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Comment by marginalia_nu | Hacker News Reader

Surely there is more farm land away from the sea than adjacent to it. How does for example fertilizer from here[1] or here[2] end up at sea?

[1] https://goo.gl/maps/Pm4JGesJZ9xELrBB8 [2] https://goo.gl/maps/rzGttw1gMchSWXREA

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For the US, there's a nice app where you can follow the watershed path: https://river-runner.samlearner.com/

Edit, direct link to the pinpoint: https://river-runner.samlearner.com/?lng=-98.92662834458773&...

[1] - down the Arkansas river to the Mississippi, and right out to sea.

[2] - down the Danube, and right out to sea.

That still dozens, if not hundreds of kilometers the fertilizer somehow needs to walk.

It doesn't walk, it flows - sometimes above ground, sometimes under - to the nearest tiny gully, creek, stream, spring, etc., with very few exceptions.

The network for the USA: https://i.dailymail.co.uk/i/pix/2016/10/21/16/3995911F000005...

It's water soluble.

Sure, but why is it pulled sideways and not down, and why does it move toward the river of all directions it could move?

For exactly the same reason the river exists in the first place. Why does the water flow to the ocean and not just sink into the ground?

A lot of it does sink into the ground though. Thats how aquifiers replenish.

I think the percentage of fertilizer in the groundwater would reach an equilibrium where just as much is going out as is coming in.

Water from shallow aquifers also flows into nearby rivers.

Some water is pulled down (along with the half of the fertilizer that's actually used), the rest is literally washed away because the soil can't absorb the amount of water being dropped on it. All the water that's flowing over the ground ends up in rivers (it's the reason they exist in the first place).

Some of it does I am sure, where some will be consumed by soil bacteria. Lots of fertilizers are salts as well and even if it goes into the soil, rain will redissolve it where it will eventually make its way to rivers.

It's 14km (8.8mi) from your pinpoint to the Arkansas, from there it's about as straight of a shot toward the gulf of mexico as you can get (via the Mississippi).

There's very few places where water does not eventually end up in the sea.

Though if it seeps into the groundwater it may take a geological amount of time.

The Mississippi and Rhine Rivers

Might be the Danube and not the Rhine in the second example. (Not that it matters.)

Probably right, good call

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