Thirsting for Adventure (Trekking in Peru: Day 2)

Thirsting for Adventure (Trekking in Peru: Day 2)

“How much water will you need for the day?” the guide asked as we prepared for our second day of trekking through the Andes.

“I don’t know, a liter?” answered one of our group members. I gave the guide a skeptical look, that number seemed dangerously low to me. Our plan for the day included ~4700ft of elevation gain through an exposed section of high altitude desert with no shade and the forecast was predicting temperatures over 90°F. Both my experience and the research I’ve done on water requirements for hikers suggested that 1L wouldn’t be anywhere near enough:

“When’s the next time we can get water?” I asked, hoping I was missing something since the guide seemed unconcerned. “We can get water when we stop at Maranpata for lunch,” he replied. I looked at the elevation/mileage cheat-sheet that I’d made up before the trip. Maranpata wasn’t that far away, but we had to climb from the Apurimac River at 5084ft (1550m) up to 9950 ft (3033m) to get there.

“Hmmm,” I paused to to do some calculations. The guide estimated it would take us ~6hrs, it was going to be a strenuous climb, and it was going to be extremely hot.  I would probably need ~4L in that time, but I could ‘camel-up’ and drink a liter with breakfast and drop that number a bit. “I’ll take 3 liters,” I concluded.

“Really? Are you sure you?” replied the guide, urging me to take less.

“Yes, I’m sure,” I replied confidently. I’d made the mistake of skimping on water during a heat wave on my AT thru-hike in Virginia and ended up suffering from heat exhaustion (complete with nausea, vomiting, and double vision). It wasn’t an experience that I cared to repeat.

The guide remained unconvinced, “Water is very heavy. Make sure you don’t take more than you need.”

“I know,” I replied.  “A lot of people skimp on water because water is heavy and they want to keep their pack weight low, but when temperatures climb over 90°F skimping on water isn’t just a bad idea, it’s dangerous! Even though its heavy, for conditions like these most hikers I know would carry 2-3 L of water.” Eventually everyone sorted out how much water they were going to carry (the range was 1.5L to 3L) and we set off on our adventure.

The trail rose steeply out of the canyon, providing us with some shade as we started our first uphill climb of the trek. Since the temperatures were already in the ’80s, we would enjoy the shade while it lasted!

The first couple of switchbacks leading up from the river seemed long and gentle, especially since our guide was leading us with a slow deliberate pace called rest-stepping (a strategy I was familiar with from high-altitude mountaineering). Down by the river at ~5000ft rest-stepping felt awkward and out of place, but as we gained elevation and the switchbacks got steeper it began to feel more natural for me.

Unsurprisingly, the distance between the fastest members of our group (me, Jari, and the guide) and the slowest people in our group began to grow as we climbed. We also lost the glorious shade, and began to split our time between hiking in the blistering heat of the sun and baking in the middle of the trail while waiting for the group to catch up.


After three hours of hiking we’d traversed 1.2 miles and reached Santa Rosa, a small oasis at 6873 ft (2095m) with shade, benches, toilets, and a stand selling beverages and snacks. We took a 10-minute break there and bought beverages. I bought a blue Gatorade, someone else bought a coke, and the Quechuean woman running the stand brought out a pitcher of mud-colored liquid and poured some into glasses for both the cook and the guide.

“¿Qué es esto? (What’s that?)” I asked, my curiosity piqued by the milky-brown liquid. “Acca,” replied the woman. “Chicha,” clarified the cook. I furrowed my brow as I tried, and failed, to translate chicha from Spanish into English. “Inca Whiskey,” elaborated the guide smiling broadly. I wasn’t sure if he was kidding, but it seemed plausible that it was some sort of home brew. The only way to know for sure would be to try some. Even though I like whiskey, alcohol seemed like a bad idea on a scorching hot day when I was headed to altitude, so I went back to drinking my unnaturally blue Gatorade.

Since our group had struggled with the first part of the climb, the guide offered to take the day-packs of the slowest group members and put them on a horse that would stay with us as we climbed. While he and the head horsemen (Gumercindo, pictured above), re-sorted gear to free up one of the horses, we headed out.

In the guides absence the group seemed willing to let me set the pace and lead the charge up the mountain. As a kid, my dad had one simple rule for hiking as a group, “you start as a group, you hike as a group, you end as a group.” So I tried to keep our group together by setting a relatively slow pace, and making sure that everyone was caught up at each switchback.

