Verified owners of water rights in the Middle and Lower Rio Grande with the right to call on releases from the Amistad-Falcon system may contract for the sale of all or part of their annual authorized amount of use to other water rights holders or their agents in the Middle and Lower Rio Grande, as long as all of the contractual sales rules are complied with. The resale of purchased water is prohibited. The use of contract sale water by buyer will not go to the perfection of seller's appropriative right. All existing contracts shall be filed with the executive director in accordance with this section.