In order to preserve the shore lines, rapids, waterfalls, beaches, and other natural features of the region in an unmodified state of nature, no further alteration of the natural water level of any lake or stream within or bordering upon the designated area shall be authorized by any permit, license, lease, or other authorization granted by any official or commission of the United States, which will result in flooding lands of the United States within or immediately adjacent to the Superior National Forest, unless and until specific authority for granting such permit, license, lease, or other authorization shall have first been obtained by special Act from the Congress of the United States covering each such project: Provided, That nothing in this section shall be construed as interfering with the duties of the International Joint Commission created pursuant to the convention concerning the boundary waters between the United States and Canada and concluded between the United States and Great Britain on January 11, 1909, and action taken or to be taken in accordance with provisions of the convention, protocol, and agreement between the United States and Canada, which were signed at Washington on February 24, 1925, for the purpose of regulating the levels of the Lake of the Woods: Provided, That with the written approval and consent of the Forest Service of the Department of Agriculture, reservoirs not exceeding one hundred acres in area may be constructed and maintained for the transportation of logs or in connection with authorized recreational uses of national-forest lands, and maximum water levels not higher than the normal high-water mark may be maintained temporarily where essential strictly for logging purposes, in the streams between lakes by the construction and operation of small temporary dams: Provided, however, That nothing herein shall be construed to prevent the Secretary of Agriculture from listing for homestead entry under the provisions of the Act of June 11, 1906 (34 Stat. 233), any of the above-described lands found by him to be chiefly valuable for agriculture and not needed for public purposes: Provided further, That the provisions of this section shall not apply to any proposed development for water-power purposes for which an application for license was pending under the terms of the Federal Power Act [16 U.S.C. 791a et seq.] on or before January 1, 1928.