The midday sun directly overhead was blazingly hot. Even in the best conditions the ~2700 ft (~823 m) of elevation gain in the 2 short miles (~3 km) between Santa Rosa and Maranpata would have felt steep, but with temperatures soaring up over 100ºF it felt even more impressive.

I found the steepness of the switchbacks particularly impressive. When I’d seen the elevation profile for the hike I’d assumed this stretch of trail would be a steep, rocky scramble straight up the mountain like the scrambles in the White Mountains of New Hampshire. Instead it was a consistently graded dirt track more like the trails I’d hiked in California, but much, much steeper. The impressive elevation gains on this hike (1800 ft in the first 1.2 miles, and 2700 ft in the the next two miles) rivaled some of the steepest sections of the trails I’d hiked on the AT and PCT. One advantage of the super-steep switchbacks was that they were so steep they created shadows, which gave us a little bit of shade to rest in.

We were taking the hike so slowly and resting so often that despite the elevation gains, the heat, and the altitude I was feeling pretty good. It also gave me plenty of time to marvel at the beauty of the trail around me and wonder at its curiosities. Per usual, I took pictures of each new flower and strange plant that I saw. I also marveled at the things I didn’t expect to see while hiking through the desert in Peru,  like the groves of bamboo tucked into the ravines. I’d always thought that bamboo was strictly native to China, but it turns out that bamboo is also native to Peru and the Americas!


As the morning turned into afternoon the energy levels among the people in the group started to drop. One person in particular was really struggling. Her pace had slowed significantly in the last hour and she was feeling nauseous. In addition, she was starting to stumble in a way that I found alarming. Unusual “umbles” (stumbles, mumbles, fumbles, and grumbles)  while hiking are classic warning signs that something is going seriously awry.

Since we were going up in altitude, we hadn’t eaten in 6 hrs, and the temperatures were excessively hot, it was hard to tell if the problem was dehydration, altitude, declining blood sugar levels, or all of the above. The next time she stumbled I suggested we stop in the shade for a few minutes to rest and drink some water. I also offered her some of my favorite electrolyte gummy candies (shot bloks). Luckily she started to feel a little better after that, and her gait and nausea began to improve.

Finally at around 2 pm we made it to our lunch destination at ~9,573 ft (2918 m). By then a lot of people in the group were feeling excessively fatigued and headachey. Since temperatures had reached 102°F and it had been about 7 hours since we last ate, dehydration and low blood sugar were definitely a part of the problem, but exertion at high altitude was also likely to be part of the problem.

  • 75% of people have some symptoms of acute mountain sickness (AMS) above 8000ft (2500 m)
    • Mild AMS: headache, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disturbed sleep, and a general feeling of malaise
    • Moderate AMS: severe headache (not relieved by medication), nausea and vomiting, increasing weakness and fatigue, shortness of breath, and decreased coordination (ataxia)
    • Severe AMS: shortness of breath at rest, inability to walk, decreasing mental status, high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE)

While we rested in the shade waiting for lunch I pulled out the pulse oximeter (Acc-U-Rate CMS 500DL, US$19.95) that I’d brought along. I’d purchased it because I was curious about how the altitude would affect my poor asthmatic lungs, and as a scientist I’d hoped that the entire group would join me in collecting data  about the effects of altitude on our physiology. I measured my oxygen saturation (SpO2) and then passed the pulse oximeter around to the rest of the people in the group. Sure enough, every single person in the group had a lower SpO2 at Maranpata than they had had that morning at the Apurimac River. Mine had dropped from 96% to 93%, but other people in the group had seen more dramatic drops. For example, the woman that had been struggling with nausea on the way up had dropped from 94% to 74%.


*The decrease in mean SpO2 levels between our campsite at the Apurimac River (94.4% +/-0.3SE, n=7) and Maranpata (86.9%+/-2.6SE, n=4) was statistically significant (p<0.03)

Luckily after resting, hydrating, and eating lunch everyone started to feel better. Besides, the rest of the day’s hike was what the guide called, “Inca flat,” which meant that there were plenty of little ups and downs, but not significant changes in altitude.


Heading from Maranpata towards Choquequirao the cacti quickly gave way to greener, lusher vegetation, and we caught our first glimpse of the Inca ruins of Choquequirao in the distance. The steep farming terraces of the lowest sector of Choquequirao seemed to be cut into the face of sheer cliffs. It was incredible to think about what kind of oasis this must have been when it was actively being farmed and maintained. Especially since only a fraction of the site at Choquequirao has been excavated.

