The plan of improvement for flood control in the Santa Ana River Basin is adopted and authorized substantially in accordance with the recommendations of the Chief of Engineers in House Document Numbered 135, Eighty-first Congress, First Session, and authorized by act of Congress approved May 17, 1950, Public Law 516, Eighty-first Congress, Second Session, at an estimated cost to the State of such sum as may be appropriated for state cooperation by the Legislature upon approval of the general plan of improvement by, and the recommendation of, the department, when funds for carrying out the project are appropriated by Congress.