When it comes to water, I've always just used a filter everywhere I go in Alaska. A small filter, like the MSR Hyperflow, is a great choice. It pumps super fast and it's only shortcoming is that it does not have a charcoal element (which improves the taste of the water.) Then again, neither do tablets, and most of the water tastes pretty good if your selective and don't just pump straight out of a swamp sink hole... though you could and it would be plenty safe enough.
The trail is criss crossed with streams virtually the entire way. I don't think you ever hike for more than an hour or two without crossing a stream and usually more like every fifteen minutes. In out group, one girl insisted on bringing TWO GALLONS of water in milk jugs just in case we didn't run across enough along the way. Each of those jugs weighs eight pounds, so she had sixteen additional pounds of water in her already overloaded pack. By comparison, the MSR hyperflow only weighs less than a pound. I took two Nalgene bottles, one that I kept topped off and drank from while hiking and one that I carried empty. When it was time to cook I would fill both so I had one to cook from and one to drink from.
Also, just to clarify after reading that guys comment about European streams. Most running water in Alaska is plenty clean as well once you get up into the mountains. When I was younger and dumber back in highschool I never had a filter and I drank straight from mountain streams all the time and never got sick from it. Along the Stampede Trail though there is a lot of swamp, and you can smell a fair amount of rotting vegetation and even see some of the nastiness in the water. Even the Sushana has kind of an orange color to it. Most of the streams you cross are not nearly as quick moving as what were depicted in the movie, with the exception of the Teklanika and the Savage they're actually quite slow. You could probably drink straight out of the Savage or the Teklanika if you wanted to, but I wouldn't reccomend it. For one it would taste kind of gritty, they're both gray with glacial silt.
moving on though
One thing I would say no one should go out there without is a dry bag, big enough to hold most everything in your pack. The trail is super soggy, and the chances of you falling over in water are pretty high. If that happens you want to have a pack full of dry clothes and a dry sleeping bag. This is one area I wouldn't skimp either. Though a Hefty bag might be adequate, it also might tear or the top might not be sealed well enough. Get an actual dry bag, even if it's one from a military surplus store.
Erik Halfacre - Moderator