Prepare
Water on the GR20
In summer, water often decides the day. Get it right and a single bottle carries you to the next refuge; get it wrong and an exposed ridge turns into an ordeal. Here's where to drink, which stages are dry, how much to carry and why to filter — nothing made up, just the reflexes that genuinely matter.
The context
Why it really matters
The GR20 is not a desert: you cross springs, streams and refuges almost every day. The trap isn't a lack of water in general, it's a lack of water in the wrong place: on a climb in full sun, on a ridge with no stream, or at a spring you were counting on that has dried up in the heat of August. The Corsican heat does the rest — you sweat more than you think, and dehydration eats away at your judgement on terrain where staying sharp is exactly what you need.
The good news: with two or three simple reflexes, water stops being a worry. That's what this page is about.
The golden rule
Ask the gardien, every morning
No map replaces today's information. Spring levels change with the year, the season, the snowmelt and the drought. A reliable spring in June can be dry in August.
The one reflex that never lets you down: before leaving a refuge, ask the gardien (the warden) whether the next spring is still flowing, and how far you need to go on what you carry. It's the advice every GR20 regular repeats, and by far the most useful thing here. Always set off with enough to reach the next confirmed water point.
Where to fill up
The refill points
You find water in two kinds of place. First the refuges and bergeries (shepherds' huts): nearly all have a water point where you can fill bottles and bladders — that's your safest planning base. Then the natural springs and streams along the trail, more frequent in the north and the valleys than on the ridges.
Among the points often cited by field guides: the fountain at the start in Calenzana, the Spasimata stream before the footbridge, the Haut Golo and Castel di Vergio area (reputed to be plentiful), or Vizzavona at the halfway point. Treat these names as landmarks, not guarantees: exact names and flow rates vary from year to year, which is why the golden rule above matters. [List to be cross-checked with your gardien and the day's conditions.]
One special case: Lake Nino and the grazing areas (pozzines). The water looks lovely but herds pass right alongside — you filter or treat it systematically, never drink it raw.
To anticipate
The dry stages
These are the sections where you set off loaded, because there's nothing — or almost nothing — between two points. Spot them on your route:
The Monte Cinto climb
On the ascent towards the highest point of the GR20, water points thin out once you've left the bottom of the valley. You climb with your reserve.
Manganu → Petra Piana
A long ridge section, one of the finest, but with no spring or river along the high route. Fill right up before leaving.
The Col de Laparo, in the south
Often dry from August onwards. In late summer, don't count on it: set off at full capacity.
The last stage to Conca
Little water on the southern finish. Better to reach Conca with a bottle to spare than to ration yourself in the heat.
How much to carry
The right amount, without loading up for nothing
Water is heavy (1 litre = 1 kg), so you adjust rather than load up blindly. The benchmarks GR20 hikers come back to:
- 2 litres minimum at the start of a normal stage, in mild weather.
- 3 litres on an exposed section or in strong heat.
- Up to 4 litres on a dry stage like those above.
Our stage planner already estimates water and calories per segment: use it to spot, stage by stage, where you'll need to set off more heavily loaded.
Health & safety
Filtering: the lesson of summer 2024
In the summer of 2024, the GR20 saw a notable outbreak of gastroenteritis: between 1 and 15 July, Corsica's regional health agency (ARS) recorded more than 230 cases and a few short hospital stays, with no serious cases. The investigation concluded that transmission was mainly person-to-person (most likely a norovirus); water was not formally identified as the cause, but the official recommendation that came out of it is clear and holds for good.
The message from the health authorities: treat or filter your water before drinking it, and wash your hands rigorously. On a 12-day mountain trek, that's exactly what you want to avoid — prevention costs a few grams in your pack.
In practice, two complementary approaches: a water filter (such as a Sawyer Squeeze or Katadyn BeFree, which screws onto your bottle or bladder) for everyday filtering, and purification tablets (such as Micropur) as a backup — light and indestructible. Filter any surface water as a matter of principle, and without hesitation in grazing areas.
Sources
Check before you go
Water points are living data: they change every season. For freshness, rely on the Parc naturel régional de Corse, on the refuge gardiens (the most reliable, on-the-ground information) and on the health recommendations of ARS Corse. Mon GR20 is a personal account: it helps you anticipate, it doesn't replace today's information.