RIPARIONS · Transferring hydrological and biogeochemical concepts from boreal to Mediterranean RIPARian zones: developing a broad knowledge framework across ecoregIONS

Science-based, sustainable management is needed to preserve the diverse and essential services provided by freshwaters. In natural and semi-natural areas, up to 90% of the total river length is in headwaters (i.e. small streams). Water quality in these “lungs of the landscape” is controlled primarily by soils adjacent to streams, i.e. riparian zones (RZs). Within RZs, the dominant source layer (DSL), a localized hotspot, contributes most of the solute and water fluxes to streams. However, the relative importance of DSL hydrological and biogeochemical processes controlling freshwater quality varies across ecoregions. The overall aim of RIPARIONS is to develop a unified knowledge framework based on DSL hydrological and biogeochemical functions across Europe to predict material transfer from soils to surface waters and consequent effects on water quality. Specifically, RIPARIONS will extend the DSL conceptual model developed in the boreal ecoregion by testing its applicability in two contrasting (sub-humid and a semi-arid) Mediterranean catchments. First, DSLs will be identified via hydrological site characterization using digital elevation models and on-site measurements. Biogeochemical investigations will link DSL processes and stream solute processing to assess stream water quality. Modelling of climate change impacts on DSL position and subsequent effects on future water quality will be assessed. Finally, a synthesis and integration of this work with previous and ongoing work in boreal and temperate sites will create a unified framework predicting RZ function and water quality across European ecoregions based on the DSL concept. While the Water Framework Directive mandates protection of RZs to maintain ecological status of rivers, it does not state how to manage them. RIPARIONS will fill this gap by identifying hotspots of water movement/processing within RZs (i.e. DSLs) that are the most influential for freshwater chemistry, and thus the most in need of protection