Attempts to create sustainable water resource management (WRM) face substantial challenges from population growth, expanding urbanisation, environmental degradation, and anthropogenic climate change. Science can provide vital knowledge and understanding to help create sustainable policy outcomes. However, the interactions between science and policy can be problematic, limiting the ability of science to contribute to sustainability. There needs to be better understanding of how science is used within WRM in order to identify the most effective uses of science. This paper will present an emerging theoretical framework for analysing how and why science is used within policy. This work considers that scientific knowledge and understanding are used widely within the policy networks of WRM, not just where scientists and policymakers meet, and hence that there is not one science-policy interface but many. To help better understand these interfaces, the framework is developed from concepts in the water governance and science-policy interface literature combined with the recognition that science is complex and evolving. The framework presented here will provide a tool to better understand the role of science within sustainable WRM by analysing the factors that might affect the use of science by stakeholders.