Yeah, that's an aquifier.

There's supposed to be a "dry" spot around where the magma pipe is, where you can safely dig through till you're below the aquifier layers, but I dunno how it works if the top layer of the pipe is itself below the aquifier.

Oh, bloody hell.
I've been on maps where there, supposedly, was an aquifer before and never had any problems... but that's just silly.

There are lots of ways to deal with them, but all are terribly annoying and most require some significant prep time. I'd sooner deal with carp than an aquifier anyday.

The only positive side to them is an infinite water source wherever you dig, and having an unlimited drainage capacity (to the point where it's possible to siphon an entire ocean into a few aquifier tiles).

[edit]Ho'shit dragon

So what insane constructions are people coming up with?

Right now I'm just putting in the beginnings of my magma managament infrastructure. I've got an aquifer which is both convenient and annoying. It makes obsidian farms easy to set up, although now I'm having slight issues in getting the dwarves to use the obsidian. I also almost overfilled the farm so I had some rather desperate wall construction and water pumping to contain the burning blood of the earth.

It seems I do have a deposit of bauxite but, alas, it is a little hard to get to. Fortunately I need to dot the place with aquifer bypasses anyway, for a future project.

Right now I'm channeling a pipe and filling it with obsidian to seal out the aquifer so I can pump magma from my magma vent into the magma pool, converting it into a giant storage reservoir. The path's all set up, I just need to get one of my lazy-ass architects to finish putting in the magma pump.

From there, oh what fun I shall have!

I have many prototypes to build.

A device to flood with magma from below, a device to rain fire from the heavens and two concepts for perpetual, self reloading and fully automated cave-in generators which may or may not work.

Also, lava curtains.

And a 10+ Z-level tall pyramid made of cast obsidian and plated in glass. Complete with tomb, trap filled catacombs and it might also vent lava from its sides.

Goddamn fucking immigrants. Every time I figure I'm just about where I can concentrate on something other than beds my population damn near doubles. Well its better than it was during my first immigration. Jumping from 9 to over 30 isn't fun. Then I jumped to 50 and just now to over 70. I'm contemplating getting everyone inside the mote and drawing up the drawbridge for awhile. It would certainly stop the thieves and the ever present marauding monkeys.

I have a plan for when I actually have some time: First, I'm going to find a river. Then, I'm going to wait 'til the water freezes - or try to make a dam - and then, I'm going to put a tower on the other side of the river. I'll then make it so the first floor of the tower is partially grated so you can see the water run below it and then I'll make a giant self-powering reverse waterfall that shoots water from the sides of the tower when a lever is pressed. Eventually I could try to make a moat around the tower that only fills - with LAVA - when a lever is pressed and then when everything attacking me fell in it I'll activate the water and then get obsidian. It'll be awesome.

The monkeys can burn in hell.

I find that covering my entrance with cage traps and stationing guards there has pretty much stopped the monkeys. First couple of seasons before I had a moat and a small standing army were hell. They came in groups of 6-7 and just completely wrecked everything they could get their hands on.

Having a small standing anything is usually good enough as long as it's in plain sight. Monkeys will typically bug out if they see any dwarves/dogs/etc in the way. Kobolds are a little more persistent but will also leave without incident (Usually) when discovered.

So first siege finally happened. It lasted about two seconds once the dwarfs meet the goblins. Granted I activated my full force of 9 Champion Wrestlers, 4 Elite Wrestlers, and 9 Wrestlers. Only about 4 of the champions and 2-3 normal wrestlers got in on the action and they decimated a force of mace goblins about twice there size. Currently they have one trapped at the bottom of a pond still alive. I don't know how it hasn't drowned yet.

Edit: Oh and sadly a few of the champions lost the babies they were carrying. That'll teach my army to fornicate on duty.