The Secretary of the Interior may, upon the expiration of ten years from the date of his approval of said map and plan of any irrigation district, release from the lien authorized by this chapter any unentered land or lands upon which final certificate has not issued, for which irrigation works have not been constructed and water of such district made available for the land.
(Aug. 11, 1916, ch. 319, § 3, 39 Stat. 508.)