How much water is needed?

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How much water is needed?

Postby Lophophaps » Wed 04 Jan, 2017 3:28 pm

This is firmly in the string, length of, category. There are too many variables, such as individual physiology, fitness, individual size, humidity, air temperature, how fast one is going, terrain steepness, pack weight and maybe if Jupiter is rising into Aquarius. So all numbers need to be applied with care. My scenario is a steepish climb for several hours, no creeks or rivers, hot day, overnight gear, plodding up the hill at a steady pace.

Note that I'm not asking how much is carried, but how much should be drunk. I carry up to seven litres when I'm unsure of the campsite water availability. Only rarely have I needed all this, and despite the weight it was good to not worry about water for the night. Parts of Tassie and other areas are nice - don't need to carry more than a litre.
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Re: How much water is needed?

Postby andrewa » Wed 04 Jan, 2017 5:28 pm

Interesting. I'm pretty tolerant to minimal water intake overall whilst walking - some seem to need water available every minute! On a hot day, I'd maybe get through a few litres. In winter walking up Mt Bogong, I can go for a few hours without a drink. My wife needs water as soon as she gets through airport security. I can manage that, plus 2-3hrs in a plane without a drink. Part of it is psychological. There's a clever little bit of your brain that drives your thirst, based on blood sodium levels - if you get dehydrated, your sodium level increases, and this stimulates the "thirst centre" to become thirsty. If you are well hydrated, your sodium levels are fine, and the thirst centre isn't stimulated. This is why you should generally only drink what you feel you need to drink (water wise, that is. Alcohol is a different matter!)

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Re: How much water is needed?

Postby wayno » Wed 04 Jan, 2017 5:47 pm

need to take a quarter teaspoon of salt for every litre drunk to be able to retain water drunk or your more likely to pee it out, being surrounded by too much water is more often my issue. eat salty food especially when its hot to offset sodium lost in sweat
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Re: How much water is needed?

Postby Hisham » Wed 04 Jan, 2017 6:01 pm

I found I was not able to hydrate myself quick enough despite around 4 litres over 8 hours and hydrolytes at three intervals. I was going uphill with a bit more up and down in very harsh sun at times and mid to high twenties degrees, probably went up 1300m and down 400m, over 16 kms.

Body was overheating and i was dripping sweat. I was feeling ill at the end of the day and even next morning slightly. I did have a slight bowel issue at the start of the day which I put down to my food intolerances, which may have been a small contributing factor.

I will make shorter days, go in much cooler conditions or remove a good bit of the uphill next time.
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Re: How much water is needed?

Postby wayno » Wed 04 Jan, 2017 6:06 pm

you'd need 2gm of sodium with that much water to absorb and retain it... on a hot day you can need up to a litre an hour on a hike.. thats about the most you can absorb
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Re: How much water is needed?

Postby RonK » Wed 04 Jan, 2017 6:28 pm

It depends on the conditions - on a two-day cycle trip in the high temps and humidity experienced in SEQ over Xmas, I became very dehydrated on the first day, despite consuming 4.5 litres of fluids in a 6 hour journey. This really knocked me out - enough to abandon the rest my planned week long trip.

On the return journey next day I drank more than 1 litre per hour - more than 6 litres of fluids - to maintain hydration.

You can monitor your level of hydration by the colour (and quantity) of your urine. CHART: Are You Dehydrated?. And obviously, if you are not passing normal quantities of urine you are dehydrated.

I also experienced some episodes of cramping and muscle spasms, indicating a lack of electrolyte.

Quoted below is a recipe for making your own electrolyte replacement supplement powder given to me by a fellow cyclist. He says a lot of people swear by this home made formula copied from originator's website. I have compared the ingredients with a commercial supplement powder (Powerbar Isoactive) and they are very similar. But the commercial supplement powder is way more expensive.

"To clarify, the mix for 100 liters is

1. 190 grams rock salt or standard table salt
2. 64 grams Diet lite salt (50% normal salt and 50% potassium chloride)
3. 31 Rennies antacid tablets (CaCO3 680mg, MgCO3 80mg)

All these ingredients are broadly available in Australian supermarkets. I have excluded zinc from the formula because it is difficult to acquire, and the amount is very small, and could easily be compensated by taking a quality multi-vitamin most days of the week.

