Any Indian allotted lands under any law or treaty without the power of alienation, and within a reclamation project approved by the Secretary of the Interior, may sell and convey any part thereof, under rules and regulations prescribed by the Secretary of the Interior, but such conveyance shall be subject to his approval, and when so approved shall convey full title to the purchaser the same as if final patent without restrictions had been issued to the allottee: , That the consideration shall be placed in the Treasury of the United States, and used by the Commissioner of Indian Affairs to pay the construction charges that may be assessed against the unsold part of the allotment, and to pay the maintenance charges thereon during the trust period, and any surplus shall be a benefit running with the water right to be paid to the holder thereof.Provided