consent of water users; expense.] The commissioners of any community ditch may alter, change the location of, enlarge, extend, or reconstruct such ditch for the purpose of providing greater efficiency in irrigation to the water users of said ditch, or when any part thereof shall have been destroyed by rain or in any other manner or for the purpose of increasing the cultivable [cultivatable] area, provided that such alteration, change of location, enlargement, extension or reconstruction shall be affected [effected] only upon the consent in writing of a majority of the water users of said community ditch, filed with such commissioners, such majority to be determined by the same rule as applies to the election of commissioners of the acequia, and provided that such alteration, change of location, enlargement or extension shall in no wise impair the rights of prior water users from said community ditch, and provided further that the expense incurred in any such alteration, change of location, enlargement or extension shall be borne pro rata by those beneficially interested in same.