Note that it is best to pulverize the Rennies tablets with mortar and pestle, then add all ingredients to a blender until well mixed and powderized.

To make 1 liter of sports drink, add 3 grams to a cordial solution. (if you want to be more exacting, add 2.8 grams). Instructions for cordials usually result in a 6% carbohydrate solution. The scientific literature recommends from 5% to 8% carbohydrate concentration for an electrolyte replacement formula.

Another option is to buy a cordial powder and add the salt powder in an appropriate volume, ready to just add water during endurance exercise."
Last edited by RonK on Wed 04 Jan, 2017 6:45 pm, edited 7 times in total.
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Re: How much water is needed?

Postby jdeks » Wed 04 Jan, 2017 6:30 pm

wayno wrote:need to take a quarter teaspoon of salt for every litre drunk to be able to retain water drunk or your more likely to pee it out, being surrounded by too much water is more often my issue. eat salty food especially when its hot to offset sodium lost in sweat


Do you have a source for this claim?
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Re: How much water is needed?

Postby wayno » Wed 04 Jan, 2017 6:47 pm

jdeks wrote:
wayno wrote:need to take a quarter teaspoon of salt for every litre drunk to be able to retain water drunk or your more likely to pee it out, being surrounded by too much water is more often my issue. eat salty food especially when its hot to offset sodium lost in sweat


Do you have a source for this claim?



numerous other sources give a similar amount of salt, give or take a bit

http://www.saltinstitute.org/news-artic ... hydration/
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Re: How much water is needed?

Postby jdeks » Wed 04 Jan, 2017 7:03 pm

wayno wrote:
jdeks wrote:
wayno wrote:need to take a quarter teaspoon of salt for every litre drunk to be able to retain water drunk or your more likely to pee it out, being surrounded by too much water is more often my issue. eat salty food especially when its hot to offset sodium lost in sweat


Do you have a source for this claim?



numerous other sources give a similar amount of salt, give or take a bit

http://www.saltinstitute.org/news-artic ... hydration/


Sorry, that link provides zero reference for their own assertions. It's just a bunch of blog-grade claims about what you apparently "need" to be doing, whith nothing to back it up.

Do you have any peer-reviewed scientific studies to back up or evidence for that claim?
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Re: How much water is needed?

Postby GBW » Wed 04 Jan, 2017 7:18 pm

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Re: How much water is needed?

Postby jdeks » Wed 04 Jan, 2017 7:55 pm

GBW wrote:https://en.wikipedia.org/wiki/Sodium_in_biology


C'mon, wikipedia? even there, still nothing to support this "you need to take 1/4tsp of salt with every liter you drink". Sorry, I'm calling baloney.


Truth is, your salts mostly stay in the body - dehydrated folks typically end up with *higher* conenctrations in their tissues as they sweat water out at a faster rate. Takes a shedload of sweating over a long time to actually deplete salts past what your diet provides.But the laast decade or so has seen a massive push of hydration psuedo-science, convincing people they need to pump brightly colored water into themselves as soon as they step outside on a warm day (thanks, Gatorade). It's recycled around the internet until it seems legit, and worse still, people buy it.

The scientific evidence on this has been established for ages - unless you are *seriously* pushing it for *at least* several hours straight, ingestion of additional electrolytes does next to nothing. People *think* it does, because the vast majority of the off-the-shelf "rehydration electrolytes" are actually mostly sugar, and a glucose hit with the water they really needed does wonders at making their cramps go away, their headache fade and generally feeling better. A gummy-bear (or a better lunch) and a tap would produce the same results for most, but that doesn't make you feel anywhere near as hardcore or sell anywhere near as much candy drink-powder.


I dont like to blow my own horn if I can avoid it, but as someone who spent a Thailand summer in a muaythai camp, my personal experiences match the studies. It took me about 2 weeks of training 6+ hours a day in 35C tropics to show signs of potassium deficiencies, and it properly sucks. The real replenishment solutions taste so bad, I got off them as soon as I could, and didnt need them for the next 6 months. The locals sure dont.

