Into the county lands assessment fund shall also be paid any surplus moneys from the sale by the county, pursuant to foreclosure of real estate taxes, of any lands lying in any district formed for diking or drainage purposes or for assessment of road improvements, over and above the amount necessary to redeem the general taxes and other assessments against them, as required by law. Any surplus from any county levy for the fund, unexpended in any year, shall be carried forward in the fund to the next year.