The water I carry depends on where I'm going and when in the year. Normally, I'll carry three large water bottles on the bike frame. In hot conditions crossing empty country, I've sometimes gone up to six bottles, the other three strapped to my front or rear racks. Also, take water treatment tablets with you.

For the weight distribution, I haven't yet gone with the 60 front and 40 rear suggestions. I'll usually have about 75 to 80 per cent in the rear and the rest in front. I have no trouble at all with the way the bike handles under this system. Personally, I'm more concerned with the side-to-side weight distribution. I'm trying to keep the weight and the bulk equal on both sides of the bike.

My load is distributed as follows.
REAR
Pannier with clothing and lock and stove fuel bottle (on the left side of the bike.)
Pannier with sleeping bag, cookware and stove and dried food (on the right side of the bike.)
Ground sheet and mattress pad rolled up and put between the panniers on the rack.
Small tool bag with tools and tire patches under the saddle.

FRONT
Handlebar bag with lights, camera, cell phone and miscellaneous equipment.
Tent strapped to front rack.
Light jacket may be strapped to the front rack, depending on the weather.
Additional water bottles, if needed, will be strapped to the front rack.

This set-up will work for a week-long tour. For a longer trip, I'd look at getting front panniers