No unentered lands and no entered lands for which no final certificates have been issued shall be subject to the lien or liens herein contemplated until there shall have been submitted by said irrigation district to the Secretary of the Interior, and approved by him, a map or plat of said district and sufficient detailed engineering data to demonstrate to the satisfaction of the Secretary of the Interior the sufficiency of the water supply and the feasibility of the project, and which shall explain the plan or mode of irrigation in those irrigation districts where the irrigation works have not been constructed, and which plan shall be sufficient to thoroughly irrigate and reclaim said land and prepare it to raise ordinary agricultural crops, and which shall also show the source of water to be used for irrigation of land included in said district: Provided, That in those irrigation districts organized prior to August 11, 1916, and whose irrigation works had then been constructed and were then in operation as soon as a satisfactory map, plat, and plan shall have been approved by the Secretary of the Interior, as in this chapter provided, such entered and unentered lands shall be subject to all district taxes and assessments theretofore actually levied against the lands in said district and in the same manner in which lands of a like character held under private ownership are subject to liens and assessments.