In determining the irrigable acreage as provided herein, the court shall consider all lands included in the district capable of being used for agricultural purposes, provided that no lands shall be found to be irrigable which are not irrigable from the plan of the irrigation works of the district; and provided that nothing herein contained shall be construed to prevent a reconsideration of the irrigability of lands found nonirrigable upon the modification or enlargement of the irrigation system whereby said lands at first found nonirrigable may be irrigated by the district system.