Sparkling Citrus Punch

2 cups cold water
1/2 can (12-ounce size) frozen tangerine or orange juice concentrate, thawed
1/2 can (12-ounce size) frozen grapefruit juice concentrate, thawed
1 bottle (1 liter) sparkling water, chilled

Mix all ingredients in punch bowl. Serve over ice. Makes 12 servings (about 1/2 cup each)