Half Dome – Yosemite Musing
The most critical part of your Half Dome hike is water treatment. The waters in the Merced and other sources in the park contain Giardia and Cryptosporidium. These are protozoa that, when injested, are intestinal parasites. That means in about 7-10 days after you return from your hike, you may get diarrhea. If untreated, the consequences can be deadly. A friend told me a buddy’s son got it and did not get it taken care of . . . and died. Yikes. While many claim that they have drunk the water for years with no ill effects, why take a chance? E-Coli from feces is a primary source. There are all kinds of animals (and people) to contribute to the problem. Boiling water works, it takes too long and is impractical on a day hike. Chemicals take at least 30 minutes to work and may not inactivate all protozoa. I suggest using a water filter pump. The three types of mechanical devices to treat water, their effectiveness and Micron rating are:
- Filter – Removes Giardia, large protozoa and some bacteria. (1.0 – 4.0 micron)
- Microfilter – Removes microorganisms, including protozoa & bacteria. (.3 – 1.0 micron)
- Purifier – Removes microorganisms, including viruses. (.018 micron)
Read the box carefully. The nomenclature can be confusing. The street name for these devices is “water filter”. However, as you can see above, the technical name implies distinct capabilities. A “water filter” does not do the job as well as a “water purifier.” Filters can remove bacteria and protozoan cysts. Purifiers can do this and remove viruses. In the Sierra (and most of the US) viruses are a nn-issue. Because of the strict EPA requirements, a true “purifier” is hard to find. A 0.2-micron pore size or less is regarded as the optimum. Be sure to read the literature to make sure that Giardia and other microscopic pathogens (disease-causing agents) will be removed.
Unrelated thought worth quoting: “Bottom’s up.”
*Mr. Half Dome – Rick Deutsch – www.HikeHalfDome.com