When lands are included in an irrigation district by means of the procedure described in this chapter, and if the district will contain after inclusion of the lands twenty thousand irrigable acres [8093.72 irrigable hectares] or more, at least thirty days before the next general election, the board shall make an order dividing or redividing the district into divisions in conformity with section 61-05-13. The divisions must be as nearly equal in size as may be practicable and they must be numbered, with one director thereafter elected by and from each division.