The water intake depends on many things, If you are living in a state where the temp throughout the year remains between 10 to 15`C the intake will be low and if you are staying in a place where the temp varies from time to time and remains between 25 to 35 and I am staying in India where the temp presently varies from 36`C to 44`C so we are advised to take around 5 liters of water daily. The water should be taken only when you need to drink and feel thirsty. Yes it is and yes it was an old saying that water gives glowing skin and flushes toxins, but scientist have proved this wrong and even kidney ailments do increase due to excess of pressure in kidneys and even hydronephrosis happens due to excess of water intake. So be careful take water only when needed.
A teenage should drink half of his/her body weight in ounces of water daily. So, if you weigh 130 pounds, try to drink 65 ounces of water each day. It might seem like a lot, but drinking enough water gives you a clear complexion, glowing skin, flushes toxins out of your body, and aids in good digestion. See nutrition.about.com/library/blwatercalculator.htm for more on this.