Human activities have affected the quality of water resources globally, threatening both ecosystem and human health. One major threat arises from excess nutrients, largely stemming from agriculture and waste water, causing eutrophication in receiving surface water bodies. For effective water quality management, knowledge of catchment functioning in terms of water and solute dynamics and the interplay of natural and anthropogenic controls is crucial. Catchments are both the focus of management

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... well as integrators of various interacting hydrological and biogeochemical processes. While most studies focus on specific processes and individual catchments, overarching spatiotemporal patterns of nutrient export from streams and their prevailing control mechanisms still need to be better understood to tailor improved water quality management. The aim of this thesis is to increase the understanding of spatiotemporal patterns of riverine nutrient export at catchment scale and to identify their dominant controls and underlying processes across a wide range of catchments on the basis of a newly assembled data set. Study 1 targets at the spatial patterns and controls of mean riverine nitrate, phosphate and total organic carbon concentrations and export dynamics across 797 German catchments. Study 2 explores spatiotemporal patterns of joint riverine nitrate concentration and discharge seasonality and controls across 290 German and French catchments. Study 3 aims to enable future knowledge gains beyond this thesis by providing the novel large-sample data set of water quality combined with data on water quantity, meteorology, nutrient input and catchment attributes for 1386 German catchments. To compile the consistent large-sample data set, water quality and quantity data from the environmental authorities of the German federal states and France were processed along with various spatial data sets characterizing the catchments. Data-driven analyses were applied to determine catchment archetypes (i.e., to classify catchments) re [...]