Long datasets for improved understanding, management and protection of groundwater

In a changing world, long datasets for groundwater have great value, as they do for all components of environmental monitoring. However, there is a global scarcity of such datasets, with few extending beyond 30 years and even fewer to 50 or 100 years. Hydrogeological investigations and groundwater management activities benefiting from long-term data are listed, the successful use of such datasets illustrated, and the reasons for their scarcity discussed.