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How Much Water You Need Daily to Survive (What Experts Say)

There is much debate, interest, and misinformation when it comes to the minimum water needed to survive. As concern grows, however, over the depletion of fresh-water resources and water systems, it’s understandable that people desire this survival information as a means of preparation and knowledge.

There is no scientific formula to determine the exact minimum amount of water needed to survive since each person requires a different amount. However, experts agree that individuals require between 90 oz (2.7L) and 125 oz (3.7L) of water a day from liquids and food in order to avoid dehydration.

The Mayo Clinic breaks this amount down into cups. They recommend 15.5 cups of water a day for men and 11.5 cups a day for women.

The human body requires water to regulate internal temperature, transport nutrients, flush waste, protect organs, and lubricate joints. Water is crucial to a healthy life, yet there is little consensus among experts and scientists as to the minimum needed to survive on a daily basis.

Row of large bottles of drinking water in a garage

So What Is the Minimum Amount of Water for Survival?

Many survival sources suggest that an average person can survive anywhere from two days to a week without liquid. However, this is only an estimate and has little scientific proof for substantiation.

There are many factors that determine how long a person can survive without water, such as age, health, weather, and level of physical activity.

Hot weather can cause people to overheat and experience dehydration at dangerous levels, as can extreme physical activity. Children, older adults, and people with certain illnesses are also more susceptible to the threat of dehydration. Therefore, the minimum water needed to survive is based on the combining factors of a body’s state of being and environmental influences.

In addition, sources of water should be taken into account in determining the minimum water needed to survive. Water is derived from both liquids and food. Foods contain different amounts of water and can contribute up to 20% of daily water intake, which adds to healthy hydration. Beverages besides water, such as tea, milk, juice, and even coffee and soda, also contain water that contributes to hydration.

There is no doubt that all living things need a minimum amount of water for survival. However, since it is nearly impossible to set an exact minimum amount, it’s best to view the water needed to survive through the lens of avoiding dehydration.

Dangers of Dehydration

Dehydration takes place when the body loses more fluids, primarily water, than it takes in. When dehydration occurs, water moves out of individual cells, and then the body is in excess of what is ingested through drinking fluids. When it reaches medical concern, dehydration indicates that a person has lost such an amount of fluid that their body loses normal, functional ability and presents medical symptoms related to fluid loss.

Some of the early symptoms of dehydration are:

  • Thirst
  • Dry mouth
  • Sleepiness
  • Headache
  • Low urine output
  • Dry skin
  • Dizziness

These early symptoms can become drastically and rapidly worse if dehydration continues, resulting in fever, low blood pressure, rapid heart rate, seizure, and even death.

Though some population groups are more at risk for dehydration than others, people and animals lose water every day through exhaled water vapor, sweat, urine, and stool. Bodies are in constant adjustment of balancing water loss and intake, which is why the body becomes unbalanced when too much water is lost.

Therefore, the minimum amount of water needed to survive is that which maintains basic bodily function in each individual and prevents severe dehydration. Some experts agree that severe hydration begins when a person loses about 10% of their total body weight to water loss. However, this can be difficult to measure, considering the many ways in which humans lose water and how rapidly it can happen.

Assessing Dehydration        

There is no exact formula for hydration, as it depends on an individual’s age, weight, level of physical activity, general health, climate, and environment. As people lose water to sweating through doing strenuous physical work or exercise, or through experiencing a hot climate, they would need to replace water loss through food and drink more so than people similar in weight and height resting in an air-conditioned room.

Therefore, it’s best to understand how to assess dehydration individually and at an early stage in order to avoid medical symptoms and being without enough water for survival. Such early indicators of dehydration can be assessed through a person’s thirst and urine:

  • Thirst: most healthy people are able to adequately meet their daily hydration needs through the indication of thirst. When hydration levels drop, the body naturally develops and presents thirst to indicate that water is required for drinking and restoring physiological balance.
  • Urine: urine output for well-hydrated individuals should appear pale yellow or colorless. Dark yellow or orange urine can be an early indicator of dehydration, and that the body needs to ingest more water.

Of course, common sense should play a role in making sure of adequate water intake. If you have been sweating due to heat and/or exertion, it’s important to drink water before any indications of thirst or dehydrated urine.

