow / slow) to navigation. Until the development of steam-driven railroads and internal-combustion-driven vehicles, if you wanted to move any considerable quantity of goods or people, your best option was a ship over either a (reasonably) calm sea, or inland rivers, lakes, and canals. Ice ran a close second, and ice roads remain vital transport routes in Siberia and Alaska. Where run over rivers and lakes, those tend to be (near) level terrain, and frictional losses are minimised. China built over 1,000 km of canals 1,000 to 2,000 years ago. Inland travel within England and Great Britain was revolutionised by the development of canals. The US opened up its interior with the Erie Canal, on which a single mule could haul an 80-foot barge laden with 40 tonnes of goods or people. Not only was the travel efficient (in terms of motive power and drovers) but it was comfortable. A four-foot-deep ditch (the Erie Canal) was immune to the rutting and mud of a road, and though the speed of travel was low, in a matter of a few days people could travel in great comfort across New York from the Hudson to Lake Erie and from there to points inland via the Great Lakes, Chicago, and Mississippi / Missouri / Ohio / Red, and other, rivers. I'd realised the political boundaries aspect looking at a map of European watersheds created by Robert Szucs: <https://www.seattlepi.com/local/science/article/Viral-maps-show-all-U-S-Europe-river-basins-in-10159099.php https://www.seattlepi.com/local/science/article/Viral-maps-s...> (Europe is in the carousel at the top, third image, isolated here: <https://s.hdnux.com/photos/54/21/22/11605137/3/960x0.webp https://s.hdnux.com/photos/54/21/22/11605137/3/960x0.webp>) It's not that national borders are specifically identified as watersheds, but in large part you can patch together current state boundaries out of watersheds and rivers, or find internal divisions (e.g., UK counties, German states, French provinces) out of watersheds. In regions in which borders were more arbitrarily assigned, as with the inland US, Middle East (o hai Sykes-Picot), and Africa, the artificiality of imposed borders is highly evident, though regional affiliations become clearer. South American countries are, as you note, more closely aligned with watersheds. It's also more evident why the north-eastern region of South America is so politically divided: it's largely composed of non-contiguous watersheds which have become their own polities. <https://s.hdnux.com/photos/54/21/22/11605136/4/960x0.webp https://s.hdnux.com/photos/54/21/22/11605136/4/960x0.webp>

thaumasiotes 2y ago
> obstacles (wide, fast rivers) and facilitators (narrow / slow) to navigation Wide rivers are slow. Narrow rivers are fast. That is the nature of fluid dynamics. Wide rivers are obstacles to movement on the land and facilitators of movement on the water; narrow rivers are worse at both of those things.
- dredmorbius 2y ago
  I could have been clearer that both descriptions were meant to be or statements. Fast rivers or wide rivers are challenging, the former as they're inherently treacherous, the latter as they're difficult to bridge. Narrow rivers can be bridged. Slow rivers can be traversed by boats, ships, barges, etc. Yes, wide rivers tend to be slow, and narrow rivers tend to be fast, all else constant, but all else is rarely constant such that there are narrow slow rivers and wide fast / treacherous ones.

jmilloy 2y ago

I think borders based on watersheds make so much more sense than those on rivers, both of which are common.

NegativeLatency 2y ago
Either seem better than arbitrary lines
- deleted 2y ago
  [deleted]
emmelaich 2y ago
Harder to find though.
- londons_explore 2y ago
  The big bit of a river is easy to find, sure. But up near the source where it splits into thousands of small tributaries which move and change a lot? That's a recipe for boundary disputes. Whereas a watershed rarely changes far, even on geological timescales.

jajko 2y ago

Even glaciers flow, otherwise they would over time become as thick as cloud layer that provides that rain drop or snow flake. Its just that speed of flow is... glacial. 1 year on glacier, once snow is compressed into ice which takes few years, is represented by maybe 1-2m layer in European Alps. Thats why glaciers have crevasses - they bend as valleys flow (or over some hard bottom bumps that weren't grinded flat yet), and it cracks at those bends. Just like say chocolate on surface of cold Snickers bar if you try same bending

brazzy 2y ago

And there was a man named Francisco Moreno who explored the area and was able to use his knowledge to resolve border disputes about some of those edge cases in favor of Argentina, making him something of a national hero. Argentina's most famous glacier is named after him: https://en.wikipedia.org/wiki/Perito_Moreno_Glacier https://en.wikipedia.org/wiki/Perito_Moreno_Glacier

gus_massa 2y ago

It was later amended to consider the top of the mountains that define the watersheds. Watersheds are difficult to determine and may change from time to time. Mountaintops are easier to determine and more permanent.

deleted 2y ago

[deleted]