The county board of any county in this state is hereby authorized, whenever it deems necessary, to create a county ditch fund, to consist of taxes collected from county levies, and all balances remaining unexpended of special ditch funds, arising from excess of assessments made on ditch improvements after the expenses thereof have been fully paid. The county board is hereby authorized, whenever necessary, to borrow from the county general fund for the benefit of the above-named ditch fund. All money so borrowed shall be, as soon as practicable, returned to the county general fund.