The county shall establish a special fund for each district to be known as rural road improvement district No. ……….. fund, and credit to said fund all contributions including money transferred from the county’s general fund, all money collected as special assessments, or special levies against the property in the district, and all money received from the sale of the bonds issued under the provisions of section 39-1648. All expenses incurred in connection with the improvement and not paid out of the general funds of the county shall be paid by warrants drawn on said rural road improvement fund.