Giardia: Giardia is a water borne parasite. It is found in all areas of California in untreated water. Other than altitude sickness, I’d say this should be your biggest concern during the hike. (If you really want to learn more about Giardia, I’d check out this link: http://en.wikipedia.org/wiki/Image:Giardia_lamblia_life_cycle.jpg ) I’ve never had Giardia, but from what I’ve heard from fellow climbers, it is very, very, very unpleasant. And while I do guarantee that you will get Giardia – or something worse from drinking untreated water in the Whitney Portal zone, it is very preventable. The best way to avoid getting Giardia is to treat all water you get from backcountry sources.
Treating water can be done a number of ways; but the most productive are through a filter or with iodine tablets. There are a variety of filter options; some involving passing the water through a charcoal based filter system; others that involve treatment with either ultraviolet light or chlorine. I personally utilize the MIOX filter system (http://www.msrcorp.com/filters/miox.asp); and while it is on the expensive side, I have never had a problem at all with it. Should you not have a filter, there is no need to fret, as there are two perfectly good low cost effective methods. First, iodine tablets. A small bottle of such tablets (Such as these: http://www.rei.com/online/store/ProductDisplay?storeId=8000&catalogId=40000008000&productId=603&parent_category_rn=4500460&vcat=REI_SEARCH ) will run you about ten dollars, and there will be more tablets than you need. Using iodine tablets is very easy. You simply use one tablet per liter of water, and after letting the water (with tablet) sit for the prescribed period of time, the water will be safe to drink. The only downside of iodine tablets is that the treated water will have a bit of an aftertaste, but this side effect is pretty much unavoidable (Almost all water treatment options leave some sort of residue). The second method is boiling water; however, this method requires one to carry more fuel for a stove, and if not done properly, can still lead to water-borne illnesses.