In a large saucepan over high heat bring water and sugar to a boil, stirring until sugar disolves. Boil 3 minutes. Transfer syrup to a bowl or other container; cover; chill until cold (at least 3 hours but will keep for up to one week).
In a large pitcher mix together juices, 3 cups syrup and 3 cups water. ***can be made one day ahead; covered and chilled***.
Fill glasses with ice and pour cooler over.
***Left over syrup is wonderful added to iced tea topped with mint leaves and lemon slices.