Little Details

I have a desert civilization that supposedly isn't near any above-ground water sources. What I'd like to know is...
How underground rivers/underground seas come to be,
How likely they are to appear beneath a desert (of the really sand-duney variety, heh),
Is the water pure enough to use, and...
Would there be any changes on the surface of the earth that somebody would notice and realize there's water down there?

[EDIT]Real-life examples would be helpful, but not necessary[/edit]

Does anyone know of good, accurate online resources about angels? (If not, can anyone recommend any books?) I'd like to use one in a story, and I've found one that looks promising but I think I'd like to make sure my information is accurate first...

This is what I have so far on the angel (Hayyel):

Hayyel is the angel of wild animals and teaches humans to take care of and love animals. Hayyel protects the wild animals of the earth. (from here)

Hayyel: Protects wild animals along with Thuriel, Mtniel and Jehiel. Pray to them to protect animals from extinction. Hayyel teaches humankind that just as the angels protect us, so were we created to protect nature. Pray to this angel to inspire humans to become the stewards of all nature that we are meant to be. (from here)

Thanks in advance. (I love this community. ^^)

Does anyone know how to colour a sword permanently? As in, to stain the blade some colour or another. I've googled it, and I haven't turned up anything. Pretty sure it's possible, just...how. Thanks in advance.

What can holding the middle finger up mean in Japan? It's been used in one of my Japanese fandoms and I don't think it's in an insulting way, even though Google says that's what Japan sometimes treats it as.
If it helps any, I can scan the relevant manga image in - just in case it means different things based on situation and all.

This site has a good chunk of information on Japanese culture written by an American who went there to teach English. Has good information, and I thought you all might enjoy it. :D