Hey All,
I've been away for some time, as we've been working really hard on something quite exciting:
let me present to you the world's first ever global ocean drainage basin map that shows all permanent and temporary water flows on the planet.
This is quite big news, as far as I know this has never been done before. There are hundreds of hours of work in it (with the data + manual work as well) and it's quite a relief that they are all finished now.
But what is an ocean drainage basin map, I hear most of you asking? A couple of years ago I tried to find a map that shows which ocean does each of the world's rivers end up in. I was a bit surprised to see there is no map like that, so I just decided I'll make it myself - as usual :) Well, after realizing all the technical difficulties, I wasn't so surprised any more that it didn't exist. So yeah, it was quite a challenge but I am very happy with the result.
In addition to the global map I've created a set of 43 maps for different countries, states and continents, four versions for each: maps with white and black background, and a version for both with coloured oceans (aka polygons). Here's the global map with polygons:
I know from experience that maps can be great conversation starters, and I aim to make maps that are visually striking and can effectively deliver a message. With these ocean drainage basin maps the most important part was to make them easily understandable, so after you have seen one, the others all become effortless to interpret as well. Let me know how I did, I really appreciate any and all kinds of feedback.
Here are a few more from the set, I hope you too learn something new from them. I certainly did, and I am a geographer.
The greatest surprise with Europe is that its biggest river is all grey, as the Volga flows into the Caspian sea, therefore its basin counts as endorheic.
An endorheic basin is one which never reaches the ocean, mostly because it dries out in desert areas or ends up in lakes with no outflow. The biggest endorheic basin is the Caspian’s, but the area of the Great Basin in the US is also a good example of endorheic basins.
I love how the green of the Atlantic Ocean tangles together in the middle.
No, the dividing line is not at Cape Town, unfortunately.
I know these two colours weren’t the best choice for colourblind people and I sincerely apologize for that. I’ve been planning to make colourblind-friendly versions of my maps for ages now – still not sure when I get there, but I want you to know that it’s just moved up on my todo-list. A lot further up.
Minnesota is quite crazy with all that blue, right? Some other US states that are equally mind-blowing: North Dakota, New Mexico, Colorado, Wyoming. You can check them all out here.
Yes, most of the Peruvian waters drain into the Atlantic Ocean. Here are the maps of Peru, if you want to take a closer look.
Asia is amazingly colourful with lots of endorheic basins in the middle areas: deserts, the Himalayas and the Caspian sea are to blame. Also note how the Indonesian islands of Java and Sumatra are divided.
I mentioned earlier that I also made white versions of all maps. Here’s Australia with its vast deserts. If you're wondering about the weird lines in the middle: that’s the Simpson desert with its famous parallel sand dunes.
North America with white background and colourful oceans looks pretty neat, I think.
Finally, I made the drainage basin maps of the individual oceans: The Atlantic, the Arctic, the Indian and the Pacific. The Arctic is my favourite one.
I really hope you like my new maps, and that they will become as popular as my river basin maps. Those have already helped dozens of environmental NGOs to illustrate their important messages all around the world. It would be nice if these maps too could find their purpose.
...Huh.
I have always thought of Arctic and Atlantic as "the cold oceans" and Pacific and Indian as "the warm oceans" (probably the Northern hemisphere bias, Everyone Knows South Is Warm). It's kinda weird to see this division map onto the "cold" two having much larger drainage basins. I mean, map projections can lie, so - is that right? Blue and green seem to penetrate a lot deeper into land than yellow and pink?
It sure looks like they do, and the dividing lines seem to be large mountain ranges (particularly the Rockies/Andes in the Americas, although I also notice the Himalayans between India+Tibet and China).
The watershed divide in the Americas is related to the plate tectonics and mountain ages. The Rockies and Andes are new, as massive mountain ranges go. They haven't been eroded much compared to the Appalachians. They formed near the west coast as oceanic plates moved toward and then under the American continents, forcing continental plates up into big mountains. East of them, it's all downhill until you hit the Atlantic (or an endoheic basin).
The Arctic and Atlantic oceans are half on the North American Plate and half on the Eurasian Plate. Those plates are moving away from each other, which doesn't make crumple zones like the Rockies or Andes. Without new big mountains, water can go from deep inland toward those coasts.
Presumably the Indian plate smushing into the Eurasian Plate and forming the Himalayas is why India mostly drains into the Indian Ocean. I'm not sure why the Indian ocean's watershed doesn't extend further inland in Africa, though. The Nubian Plate and Somali Plate are moving away from each other (the East African Rift), with the wacky Victoria microplate trying to spin around. I can't tell if the mountains that divide the oceanic basins are preexisting or a result of the rift.