But I've never felt like that in Australia, nor have I needed electrolytes, before or since - not even in my cross-country/triathlon days. Simply not doing that level of exertion, for that length of time. Very, very unlikely anyone would do that hiking, even in here in Aus.

But individual anecdotes are just that, so:

https://bringyourownlentils.blogspot.co ... -myth.html

http://www.weightymatters.ca/2015/05/yo ... ed-to.html

The supporting studies are linked in the articles. Plenty more on google scholar if you care to look.

Or dont - it's your money.
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Re: How much water is needed?

Postby Ant71 » Wed 04 Jan, 2017 8:24 pm

Not sure if this is the right place to ask or not I was going to start a topic but this is on a similar line. So what is the best way of storage for water. I have a 2 litre hydration bladder and a 1 litre water bottle but what is best if I need more? Thanks
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Re: How much water is needed?

Postby Gadgetgeek » Wed 04 Jan, 2017 10:22 pm

jdeks, conditioning also matters a lot. To someone less used to the heat, they will sweat out more salt. I have buddies who are athletes who won't stain a black shirt with salt, they sweat near pure water, and I sometimes wonder if I'm about to grow crystals. A lot of people on a western diet run high on soduim, but can short themselves on magnesium or calcium first, so there are no easy answers.

My how much is enough, is a liter per hour.
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Re: How much water is needed?

Postby Hisham » Wed 04 Jan, 2017 11:03 pm

Yea I'm still not sold either way but good discussion. It's a body of evidence that proves a theory. It's probably all a little true.

I've taken and given electrolytes and thought there was a good outcome on multiple occasions, but maybe it was other factors or a placebo. And that first link jdeks references doesn't discourage the placebo treatment btw.
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Re: How much water is needed?

Postby wayno » Thu 05 Jan, 2017 3:17 am

Gadgetgeek wrote:jdeks, conditioning also matters a lot. To someone less used to the heat, they will sweat out more salt. I have buddies who are athletes who won't stain a black shirt with salt, they sweat near pure water, and I sometimes wonder if I'm about to grow crystals. A lot of people on a western diet run high on soduim, but can short themselves on magnesium or calcium first, so there are no easy answers.

My how much is enough, is a liter per hour.


no they don't, i dont have study references to hand but i've read scientific studies that show you can sweat half the amount of salt for a given volume of sweat if you are aclimatised, compared to unaclimatised people. aclimatised people sweat more water than unaclimatised people, but in the end they still arent sweating any more salt than an unaclimatised person, and the amount of salt you sweat can also be affected by the amount of salt you regularly ingest, you loose more when you are regularly ingest more.
Tim Noakes a prominent physiologist had references on this, an if people are so intent on wanting the exact referneces, make the effort to use google, i spend enough time writing responses on here, it leaves me with less time to do the research but i can tell you i have read what i'm talking about and it can be from text books and not necessarily from the internet, i've read a lot and i dont have a list of everything i've ever read
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Re: How much water is needed?

Postby ofuros » Thu 05 Jan, 2017 5:00 am

Lophophaps wrote:Note that I'm not asking how much is carried, but how much should be drunk.


The body can only process about a litre of water per hour...& frequent small intakes during you're walk are better than one large guzzle.
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Re: How much water is needed?

Postby wayno » Thu 05 Jan, 2017 5:10 am

your gut can only absorb a litre per hour and ideally with some added salt to help speed the process, if you add sugar to the drink then absorption decreases in proportion to the extra sugar added... i couldnt tell you the exact figures on how much it drops for the sugar taken, but the hammernutrition site recommends avoiding taking any sugar at all and rely on carbs for energy because carbs dont slow down the abrsorption of water as much and dont require as much dilution in the gut to be effectively absorbed. plus high protein and fatty foods will slow down water absoption 2 because those foods are held in the stomach a long time to be digested and they use up a lot of water in their digestion. 8 times more for protein compared to carbs, i read that in a text book by Dr Tim Noakes physiologist. "the Lore of running"
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Re: How much water is needed?

