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[Heliomance]

Am I right in thinking that enough pumps will allow you to make a hole in a river long enough to put a wall down and pierce it, digging from above water level into the bedrock underneath? If so, how would I go about doing this, bearing in mind I have no magma, and the prohibition from building from above?

[Diablous]

It is possible, but I am not sure how to do it.

[Dude_Jebawe]

It's possible, just remember to pump the water upriver, and use walls to make sure it doesn't have anywhere to flow except down.

[Derakon]

It's certainly possible. You use a setup something like this:

Code: [Select]

Top-down view
River is flowing right-to-left
..........    .: floor
~~~%%~~~~~    ~: water    =: horizontal axle
~~~%%~~~~~    %: screw-pump pumping to the west
~~~%%WWW~~    W: water wheel    *: gear assembly
....*=*...The screw pumps have to be resting on floors, of course. Once you get them pumping, the spaces behind them should be clear of water, so you can go down (dig a staircase into the side of the river) and construct walls behind them. At that point you can turn the screw pumps off; the water flow will simply stop at the walls and won't overflow.

[Heliomance]

I have a waterfall upstream - that's gonna muck things up somewhat, isn't it?

[Dude_Jebawe]

Strangely, no it won't. At least I don't think it will...

[nenjin]

I think they do generate additional pressure. At least, that's what I've seen when I dug underneath an underground river and tested pressure through a flood lock.

[Rat Of Wisdom]

Well, water attempts to return to its original level, which in the case of a stream with a waterfall is the level of said waterfall. But presuming you pump it out fast enough, this shouldn't be an issue. And I'm pretty sure pumps reset the original level to whatever level the pump is on. Anyone care to confirm?

(Also, this begs the admittedly undwarfy question of why you don't just dig a tunnel underneath the river from the side.)

[Quietust]

If you build a dam below a waterfall, the river will overflow.

[Heliomance]

Well, water attempts to return to its original level, which in the case of a stream with a waterfall is the level of said waterfall. But presuming you pump it out fast enough, this shouldn't be an issue. And I'm pretty sure pumps reset the original level to whatever level the pump is on. Anyone care to confirm?

(Also, this begs the admittedly undwarfy question of why you don't just dig a tunnel underneath the river from the side.)

Aesthetics. I want the only access to my underground mausoleum/necropolis to be through the river.

[Rat Of Wisdom]

Aaaah of course.

Well, incorporating Quietust's input, I suggest you tunnel up to the waterfall, dam it with floodgates upstream, construct your tomb entrance (might I suggest a 3x3 stairwell in the center of your river, simply an up/down staircase surrounded by walls, provided the river is at least 5 tiles wide?), make absolutely sure it's floodproof (might want to extend the tower 1 z-level above the river's surface to be sure, and ensure bridge access) and release the floodgates. Voila, an entrance surrounded by rushing water.

[Neyvn]

Make it more epic by having bridges form walls to the waters edge so that when you activate the bridges they come up, allowing access to the city, but then when you activate it again, they go down once again allowing the water to flow over them making the city completely impenetrable...

Doing this though would be a challenge and a half...

[Rat Of Wisdom]

[awesome bridge idea]
Doing this though would be a challenge and a half...

Not necessarily, I am thinking.

Code: [Select]

AAAAAAAAAAC
B         C
B         C
B         C
B         C
B         C
B         C
B         C
B         C
B         C
BDDDDDDDDDD

A - Raises ^
B - Raises <
C - Raises >
D - Raises V

I guess?

[Shrike]

My suggestion: build a bypass. Dig out an area beside the river to route the water through, with a drawbridge to control the flow at the far end of the river (so you can close it up when necessary.

Build some waterwheels controlling pumps that ONLY dump into the bypass, and floor over the whole area before you start pumping so the water can't fall back in your way.  Then, in the places where the water is pumped out, you can start wall construction once the water level is consistently down (behind the pump line) to about 4.




Alternatively: you mentioned a waterfall. You could dig out areas to the sides of the waterfall, build walkways (bridges or floors) and make a retractable bridge umbrella in the path of the waterfall. You can then get a dry area under the waterfall, and just pump the water downstream to get the water down far enough to start digging and building. and when finished, you can collapse all the waterfall sidewalls or open the bridges or deconstruct everything. This one's probably the easiest option, as it reduces the amount of risk (from attack) that your dwarves risk for this long-term project.

[bmaczero]

The pump method worked fine for me when I needed to carve channels in the riverbed and put mechansim-linked hatches over them:

http://www.mkv25.net/dfma/map-7914-jadedoors

I heard somewhere I'd only need 6 pumps, 3 on each side, to drain a 4-wide river, and while that did mostly keep the water away, I was getting too many "Urist McOblivious cancels Construct Building: Build Site Submerged."