The key goal of the second Assessment of Transboundary Rivers, Lakes and Groundwaters is to keep the state of shared water resources in Europe, Caucasus and Central Asia under scrutiny. It aims to facilitate informed decision-making on their management, provide the basis for continuous bilateral and multilateral cooperation under the Water Convention, and support all actors involved at the national, transboundary and regional levels. More than 150 transboundary rivers, 40 lakes and some 200 transboundary groundwater occurrences have been assessed in close cooperation with the national environment and water administrations in the European and Asian parts of the UNECE region, and high attention is being devoted to the countries with economies in transition which are facing the biggest challenges