the Additional Act to the Treaty of Bayonne, in its Article 11

“Article 11: When in one of the two States it is proposed to construct works or to grant new concessions which might change the course or the volume of a watercourse of which the lower or opposite part is being used by the riparian owners of the other country, prior notice will be given to the highest administrative authority of the Department or of the Province to which such riparian owners are subject by the corresponding authority in the jurisdiction where such schemes are proposed, so that, if they might threaten the rights of the riparian owners of the adjoining Sovereignty, a claim may be lodged in due time with the competent authorities, and thus the interests that may be involved on both sides will be safeguarded. If the work and concessions are to take place in a Commune contiguous to the border, the engineers of the other Country will have the option, upon proper notice given to them reasonably in advance, of agreeing to inspect the site with those in charge of it.”