Every person, company or corporation owning or controlling any ditch, canal or conduit for the purpose of irrigation shall, during the time from April first to the first day of November of each year, keep a flow of water therein sufficient to the requirements of such persons as are properly entitled to the use of water therefrom: provided, however, that when the public streams or other natural water sources from which the water is obtained is [are] too low and inadequate for that purpose, or when the board of directors or governing body of an organization or entity furnishing water deem it in the best interests of that organization or entity to adjust the dates of availability and provide for termination of irrigation water, then such ditch, canal or conduit shall be kept with as full a flow of water therein as may be practicable, subject, however, to the rights of priority from the streams or other natural sources as provided by law.