The success of development programs depends on the role of underlying institutions and the impact synergies from closely related programs. Existing literature has limitations in accounting for these critical factors. This paper fills this gap by developing a methodology, which can quantify both the institutional roles in impact generation and the impact synergies from related programs. The methodology is applied to the Kala Oya Basin in Sri Lanka for evaluating the impacts of three development programs and 11 institutions on food security. The results provide valuable insights on the relative roles of institutions and the varying flow of impact synergies both within and across impact pathways.