And by the way, it's not the first time you try to show a discredit upon a right information, so I frankly ask you to try to search the root of a problem before you try to continue the confusion next time.
Now, I don't trust the wiki 100% but I've experienced a lot of things so THESE are right:
http://df.magmawiki.com/index.php/Underground_riverhttp://df.magmawiki.com/index.php/Underground_poolSo sir, please, next time you're confused,
don't make it into a bandwagon.
The previous case had you stating that "doesn't care about anything anymore" makes dwarves into alcoholics, and it looked like a lot of people believed your wrong conclusion.
P.S. If you couldn't extract the information from the above links (just in case, I don't try to be funny or to insult you), this is the right info:
Currently all the main features (except for rare magma pools in plains) are in mountain regions. So if you haven't got a mountain as a part of your embark rectangle, you don't have any water.
If you have a mountain tile or a few in your embark rectangle, the features like UG water/pool may be only under those tiles, so it limits the area of exploration drastically.
The very promising feature of the next release is the avaliability of non-mountain features which we were waiting for since the move from 2d to 3d DF.
P.P.S.
I've found underground pools, rivers, and magma pipes in non-mountain biomes.
Now, let's return to you stating that you have a prove of a common fact being wrong. I really want to see the save of the game with an underground river as a non-mountain feature. It sounds as a bug because nobody else saw it, so please upload it to
http://dffd.wimbli.com/ and let us check. I'll pm Toady One and ask how did it happen, it's the only good way to get fast real answers.