All or any part of any land, right-of-way or easement required for any work of channel excavation, enlargement, rectification or control or for any site for the construction of any weir, forming part of or incidental to any plan approved by the state for flood control in the Sacramento or San Joaquin Valleys, which land, right-of-way or easement or weir site has been or may hereafter be acquired by the state, may, at the request of the board and with the approval of the Department of General Services, be sold to the drainage district at a purchase price equal to the cost thereof to the state, to be determined by the Department of General Services, and upon payment to the state of the purchase price, may be conveyed to the drainage district, or to the United States, as may be requested by the board.