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Environmental data are the key to defining and addressing water quality and quantity challenges at the catchment scale. Here, we present the first large-sample water quality data set for 1386 German catchments covering a large range of hydroclimatic, topographic, geologic, land use, and anthropogenic settings. QUADICA (water QUAlity, DIscharge and Catchment Attributes for large-sample studies in Germany) combines water quality with water quantity data, meteorological and nutrient forcing data, and catchment attributes. The data set comprises time series of riverine macronutrient concentrations (species of nitrogen, phosphorus, and organic carbon) and diffuse nitrogen forcing data (nitrogen surplus, atmospheric deposition, and fixation) at the catchment scale. Time series are generally aggregated to an annual basis; however, for 140 stations with long-term water quality and quantity data (more than 20 years), we additionally present monthly median discharge and nutrient concentrations, flow-normalized concentrations, and corresponding mean fluxes as outputs from Weighted Regressions on Time, Discharge, and Season (WRTDS). The catchment attributes include catchment nutrient inputs from point and diffuse sources and characteristics from topography, climate, land cover, lithology, and soils. This comprehensive, freely available data collection with a large spatial and temporal coverage can facilitate large-sample data-driven water quality assessments at the catchment scale as well as mechanistic modeling studies. QUADICA is available at https://doi.org/10.4211/hs.0ec5f43e43c349ff818a8d57699c0fe1 (Ebeling et al., 2022b) and https://doi.org/10.4211/hs.88254bd930d1466c85992a7dea6947a4 (Ebeling et al., 2022a).

Sozialwirtschaftliche Organisationen werden in ihren Entscheidungen von starren Vorgaben und Richtlinien limitiert. Insbesondere im Finanzmanagement müssen sich diese an die Bedingungen der öffentlichen Fördergeber*innen anpassen. Die Notwendigkeit, in dieser Ausgangslage flexibel zu handeln, wird als Erfolgsfaktor in der Bewältigung von unerwarteten Ereignissen analysiert. Speziell wird in der Arbeit untersucht, wie die Flexibilität im Finanzmanagement während der Covid-Krise 2020 beurteilt wird. Für die Beantwortung der Forschungsfrage wurden Leiter*innen von Frauenberatungsstellen, welche als Frauenservicestellen der Stadt Wien (MA57) gefördert werden, interviewt. Mithilfe der qualitativen Inhaltsanalyse nach Mayring wurden relevante Aussagen über das allgemeine Finanzmanagement, das Finanzmanagement während der Covid-Krise 2020 sowie die Flexibilität als Vorteil für zukünftige Herausforderungen ausgewertet. Die Arbeit bestätigt die Annahme, dass die Notwendigkeit zur Anpassung ein Dauerzustand im Finanzmanagement ist. Die geringe Finanzierungs- und Planungssicherheit muss durch das Engagement und die Aufopferungsbereitschaft der Mitarbeiter*innen ausgeglichen werden. Langfristig müssen für die Herausforderungen der Zukunft mehr Ressourcen aufgebaut und langfristige Finanzierungsformen durch die öffentliche Hand bereitgestellt werden. Social economy organisations are limited in their decision making through rigorous guidelines and requirements. Those organisations have to adhere to the requirements of public funding bodies, especially in their management of finances. The necessity of flexibility under these conditions will be analysed as a factor of success in regard to overcoming unanticipated events. Specifically, this thesis analyses how flexibility in finance management is assessed throughout the Covid pandemic 2020. To answer the research question, managers of women’s counselling centres, which are funded as part of the women’s service centres of the city of Vienna (MA57), were interviewed. Through qualitative content analysis following Mayring, relevant statements were analysed in regard to finance management, finance management during the Covid pandemic 2020, and flexibility as a benefit for future challenges. The thesis confirms the hypothesis that the necessity of adapting is a permanent condition in finance management. The small finance- and planning reliability is compensated through devotion and self-sacrifice of the employees. For future challenges it is necessary in the long run to acquire more resources and longstanding forms of financing through public authorities. Abweichender Titel laut Übersetzung der Verfasserin/des Verfassers Masterarbeit Wien, FH Campus Wien 2023

