The study is dedicated dynamics of groundwater quality in the Mykolaiv region (Ukraine) during the period from 2021 to 2024. It was determined that the concentration of chlorides, sulfates, and mineralization in water in 2022 increased by 2-3 times (1190 mg/dm3) compared to 2021 (453 mg/dm3), which is due to the use of sea water in the central water supply and the consequences of a man-made disaster that arose under the influence of military operations. Trends in changes in water quality depending on the season and the influence of various factors on the geochemical composition of underground water resources are analyzed. The results obtained indicate a change in groundwater quality. According to the water quality classification according to the Water Pollution Index (WPI), the observed trend indicates a transition from water of quality class II, characterized as "clean water", to water of quality class III, which reflects a moderate level of pollution.