The Secretary of the Interior be, and he is hereby, authorized, in his discretion, to grant concessions on reservoir sites, reserves for canals or flowage areas, and other lands under his jurisdiction which have been withdrawn or otherwise acquired in connection with the San Carlos, Fort Hall, Flathead, and Duck Valley or Western Shoshone irrigation projects for the benefit in whole or in part of Indians, and to lease such lands for agricultural, grazing, or other purposes: Provided, That no lands so leased shall be eligible for benefit payments under the crop control program, or the soil conservation act: Provided further, That such concessions may be granted or lands leased by the Secretary of the Interior under such rules, regulations, and laws as govern his administration of the public domain as far as applicable, for such considerations, monetary or otherwise, and for such periods of time as he may deem proper, the term of no concession to exceed a period of ten years: Provided further, That the funds derived from such concessions or leases, except funds so derived from Indian tribal property withdrawn for irrigation purposes and for which the tribe has not been compensated, shall be available for expenditure in accordance with the existing laws in the operation and maintenance of the irrigation projects with which they are connected. Any funds derived from reserves for which the tribe has not been compensated shall be deposited to the credit of the proper tribe: Provided further