Postby Xplora » Thu 05 Jan, 2017 5:37 am

Hyponatremia is a very complex subject but it is also very real. Salts are lost from the body during exercise and urination and there is much written about that (peer reviewed). You can do the search if you want as I just did. Drinking too much water can destroy the salt balance and cause death. Here are some articles you can read if you want good information:
http://www.mayoclinic.org/diseases-cond ... n-20031445
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4192979/
https://www.kidney.org/atoz/content/hyponatremia

The brain can adjust to the chronic form which may account for the acclimatization effect. Knowing the level of sodium in your body is a bit tricky in the field. Having too much can also be a problem. I am unsure if Wayno is totally correct about the need to have salt in the water in order for the body to take up the water but there is evidence to say salt in the water is needed to treat the problem and his ratio seems to correlate with the evidence.
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Re: How much water is needed?

Postby wayno » Thu 05 Jan, 2017 5:42 am

you dont have to have salt in the water you drink to absorb it, but having small amounts of salt can speed up absorption and retention of the water
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Re: How much water is needed?

Postby Lophophaps » Thu 05 Jan, 2017 6:50 am

Ron's Are you dehydrated? link is useful. On a recent walk my colour varied from normal to the second and third last. However, there was nothing adverse, just tired. Some days my clothing was like a salt mine, and others it was just sweaty.

I've been eating salted nuts on walks. Apart from the salt the energy content is high, over 2200kJ/100 grams. This seemed to give me enough salt

Jdeks' link http://www.weightymatters.ca/2015/05/yo ... ed-to.html is helpful. There's too many unsupported claims about food. I saw on yesterday, where a blender manufacturer claimed “More than just a blender, the NutriBullet breaks down whole fruits & veggies to extract the maximum nutrition from your food.” Rubbish. So it seems to be with electrolytes. I take the six hour time cited in the link, er, with a grain of salt. Individuals and circumstances vary. However, it seems from that link that only after several hours of sustained exercise is electrolyte replacement necessary.

I accept Wayno's advice that “I have read what I'm talking about and it can be from text books and not necessarily from the internet, I've read a lot and I don’t have a list of everything I've ever read.” The internet is useful, but much is not sourced properly or based on facts. I like to check things from three independent sources, and then maybe find a book.

Ant71, I carry two DIY wine casks, four litres and 120-150 grams each. There's also spare cask, about 40 grams. This gives me a good reserve for long days away from water and in case a cask breaks.

A summary; please advise if this is correct.
* The body can take about a litre of water an hour.
* Salt is good for retaining water.
* Electrolytes are needed for longer days of substantial exertion.
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Re: How much water is needed?

Postby wayno » Thu 05 Jan, 2017 6:59 am


A summary; please advise if this is correct.
* The body can take about a litre of water an hour.
* Salt is good for retaining water.
* Electrolytes are needed for longer days of substantial exertion.


I agree with the first and last point
as for salt is good for retaining water , depends on the amount of salt , but in general as long as you're not taking a ridiculously high amount of salt in the tens of grams when you're not hyponaraemic, then yes salt can help you retain water when you are ingesting a lot of water and at risk of running low in sodium, but taking oo much sodium has a diuretic effect as the body flushes the excess out, but for prolonged exercise it becomes harder to have too much salt idealy dont live on a high salt diet because you will be peeing out excessive amounts of water to start with... you want high salt intake on the days you are exercising heavily in the heat
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Re: How much water is needed?

Postby Moondog55 » Thu 05 Jan, 2017 7:34 am

Because I lived in The Alice a while ago I always tend to worst case scenario, 5 litres per person per day in hot weather, so if it is really hot I don't walk too far obviously, not that I do much summer walking these days
Water use and fitness seem to go together also, fitter people start to sweat more heavily at a later time/higher body temperature which has a bearing.
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Re: How much water is needed?

Postby jdeks » Thu 05 Jan, 2017 8:55 am

wayno wrote: the hammernutrition site recommends avoiding taking any sugar at all and rely on carbs for energy because carbs dont slow down the abrsorption of water as much


If that's what they say, then I'd questions "Hammernutrion"s credibility - sugar IS pure "carbs". This is what I mean about prolific psuedoscience.

ofuros wrote:
The body can only process about a litre of water per hour...& frequent small intakes during you're walk are better than one large guzzle.


Sorry, but in the absence of some supporting research, I'd contest that last half.

