The governing body of any city or the board of commissioners of any water resource district desiring to use an existing drain under the jurisdiction of the county board of drainage commissioners, with or without modification, as a watercourse or channel to provide a water supply for the city or water resource district, may make application therefor to the board of drain commissioners of the county in which such drain is located. In such application there shall be set forth a comprehensive plan of joint use and of any proposed extensions, changes, connecting canals, mains, or other contrivances for conducting the flow of water in, to, or from said drain and an offer of payment by the city or water resource district in a definite sum as a proportionate share of the cost of the existing drain, and a sum certain or a percentage offer for future maintenance costs.