This synthesis publication contains lessons from assessments of interlinkages, trade-offs and benefits in managing water, energy and land/agriculture, as well as protecting the environment in transboundary basins in Southern Europe, the Caucasus, Central Asia and North Africa. These have been drawn from the collective experience of Parties to the Water Convention and other States, joint bodies, as well as other stakeholders who participated in these nexus assessments. The synthesis publication consolidates the methodology for assessment of nexus issues and for identification of solutions in transboundary basins, developed under the Convention on the Protection and Use of Transboundary Watercourses and International Lakes in 2013-2015.