Kölsch (not Koelsch) is one of my favorite light beers to brew.
Let me look in this month's BYO magazine, it had several pages on this beer...
they don't mention water profiles at all. they say over and over that the key to kölsch is the malt, hops, and especially the yeast being given the right temperature (pseudo-lager).
I have pretty hard tap water, and my kölsch comes out fine...I don't seem to have any of the problems associated with light beers made with hard, high pH, high bicarbonate water.
good luck!