(a) Authority of Secretary.—The Secretary, in the administration of the System, may maintain central warehouses at System units.

(b) Appropriations.—

(1) Availability.—Appropriations made for the administration, protection, maintenance, and improvement of System units shall be available for the purchase of supplies and materials to be kept in central warehouses for distribution at cost, including transportation and handling, to projects under specific appropriations.

(2) Transfers between appropriations.—

(A) Authorization.—Transfers between the various appropriations made for System units are authorized for the purpose of charging the cost of supplies and materials, including transportation and handling, drawn from central warehouses maintained under this authority to the particular appropriation benefited.

(B) Availability of supplies and materials and transfers in subsequent years.—Supplies and materials that remain at the end of any fiscal year shall be continuously available for issuance during subsequent fiscal years and shall be charged for by transfers of funds between appropriations made for the administration, protection, maintenance, and improvement of System units for the fiscal year then current without decreasing the appropriations made for that fiscal year.

(c) Limitation on Purchase of Supplies and Materials.—Supplies and materials shall not be purchased solely for the purpose of increasing the value of storehouse stock beyond reasonable requirements for any current fiscal year.