1. The costs arising from the construction of the works referred to in annex I to this Convention, with the exception of costs in respect of the hydroelectric plants and their appurtenant works, shall be borne in equal proportions by the Contracting Parties. Such costs shall also include costs relating to the installations for protection and adaptation referred to in article 3, paragraph 2, of this Convention. Payments in respect of such costs shall be made by each Contracting Party commensurate with the progress of the works, in accordance with paragraph 2 of this article.