The intention of the Commonwealth is hereby declared to repay without interest to the municipalities respectively all moneys so advanced in not more than fifteen equal biennial installments, commencing not later than three years after any such moneys were advanced. Such payments are intended to be made biennially by appropriations to the Department of Forests and Waters for the purpose of repaying moneys due to municipalities which shall have advanced the same for the construction and completion of projects and improvements for the conservation of water and the control of floods.
32 P.S. § 804