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[spelley]

Hey all. I am currently attempting to plan out a cistern/reservoir from a Brook for wells and various traps. I'm fairly new to DF and have never actually built a proper reservoir before and just have a couple of questions, mostly around security. This fortress is in a biome that freezes in Winter.

1) I've heard that creatures can pass through fortifications if the water is at 7/7. Is there an alternative that is Building Destroyer-proof while the Cistern is actively filling?
2) I've also heard that Flood Gates have a tendency to get "clogged" and not operate properly. Is there a way I can use Bridges instead? My plan is basically this:
~ = Water
| - = Walls
c = Channels
B = Bridge
P = Pressure Plate
             BBB
~~~~~~BBB~~ ->
~~~~~~BBB~~ ->
~~~~~~BBB~~ ->
      |ccc|-     
      |BBBB|
-----|BBBB|--
|ccccccccccc|
|ccccccccccc|
|ccccccccccP|
---------------

The plan is basically to have 2 sets of bridges, linked up to a pressure plate. When the water level goes below a certain level, it will trigger the pressure plate which will lower the bridge in the brook to the South (blocking the flow of water) and raise the bridge in the Cistern's path to the East, uncovering the path into the reservoir. The pressure plate will also have a kill switch lever somewhere. Would this work at all? Am I missing something?

3) Lastly, can I build walls over Brooks? (just thinking of this now while at work so can't just test it) I'd like to cover up all my Bridges and whatnot and put roofs on everything so I don't have to worry about anything getting into my water supply.

Thanks everyone and sorry if this is described somewhere else.

[Fleeting Frames]

Filling up through a grate could work, so long as building destroyer doesn't have path to the grate. (Absolutely guaranteed if you have the water go through 2 sequential grates.)

I theorize that perhaps a statue flanked by fortifications might work as well, but have not tested this.

However, note that Brook's cyan surface acts as floor and spawns only vermin fish inside it - while I wouldn't claim the impossibility of an aquatic titan spawning in eight in 768 chance, I've yet to see any actual creatures inside one. (So yes, you can build walls over them.)

If you're on a map where cave-ins don't transform, you could also cave in the brook surface to desired point instead of using a grate.

And yeah, the two-stage filling with bridges (either raising to block sideways flow or retracting to block up or down flow) could work as well if for some reason you can't use grates.

There are some advantages to using floodgates over raising bridges, though:

1. A floodgate will not kill/destroy whatever less than enormous creature is caught in it.
2. A floodgate that failed to close at desired time due obstruction will automatically close once obstruction is removed. (Though note that if the signal is sent too soon after last toggle, the floodgate will ignore it.)
3. Every time a bridge toggles, it causes the map to stutter, even if it has literally 0 effect on the pathing of anything.
4. Raising bridge will let water through when "closed", floodgate when opened.
5. A floodgate can be destroyed by building destroyer - thus releasing water or magma to trap or drown or burn them.

But yeah, there are in-depth wiki articles on well & cistern design as well as bridges, floodgates, brooks. Though they don't contain quite all of the above :p

[spelley]

Thanks for the reply!

So what I'm gathering is that yes, my design above could work, but due to the fact that a Building Destroyer is...very unlikely (might be technically impossible without a bug?) to spawn in a brook (and can't get IN the brook unless I dig into the surface and leave that hole accessible), I likely can just stick with the same design, just with Flood Grates and walling them up on the surface of the brook and an underground maintenance tunnel perhaps "just in case" to protect from surface-dwelling Building Destroyers.

[Fleeting Frames]

I don't understand your schematics, sadly. Are they supposed to be zx levels or xy levels?

Flood Grates → Floor Grates*. Buildings can't be destroyed from underneath so long as they can't be pathed to, this is just an alternative BD-safe possibility.

Or if you mean Flood Grates → Flood gates, sure yeah - it's just that you're not likely to have any danger come from there....Other than flooding your fortress if you do it wrong, I guess.

I'm not sure why you would need to wall them up on the surface. In a flowing brook your water isn't going to flow higher than 1z below the brook if you go through an u-bend and rivers don't flood over. 

[Montieth]

Build your underground channel from the water source to a pool that's 1 Z level lower but with a pressure relief diagonal. Then add a pump house above it with manually pumped pump. The Pump pulls from the dirty cistern through a grate. Critters and Building Destroyers can't get up through grates. Pumps CAN pull through the grate. The pump then feeds your fresh water cistern that's inside the fort. Add a set of gates on both sides for closing things off for added security and peace of mind.

