A review of open data for studying global groundwater in social-ecological systems

Global data have served an integral role in characterizing large-scale groundwater systems, identifying their sustainability challenges, and informing on socioeconomic and ecological dimensions of groundwater. These insights have revealed groundwater as a dynamic component of both the water cycle and social-ecological systems, leading to an expansion in groundwater science that increasingly focuses on interactions between groundwater with ecological, socioeconomic, and Earth systems. This shift presents many opportunities that are conditional on broader, more interdisciplinary system conceptualizations, models, and methods that require the integration of a greater diversity of data in contrast to conventional hydrogeological investigations. Here, we catalogue 144 global open access datasets and dataset collections relevant to groundwater science that span elements of the hydrosphere, biosphere, atmosphere, lithosphere, food systems, governance, management, and other socioeconomic system dimensions. The assembled catalogue offers a reference of existing data for use in interdisciplinary assessments, and we summarize these data across their primary system, spatial resolution, temporal range, data type, generation method, level of groundwater representation, and institutional location of lead authorship. The catalogue includes 15 groundwater datasets, 23 datasets explicitly linked with groundwater, and 106 datasets with implicit or potential groundwater connections. We find the majority of datasets are temporally static and that temporally dynamic data availability currently peaks during the 2000-2010 decade. Only a small fraction of temporally dynamic data are explicitly linked to groundwater, representing a significant opportunity for future work to address. We find that most groundwater datasets are generated by a small number of countries, including the USA, Germany, the Netherlands, and Canada. We raise three themes of possible priorities for future global groundwater data initiatives, which include: data improvements through more explicit integration of groundwater and prioritizing observed and temporally dynamic data; elevating regional and local scale data and perspectives to address challenges relating to equity and bias; and advancing and promoting data sharing initiatives founded on reciprocal benefits between global initiatives and data providers.