This study assesses the quality of groundwater in the Odra River Basin in Poland, focussing on environmental health risks, temporal variability, and their association with salinity indices. A new indicator, the Groundwater Safety and Availability Index (GSAI), was developed to evaluate groundwater resources by integrating health risk and resource quantity factors, providing a novel tool for ranking water resources and informing environmental and administrative decision-making. Groundwater samples were collected between 2005 and 2021 and analysed in accordance with national standards. The results demonstrate an improvement in groundwater quality over time, indicated by a reduction in Health Index (HI) values, particularly in Lower Silesia, Lubusz, and Silesia. Significant correlations were found between HI and NO₃