A sufficient water intake is needed to combat dehydration, which saps energy, causes fatigue and reduces concentration. The standard 'eight glasses a day' of water, which equates to two litres, has been widely reported as the recommended daily intake for water.
The reason for the figure eight is this: Our bodies loss on average 2.5 litres of water a day. In order to maintain a healthy body that 2.5 litres needs to be replaced. Our bodies take in about 20% (or 500mls) of the liquid required through foods, leaving two litres, or eight glasses, needing to be drunk as water.
Generally consuming an amount of water which means that you are not ever thirsty will mean you are getting around the required eight glasses.
There are factors which will alter the amount of daily water intake required. Exercising causes increased fluid loss. For prolonged exercise, a sports drink may be appropriate, as they help combat sodium fluid loss from sweating.
In warmer temperatures it is also important to increase hydration intake. It is also important to boost intake when suffering from vomiting, diarrhea or fever, as these symptoms cause the body to lose fluids.
While water is the optimum way of taking in fluids, do not over look watery fruits and vegetables as a way of getting your daily fluid intake. Vegetables such as lettuce and cucumber, and fruits such as melons, oranges, tomatoes and pears, are particularly good.