The Secretary of the Interior, after notice and hearing, is authorized to cancel trust patents issued to Indian allottees for allotments within any power or reservoir site and for allotments or such portions of allotments as are located upon or include lands set aside, reserved, or required within any Indian reservation for irrigation purposes under authority of Congress: Provided, That any Indian allottee whose allotment shall be so canceled shall be reimbursed for all improvements on his canceled allotment, out of any moneys available for the construction of the irrigation project for which the said power or reservoir site may be set aside: Provided further, That any Indian allottee whose allotment, or part thereof, is so canceled shall be allotted land of equal value within the area subject to irrigation by any such project.