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[Raven]

So, quick question. I managed to create a cistern of two Z levels in my fortress, without (hopefully) flood the interior (in my next design i'll add a floodgate for more safety)

basically the design is what follows:

I have my river source on the surface, SEVEN Z levels deep underground i built my reservoir, channeling up the sixth z level (the one above) in order to prevent the water being laced with mud

I prevented the flood by making a diagonal entry for the water flow on the seventh z level, on the reservoir entrance

everything seems workin fine, but I have a doubt: the floor is laced with mud and the above Z level is "open space"

should it be filled with water too? Do i need to have 2 z levels filled with water? (i could do it with some floodgate play but it's risky

Or having a one z level with 7/7 water and one with open space above is enough to prevent contaminated water?

[delphonso]

So the 2 Z-level thing is referencing 2 Z-levels of water. Since you currently have only 1 Z-level of water (plus a z-level of open air) you're not going to get completely clean water on each bucket pull. You should add some extra water to make sure it's clean.

It doesn't need to be a full 7/7, though - you can have the second level at 3/7 or whatever and it should be fine. Be warned, it will go down quicker than you expect. I've found it better to build a pretty deep well (5 Z-levels or so), fill it up, then not worry about refilling for a long time.

[Raven]

So the 2 Z-level thing is referencing 2 Z-levels of water. Since you currently have only 1 Z-level of water (plus a z-level of open air) you're not going to get completely clean water on each bucket pull. You should add some extra water to make sure it's clean.

It doesn't need to be a full 7/7, though - you can have the second level at 3/7 or whatever and it should be fine. Be warned, it will go down quicker than you expect. I've found it better to build a pretty deep well (5 Z-levels or so), fill it up, then not worry about refilling for a long time.

I noticed that I made a small mistake when i planned it because i put a diagonal digging on the second last floor, so the water stopped on the last floor

also, is it true that buckets go between floor grates? I need to build them to prevent swimmers to go into the river, reach the reservoir and invade the fort

what if I put a fortification before a floodgate? will building destroyers be able to pass through the first and smash the second if they can swim?

[delphonso]

Fortifications are safer, however moving water may push enemies and objects through it.

Floodgates and grates can be destroyed by building destroyers. Wells can send buckets down through grates, I believe - been a while... I think drawves can reach through grates to get water from below but only the Z-level directly below, while wells have a 30 Z-level reach or something.

Don't forget draw bridges are an option. A raising bridge will block or allow water at the pull of a lever and are pretty much indestructable (only break if you try to crush megabeasts with them.)

[Raven]

Fortifications are safer, however moving water may push enemies and objects through it.

Floodgates and grates can be destroyed by building destroyers. Wells can send buckets down through grates, I believe - been a while... I think drawves can reach through grates to get water from below but only the Z-level directly below, while wells have a 30 Z-level reach or something.

Don't forget draw bridges are an option. A raising bridge will block or allow water at the pull of a lever and are pretty much indestructable (only break if you try to crush megabeasts with them.)

ooh right, the drawbridge works like a floodgate and it's indestructible

about the floor gate, if the enemy is the z level below it shouldn't be able to go up and break the obstacle if I recall it correctly, it should work like this with floor doors too

[PatrikLundell]

Fully submerged fortifications can be passed without any problem by swimmers (and moving water can push things through partially submerged ones).

If I was to draw water from a river (as opposed to my standard method of using an aquifer), I'd make a "high" cistern at two levels below the river and have two raising bridges at each end of the tunnel feeding it, with that tunnel at the level below the river. I'd operate one drawbridge at a time, so I'd let water into the tunnel, raise the outer bridge, then open the inner one, let it drain, raise the inner one, then open the outer one... repeatedly until the cistern is full. I'd build the "real" well cistern lower than the first one, controlling access with a drawbridge and have a de-pressurizing diagonal at the top level of the well cistern.
I'd normally leave that drawbridge open, with the exception being the top cistern filling period. This means the well cistern will automatically top up from the upper cistern, with the de-pressurizer ensuring it won't overflow (and the drawbridge acting as a fail safe for design errors as well as filling time safety control).
The reason I want two cisterns is because it allows me to keep the well full without having constant access through the water (it's possible to arrange wall grates such that they can't be destroyed by building destroyers, as an alternative, but I wouldn't trust it), and it also provides water during winter, if the surface is freezing. In addition to that, the top cistern filling can be done when that cistern is half empty as a series of filling actions, rather than having to keep a constant eye on the water level in the tunnel.

Flood gates are rather useless, unfortunately, as they can be destroyed by building destroyers and be blocked by an errant sock, while drawbridges don't have that problem. As I see it, they are useful only for flavor or if you deliberately want to design weaknesses into your fortress. There might be some niche where action timing makes a case for the floodgate (bridges act 100 ticks after the trigger, but I don't know if floodgates are immediate or have the same delay).

[A_Curious_Cat]

Flood gates are rather useless, unfortunately, as they can be destroyed by building destroyers and be blocked by an errant sock, while drawbridges don't have that problem. As I see it, they are useful only for flavor or if you deliberately want to design weaknesses into your fortress. There might be some niche where action timing makes a case for the floodgate (bridges act 100 ticks after the trigger, but I don't know if floodgates are immediate or have the same delay).

Floodgates have the same delay as bridges.

[Raven]

thank you everyone

[Raven]

so here's my well area



first z level of the reservoir, notice the double safety, diagonal digging and retract bridge


bottom floor of the reservoir... this should've had a wall to block the excess water, guess what, stupid dorf building the wall on the opposite side of the wall -.-

[Leonidas]

I find that it's much easier and safer to dig out a cistern with U/D staircases, then channel out the columns where the wells will go.

And instead of defending the well from the reservoir, try defending the reservoir from the river. Any time you tap into water or magma, put a blocking bridge at the natural source. That way, it's easy to drain all the pipes and reconfigure your system.

[Raven]

I find that it's much easier and safer to dig out a cistern with U/D staircases, then channel out the columns where the wells will go.

And instead of defending the well from the reservoir, try defending the reservoir from the river. Any time you tap into water or magma, put a blocking bridge at the natural source. That way, it's easy to drain all the pipes and reconfigure your system.

yes following your advice i put two drawbridges, one before the reservoir, controlling the water flux and another at the source near the river (pic not included but you can imagine)