The human body is roughly 70% water. Water forms the fluid inside follow ourselves, and the the fluid part of our blood. There are other fluids such as cerebrospinal fluid and fluids in our joints. Everything that happens in body is a chemical reaction in a solution of water and other elements.
Water is used by the body to flush out the waste products of those chemical reactions. Proteins, when metabolized, produce ammonia, which is converted to urea in the liver and filtered out by the kidneys, in a process called urination. Water is used by the body to thermoregulate. It is pushed out of the pores of the skin as perspiration, where it evaporates, taking away excess heat.
Water needs to be replenished almost constantly in order for the body to maintain the functions for life. The amount of time that one can go without water is variable, depending on how hot it is and how much activity is doing. Usually, the human body can go only a few days without taking in water, or it can last a week or more. The longer one goes without water, the more discomfort one will experience. When the body gets low on water, it signals thirst.
Most of the water available for use in perspiration and filtration circulates as the liquid part of blood. A severe lack of water in the blood is called dehydration.
The process by which the body produces perspiration is by pushing sodium chloride out of the pores through sweat glands, and water follows the sodium. Since sodium chloride is the same as table salt, skin will have a salty taste on it after perspiring. The salt that is carried out by perspiration is not reabsorbed, and it has to be replenished.
Sodium is a component of salt that is used by the body in neuron and muscle action. In combination with potassium, sodium is necessary for nervous system functions to work. Sodium and potassium are called electrolytes. When sodium is lost in perspiration, it is not available as an electrolyte and severe problems can occur. The condition of too little sodium in the blood is called hyponatremia. Sodium and potassium function in a balance with each other. There is a range of proportions within which that balance is maintained.
Too little sodium can also result in the symptoms of too much potassium. This can manifest itself as muscle cramping and the natural defense against too much potassium is vomiting. If you begin to vomit from sweating too much you will be in real trouble.
Dehydration can be avoided by carrying water with you whenever you engage in strenuous activity. At the gym, you are able to buy bottled water or drink from a drinking fountain. In the wood, there are rarely any drinking fountains or bottled water. At times there will be water in lakes and streams, and although it is not advisable to drink untreated water from natural sources, in an emergency you may have no choice. This too can lead to problems if the water happens to be contaminated.
When you go hiking, you should carry a minimum of two liters of water, or more if you plan on being out for a long time. You can carry water in a hydration bag or bladder that is in your backpack. This allows you to drink your water without stopping taking off your pack and opening and closing a water bottle. You can also carry your water in water bottles, like Nalgene or Camelback. These bottles have standard-sized openings which make them compatible with many available water filters. Bottled water from a store is very convenient and tends to be very lightweight in terms of the weight of the bottle itself, but it is expensive and not the most efficient use of plastic.
Speaking of water filters, there are many options for treating water that comes from the environment. First there are water treatment tablets that are made of chlorine or iodine, which disinfect water by killing microorganisms that may be in it. The drawback of tablets is that you must wait a significant amount of time for the water to be safe and also for the aftertaste of the tablets to evaporate. The tablets themselves are not particularly harmful but their taste can be objectionable.
The water filter is another way to obtain water from lakes and streams. Water filters are available in a number of configurations such as pump operated filters, gravity feed filters and straws that you drink through, like any soda straw. Pump filters and gravity feed filters usually have replaceable filter elements so that you can renew them after a period of use should they become clogged or broken. Some pump filters can operate as gravity feed filters by adding a plastic bag and hanging it above the filter. Hand pump filters can be cumbersome and slow since each movement of the pump draws a small amount of water.
Another method of treatment is the ultraviolet light method. The steripen has been available for many years. It uses an ultraviolet lamp to render