If a forest preserve district organized under the Downstate Forest Preserve District Act has, either before or after the effective date of this amendatory Act of 1991, adopted a comprehensive policy for the management and maintenance of the streams, lakes, ponds and water courses located on the property owned by the district, the power conferred on a county board under Section 5-1104 shall be exercised in a manner consistent with such comprehensive policy and only pursuant to an intergovernmental agreement between the forest preserve district and the county specifying in detail the respective obligations of the parties.
     A county may, either before or after the effective date of this amendatory Act of the 97th General Assembly, enter into an intergovernmental agreement with any forest preserve district within the county that exempts the forest preserve district from compliance with county zoning ordinances.