Nutrition
How much water to take on a walk
Guideline quantities based on duration and heat, how to spread out your drinking and what to do with water from springs and streams.
As a guide, allow between 0.5 and 1 litre of water for every hour of walking, increasing the amount in hot weather or on steep climbs. It is better to take small sips every 15 or 20 minutes than to drink a large amount at once. Never assume that water from natural springs or streams is safe to drink.
6 min read · updated 14 September 2026
As a practical guide, allow between 0.5 and 1 litre of water per hour of walking. The lower end of that range applies to mild weather and a gentle pace; the upper end applies to heat, direct sunshine or sustained climbs.
Guideline quantities
- 2-hour walk, mild weather: 1 litre.
- Half a day (4–5 hours): 1.5–2 litres.
- Full day (7–8 hours): 2.5–3 litres.
- Summer, above 30 °C or an exposed route with no shade: add at least half a litre for each planned hour.
These figures are a starting point, not a universal rule: consumption depends on your weight, pace, temperature and humidity. Adjust based on your own experience and note how much you had left over or how much more you needed.
Drink before you feel thirsty
Thirst appears when you are already short of fluid. Take a few sips every 15–20 minutes rather than drinking half a litre in one go at a stop. Start the walk already hydrated: drink half a litre in the hour before setting off.
Salts, not just water
On long walks in hot weather, you lose sodium through sweat. If you will be walking and sweating for more than three or four hours, alternate water with an electrolyte drink or eat something salty. Drinking only water in large quantities without replacing salts can cause discomfort, cramps and, in extreme cases, hyponatraemia.
Springs and streams
Do not assume any spring is a reliable water source: springs may be dry in summer or unsafe to drink from. Check the official trail description or ask the local visitor centre beforehand. If you are going to drink natural stream water, treat it: use a 0.1–0.2 micron filter, water purification tablets or boiling. Always collect water upstream of grazing land and paths.
Warning:Dizziness, headache, hot and dry skin, confusion or nausea in hot weather may indicate heatstroke. Stop the activity, find shade, cool the person down and call 112: this is a medical emergency, not simply tiredness.
Sources and references
General safety information only. It does not replace specific mountain training or emergency services (112 in Spain and the EU).