Both in water management and in research policy there is a call for more integrative approaches to tackle large societal challenges. This requires collaboration in networks of actors with different institutional and geographical backgrounds. However, our understanding of the European water research network is limited. Applying social network analysis to data from projects in Framework Programmes 1 to 7, we identify central actors in the network and explore their institutional and geographical characteristics. Compared to the generic research network arising from all projects in the Framework Programmes, the water research network turns out to consist of organisations that are geographically more diverse and more equally distributed across different organisation types. Although the diversity of the network has increased over time, the traditional knowledge producers, higher education organisations and publicly-funded research organisations from the EU15, have kept their position in the network centre over time, resulting in a stable core since the 1980s.