This paper proposes a novel fuzzy evidential rule-based (FERB) system to represent uncertain expert knowledge. The fuzzy evidential reasoning framework is introduced to model epistemic uncertainties including nonspecificity, vagueness, as well as local and global ignorance in the knowledge base. A computationally efficient formulation of the FERB system using an uncertain IF-THEN rule matrix is presented. Inference is performed through determining the fired rules followed by fuzzy Dempster-Shafer combination of activated belief structures. The application of the proposed FERB system is investigated using a case study of risk assessment for drinking water. Finally, the proposed FERB system is tested through data that were available for a water distribution network.