With progress in hydrological sciences having been largely thwarted by the spatial and temporal complexity of involved processes, we believe the advent of new technologies, interdisciplinary approaches, innovative concepts and models to be key pillars for ultimately designing and implementing a sustainable management of water resources. In this respect, we intend to leverage past investments into innovative water resources research in Luxembourg and propose a doctoral training unit (DTU) in hydrology entitled ‘Towards a holistic understanding of river systems: Innovative methodologies for unraveling hydrological, chemical and biological interactions across multiple scales – HYDRO-CSI’.We believe the advent of a new generation of field portable devices, combined with air- and space-borne instruments, delivering environmental data at unprecedented spatial and temporal scales, to open entirely new vistas as to our holistic understanding of how catchments collect, store and release water and pollutants. The PRIDE programme offers a unique opportunity to LIST to play an active role in an international research effort that ultimately targets to overcome the technological limitations that have stymied progress in water resources research for decades. Eventually, the HYDRO-CSI DTU is meant to be a cornerstone in our institutional research strategy – preparing a new generation of highly skilled scientists and managers in the water domain. More specifically, our objectives unfold as follows:•Understand the fundamental hydrological functions of catchments (collection, storage and release of water).•Investigate how flow sources and flow paths control streamwater and groundwater chemistry and microbiology.•Synthesize improved theories linking hydrological functions and system heterogeneity as a foundation for models delivering more reliable predictions under global change.•Design, craft, test and bring to the market new technological solutions for overcoming the current status quo in hydrological sciences.•Propose an excellent doctoral education in water resources research through an interdisciplinary PhD research programme – ultimately preparing the PhD candidates for embracing careers in universities/research institutions, administrations or industry.