The process of preparation of the Second Assessment included a series of subregional workshops which were important events to build capacity in the different countries and subregions and to promote transboundary dialogue and exchange. This is all the more important in the transboundary context and in a region as broad as the UNECE one, where methods for water assessment and classification differ greatly between States — and not only between European Union (EU) members and non-EU countries. In order to reach a common understanding about the status of shared waters, the existing trends and the actions needed to improve the situation, the availability of reliable and comparable information is of the utmost importance.