How much is there?
Also, do you care about the rivers? Veldmaarschalk theorizes that removing them would have no effect on gameplay. Of course, rivers would no longer show up (as their own province), and the map would look somewhat weird (as the grayscale would reflect some province other than the bluish river), but province ids would be freed up and compatibility with HoI/Victoria might be maintained.
Also, do you care about the rivers? Veldmaarschalk theorizes that removing them would have no effect on gameplay. Of course, rivers would no longer show up (as their own province), and the map would look somewhat weird (as the grayscale would reflect some province other than the bluish river), but province ids would be freed up and compatibility with HoI/Victoria might be maintained.