All money placed to the credit of the reclamation fund in pursuance of sections 397 and 398 to 400, of this title shall be devoted exclusively to the completion of work on reclamation projects begun prior to June 25, 1910, as hereinbefore provided, and the same shall be included with all other expenses in future estimates of construction, operation, or maintenance.
(June 25, 1910, ch. 407, § 4, 36 Stat. 836.)