Whenever two-thirds of the irrigable area of any project, or division of a project, shall be covered by water-right contracts between the water users and the United States, said project shall be required, as a condition precedent to receiving the benefits of sections 371, 376, 377, 412, 417, 433, 438,1

462, 463,1 466, 467,1 473,1 474,1 478, 493, 494, 500, 501, and 526 of this title to take over, through a legally organized water-users’ association or irrigation district, the care, operation, and maintenance of all or any part of the project works, subject to such rules and regulations as the Secretary may prescribe, and thereafter the United States, in its relation to said project, shall deal with a water users’ association or irrigation district, and when the water users assume control of a project, the operation and maintenance charges for the year then current shall be covered into the construction account to be repaid as part of the construction repayments.