70 ILCS 605/2-8
When a ditch, covered drain or levee is, or has been, constructed by mutual license, consent or agreement, either separately or jointly, by the owners of adjoining lands so as to make a continuous line across the lands of such owners, or when the owner of adjoining land is permitted to connect a ditch, covered drain or levee with another already so constructed, or when the owner of lower land connects a ditch or covered drain to a ditch or covered drain constructed by the owner or owners of upper lands, or when the owner of land protected by a levee has contributed to the cost of the construction, enlargement or reconstruction of a levee upon other land, such ditch, covered drain or levee shall be deemed to be a drain or levee for the mutual benefit of all lands connected to, or protected by, it. The mutual license, consent or agreement required in this section need not be in writing, but may be established by parole or inferred from the acquiescence of the parties. When a ditch, covered drain or levee is privately constructed through or on a tract of land and the ownership of such tract is thereafter divided, such ditch, covered drain or levee shall thereupon be deemed a drain or levee for the mutual benefit of all the portions of the original tract connected to, or protected by, such ditch, covered drain or levee.
70 ILCS 605/2-8