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Hiker resting in the shade with an empty water bottle on a hot summer day

I have lost my drinking water

Your bottle has leaked or the spring has run dry, the day is warm and the way is still long – now it matters to save sweat and not take risks with untreated water.

First

  1. Reduce exertion and sweating, seek shade or shelter from wind.
  2. Assess nearby water sources: running, clear water is usually easier to treat than standing or cloudy water.
  3. Do not drink water that smells of chemicals, has an oily sheen or lies downstream of industry, settlements or fields without knowing each method's limits.

Call emergency services if

  • Signs of severe dehydration or heat illness
  • Confusion, impaired consciousness
  • No water reachable and no safe way back

Emergency numbers for Austria · Change region

What is happening

A bottle has leaked, the hydration bladder has burst, the spring on the map has dried up in midsummer – or you simply brought too little. On a warm day with a climb, the body loses a lot of fluid through sweat, often more than you notice.

Thirst is a late signal. Before it, performance and concentration drop, and headache, irritability and dark, scant urine appear. Later come dizziness and confusion. In heat, lack of water can turn into heat illness – and then it is an emergency.

The second danger is the temptation to drink anything. Even crystal-clear stream water can contain pathogens that cause diarrhoea hours or days later – which makes the fluid loss worse. Water with chemical contamination (smell, oily sheen, downstream of industry or fields) cannot be made safe with simple means.

What matters: save sweat rather than hoarding water, realistically assess the way to the next reliable water source or back, always treat water from nature – most reliably by boiling – and turn back or get help in good time.

Step by step

  1. Phase 1

    Immediately

    • Rest in the shade or out of the wind and slow your pace considerably.
    • Take stock: how much water is left, how far is it to the next safe water point, hut, village or car?
    • Look on the map for staffed huts, wells, villages and bodies of water.
    • Decide: the known way back is often the safer choice than an unknown way forward.

  2. Phase 2

    Over the next hours: save sweat

    • Rest in the worst heat and walk in cooler hours – but not through unknown terrain in the dark.
    • Cover your head, protect your skin from the sun, keep your clothes on so your skin is not exposed to the sun.
    • Drink the water you have in small sips rather than saving it until you collapse.
    • No alcohol; eat little and nothing very salty while water is scarce.
    • Watch for warning signs: dark urine, headache, dizziness, unusual exhaustion.

  3. Phase 3

    Water from nature

    • Choose the best available source: running, clear, ideally above settlements, pastures and paths.
    • Let cloudy water settle or pre-filter it through a cloth – this makes it clearer, not safe.
    • Boiling is the most reliable method: bring to a rolling boil; at high altitude longer, following official recommendations.
    • Dose tablets only as the manufacturer states and wait the full contact time.
    • Portable filters typically hold back bacteria and protozoa, but usually not viruses and not chemicals.
    • Melt snow rather than eating it and treat the meltwater; never drink seawater or urine.

  4. Phase 4

    If it becomes critical

    • If there is confusion, impaired consciousness or signs of heat illness, call the local emergency number (112 in the EU) at once.
    • Move the affected person into the shade, loosen tight clothing, and wet and fan them if water is available.
    • Do not leave a confused person alone and do not let them walk on.
    • If no water is within reach and there is no safe way back, call for help in good time – not only once your strength is gone.

What to watch out for

  • Clear does not mean clean

    Pathogens are invisible. Always treat even crystal-clear water from a mountain stream.

  • Chemical contamination

    Boiling, tablets and most filters do not remove chemicals. Avoid water that smells, has an oily sheen or lies downstream of industry, mining or fields.

  • From exhaustion to heatstroke

    If someone becomes confused, staggers or reacts strangely in the heat, it is an emergency. Call for help and cool the person; do not walk on.

  • Diarrhoea makes everything worse

    An infection from untreated water costs extra fluid, often exactly when you have least of it.

  • Cold is deceptive

    In the cold you feel less thirsty but still lose fluid through breathing and exertion. Drink regularly in winter too.

  • Only water, no food

    Drinking very large amounts of plain water during long exertion without eating can upset your salt balance. On long trips, eat something along the way too.

Common mistakes

  • Saving water until exhaustion instead of saving sweat.
  • Carrying on at the same pace in the midday heat.
  • Drinking from a stream just because the water looks clear.
  • Thinking a filter protects against everything.
  • Eating snow instead of melting it.

Prepare in advance

  • Carry more water than you estimate, plus a reserve – considerably more on hot days.
  • Check water points along the route in advance and remember that springs can dry up in summer.
  • Always carry purification tablets as a light backup.
  • Split water between two containers rather than relying on one bladder.
  • In heat, start early and plan rest stops for the hottest hours.

Special consideration

Children and older people
Children often say late that they are thirsty, and older people often feel thirst less. Offer them drinks regularly and watch for changes in behaviour.
Dogs
Dogs also need plenty of water in warm weather and overheat quickly. Their needs belong in your water planning.

Sources

  • Making Water Safe in an Emergency · Centers for Disease Control and Prevention
  • Boil water – Technical brief · World Health Organization, 2015
  • Wilderness Medical Society Clinical Practice Guidelines for Water Disinfection for Wilderness, International Travel, and Austere Situations: 2019 Update · Wilderness & Environmental Medicine (Wilderness Medical Society), 2019
  • Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2019 Update · Wilderness & Environmental Medicine (Wilderness Medical Society), 2019

Your situation

Available water
Equipment

Matching entries

0 rules apply

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Basics for this situation

Why: Always applies to this situation – regardless of your answers.

All rules of this situation (8)

  1. [not active] If Available water = Cloudy or standing water

    Clarify cloudy water first – then disinfect.

  2. [not active] If Available water = Snow / ice

    Melt snow rather than eating it; still treat the meltwater.

  3. [not active] If Available water = Seawater

    Never drink seawater. Only distillation removes salt.

  4. [not active] If Available water = Rain likely

    Collect rain with clean surfaces and containers.

  5. [not active] If Equipment = Metal pot and fire / stove

    With a pot and fire, boiling is the most reliable method against pathogens.

  6. [not active] If Equipment = Purification tablets

    Dose tablets per manufacturer and wait the full contact time.

  7. [not active] If Equipment = Portable filter

    Filters typically remove bacteria and protozoa, but usually not viruses and not chemicals.

  8. [not active] If Equipment = None of these

    Without equipment: consider SODIS with clear PET bottles – note its limits.