[Skorpion]

I'd suggest filling your cistern with screw pumps hauling the water up through a floor grate. You can pave over the river to have an unpathable grate in the middle for maximum flow, too.

I'm a serial abuser of masonry with my forts. It's indestructible, it gives dorfs work to do, AND it uses up the shittons of stone my mining generates.
Even when turned into blocks it's great; blocks are lighter, the masonry's more valuable, AND the heavy work gets done nice and safe underground AND trains Masonry skill.

[Daris]

What I do is dig my reservoir (2-z deep) and a 2-wide path to the river/brook, without connecting it in any way to my fortress.  Since my reservoirs are always multiple z belowground, I put one raising bridge at the top of the path and one at the bottom.  Then fill the cistern to ~5/6 on the top cistern level, close both bridges, and only then channel a hole for the well.

Wells don't use water at a high rate.  When it's time to re-fill, it's sufficient to use the bridges as a water lock - open the top one until the space between is filled with water, then close the upper and open the lower to allow that water into the cistern.  At no point does any critter have an unobstructed path into the fortress, and it's low-tech.

You can build walls and floors over a brook, but doing so destroys the brook's surface which is generally undesirable to me.  Brooks are good fishing spots with no danger of the fisherdwarf falling into the water.  I do build over brooks but only to the extent it's unavoidable for courtyard security.

[Dunamisdeos]

Spoiler: I made a help (click to show/hide)

Here is all of the security you need. I highly recommend putting drains at all walkable parts just in case you need to remove something, but its not "necessary".

Nothing can break grates from below and water can move through them. Therefore nothing from your water source (river, caverns....) can get into your fort through the water system. You can even set grates to retract via lever at need.

[spelley]

I actually really like this one Dunamisdeos! If I want to zero-out the pressure, I just need to have diagonal wall constructions/unmined blocks somewhere after the last bridge correct as per the Pressure article in the Wiki? The only other dangerous part is digging under the water supply in a safe way, but if I build this in winter when the water is frozen, that shouldn't be an issue I'm guessing

[Montieth]

I actually really like this one Dunamisdeos! If I want to zero-out the pressure, I just need to have diagonal wall constructions/unmined blocks somewhere after the last bridge correct as per the Pressure article in the Wiki? The only other dangerous part is digging under the water supply in a safe way, but if I build this in winter when the water is frozen, that shouldn't be an issue I'm guessing

I prefer to NOT rely upon the frozen water source to prevent things being an issue. I generally dig up under the water source and don't breach the ceiling until everything is set. If I do have an ability to dig out the hole from above and it's frozen. I'll do so quickly and add a grate in the drain. This prevents useful things like wood getting sucked down the drain into the fetid cistern.

[Dunamisdeos]

I actually really like this one Dunamisdeos! If I want to zero-out the pressure, I just need to have diagonal wall constructions/unmined blocks somewhere after the last bridge correct as per the Pressure article in the Wiki? The only other dangerous part is digging under the water supply in a safe way, but if I build this in winter when the water is frozen, that shouldn't be an issue I'm guessing

That is exactly true. I generally have wells and such along the side of the pipe with diagonal blocks to let the water in. You can block off those with bridges, too.

Now, it depends on the water source, but I usually pierce it from ABOVE if possible to avoid drowning. The trick is to tunnel right up to the side of the water source, then use channeling to connect it to the pipeline. You can use the same great grate (tee hee) tactic to make it safe.

Spoiler: Image made (click to show/hide)

Also, feel free to use stairs underneath those grates. Makes it easier to get up in those places if a vampire dies in your water supply.

Now, if you are, for instance, piercing an aquifer from below (or any other situation in which water will fill the space you arer mining from), I usually do so from a large room. If you create a space that is say, 10x10 and pierce it in one spot on the far end from your pipeline, it cannot fill the room fast enough to drown your dwarves, and they can escape before the water enters the pipe/reservoir.

[spelley]

I greatly appreciate the diagrams, it makes a lot of sense and now I'm going to work on my self-filling, multi-stage reservoir!

But I mostly appreciate the "a tree" label.

[Dunamisdeos]

Well, it could have been a green cloud. That would have just been confusing.