The complexity of water, food and energy security is analysed from the perspectives of (i) water and food and (ii) water and energy and their interconnectivity and focuses ultimately on water as a primary input into processes, the entry point for participants of the Third World Irrigation Forum. The paper provides an overview of trends in water, food and energy security, highlights the interconnectivity between the various elements and introduces the water–food–energy nexus as a tool for improving productivity and sector policies, avoiding unintended consequences on other sectors. Invariably, there will be trade-offs and the challenge is to find combinations of measures that have a net positive outcome. In order to quantify security in the three elements and the trade-offs between them, emerging modelling approaches for the nexus are discussed. Sub-theme 3 of the forum focuses on productivity and technology interventions1 and sub-theme 2 on stakeholder interaction. The combination of modelling, technology innovations and stakeholder participation in a water–food–energy nexus approach leads to better understanding of linkages and more robust policies and is used to derive recommendations for an enabling policy environment.