The Department of Natural Resources shall protect against and prevent encroachments upon the Illinois and Michigan Canal. The Department may change and improve the canal to provide for any other use in connection with conservation or recreation which the Department considers advantageous to the State. No permission now or hereafter granted, which results in obstruction to the navigable condition or capacity of any portion of the canal or interferes with its use for any of the purposes named shall operate in any way whatever to deprive the State of any of its rights in the canal or canal lands and all obstructions or structures now or hereafter erected or placed in the canal shall be subject to removal upon the order of the Department of Natural Resources. However, the use of the Sag channel of the Sanitary District of Chicago shall not be prevented nor shall it be considered an obstruction within the meaning of this Section, but the State may require, in the development of its waterways and the use of the Illinois & Michigan canal such changes in the crossing of the Illinois & Michigan canal by the Sag channel as may be necessary for the use of the Illinois & Michigan canal by the State.