The Secretary of the Interior may, in his discretion, withdraw any public notice issued prior to February 13, 1911 , under section 419 of this title , and he may agree to such modification of water-right applications duly filed prior to February 13, 1911 , or contracts with water users’ associations and others, entered into prior to February 13, 1911 , as he may deem advisable, or he may consent to the abrogation of such water-right applications and contracts, and proceed in all respects as if no such notice has been given. (Feb. 13, 1911, ch. 49, 36 Stat. 902 .)