There have been several calls made for hydrologic synthesis research: namely activities which unify diverse data sources across sites, scales and disciplines to uncover new connections and to promote a holistic understanding of water science. This paper draws on the NSF-funded Hydrological Synthesis Project (HSP) run by the University of Illinois at Urbana-Champaign to elucidate mechanisms, benefits and challenges of implementing hydrologic synthesis research from the perspectives of participants in a pilot research study. Two broadly different mechanisms of implementing synthesis were adopted in the HSP: 6-week Summer Institutes in which Ph.D. students conducted team-based research under the guidance of faculty mentors, and focused workshops which disseminated knowledge and shared experiences between scientists at many different career levels. The Summer Institutes were a test bed in which new ideas could be explored, assisted students in developing a wide range of skills, and were highly productive, but posed challenges for mentors and students because the ‘new’ research topics initiated during the Institutes' programmes needed to be completed in competition with students' ongoing Ph.D. research or mentor's existing research programs. The workshop-based model circumvented this conflict and was also highly productive, but did not offer the same opportunity to experiment with new ideas as part of the synthesis research. Leadership, trust, flexibility and long gestation times were all important to bringing synthesis research to a positive resolution. Funding models that embrace the exploratory aspects of synthesis and provide adequate support to mentors and students over these long timescales would facilitate future hydrologic synthesis research. Copyright © 2011 John Wiley & Sons, Ltd.