Nitrate excesses in freshwater ecosystems is a major challenge that Society needs to face in the next decade as reflected in the H2020 and Spanish Research and Technological Plan priorities. CANTERA will investigate key aspects of the N cycle at the stream-riparian interface which are fundamental to anticipate N excesses and identify control points of ecosystem N removal within Mediterranean fluvial networks. The objective of CANTERA is to understand how extreme hydrological events influence nitrate concentrations and fluxes in headwater streams by examining nitrate accumulation patterns in riparian soils, and nitrate transfer from terrestrial ecosystems to streams. CANTERA will also investigate the environmental factors limiting in-stream nitrate retention and removal along fluvial networks. The results obtained will provide evidence of how extreme hydrologic events compromise water quality and impact on the functioning of Mediterranean riparian-stream ecosystems. CANTERA will provide quantitative knowledge on the buffer potential of natural green infrastructures to cope with N excesses as a function of climatic and hydrological conditions. Our findings will contribute to anticipate climate change impacts in Mediterranean regions and protect, restore, and more efficiently manage streams and their riparian zones as essential components of our natural capital.