Water content of the human body is gradually on the wane as age progresses, dehydrating our internal systems to multifarious complicacies, culminating in the decay of the system altogether if due precautions are not taken well in time.
The intrauterine period is whole water and it comes down to 80% as the baby is born, and with adulthood, it is even worse with less than 70%. It goes on declining even to the level of 45% to 40%, advancing death and reducing system stubbornness.
I have heard good and dedicated doctors saying that more than fifty diseases have less chance of pervading the body with enough intake of water. Many problems relating to stomach, intestine and blood transfusion systems and many diseases from headache to cancer can be cured by water therapy.
Water is a body-purifying agent and it washes our bodily dirt like a washing machine cleaning our clothes. But, how much to drink it depends upon you as no specific answer with uniformity and consensus is available, though the answer is enough and as much and with as short duration as you can.