Tax funds transferred to and held by the treasurer of the drainage district shall be used for the specific purposes as listed in section 31-401. All expenditure of such funds shall be made by the board of directors upon the order of the board. The secretary of the drainage district shall once each year have published in a newspaper of general circulation in the drainage area a brief statement of the past year’s financial operation of the district. Such statement shall be based on an annual audit of the district accounts.