Place the berries, water and sugar into a heavy bottom saucepan. Bring the mixture to a boil. As soon as it starts to boil turn down to low. Simmer for about 3-4 minutes stirring as needed so it does not stick to the bottom of the pan.
Meanwhile; stir the cornstarch into the 2 tablespoons of water. Stir the cornstarch mixture into the blueberry mixture.
Turn the heat back up and bring to a boil, stirring the whole time. Cook for a minute or so. The mixture will thicken quickly. Shut off, remove from heat, transfer to a glass bowl and let cool to room temperature.
Remove the chilled cheesecake pie from the refrigerator, pour the blueberry sauce on top.