Assessing groundwater quality globally requires overcoming several challenges. Methodological challenges involve using the right approach to prioritize parameters, upscale local studies, consider direction of flow and timescales, and define correct sampling procedures. Other challenges are related to data availability (data that either does not exist or it is not public), and to rapidly changing external factors that might affect groundwater quality, as climate change. However, new opportunities are on the rise, as Earth observations (EO) tools, and Citizen Science. Please go to each subtab under “Challenges & Opportunities” to find more information.