It is always smart to minimize the risks of drinking contaminated water. This is especially true for those taking a more relaxed approach to water treatment. But even if you decide to rigorously treat your water, you still want to collect it from the safest possible sources.
Following is a synthesis of my research regarding the best sources of drinking water. It is interesting to note that the first three pieces of advice tend to go against common practice.
— One shouldn’t assume that moving water is uncontaminated. In fact, turbulence can stir up the nasties. Having said that, there is some scientific basis for believing that a lot of turbulence in a water source reduces the prevalence of one common source of pollution: protozoan cysts (especially Cryptosporidium and Giardia). One such study can be found at PubMed Commons: http://www.ncbi.nlm.nih.gov/pubmed/17568382. (Thank you Andrew O. for sharing this information.) One additional qualification: in the spring, with water temperatures low and volumes high from runoff, there is potentially less of a threat. The same is true for any higher volume water source, though still no guarantee. A valuable piece of advice from an unknown source summarizing this perspective: “the solution to pollution is dilution.”
— An extension of the above advice is to drink lake water when springs or streams are not available, if the bottom consists of rocks and sand. A thick, mucky bottom indicates stagnation. In addition, larger bodies of water act as settling basins. Drink from the outlet stream where the settling influence is greatest. [Note: It is sometimes claimed that taking water from the surface of larger lakes is better because it has been subjected to the cleansing influence of ultraviolet light. This might be true, but my research has not corroborated it one way or the other.]
— Cold water is no guarantee of non-contamination; cold water that appears clean might not be. The warmer the water, the higher the levels of potential contamination. In the winter and early spring, the microorganisms of concern die off or are less of a threat. As the water temperatures go up, the microorganisms start growing, and, by midsummer the potential threat is at its peak.
— Good spring water or small streams are the hiker’s best source of drinking water. Don’t automatically assume, however, that a spring is clean; it depends upon its source. Springs and streams with any noticeable smells or extra plant and animal life should be treated with suspicion.
— When drinking from springs, seeps and streams, the higher the elevation of the watershed and the smaller the watershed the better. With small streams, walk upstream a bit to get a sense of its character and see if its source is a spring.
— If available, deep well water is usually safe because it has been filtered while passing through the underlying soil.
— Melt snow taken from remote snowbanks in higher elevations or from freshly fallen snow, but do not assume that all snow is safe. Be wary of spring snow runoff; when it washes over the ground, it can pick up contaminants.
— Drink as much water as you can from known clean sources at the trailhead before starting out and upon returning. Also, when in the backcountry, drink as much water as you can from the highest quality sources (often referred to as “cameling”).
— If high-quality water sources are not available for a period while hiking, do not compromise your health by drinking from questionable water sources. Humans can generally go without water for many hours or even a day or two without jeopardizing their health. Obviously, one’s sense of comfort (mental and physical) will likely be compromised.
— When possible, ask knowledgeable people about their experiences with water sources in an area. I regularly come across experienced backcountry travelers who say they have been drinking backcountry water for years without treatment of any kind. I acknowledge that this is not a scientific sampling, but it is interesting nonetheless.With which of the above pieces of advice do you agree? Disagree? Would like to qualify or add to?