An additional one million acres of arid lands within each of the States of Colorado, Idaho, Nevada, and Wyoming is made available and subject to the terms of section 641 of this title, and the States of Colorado, Nevada, Idaho, and Wyoming are allowed under the provisions of said section said additional area or so much thereof as may be necessary for the purposes and under the provisions of said section.
(May 27, 1908, ch. 200, 35 Stat. 347; Mar. 4, 1911, ch. 285, 36 Stat. 1417; Aug. 21, 1911, No. 7, 37 Stat. 38.)