On long-distance backpacking trips we don’t take the same things for granted that we do at home and as a result we can gain some insights into our privilege and how it affects the way we hike our hikes, and pack our packs. This is the second post in a series of three in which I discuss how science and privilege influence the way I pack my pack.
- Food: Our ability to regulate blood sugar levels (glycoregulation).
- Water: Our ability to regulate water and minerals (osmoregulation).
- Shelter/Heat: Our ability to regulate body temperature (thermoregulation).
Unpacking my Invisible Knapsack: Water
In 1989 Peggy McIntosh wrote a famous essay in which she likened privilege to “an invisible weightless knapsack of special provisions, maps, passports, codebooks, visas, clothes, tools and blank checks.” What follows is a list of water-based privileges that hiking the trail has made me more aware of:
- I don’t have to be thirsty. Living in New England in the age of modern plumbing means that this is usually a privilege that I can rely on. Typically all I have to do is walk into the kitchen or bathroom and turn on the faucet to get as much water as I want. On the Appalachian Trail there were frequently springs, streams, rivers, or ponds from which water could be acquired, although during the late summer months many of the springs/streams were dry and more advanced planning was necessary to avoid running out of water and being thirsty. On the Pacific Crest Trail this year (2014) as I hike through the desert in a record-breaking drought, the availability of water will be more of an issue.
- The water I drink won’t make me sick. First world privilege and modern sanitation means that the water I have access to in my home is unlikely to make me sick. On the trail, the water coming directly out of the springs is unlikely to make me sick, however, water from streams, rivers, and ponds may be contaminated with giardia and e. coli. The streams in Maine (for instance) are often fed from beaver ponds and may be contaminated with giardia.
- I’ve never been so desperate for water that I’ve knelt down and tried to lap it out of a mud puddle. Walking through the streets of Boston I’ve never been tempted to drink water from a mud puddle. During an uncharacteristic heat wave on a 20 mile day when I miscalculated the amount of water I needed to carry and ran out 5 miles short of the next spring… that mud puddle was a very tempting source of water indeed!
- I don’t have to pay attention to how much water I drink. When there is a faucet with running water in the room next door I don’t worry or pay attention to how much water I drink because I can always get more whenever I want. On the trail I sometimes end up rationing my water if I start to run out sooner than I expected or if I don’t know when or where I’ll have access to water again.
- There will be water available when I need/want it. The joys of modern plumbing in a water rich environment means that this us usually true for me. On the Appalachian Trail in the spring, water was abundant, but some knowledge of where the next sources of water were likely to be was useful. On the Pacific Crest Trail in the desert during a drought, I expect that I will need to be much more careful when it comes to figuring out where to get my water and how much to carry.
- My behavior does not affect the availability and quality of my (or other people’s) drinking water. Typically at home in New England I don’t have to worry about how my behavior is affecting the public water supply. There are also regulatory agencies (like the EPA) which help ensure the quality of my drinking water. On the trail, however, people washing themselves and or their dishes in the rivers and streams can have a direct impact on the quality of the water I drink… never mind whether or not they decide to use the riverbank as their personal latrine.
- I know that if I run out of water other people will share theirs with me. If people on the trail have extra water they are typically willing to share it. Also, on the Appalachian Trail in regions where water is scarce trail angels often provide water caches along the roadsides for thirsty hikers.
- I will be allowed to use public restrooms. White middle-class privilege means that I can use most public restrooms without being harassed. Many businesses, however, require that you make a purchase in order to use their restrooms and, as a hiker, seem to be much more confrontational about making sure that you actually purchase something before allowing you to use the restroom.
- The research that I use to determine how much water I need is based on people that are likely to have physiological requirements similar to mine. White privilege means that this is usually true. Most of the data is, however, based on men and less data seems to be available about women.
Packing My Pack: Water
To ensure proper hydration while backpacking you need to match your fluid intake (from food and beverages) to your fluid losses (through urination and sweating). Dehydration, defined by a 2% drop in body weight, results in impaired physiological and psychological performance, further dehydration can impair the bodies ability to regulate temperature and increase the risk of developing heat stroke. For every 1% drop in body weight from sweat, core temperature goes up by 0.15 to 0.20 degrees Celsius and increases heart rate by 3-5 beats per minute. It is also important to note that over-hydrating can result in electrolyte depletion and hyponatremia. Symptoms of heat exhaustion and hyponatremia are easily confused (dizziness, headache, nausea, and muscle aches), however symptoms of heat exhaustion are relieved shortly after improved fluid consumption whereas symptoms of hyponatremia continue or worsen with additional fluid consumption. On the other temperature extreme, dehydration can hasten the symptoms of hypothermia (click here for an overview of hydration for backpacking).
Though data specific to the hydration requirements for recreational backpacking are minimal, the US military has many similar hydration requirements and a well-established set of guidelines for hydration and fluid replacement (2010). These guidelines are based on the environmental heat exposure determined by wet bulb global temperature (WBGT=0.7Tw+0.2Tg+0.1Td), which includes a measure humidity (Tw, the natural wet bulb temperature), radiant temperature (Tg, the globe thermometer temperature), and dry air temperature (Td, the dry bulb temperature) and as well as the intensity of the work performed (see the graph below):
Water Requirements (NOTE: Current Standards State Consumption should not exceed 11.4L/day)
A common clinical method for estimating fluid replacement volume is the Holliday-Segar method, which suggests that water loss is related to caloric expenditure. This method was initially developed for hospitalized patients where they estimated that each day patients lost 100 ml of fluid for each 100 calories they burned. This is where the rule of thumb that you need 1 ml of water for each calorie that you burn comes from (their actual model had a variation based on initial body weight as well). Assuming that the same relationship between fluid loss and calories burned exists for backpackers (I’m a bit dubious) you would estimate that for a typical day in which you burn 5000 calories, you would need a total of 5L of water. On the AT, at moderate temperatures, I consumed an average of 4L of water a day (2L while hiking, 1L to rehydrate my dinner, and 1L in the evening/morning prior to hiking). If outside temperatures exceeded 80 degrees Fahrenheit I would typically drink 1 additional liter of water a day at lunchtime. My water consumption was typically less than that of my male counterparts on the trail who usually drank at least 1L of water/day more than I did. If you assume that athletes have a higher percentage of muscle (which is 70-75% water) and a lower percentage of body fat (which is ~10% water) compared to patients in the hospital, you might estimate higher fluid volume replacement requirements for athletes. Allowing for differences in body fat percentages, this might help account for some of the gender based variations in water replacement requirements that I observed as well.
Are there other ways that privilege and science influence your relationship with water and how much water you carry?