A good guide is to drink 500ml of water per hour or moderate intensity exercise in moderate temperatures. This will very considerably if the weather changes, the activity becomes more/less strenuous or you are stopped for a break.
First things first, I am not a doctor or a medical professional. The limit of my expertise in this area is a few sports science modules at university, common sense and personal experience. Please take all of the below as relatable advice, rather than medical gospel.
Hiking and specifically hill walking is usually classed as moderate exercise, during which, you will lose water through increased sweating and an increased breathing rate. This is above your usual rate of water loss of you were sitting at home or in the office. The amount of water you lose is really difficult to estimate as it will vary on the intensity of exercise, the outside temperature and what you are wearing. There are also about a million other factors to consider as well but those are the main 3 we will look at in this article.
So, knowing that whatever we do in terms of hydration is likely to be wrong, we have to approximate and estimate based on a rule of thumb that gives us a rough ball park for our water consumption. I use the rough guide of drinking half a litre (500ml) of water per hour whilst hiking in moderate temperatures.
Once I have that as my base line, I can then think about the hill intensity, I’ll try and drink more going up hill rather than down hill as the exercise is more intense. Also the outside temperature, if it is a baking hot day, clearly I will increase from the 500ml per hour water intake.
What should I Drink?
The most basic thing you can drink that is easily consumed and readily available is water. Water is the majority of your body weight, and is critical for your body to function properly. I always drink water when I am hill walking. However, there are other options you can look at. Sports/Isotonic drinks are water based but also contain a combination of electrolytes and carbohydrates as well.
I tend to choose water because I can easily refill my bottles on the walk and I don’t like the overly sweet sports drinks. However, replacing lost electrolytes and increasing your carbohydrate intake can be advantageous if you struggle to eat enough during the day. Other options that I steer away from are fruit juices, fizzy drinks and any milk based drink. Keeping these cold is difficult, and fizzy drinks will get shaken up in your pack, potentially making a bit of a mess.
I use two bottles to drink from on the hill, that are the same size (0.5 litres) as well as sometimes carrying 1 litre extra in my pack. I will then look to refill these bottles at every opportunity to keep as close to 2 litres in total as much as I can. Mine are similar to these bottles , which are leakproof and BPA free. I also like the size of these so that I can easily drink and refill from them on the move.
Before your Hike
It’s a good idea to ensure that you are sufficiently hydrated before you start your walk. If you aren’t, you will be constantly chasing your water requirements and start off on the wrong foot, so to speak. A good rule of thumb for drinking prior to your walk is to aim for 250ml per hour prior to your walk. The way I manage this is that I will work out what I should drink during the drive to the hill. Let’s say that it is a 4 hour drive to the start of the walk, I will pack an extra 1 litre (4x250ml) water bottle in the car and aim to finish it when I arrive taking small sips throughout the drive.
During your Hike
The rate of your water intake will vary a lot depending on the weather during your hike. A moderate temperature would require you to drink 0.5L per hour during the walk. At warmer temperatures, this can increase to 1L per hour or even more. Clearly if you are drinking 1L of water per hour and plan to walk for 6 hours, you would need to carry 6 litres of water for one days walking.
Personally, with the other equipment I carry, this would put my rucksack weight over what I feel comfortable carrying for a day out. The way that I reduce this weight is to, during my planning time, is to identify possible water refill points during the walk. I’ll recap what to look for in a refill point later in this post.
If you feel thirsty, you are already dehydrated. It is really important to keep on top of your hydration during the day, dehydration can cause headaches, joint pain, muscle stiffness, vomiting and eventually death in extreme circumstances.
After your Hike
I try and drink 0.5 litres of water immediately on finishing my walk. I will have a bottle of water in the car that I can use separate to the water I have with me on the walk itself. This just makes sure that any shortfall in my water intake is covered off pretty quickly afterwards. I will then sip on water all the way home to keep me topped up until I get back.
One other pleasant thing to do is to stop at a nearby pub at the foot of a hill and have a cold refreshing beer (other drinks are available). One thing to note, is that alcohol is a diuretic and you will lose water, even though you are drinking another drink.
How to Find the Perfect Water Refill Point
During the planning phase of a trip I will think about my water plan and, if I need to refill my water bottles, where I might be able to do that during my route plan. When looking at the map, I am looking for streams and rivers that I will cross or pass nearby, ideally on steep ground. I will discount any standing water such as ponds/lochs, instead looking for the point where the water might flow into the lake.
When you are on the walk, I will be searching for running water that is above human habitation (almost always on hill walks), ideally white water where the water is running quickly and away from any livestock or animals that might contaminate the water supply. If the water ticks all of these boxes, I am comfortable drinking without treating the water.
If I cannot easily access clean, flowing water, I may need to consider purification of the water to make sure that I do not have any gastro-intestinal issues or feel unwell on the hill. Water filters will take out any of the larger contaminants, but I also carry purification tablets that you can add to the water to ensure there are no chemical or organic contaminants that a filter might miss.
The other option, is to purify your water using UV light. This is not something that I have done before but looking at a UV water pen, you stir the water in your bottle with the pen for about a minute, purifying it in the process – certainly something that I would use if I am ever lucky enough to get one.
In Conclusion
Plan ahead. Look out for water refill points on your route. Before your hike, aim for 0.25L per hour prior to starting off on your hike. During the walk, your water requirements will vary on the level of exertion and outside temperature, keep on top of your hydration to ensure you do not become dehydrated. If you are thirsty, you are already dehydrated. After your walk, continually sip water to cover any shortfalls in your hydration strategy.
I hope that this has been useful, let me know what else you want me to explore in my future posts!
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