Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[CarbonNitride]

I have a reservoir I want to fill that's 3z levels underneath a river. the cistern is connected by a 3 wide hallway, simply letting the water flow through the hallway and fill the reservoir is too slow. Anyone have any ideas how I can speed this up?

[NecroRebel]

It's probably too late now, but you'd have had better results from a 1-wide hall than a 3-wide. A 1-wide hallway lets you take advantage of water pressure more efficiently and causes less loss due to evaporation. Damming the river so all the water goes downwards might help somewhat, however.

[randyshipp]

My plan (perhaps different than the OP) is to build a windmill-powered screw pump at the edge of the river which will dump into a drain that will lead, via a 1-tile wide passageway, to my reservoir a few z-levels below.  There is a hallway through which the cistern's original builders got in.  My plan is to floodgate that off and install a pressure plate on the cistern side of the floodgate, set to trip at 6/7 water.  This will be attached to the gears connecting the windmill to the pump.  So, is this plan going to work (without somehow flooding my fort through the well shaft above the cistern)?  I envision that the pump will start and water will be pumped down the corridor until both the cistern and the fairly long aqueduct are 6/7 deep, at which point it'll shut off until well-drinkers and evaporation bring it back below 6/7, then it'll briefly start up again, kind of intermittently topping off the cistern.

Am I missing any aspects of dwarven engineering or DF pressure-physics that will be a problem?  Thanks in advance.

[Girlinhat]

The dam probably won't matter a whole lot, but a narrow hallway would.  Still, ultimately, you're restricted by the amount of water flowing through the river, and if you've diverted the entire river into this pit, there's no way to increase the flow.  Water only arrives at the river's mouth at a certain rate.

That pressure plate setup should work as well.  For extra security, use a pressure-nullifying diagonal path.  When water or magma moves straight, it builds pressure.  When it has to pass through a diagonal slit, it has no pressure.  Thus, if your well hole is surrounded by diagonals, it won't pressure through.  Note though, you either need these diagonals to reach the floor of the cistern, or create a floor for them.  If you leave the bottom open, pressure will shoot up that direction.

[randyshipp]

Just to be certain (I LIKE this fort and want to delay the worst best of the FUN until I've got a handle on some of these sorts of issues) here are some screenshots of my planned cistern-filler:

OK, right at the bend in the River Wall (funny story that...did you know that Trolls can walk across frozen rivers and into your fort if you don't have a River Wall?) you can see a dwarf next to the channeled out drain for the river pump, and the blue "open space" tile.  The two squares south of that hole will, once the wall section is demolished, house the pump, pumping from the south:

Spoiler (click to show/hide)

Here's the level below, where you can see some construction going on around the spot where the drain goes through the clay of the riverbed.  To the northwest, you can also see the Well Room, which is now located underground after I realized they don't work in winter if they're above ground (&*^@*&^$*^!!!):

Spoiler (click to show/hide)

Finally, here's the level below that, where the TOP level of my 2 z-level cistern is.  You can see the original construction tunnel to the SE of the cistern, with two floodgates and the pressure plate between them (the inside floodgate was the original one and will just be left open):

Spoiler (click to show/hide)

So, this should cut off the flow of water BEFORE it has a chance to pump up through the wellbore, right?

Thanks for the help and for putting up with my paranoia!

[wuphonsreach]

The goal with a cistern is to fill it once, then you generally never need to fill it again.

On the top Z-level of the cistern, you absolutely have to have a diagonal pressure regulator somewhere in the system.  Usually right before the pipe drains into the cistern.  This will ensure that the water, as it enters the cistern, becomes depressurized and will never rise above that Z-level.  So if Z120 is the top level of the cistern, the empty hole for the bucket is Z121, and the actual well room goes up on Z122. 

The cistern should be 1-3Z deep (I generally go with 3Z deep) and filled enough so that the top Z-level of the cistern is in the 3/7 to 5/7 range.  You don't want it filled to the brim as 7/7 water + fortifications = easy passage.

Which means you need a floodgate on the intake, or you need to fill the cistern using a screw pump.  Some way of stopping the water from flowing in from the source. Personally, I prefer the screw pump method now for a variety of reasons:

- Manually operated screw pumps work fine for filling cisterns.  It's a small risk window.
- If you have flooding, just stop pumping.
- If the pump gets destroyed, nothing gets flooded.
- The output from the pump can be put through 2-3 fortification tiles before going down into the cistern tunnel.  If a building destroyer destroys the pump, the excess water in the fortification tiles will backwash, exposing the fortification tiles and preventing passage.
- Lastly: because screw pumps are water multipliers.  If you use a screw pump to drain a small-medium muddy pool, you will find that you get a lot more water out of the pool to fill your cistern.  Which means you will not have to completely drain a 10-tile muddy pool in order to fill a 10-tile cistern.  Instead, you will probably only take the water level down to 2/7 or 3/7.

[randyshipp]

Can you help me understand the sequence of events that might lead the setup (as I described it) to flood upward through the wellbore?  I'm not doubting, I just know that DF physics != real physics (and I know I have a lot to learn about dwarven engineering) so I want to learn from this practical example.

[Girlinhat]

Basic water pressure:
Water at rest will expand horizontally if able, turning a 7/7 into 3/7 and 4/7 in adjacent tiles, until it reaches equilibrium.
Water above any square of water will path towards the next available open square below itself.  This teleports a square of water from the top of a cistern to an opened doorway instantly, and simulates pressure because all the water will quickly attempt to teleport to the new opening.
Diagonal movement is restricted to normal spreading habits, and water will not teleport to a diagonal square.

Thus:

Code: [Select]

#WWW#
#WWW#  #
#WWW#  #
#WWW   #will become

Code: [Select]

#www#
#WWW#W#
#WWW#W#
#WWWWW#due to pressure pushing the upper most level to the next available square below itself.  This does not mean a direct down path, it means any Z level below the one it currently occupies.

Also note, due to the way teleporting does not push or influence any items along the way, a highly-pressurized reservoir, when released, can leave something directly at the opening relatively untouched.  Because of this, if you neutralize pressure using a diagonal, you can be more certain of pushing things, and also conserve some water as the flow will be slower and thus get more bang for the buck.

Magma will not pressurize normally, and will never path upwards of its current position.  It doesn't teleport below itself.  However, a screw pump breaks this rule, by putting a square of water/magma into the next available position it can path to, same as pressure in water.  Thus, you CAN pressurize magma using screw pumps, and can cause artificial volcanoes, as long as your magma reservoir is above the intended volcano point.