Establishing a network of hydrological observatories in Europe still faces some challenges due to the fragmented and dispersed research landscape and lack of community awareness. There are, however, examples of excellent cutting-edge hydrological research being performed at well-established, highly-instrumented hydrological observatories, such as the Attert basin in western Luxembourg, the HOBE catchment in Denmark, the UARC catchment in Italy, the HOAL catchment in Austria, and national networks such as the TERENO catchments in Germany, and OZCAR catchments in France (see Bogena et al., 2018). A unique feature of these hydrological observatories is the measurement of hydrologic variables relevant to process-driven modeling. These catchments can serve as a community-driven core for a European data and experimentation platform of hydrological observatories. As a step towards establishing a wider network of hydrological observatories, this 8th Galileo Conference aims at developing a common data and experimentation platform to make data from several existing hydrological observatories accessible and readily available to the research community. In a subsequent step, such a platform could be expanded to include models and tools for data analysis and hydrological forecasting. This would also allow a model-driven design of catchment experiments.

We envision the development of new modeling approaches that rely less on calibration but are rather based on insightful analysis of landscape heterogeneity and process complexity through systematic learning from innovative hydrological observation data and a synergetic data analysis approach using novel data exploration methods. The development of a European model-data driven framework enables the design of hydrological experiments to gain knowledge for the development of new hydrological theories. For example, large-scale labeling and tracer experiments as well as interdisciplinary measurement programs, including climatology, hydrogeology, hydrology, and vegetation sciences, can be conducted to embrace new scientific perspectives. Envisaged research partnerships with existing European networks (e.g. International Soil Moisture Network, Global Runoff Data Base, eLTER) leverage these efforts by the multi-variate catchment-scale observatory focus of this conference.