The plan of improvement for flood control and water conservation on Cache Creek, including Clear Lake, in Yolo and Lake Counties, is hereby adopted and authorized generally in accordance with the recommendations relating thereto contained in the interim report of the Department of Water Resources entitled “Comparison of Alternative Wilson Valley and Guinda Projects on Cache Creek,” dated April, 1958, at an estimated cost to the State of such sum as may be appropriated for state co-operation by the Legislature upon the recommendation and advice of the department.