OKay so I've sorted out one of the reasons I was getting stagant water so readily... I'd been going to heavily tree'd areas, which apparently (now that I'm reading what it's telling me as I search) means I'd been picking swamps and marshes repeatedly.
However, either I'm still missing something, or the stagnation code is a little messed up.
This latest attempt I genned a world with default settings with the exception of pushing the amount of minerals up to the next notch (I do not like it when the first worthwhile supply of metal I find is adamantine). It means goblins will come at me sooner and more furiously, but at least I'll have more than fish leather to protect my dwarves with.
Definitely a _forest_ biome, and I found a 4x4 area that was entirely flat (YAY!) with a river running straight through the middle in a temperate climate (thank goodness for icing up). So far so good. No little ponds touching the river, upon inspection it's clean... so I build right over the top of it, make a nice 17 radius circular wall, cover the water with flooring and then remove it (which makes it random-soil topped), build a cistern on top, and then start to build a little pump stack so I can have a freshwater cistern above ground (and a decorative ice rink in the middle of winter). The moment I have a dwarf to channel through that so that I can get at the water,
*bam* the whole thing goes stagnant.
"No worries" I figure, since the pump stack should clean it up anyway... I build the bottom pump, flood things a bit (so the ground is definitely going to be muddied and plantable) and um, okay so I drowned a dwarf doing that. It's just one dwarf and they'll make more. I build up the cistern two more levels, put the windmill in place, strip the pump stack area and rebuild it to get rid of the mud there, and wait for winter to extract the drowned dwarf... Winter comes, I tunnel through the ice to the dwarf and bury him so he won't hang about messing with the ambience (CHALK! SO CLEAN!), and build the middle pump so that when spring comes the cistern will fill up.
Well, spring came, and it filled up, and the moment I look into it...
stagnant water [7/7].
I do not see what I could possibly be missing. Is it
supposed to stagnate instantaneously like that? Am I supposed to make an exit channel so the water always has a way out or what?