Your gut may only be able to absorb ~1L per hour, but it doesnt matter how you get it - water in is water in. It'll sit in your stomach until its absorbed. Aside from feeling like a walking water balloon, theres no real reason that sculling a bottle wont rehydrate you just as well as sipping it over an hour. As long as you puke it all out again, it's probably better - in my experience, people sipping to 'keep up' usually rely on symptomatic thirst and don't end up sipping enough (then think they need electrolytes). At least if it's in you, it's there to be absorbed.

Xplora wrote: Salts are lost from the body during exercise and urination and there is much written about that (peer reviewed). You can do the search if you want as I just did. Drinking too much water can destroy the salt balance and cause death.


Agreed. But the point I'm making is that most of the research indicates that to put this balance so far out of whack that you *need* to start drinking extra electrolytes, you need to be doing sustained exertion beyond what you'd see hiking, for quite a few hours. Just because salt is lost in sweating, doesn't mean you need to drink some to replace it. The body is very good at self-regulation - the salt you sweat out goes with enough water to keep the balance.

This is purely an anecdote and not any sort of evidence, but stories are fun:

When I hit the electrolyte wall in Thailand, I didn't get cramps or headaches - over about two days I got increasingly tired and weak, lost all my appetite and then nausea and the runs. Thought I'd eaten something bad or caught some odd asian flu. I was pounding about 8L a day and I had some yummy sports drink sachets too which I kept doing, so I ruled out dehydration. Then one afternoon, I basically collapsed. Literally just limbs didnt have the power to move, wasn't sure where I was or what's going on. Someone got me a gatorade and that got me on my feet long enough to get in a cab.

When I got to the hospital, they saw I was a white guy in sports getup, and went straight for an IV. I insisted I was drinking enough and showed them the little sports drink sachets I had, and the doc just laughed. About 20 minutes on the drip and I felt like superman. My potassium had bottomed out (the rest wasnt far behind). Most off-the-shelf powders don't really offer much K+ because theres a risk that people will drink too much (for the taste) and cause other problems.

The gave me some concentrates which tasted like cough syrup and seawater, and told me to tone the training down for a few weeks until I adapted. Fast forward a month or so and I was doing 6-7L a day of just bottled water, and feeling fine.
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Re: How much water is needed?

Postby neilmny » Thu 05 Jan, 2017 9:19 am

Getting back to the OP's question.

I carry 3 litres and this gives me about 24 hours worth which would include making a couple of cups of coffee and rehydrating 1 meal.
I'm not inclined to walk to places where there is no water but if there was a limited supply I would top the 3 litres up at any good opportunity.
As a recovered CAD patient one thing I don't do is allow myself to dehydrate.

Maybe the mods ( Lops :) )should split the salt intake topic of into it's own thread.
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Re: How much water is needed?

Postby slparker » Thu 05 Jan, 2017 9:39 am

A summary; please advise if this is correct.
* The body can take about a litre of water an hour.


there is a finite rate of water absorption by the stomach and small intestine. this rate is around 1l an hour, give or take.

* Salt is good for retaining water.

The way that water is retained by the body is by a variety of hormones that are activated when blood volume drops and blood concentration increases (because of sweat loss). These hormones concentrate the urine (that is, reduce the water lost in the urine). The sodium added to the diet is there to replace the sodium lost in sweat; it doesn't directly contribute to water retention per se; although it is true that in people with impaired heart or kidney fiunction that there is a more linear relationship to salt in the blood and diet to blood volume (that is 'water retention').

Only endurance athletes in hot humid conditions need to worry about hyponatraemia - that is highly diluting the blood by excess water ingestion. Most walkers even on hot days are much more likely to have heat exhaustion (low blood volume due to loss of water and electrolytes) before they encounter hyponatraemia. there is always a possibility of hyponatraemia of a walker really decides to overhydrate but I doubt if this is a massive risk in what is a leisure, not a competitive, pursuit.

* Electrolytes are needed for longer days of substantial exertion.

Electrolytes are required to replace what is lost in sweat. A normal diet furnishes the electrolytes that you need so regular eating of snack foods like muesli bars, nuts and fruit gives you the electrolytes that you require. In most cases there is no need to add salt to water unless you aren't eating through the day, but there is probably nothing wrong with it unless you make the concentration too high in your electrolyte replacement drink - in which case the body will need to remove the excess sodium via the kidneys, requiring more water to do so.

