In a large kettle, simmer rhubarb and water until rhubarb is soft. Cool; strain through several layers of cheesecloth. Measure 4 cups juice and return to kettle with the sugar. Heat until sugar is dissolved. Chill.
Refrigerate or freeze any remaining rhubarb juice for another batch. Combine orange and lemon juices and rhubarb mixture. Refrigerate until ready to serve. Just before serving, stir in ginger ale and strawberries if desired. Serve in chilled glass over ice. Yield: about 12 cups.