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[Shurhaian]

I've figured that one of the big reasons why so many people are reporting that fishing is much less useful than before ("I have no fish anywhere!") is because the fish are all getting bundled up at the exit end of the river/stream by the force of the flow where they get hit against the walls over and over again until they die.

Actually I have to disagree on this. Aside from the question of whether or not fish can be killed that way, being vermin, the real problem is in maps without flowing water; pools and the flooded portions of caverns are lacking in fish(except turtles and/or lungfish as appropriate). The map I played on that had a brook was loaded with enough fish that four fisherdwarves couldn't exhaust the supply.

[LemonFrosted]

My brook had plenty of fish.

My river had thirty dead carp bundled up in the exit square.

[Syff]

Yeah, that's my question. I (will) have the magma pumped up to the top of a cavern, where it will flow out and fall down about 10 z levels and then pool at the bottom 3-4 z layers. In this instance, will the magma still act pressurised and flow up through a channel in a partially submerged room?

The flowing magma will not act pressurized, as magma does not have pressure.

However, if the pump is active, it may choose to place the magma inside the partially submerged rooms if it can pathfind to them through 7/7 magma orthogonally connected to the pump output.
This means your 10z drop will have to back up before it can start flooding said rooms, but it can if left unattended.

From the OP:

Pumps do not "give magma pressure"; the pump moves the magma according to the rules of pumping, which can span z-levels, but after it has been placed by the pump, the magma moves only according to its own rules, which do not include pressure.

[Kuraudo]

I find it a relief that pressure (and magma's lackthereof) still works as described in this excellent post.

[TheDancinZerg]

Thank you for this!

[Deathworks]

Hi!

First of all, I need to say that the "flowchart" in the first post is really awfully cute. I really like it.

Secondly, as far as I recall, people have reported that pressurized water has become much more vicious in 2010 - which would not mean that the basic rules have changed, but that more care needs to be applied.

Deathworks

[Kaos]

I have a question/observation regarding
number 3: can't fall or under pressure, and
number 2: over 7/7 water - teleport


What if it's a combination of both? like it can't fall because is over 7/7 water AND is under pressure?


Scenario:
A river, over the river build a floor, on the floor build a pump, pumping in the same directions as the river flows


In my fortress (genned in 31.21 and updated to 31.25) I did just that in an attempt to drain a river to dam it, the river is 4 tiles wide flowing from north to south, on a section of the river I built a 2x3 floor (enough to fit 3 pumps powered by a water wheel on the 4th lane) on the floor I built a water pump, pumping from the north, at the right I had I water wheel providing power, after I built the first pump, I forgot about it and when I returned, the river tile where it was pumping from is keept empty or 1/7, the surrounding river tiles 2/7, the problem is the output I got a big circular 3/7 2/7 1/7 flood on the ground surrounding the river, (I was expecting that the output water would simply fall ontop of the 7/7 water down-stream and teleport to the map edge on the south)... instead a good portion (about 6x4 tiles) of the river on the south where it drains is 1/7 2/7 3/7.


So the water is spreading like number 2 says, but what about the downstream effect???

[Girlinhat]

If water is over 7/7 water, then it is under pressure.  If it cannot path, such as it's a single 2/7 tile on top of a 7/7 layer in a sealed cistern, then it will spread as if it were on solid land, turning into 2x1/7 tiles.  Ironically, because of the positioning, the water will dance atop the water layer, moving around rapidly in some sort of pattern.

In your attempt to divert river flow, this won't really work because the water will leave the river, appear a bit downstream, and then spread out, backwashing towards the pump as it naturally spreads.  You're much better off diverting water flow into a pit, digging this pit to the map's edge, and then smoothing the stone and carving a fortification at the edge.  This allows water to drain freely, and you can place hatches to control when the river is diverted or flowing normally.  When you try to drain a river into itself, it usually doesn't work.  You CAN drain a river upriver of itself, by having the pump move water in the opposite direction as the water flows, and a lot of the water will re-absorb into the river, though you'll still have widespread flooding.

[Kaos]

If water is over 7/7 water, then it is under pressure.  If it cannot path, such as it's a single 2/7 tile on top of a 7/7 layer in a sealed cistern, then it will spread as if it were on solid land, turning into 2x1/7 tiles.  Ironically, because of the positioning, the water will dance atop the water layer, moving around rapidly in some sort of pattern.

In your attempt to divert river flow, this won't really work because the water will leave the river, appear a bit downstream, and then spread out, backwashing towards the pump as it naturally spreads.  You're much better off diverting water flow into a pit, digging this pit to the map's edge, and then smoothing the stone and carving a fortification at the edge.  This allows water to drain freely, and you can place hatches to control when the river is diverted or flowing normally.  When you try to drain a river into itself, it usually doesn't work.  You CAN drain a river upriver of itself, by having the pump move water in the opposite direction as the water flows, and a lot of the water will re-absorb into the river, though you'll still have widespread flooding.

Let's get this straight:


1) what a pump does is grab 7/7 (or whatever amount) of water in its input tile (leaving it empty) and place it in its output tile, right?
so the first "cycle" of a pump will get the 7/7 "wall" of water and place it over its output tile (in my case open space "floor", with 7/7 water "wall" below, with a river "floor" tile below that)


2) Next up, the input tile (that's empty now) will start getting water back by spreading from the surrounding tiles (or maybe the river floor tile generates water itself?? nope, the river source floor tiles are the ones that do that!)


3) the 7/7 wall of water falls because is above open space floor tile??
4) when it finds the 7/7 wall of water below shouldn't it teleport? it can find a path through the river water up to the outflow of the river that's usually 4/7's, 5/7's and 6/7's??
5) In my observation it did spread (not sure if before or after teleporting, by your post I'm under the understanding that it did teleport but not all the way to the outflow downstream, instead to a few tiles downstream and then it spreads???  )
6) the other weird thing was the effect it caused downstream, the last 6 tiles of the river had 2/7's 3/7's and even 1/7's??? and I just used 1 pump!!! what drained the river outflow??



By throwing water on top of 7/7 of river, shouldn't it path to the edge where there are 6's and 5's or doesn't it path that far away? or maybe there's a priority for the scenarios? like it checks if it easier to spread or path a long way???

[slawr34]

You, good ser, are long overdue for the Urist medal for *!!SCIENCE!!*