; and (B) is available for reuse for any purpose, whether or not the water has been treated to improve the quality of the water. (31) Enforceability date The term enforceability date means the date described in section 12(a). (32) Exchange The term exchange means a trade between 1 or more persons of any water for any other water, if each person has a right or claim to use the water the person provides in the trade, regardless of whether the water is traded in equal amounts or other consideration is included in the trade. (33) Fourth priority water The term fourth priority water means Colorado River water that is available for delivery in the State for the satisfaction of entitlements— (A) in accordance with contracts, Secretarial reservations, perfected rights, and other arrangements between the United States and water users in the State entered into or established more recently than September 30, 1968, for use on Federal, State, or privately owned land in the State, in a total quantity not greater than 164,652 AFY of diversions