A bit vague.
After digging the pit, I would define a Pit/Pond zone on/next to the pit, which needs to be then further defined as a pond, rather than the drier alternative. Then you need buckets, naturally. And you need dwarves not busy with something else who can take on the job of putting water in the pond. Oh, and access to water to pick up in the buckets. Beware buckets that are now full of lye, or something, thus not used for water.
Once you get this moving (or report back that "naw, I did all that, and it's still not happening", and someone else gives you the clincher that gets you moving), then your homework is to see if a larger zone means more water moved at once, or many 1x1 zones defined along the edge of the Pond, or... well...
Personally, these days I get water (regardless of the surface conditions) from the caverns.
- Dig exploration shafts to identify useful subterranean space with water in it,
- Set to be dug channels from a handy point somewhere in your main fortress down to the layer immediately above where you'd break through,
- Let one miner (that takes on the first channel, and then digs himself into a hole with the second) do most of the shaft-digging work... he'll stun himself each time he undermines himself but (and this is fixed again, after one version where it was dangerous to do) shouldn't gain any injuries from doing so,
- Set an 'escape tunnel' from the tile next to the bottom (non-cavern) part of this shaft to an escape stairwell (possibly your exploration shaft), if you have a second/third miner, they can start digging that, even complete it, but if the first gets to the bottom first he can dig himself out that way, before he starves/dehydrates,
- (Alternately, dig sideways just above the cavern roof, i.e. just the escape tunnel bit, with no shaft. Quicker to haul water up than a well 10, 20 or 30 Z-levels high, but then if the Wellhead is that deep instead, the hauling takes time... Swings and roundabouts.)
- Clear any valuable debris away from the bottom (set to dump it, perhaps), and I'd do it for everything, just to keep things neat, meanwhile, you can have already have set the well to be built at the top (wherever that might be),
- Set to channel the breakthrough into the cavern (this one will be done from the side, in the 'escape tunnel'),
- Optionally, set a 1x1 retracting bridge over this gap, and before the next step get it connected to a lever, pour discourages les fliers,
- Build a wall next to the shaft in the escape tunnel (might be a good idea to retract the bridge, to avoid the dwarf standing on it and walling himself in, or make sure that it's the right way round for normal work-direction preferences to kick in),
- You now have a working and fairly safe well-head into the caverns. Weather-proof. Desalinating (as all wells are), and generally proof against water-loss,
But for an even safer (while in use!) underground water-source, dig out a cistern area, above which there is a vantage point where a well (or wells!) dips into, to the side of the underground caverns, set up floodgates in the prepared feed tunnel before
breaching into the cavern lake involved, then (when floodgates operational, and briefly opened) carve fortifications (after smoothing that tile) in the last bit of wall, from the floodgate tile to the lake one. Shut the floodgate immediately on breach, if the fortification dwarf hasn't had the sense to run to your pre-arranged exit. Open back up when the escape is guaranteed. When there's sufficient water under the wells (and more), you can close the floodgates again
, on a semi-permanent basis. You should now have a safe amount of water, and you can open the floodgates when you want to refill, and you can see that there's nothing dangerous that's likely to exploit dwarven physics to get through the fortifications.
But that's more work. I usually set to doing that after getting the initial wells sorted out, in order to remove the final threat of fliers randomly sneaking up those wells, when not noticed and guardable against (and, also, giving a spate of "dry well" notifications, when you do so...). The cavern-cistern wellheads should serve you well, and yet you have the mechanical wherewithal to prepare an expanded cistern area if you really
want even more wellheads and can't fit them above the original cistern area.