Notwithstanding the provisions of Section 73-18-7 N.M. Stat. Ann. and in lieu thereof, the board of directors of any conservancy district created prior to 1930 embracing land situate in four or more counties and having more than one hundred thousand acres shall determine and establish by resolution the annual assessments to be made from year to year against real property within the district pursuant to the reclassification of property adopted pursuant to Section 73-18-6.1 N.M. Stat. Ann.. Such assessment may be modified in like manner from time to time, but not more frequently than once in every five years.