Sec. 1. In all counties having a County Auditor and containing a population of not less than seventy-five thousand (75,000), and not more than eighty thousand (80,000), as shown by the last preceding Federal Census, and in which there are Navigation Districts, Water Improvement Districts and Water Control and Improvement Districts, the County Auditor shall not exercise control over the finances and affairs of such Navigation Districts, Water Improvement Districts, and Water Control and Improvement Districts (or other districts created for improvement or conservation purposes, which are not administered by the Commissioners Court of such counties), but he shall annually, between July 1st and October 1st, carefully audit all books, accounts, records, bills and warrants of any such District for the year ending the 30th of June preceding, and file his report of such audit with the County Clerk of such county.