The general stress response (GSR) enables bacteria to sense and overcome a variety of environmental stresses. In alphaproteobacteria, stress-perceiving histidine kinases of the HWE and HisKA_2 families trigger a signaling cascade that leads to phosphorylation of the response regulator PhyR and, consequently, to activation of the GSR σ factor σEcfG. In the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens, PhyR and σEcfG are crucial for tolerance against a variety of stresses under free-living conditions and also for efficient infection of its symbiotic host soybean. However, the molecular players involved in stress perception and activation of the GSR remained largely unknown. In this work, we first showed that a mutant variant of PhyR where the conserved phosphorylatable aspartate residue D194 was replaced by alanine (PhyRD194A) failed to complement the ΔphyR mutant in symbiosis, confirming that PhyR acts as a response regulator. To identify the PhyR-activating kinases in the nitrogen-fixing symbiont, we constructed in-frame deletion mutants lacking single, distinct combinations, or all of the 11 predicted HWE and HisKA_2 kinases, which we named HRXXN histidine kinases HhkA through HhkK. Phenotypic analysis of the mutants and complemented derivatives identified two functionally redundant kinases, HhkA and HhkE, that are required for nodulation competitiveness and during initiation of symbiosis. Using σEcfG-activity reporter strains, we further showed that both HhkA and HhkE activate the GSR in free-living cells exposed to salt and hyperosmotic stress. In conclusion, our data suggest that HhkA and HhkE trigger GSR activation in response to osmotically stressful conditions which B. diazoefficiens encounters during soybean host infection., Molecular Plant-Microbe Interactions, 35 (7), ISSN:0894-0282

Human activities, especially agricultural practices, have significantly altered the Earth’s landscape and the global cycle of nitrogen. In Europe, diffuse nitrogen (N) input from agriculture has been identified as a major driver of marine eutrophication. Despite a long history of measures, little improvement in groundwater and surface water quality has been observed. Recent studies have attempted to provide insights into nitrogen dynamics at the catchment scale, helping to explain the causes and effects of persistent water quality problems. However, there is a lack of large-scale, long-term studies that provide insights into both biogeochemical and hydrological N legacies under different landscape settings. Here using data of more than 100 German catchments of the last seven decades, we synthesis the nitrogen transport and retention dynamics, as well as their dominant (landscape and climate) controls in a large-sample setting. To this end, we adapted the mHM-SAS model (Nguyen et al., 2021) to reflect regional-scale biogeochemical and hydrological N legacies, taking into account the historical development of both diffuse and point sources. The underlying parameterizations were constrained using instream N concentrations. We found high heterogeneity in catchment responses to N inputs. The fractions of N surplus that were stored in the soil, removed by denitrification, stored in the subsurface, and finally exported to the stream vary over a wide range. Our analysis of the long-term (1950-2014) average N balances from all catchments suggests that a majority (mean = 57%) of N surplus was removed by denitrification, followed by stream N export (27%) and the rest was stored in the catchment (16%). Despite the reduction in N surplus after 1990s, biogeochemical legacy reflected in the soil N build-up showed an increasing trend over the analyzed period (1950-2014) across a majority of the study catchments. As for the hydrologic legacy, we found a varying range of mean transit times of discharge between 3.5 years and 13.1 years (95% confidence interval) among the analyzed catchments. Overall, our large-sample analysis provides a detailed overview of biogeochemical and hydrological N legacies across Germany; and thus provides useful insights for an improvement of agricultural practices and water quality management in Central European landscapes.Nguyen, V.T., Kumar, R., Musolff, A., Lutz, S. R., Sarrazin, F., Attinger, S., & Fleckenstein, J. (2021 WRR - in revision). Disparate Seasonal Nitrate Export from Nested Heterogeneous Subcatchments Revealed with StorAge Selection Functions. https://doi.org/10.1002/essoar.10507516.1

Environmental data are critical for understanding and managing ecosystems, including mitigation of degraded water quality. Therefore, we provide the first large-sample water quality data set of riverine water quality combined with water quantity, meteorological and nutrient forcing data, and catchment attributes for Germany in a preprocessed and structured form. The QUADICA data set (water QUAlity, DIscharge and Catchment Attributes for large-sample studies in Germany) covers 1386 German and transboundary catchments with a large range of hydroclimatic, topographic, geologic, land use and anthropogenic settings. The data set comprises time series of riverine macronutrient concentrations (species of nitrogen, phosphorus and organic carbon), discharge, meteorological and diffuse nitrogen forcing data (nitrogen surplus, atmospheric deposition and fixation). The time series are generally aggregated to an annual basis; however, for 140 stations with long-term water quality and quantity data (more than 20 years), we additionally provide monthly median discharge and nutrient concentrations, flow-normalized concentrations and corresponding mean fluxes as outputs from weighted regressions on time, discharge, and season (WRTDS). The catchment attributes include catchment nutrient inputs from point and diffuse sources and characteristics from topography, hydroclimate, land cover, lithology and soils. QUADICA is a comprehensive, freely available, ready-to-use data set that facilitates large-sample data-driven water quality assessments at catchment scale as well as mechanistic modeling studies. We hope to stimulate the hydrological and water quality communities to provide similar data sets to create novel research opportunities, increase our understanding of catchment functioning, and ultimately improve water quality management.

