In a large saucepan, combine the rhubarb and water. Bring to boiling; reduce heat. Cover and simmer for 5 minutes. Remove from heat; cool slightly. Strain rhubarb mixture, pressing to remove all juices. Discard pulp. Add sugar, lemonade concentrate, and lemon juice to rhubarb juice, stirring to dissolve sugar. Cover and chill for 2 to 24 hours.
To serve, combine rhubarb mixture with chilled lemon-lime beverage in a punch bowl or large pitcher. Serve with crushed ice. If desired, garnish with fresh mint and/or lemon slices. Makes ten 8-ounce servings.