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[denito]

I was going to build a bridge of screw pumps over the top of a river, to try to create an air cavity at the pump intakes that I could build floodgates in.  But what to do with the extra water?  It would come out going downstream but lie on top of the river, and flood the world.  I didn't have an aquifer to dispose of it in.

Then I had an epiphany:  no dummy, don't point the pumps downstream, point the pumps back UPSTREAM!   

I remembered that in the wiki, it says the way a river works is that when the source tiles go below 7/7, it adds more units of water.  So I thought, what if you dumped water on top of the source tiles, so there was always 7/7 water at the source ?

Instead of taking water out of the river and letting it be replaced, take the water from just downstream of the source and recycle it back to the beginning!  It's brilliant!  Screw pumps are so efficient that nearly 100% of the water gets recycled in closed loop, meaning almost no water flows to the rest of the river!

When I thought of this, I couldn't believe it.  Could it really be that easy?  YES!  It can!  Take a look at the video:

http://mkv25.net/dfma/movie-1879-waterdam

For those who don't feel like watching the video, here's a diagram.  A wall of pumps picks up water near the source of a river and dumps the water right on top of the source tiles, so that new water doesn't come in.  Drawbridges to either side keep the water from spilling out:

Code: [Select]

  (map edge)
....||7365||.....
....||7777||.....
....||7777||.....
....||^^^^||.....
....||^^^^||.....
......~~~~.......
......1111.......
......1212.......
......2323.......

|| = drawbridge "wall"
^^ = pump pumping north
~~ = dry riverbed
11 = low water below
77 = water on top
.. = ground


[guale]

I thought of something like this when I was damming a stream for shits and giggles on a map with no magma but it felt like cheating so I went with six pumps putting the water on the bank.

[Quietust]

This is actually the method I regularly use when I need to dam a river - my last 3 forts all used it at some point (2 with brooks, and one with an underground river).

[loser]

This is actually the method I regularly use when I need to dam a river - my last 3 forts all used it at some point (2 with brooks, and one with an underground river).

Like every bit of advice I can recall reading from you, Quietust, Denito's tip must be solid.

How can you make it work with multi-level rivers?

[denito]

This is actually the method I regularly use when I need to dam a river - my last 3 forts all used it at some point (2 with brooks, and one with an underground river).

Like every bit of advice I can recall reading from you, Quietust, Denito's tip must be solid.

How can you make it work with multi-level rivers?

Oh definitely; when Quietust answers a post, you know there will be some solid information in his reply!

As for the multi-level river thing:  You could definitely skim off the topmost level of water with this method, which would allow you to build a floor+wall across the river at the surface level.  So the real question is, what happens when you pump off pressurized water from the bottom which is coming out from under the wall?

I'm not sure whether I think it would work or not.  BUT consider this:  pumps have a wall on the output side and a walkable tile near the input side, so they are themselves much like a floor and a wall.  So in a sense the top level is already sucking water out from underneath a wall; doing the next level would be a repeat of that.  The only question is, does going from 2 deep to 3 deep water represent a significant change in pressure-behavior?  What you would have is something like this:

Code: [Select]

(side view)

36577<-
7777777^<-
7777777777^

3657 = water on top of river
7777 = solid water
<- = pump facing left
^ = water being sucked upwards
I think I can test this in the same fort as I used to demo the 1 Z level version, by channeling out some of the riverbed.

[Thomas Winwood]

Of course, the ultimate test is finding a major river and then damming that using its own water.

[darkflagrance]

Of course, the ultimate test is finding a major river and then damming that using its own water.

The real question is whether or not it works for oceans.

[Qwernt]

Now I wonder, is the water still "moving", IE could you somehow get a waterwheel on there too?

[loser]

Of course, the ultimate test is finding a major river and then damming that using its own water.

The real question is whether or not it works for oceans.

Not only might it work for oceans, but it would also allow you to let the ocean back in around the under water fort you build where the ocean isn't, without any sign of wall or dam.

Let's assume a 3 z-level ocean.

We install the top set of pumps around the edge, just above the top layer of the ocean.  This will keep additional water from the top layer from being added.  Now we just need to get rid of the water in the middle of the top layer.  I've never used an automated bridge to destroy water, but I guess that would work.  Just make a drain from the top layer of the ocean into your water-destroying room or complex.

Once this is done, water in the ocean would only exist at the edges where it is being picked up by the pumps and put back by the pumps.  So, set a little inside these pumps, we build another series of pumps that do the same thing for the next layer down, and drain the middle of the next layer in the same fashion.

Repeat for the third layer.

We build Lab of the Seas or whatever in the middle, then we turn off the third and bottom layer of pumps.  This allows the third and bottom layer of the ocean to refill.  We then take those pumps apart, as well as whatever they're built on.

Repeat for the second and first layers of the ocean.

The only sign of the dike are the partial rings of stones or blocks at the bottom of the ocean.

This is all assuming that the water-generating edges of the ocean do not pressure-flood the middles of the second and third layers of the ocean while the pumps are running.  I'm not sure an ocean would allow this, at all.  But there it is for whatever it's worth.

[Savok]

Sorry, but AFAIK this knowledge has been around forever... well, since right after 3D came out.

*checks wiki*

egads! Nobody edited the wiki to state this! *embarrassed*

[darkflagrance]

Sorry, but AFAIK this knowledge has been around forever... well, since right after 3D came out.

*checks wiki*

egads! Nobody edited the wiki to state this! *embarrassed*

Yes, theoretically it's the same principle as pumping back into the aquifer, but it's just counterintuitive enough, combined with the alternative suggested by everyone else and the wiki, that prevent it from being more commonly passed around.

It's like Brunelleschi (or was it Columbus?) and the egg that could stand on its narrow end without any supports.

[qoonpooka]

Why the windmills?  If you want to get REALLY dwarfy you should use water wheels upstream of the whole affair and let the water flowing in power the pumps that stop it from flowing, etc, etc.