Sorry I abandoned this for so long. I want to thank you all for your input, and address some things that were said directly.
Personally I'd build a small repeater with water (smaller is better) which cycles every couple of seconds, then have the output of that going to a large dwarven computer using water-based logic gates to do binary counting and possibly some arithmetic. This would be much more reliable and would remove many of the problems with evaporation/random water flow. As an added bonus you can link it to spike traps to display the output in the corpses of your enemies!
This is pretty much what I'm doing. The spike traps I've replaced with crystal glass floor tiles in a level above, which display either muddy or water tiles, depending on the state of the corresponding cell. Prior to my reading of the responses, when I believed water worked in a predictable way, I had planned to use pools of varying sizes to time out various intervals, which would empty into other sized pools, and so on...
Closing doors destroy water, closing floodgates destroy water, closing and opening bridges destroy water (on the tiles the bridge occupies after its state changes).
There are allegedly 1200 ticks in a day, 28 days in a month, three months in a season, and four seasons in a year.
Hmm, useful information, even if it doesn't give me much hope for this. You say allegedly. Where does that info come from? Also is there a way to get the game to... wait, I can one-step the game while it's paused, can't I? doesn't that make it use one tick? Also, to save me the extra quote, thank you for the link, truely, even if I accomplish this,my dwarfs will be standing on the shoulders of giants...
metaphorically, of course. Dwarves don't use mounts, do they? Oh god, I need to mod this in.
In theory, if there is a risk of water being lost, you can also rig another mechanism to refill chambers from an infinite water source triggered by a pressure plate.
Yes, and using hydro-static water pressure to acivate that system could work, if I understand Dwarf Water correctly.
...I'd suggest "larger is dwarfier"...
Fix'd. But seriously, a larger system seems to make this worse, I think, especially when one of the things I need is for chambers to empty of water reliably.
Not directly. You need to build an AND gate. Link each plate to a different door and arrange the doors in series.
I prefer the predictable timing of pressurized water. To slow things down, rely on the known 100-tick timing delay on floodgates and bridges.
I figured on using the AND gate, I just felt it would be more elegant to have the multiple requirements. as for the timing delay, I was given to understand that quality of craftsmanship had something to do with this. Does the same delay apply to triggers attached to say, a gear box? Is there a chart?