Numerous approaches have been suggested for differentiating point and diffuse sources of nitrate contamination, including nitrate stable isotopes, microbiological analyses, genetic markers and chemical markers. Each approach has its own strengths and limitations. As a result, the most appropriate approach to use largely depends upon the scenario and the context of the study. However, available data on nitrate source determination is highly fragmented and approach dependent, with very little if any interface between the different techniques. This makes it difficult for stakeholders to identify the most suitable approach to adopt in a specific scenario. Therefore, this paper examines the development and application of a decision-support tool to support environmental forensics studies for nitrate contamination. In particular, this tool can support policy makers, regulators and operators within the field in understanding the environmental hazards and processes resulting from nitrate contamination, and to implement appropriate actions for limiting the impacts that may arise from such contamination. The tool was developed using the IDEF0 modelling system, and evaluated by interviewing key stakeholders who suggested a number of important implications for practice.