The Ministerial Corporation may, by order published in the Gazette, declare that any water source and all of the entitlements, which authorise the taking of water from that water source, shall, on and from such date as may be specified in the order (being the date of its publication or a later date), be subject to a volumetric water allocations scheme prepared under section 20X or may, by a like order, declare that a scheme already in force shall be subject to a modification so prepared.