The United States of America is hereby authorized, in conformity to the laws of the State of Nebraska, to appropriate, develop, and store any unappropriated flood or unused waters, in connection with any project constructed by the United States pursuant to the provisions of an Act of Congress approved June 17, 1902, being An Act providing for the reclamation of arid lands (32 Stat. L. 388), and all acts amendatory thereof and supplemental thereto. When the officers of the United States Bureau of Reclamation determine that any water so developed or stored is in excess of the needs of the project as then completed or is flood or unused water, the United States may contract to furnish such developed, stored, flood, or unused water, under the terms and conditions imposed by Act of Congress and the rules and regulations of the United States, to any person who may have theretofore been granted a permit to appropriate a portion of the normal flow of any stream, if the water so appropriated shall, during some portion of the year, be found insufficient for the needs of the land to which it is appurtenant. The United States and every person entering into a contract as herein provided shall have the right to conduct such water into and along any of the natural streams of the state, but not so as to raise the waters thereof above the ordinary high water mark, and may take out the same again at any point desired, without regard to the prior rights of others to water from the same stream; but due allowance shall be made for losses in transit, the amount of such allowance to be determined by the Department of Natural Resources. The department shall supervise and enforce the distribution of such water so delivered with like authority and under the same provisions as in the case of general appropriators.