Up to 70% of the total body weight is due to water. Although it is present in all parts of the body, it is more in organs such as lungs and brain and fluids such as blood, lymph, saliva and secretions by the organs of the digestive system. Most people believe that we feel thirsty whenever our body needs more water. While this is true, recent research studies have indicated that there are several other indicators of inadequate water in some or all parts of the body. Ignoring these indicators can lead to several major diseases that medicines may cure but not treat.
The ratio of the water content in and outside the cells of the various organs is very important. As age advances, water content in the cells decreases. Since the water content in each cell plays a vital role in maintaining is normal function, inadequate water can lead to loss of some functions. Loss of functions results in specific signs and symptoms. Water is necessary for all chemical reactions in the body and to maintain normal health. Just as water helps a seed grow into a tree, it also helps our body grow from birth to adulthood. The flow of water inside and outside the cells generates energy. This energy is stored in the body along with other chemical sources.

The energy generated by the water in the cells helps transmit impulses in the nerves. It helps in the formation of a glue-like material that generates the solid substances in the walls of the cells to be "stuck" to each other. It transports the chemical substances produced by the brain that carry its messages to different parts of the body. Just as there are lanes on a main road for different types of vehicles, chemical substances of the brain are transported in the "water lanes" along the length of the nerves. Water content in the body influences the functions of the various proteins and enzymes that are dissolved in it.

Water helps maintain the moisture of the lining of the internal organs of the body. It maintains normal volume and consistency of fluids such as blood and lymph. It regulates body temperature. It removes "poisons" or "toxins" from the body through urine, sweat and breathing. Water is essential for regulating the normal structure and functions of the skin. The body loses about four liters of water every day. It is therefore necessary to replenish this volume by drinking at least the equivalent amount of water every day. Inadequate intake of water can lead to dehydration.Cold water from natural sources is fit for drinking because of six main reasons:

Lowers the body temperature.
Dilutes the blood to the required consistency.
Promotes excretion of poisons from the skin in the form of "evaporation".
Stimulates the normal functions of the kidneys and therefore increases the rate of removal of "poisons" from the body through urine.
Increases movements of the intestines.
Facilitates formation and passing of soft stools.
Sipping hot water has several benefits too:

For example, as soon as you drink hot water, there is instant stimulation of the inner lining of the stomach and contraction of its blood vessels. Thus, you are less likely to suffer from increased acid secretions in the stomach.
Hot water cleans the stomach, relieves heartburn, belching, flatulence, acute indigestion, vomiting and cramps in the abdomen.
It is important to remember that hot water should be sipped and not gulped.
Hydrotherapy is a branch of healing systems that deals with the management of diseases such as headache, constipation, high blood pressure, etc. by using water, either as an external application or taken internally or both.