If such contract relates to the building or maintaining of a dike, levee or sewer in any city or drainage district, such city or drainage district shall be a party to the contract, and if outside of any city or drainage district, the county commissioners shall be a party to it. If the contract relates to the diversion of a watercourse, every city, drainage district, and county below, or partly below, the initial point of diversion, through which such watercourse flowed before the time of diversion or would flow after the time of diversion, shall be a party to the contract.