615 ILCS 5/8
The Department of Natural Resources shall receive from any citizen complaints as to any invasion of or encroachment upon any rights of the State, or of any citizen of the State, with reference to any of the public bodies of water of the State, or as to any interference with the right or claim of any citizen to use or enjoy any public water of this State, and upon being requested so to do, the Department, in its discretion, may hold a public hearing for the purpose of taking evidence with reference to the subject matter of the complaint, and of hearing all persons who may appear upon behalf of, or in opposition to the petition, and at the conclusion of the hearing it shall enter an order defining the rights and interests of the parties, and prescribing their duties.
615 ILCS 5/8