Minimal Required Daily Water Intake

Between food, fluid, and water sources, in order to avoid dehydration, there are baseline recommendations as to how much water people should consume in a day.

For women, the recommendation is 90 ounces (2.7 liters) of water from all beverages and food per day. For men, the recommendation is 125 ounces (3.7 liters) daily.

However, it’s important to realize that these recommendations are, on average as well as just general guidelines. They don’t represent scientific data, nor do they apply to specific individuals. In addition, these daily water intake recommendations don’t indicate a minimum amount of water needed for survival, as that is nearly impossible to calculate.

Understanding Freshwater Scarcity

Though it seems that water is plentiful, experts estimate that only 3% of global water is fresh water and even less than that is accessible to properly use for drinking, bathing, and irrigation. Unfortunately, this water scarcity is a fundamental survival problem in many areas of the world, and many water systems are becoming stressed. The main stressors and threats affecting water within global ecosystems are:

  1. Pollution: Water pollution is created through many sources, such as pesticides, fertilizers, and human and industrial waste. Harmful bacteria from waste can contaminate water, making it unfit to use for drinking or bathing. Other toxic substances build up in the environment over time, potentially affecting the food chain and sources of hydration.
  2. Agriculture: Agriculture requires a large percentage of accessible fresh water. Yet many irrigation systems are inefficient, thereby depleting resources and drying out rivers, lakes, and underground aquifers.
  3. Population Growth: The rapid growth of the human population and resulting development and industrialization has created water stress. Human usage is reaching unsustainable levels, with additional pressure for freshwater growing each day.
  4. Climate Change: Patterns of changing weather are altering water systems, causing shortages and droughts in certain areas and floods in others. These changes also result in water stress.

Understanding threats to freshwater systems and how they can be mitigated is important when considering how much water is needed at a minimum for survival as a global population.

Minimum Water Storage for Survival

Experts recommend that people store a minimum amount of fresh water in case of emergencies, natural disasters, system disruptions, and/or contamination. Most survival guidelines suggest storing one gallon of water per person, per day, for a minimum of three days. This allows for fresh water for drinking and some for hygiene.

Using three days as a minimum should be enough for minor emergencies during which access to fresh water is limited on a temporary basis. For those who wish to store water in case of more devastating conditions, a safe minimum of two weeks is recommended.

Cases and/or gallons of fresh water can be stored in a dark, cool environment.

Recommend Emergency Water Preparation Products

Here are a few Amazon links to products that will help you be prepared for a potential disaster or temporary loss of potable water.

  • 3.5 Gallon Stackable Water Containers– I recommend keeping a few of these stored in random places around the house. They could be a lifesaver if you are cut off from your main water supply. These are great for keeping in the garage or back of a vehicle. Storing at least 1 per person as backup drinking water wouldn’t be the worst idea ever.
  • 55 Gallon Water Storage Tank– I feel like every family should have at least one of these full and ready to go at all times.
  • 550 Gallon Water Storage Tank– If you live in a desert or just planning for worst-case scenarios, this is something to consider. However, if you live near a natural freshwater source, it might be overkill.
  • Water Purification Tablets– These are an important backup solution if your water supply ever becomes contaminated during a disaster.
  • Water Drum Siphon Pump– If you have a large storage tank, this is a must-have. It will help prevent contamination.
  • Small Portable Stove– Another backup plan in case your water source is contaminated. Boiling is the best way to purify water.

Recommended Food Storage Products

Besides stockpiling water, you will also want to set aside some emergency food for long-term storage. I highly recommend the products at My Patriot Supply. Rice and beans are a great place to start, even if you store nothing else.

Af you want to learn how to store dry foods for long-term storage yourself, check out my article on Storing Rice and Beans for the Long Term, which covers a sound methodology that can apply to almost any dry food.

Related Questions

How long can you live without water? People can survive without water for approximately 3 days. This number can vary based on activity level and other environmental factors like extreme heat.

Does tea count as water intake? Tea does count as water intake, which runs counter to some conventional wisdom regarding its diuretic effect. The diuretic effect does not offset the rehydration process.

For more, check out How Much Emergency Water Should I Stockpile and Store Per Person?