In a Dutch oven, bring the rhubarb, strawberries, sugar and water to a boil. Reduce heat; simmer, uncovered, for 5-8 minutes or until rhubarb is tender. Press through a sieve; discard pulp. Stir in gelatin and lemon juice until dissolved.
Transfer to a freezer container and freeze, stirring occasionally, until firm. May be frozen for up to 3 months.
To use frozen rhubarb mixture: In a punch bowl or several pitchers, combine equal amounts of rhubarb mixture and ginger ale. Or for one serving, combine 1/2 cup rhubarb mixture and 1/2 cup ginger ale in a glass. Garnish with rhubarb curls if desired. Serve immediately. Yield: 22 servings (1 cup each).