In a saucepan, combine the blueberries, sugar, 2 tablespoons water and lemon juice; cook and stir over medium heat until sugar is dissolved.
Combine cornstarch and remaining water until smooth and cornstarch is dissolved. Stir into berry mixture. Bring to a boil; cook and stir for 1 - 2 minutes or until thickened. Refrigerate at least one hour before serving.