If you are a heavy sweater, if it is especially hot and humid and if you are working very hard it is quite possible to overwhelm your capacity to replace fluid and electrolytes lost in sweat even with regular ingestion of fluid and electrolytes. This is a condition called heat exhaustion and is definitely a risk for those walking in hot and humid environments. The best prevention is to lower your work rate in a background of regular water and electrolyte replacement, walk in the cooler part of the day and to 'preload' with water during the evening so you start the day fully hydrated.

As someone has already mentioned, monitoring urine concentration is a good way to see how much fluid you need to replace as there is a direct correlation between urine concentration and blood water volume. There is a delay here so it is possible to get dehydrated before you know it.

In hot/humid weather walk slowly in the cooler part of the day, drink up to 1l and hour in proportion to urine concentration and eat regularly - there is no mystery to it.
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Re: How much water is needed?

Postby taipan821 » Thu 05 Jan, 2017 9:46 am

Lophophaps wrote:This is firmly in the string, length of, category. There are too many variables, such as individual physiology, fitness, individual size, humidity, air temperature, how fast one is going, terrain steepness, pack weight and maybe if Jupiter is rising into Aquarius. So all numbers need to be applied with care. My scenario is a steepish climb for several hours, no creeks or rivers, hot day, overnight gear, plodding up the hill at a steady pace.


easy answer... make notes. I have found that normal day (not hiking, aircon etc) I drink 3-4 litres, hiking I might drink 6 litres (walking on a track) SES searches I'll be drinking 8-10 litres a day (heavy hot clothes, search gear, walking in a straight line regardless of the terrain)
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Re: How much water is needed?

Postby Lophophaps » Thu 05 Jan, 2017 10:02 am

taipan821 wrote:easy answer... make notes. I have found that normal day (not hiking, aircon etc) I drink 3-4 litres, hiking I might drink 6 litres (walking on a track) SES searches I'll be drinking 8-10 litres a day (heavy hot clothes, search gear, walking in a straight line regardless of the terrain)


Keeping track of water from containers is easy for me, if approximate. About four litres in the wine cask at the start, about one litre at lunch, three litres drunk. However, this is approximate, and there's no viable way that can measure precisely how much is drunk from containers. This is compounded when a creek or river is reached, with a mug or so of water drunk and the water container topped up. I'd drink perhaps six litres on a hot day and/or a steep long climb
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Re: How much water is needed?

Postby Grose Chick » Sun 12 Feb, 2017 1:47 pm

I'm not offering any recommendations or suggestions, only sharing what I have experienced. I recently walked from Burra Korain in the Grose valley to acacia flats. It took about eight hours, and the weather was extraordinarily hot and humid. I had oats and coffee for breakfast, then filled my canteen (940ml) and my sawyer mini filter bag before heading off. I ate granola bars and salted mixed nuts along the way. The canteen was nearly empty when I arrived. I jumped into Govetts creek to cool down, set up my tarp shelter, refilled my canteen and had a nap for about 3 hours. I woke up about six, cooked dinner, had another cup of coffee, and as it got dark, went back to bed and slept for eight hours straight. I woke up the next morning feeling great. This is pretty typical water consumption for me on hikes, and according to what I read everywhere, I should be dead. But it seems to work for me. If, I notice my urine is getting darker, I will make an effort to drink a bit more, but even that doesn't happen often.
Quite frankly, I'm bewildered by everything I read on the subject. It simply does not match up to my personal experience.
I allow two litres a day for hot days, and that's including water for cooking and coffees.
Does anyone have any explanations for this?
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Re: How much water is needed?

Postby Neo » Sun 12 Feb, 2017 1:59 pm

Grose Chick just unique and lucky I'd say. If i didn't see your hello post id have guessed that you are three foot tall with an extra kidney.
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Re: How much water is needed?

Postby Grose Chick » Sun 12 Feb, 2017 2:05 pm

Neo wrote:Grose Chick just unique and lucky I'd say. If i didn't see your hello post id have guessed that you are three foot tall with an extra kidney.

:lol: :lol: :lol:
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