As we got closer to the first visible ruins of Choquequirao (Phaqchayuq, or “the one with the waterfall”), which sports at least 80 agricultural terraces I noticed the unmistakable  purple star-shaped flowers of the nightshade family mixed in among the vegetation. They reminded me of the potato plants that used to grow in my grandfathers garden. I wondered if this plant might be among the 2,500 varieties of potato cultivated in the Andes, and if its ancestors had escaped from the Inca terraces centuries ago.

Even though the two miles (3km) from Maranpata to the Choquequirao campsite were relatively flat, the pace of our group as a whole was still incredibly slow. As the sun dropped behind the ridge a sense of disappointment welled up within me. One of Choquequirao’s claims to fame is that it contains the only known Inca site dedicated to the sunset and I’d really been looking forward to watching the sunset from that amazing site. It was only as I realized that I wasn’t going to get to watch that sunset that I began to understand that the speed of our group might have a negative impact on our itinerary and on my vacation.

After settling in among the terraces at the Choquequirao campsite and admiring the beautiful mountains around us, Jari and I headed into the dining tent for tea, snacks, and cocoa. It turned out that he was just as disappointed about missing the sunset at Choquequirao as I was and was concerned that the slow pace of our group might prevent him from getting to visit the ‘Llamas del Sol (Sun Llamas)’ at Choquequirao the next day. I had no idea what the Llamas del Sol were, but I was excited to find out, so I said that I’d happily explore them with him.

Eventually everyone else from the group filed in and we ate dinner. Once again the cooks prepared a real feast for us, including something that I’d never eaten before, lupine salad (ensalada de tarwi). “I had no idea that lupine was edible,” I commented as the guide described each dish. “Usually it isn’t,” he explained, “raw lupine beans are poisonous, but the Inca learned that if you soak the lupine beans in the river for two weeks they become edible.” I was curious about what the white beans from the pretty purple flower tasted like, so immediately tried one. Their flavor was absolutely unique. They were slightly bitter, nutty, and vaguely reminiscent of bug spray, but still surprisingly good. I took a heaping serving of them and enjoyed imagining that they might act like a natural bug repellent.

While the cooks prepared bananas flambé for dessert,  Jari quietly asked the guide if we were going to get to be able to check out the Llamas del Sol at Choquequirao the next day. The guide explained that to see the llamas we’d have to hike half-way down the mountain and back up again, and that it would be way too much for our group. “Yes, but I would still really like to do it,” insisted Jari. “Count me in!” I added.

The guide sighed, “I don’t know why Jari is fascinated with dead llamas. We’ll see plenty of live llamas on this trek without having to do any extra hiking.” I still had no idea what the Llamas del Sol were, but I was intrigued, especially since it would involve extra hiking. “The two of us (Jari and I) could go check out the llamas and then catch up to everyone afterwards,” I proposed. Although the guide wasn’t enthusiastic about it, he gave an affirmative nod, “that could work.” Jari and I would get our adventure at Choquequirao!

–Next Installment: Day 3-Choquequirao and the Llamas del Sol–


Summary: Day 2 by the numbers

  • Apurimac River (5084ft/1550m) to Santa Rosa (6873 ft/ 2095m)
    • Distance: 1.2 miles (2 km)
    • Elevation gain ~1800 ft (~550m)
    • Predicted hiking time (actual): 1.5 hrs (3 hrs)
  • Santa Rosa to Maranpata: 9,573 ft (2918 m)
    • Distance: 2.1 miles (3 km)
    • Elevation gain: 2700 ft (~823m)
    • Predicted hiking time (actual): 1.5-2hrs (4 hrs)
  • Maranpata to Choquequirao Campsite: 9950ft (3033m)
    • Distance: 2.1 miles (3 km)
    • Elevation gain: ~0ft (‘Inca flat’ as described by guide)
    • Predicted hiking time (actual): 1.5hrs (3 hrs)
  •  Totals: 5 miles (8 km)
    • ~4700 ft (~1400 m) elevation gain
    • Predicted hiking time (actual): 4-5 hrs (~11 hrs: 7:30 am to  6:30 pm)

Backpacking Science and Privilege: Water


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.

  1. Food: Our ability to regulate blood sugar levels (glycoregulation).
  2. Water: Our ability to regulate water and minerals (osmoregulation).
  3. 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):

Image result for military desert water requirements data

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?