Potable groundwater resources are under threat as a result of industrial development and an increase in fertilizer use. The protection of groundwater supply may require the establishment of groundwater source protection zones (GSPZ) to allow protective measures. The aim of this study has been to develop a new approach to groundwater source risk assessment (GSRA). The risk has been defined as the greatest of the risks identified for individual potential sources of contamination (PSCs). The risk resulting from a PSC is the combination of its adverse impact on groundwater, unwanted event probability, its adverse effect and annoyance for the population. A multi-criteria assessment has been designed to estimate the indices of potential groundwater impact of industrial facilities and non-inert waste landfills, using the range and weight method. The application of the approach proposed has been tested on an idealized model under three scenarios, involving various industrial PSCs and fertilization. The overall nitrogen load was compared to the maximum effective nitrogen load for the crops in question. The sensitivity analysis conducted for this methodology has revealed that the main factors affecting the risk to water supply are non-reactive contaminant mass load in PSC leachate and the ratio of groundwater volume abstracted from the wells to the amount of water flowing from PSCs to the wells, which determine the dilution degree of contaminant mass. This proposed interdisciplinary approach to GSRA should provide a robust basis for making decisions about GSPZ establishment and for the development of a groundwater risk analysis methodology.