(1) "Appraisers" means the board of appraisers;(2) "Supervisors" means the district board of supervisors;(3) "Board" means the board of county commissioners;(4) "Auditor" means the county auditor;(5) "Treasurer" means the county treasurer; and(6) "Maintenance", "maintenance of the system of improvements", "maintenance work", and other terms of similar import, mean and include not merely operating expenses and such upkeep and other work commonly classed as maintenance as shall be necessary to restore and preserve the district's system of improvement and the machinery and equipment operated in connection therewith in the same or as good condition as when originally constructed and installed, but also: (a) The making of such changes in and betterments to the original works, improvements and installations as shall, subject to the approval of the board, be by the supervisors deemed necessary to put the system of improvements into such condition that it shall provide adequate drainage and protection from overflow for the lands within the district as contemplated and intended by the original construction and any enlargement and extension thereof thereafter made; and (b) all costs and expenses incident to any determination or redetermination of benefits and apportionment of costs made under the terms of this chapter.