For the sake of food production, nutrients like nitrogen (N) are applied on agricultural land to supply crops. However, due to common agricultural practice, the amount of N provided very often significantly exceeds the uptake potential of the plants resulting in a N surplus that accumulates in the soil. Organic soil nitrogen is slowly transformed to nitrate, which is then mobilized by water and moves through the subsurface, with the risk of contaminating receiving water bodies. High nitrate loads cause poor chemical states for 27% of all groundwater bodies in Germany and foster eutrophication in lakes and rivers and by this a loss of biodiversity. The main problem are legacy issues of nitrate pollution, because there is a time lag between N input and nitrate mobilization and transport. Research on nitrate travel times is highly relevant for a reliable prediction of the capability of catchments to store, buffer and release nitrate. However, it is not clear how long nitrate is stored and transported in catchment’s storage. For this study, a 11 km2 headwater catchment with mixed land use within the Northern lowlands of the Harz mountains in Germany was investigated from spring 2017 until the end of 2020. A monitoring program was set up, starting with biweekly samples for the first two years and daily samples for the remainder, with sub-daily samples during precipitation events. Samples were taken from stream water and when available from precipitation water. Nitrate concentrations as well as isotopic signatures of water (δ18O and δ2H) and nitrate (δ18O and δ15N) were analysed. To investigate nitrate travel times, the numerical model tran-SAS (Benettin and Bertuzzo, 2018) was set up und modified for this catchment. Here, a time-variant power law function was used as rank StorAge Selection (SAS) function to select the composition of fluxes considering their age. Nitrate with a distinct δ18O from water, formed during microbial activities in the upper soil zone is transported with leaching water into the subsurface storage where denitrification with the corresponding isotope fractionation occurs. The combination of stable isotopes of water and biogeochemical equations to describe the forming of nitrate isotopes and the fractionation of nitrate isotopes during denitrification, which depends on transit times is a novel tool to investigate nitrate age and nitrate transport. Together with the usage of a SAS-based transit time model to simulate nitrate transport and denitrification in the subsurface, tran-SAS is transformed into a simplified reactive transport model (RTM).A decoupling between nitrate age and water age as well as between nitrate travel times and water travel times is expected. Especially during precipitation events catchment’s processes and travel times are changing due to altering hydrological conditions. The model allows to investigate the age of water and nitrate during different hydrological conditions. This will become more and more important considering more frequent hydrological extremes (droughts and floods) and associated N mobilization in agricultural catchments.

Water transit time distributions (TTDs) are important descriptors of hydrological functioning and solute mobilization in catchments. The use of transport models based on StorAge Selection (SAS) functions is promising for characterizing non-stationary TTDs. Model parameters are typically calibrated using tracer concentration in inflow (e.g., precipitation) and outflow (e.g., streamflow) in order to obtain suitable values of SAS function parameters and, thereby, simulate TTDs at catchment-scale. However, due to uncertainties in tracer data and equifinality problems in SAS modelling, modeled TTDs can be subject to considerable uncertainty. Therefore, we need alternative and independent methods that can help constrain model parameters. An example is the young water fraction (Fyw), which quantifies the proportion of catchment outflow younger than approximately 2–3 months. Our work attempts to explore the robustness of Fyw in constraining SAS model parameter values and, in turn, reducing predictive uncertainty of TTDs in multiple contrasting sub-catchments in the Central European Bode River Basin. We simulated TTDs using sparse (i.e., monthly) stable water isotope data (δ¹⁸O) in streamflow for calibration in an experimental SAS modelling framework. In a subsequent step, we directly compared the model estimates of long-term average (marginal) TTDs with Fyw derived from the seasonal cycles of δ¹⁸O measured in precipitation and streamflow. Our results showcase if and to what extent Fyw is a valuable additional constraint to infer SAS parametrizations as well as improve TTD predictions and the characterization of water age selection dynamics, and identify potentials and gaps in isotope-based TTD models. Our results also show how the effectiveness of Fyw in reducing the predictive uncertainty of TTDs may depend on the water use by plants and land use change across physiographically different sub-catchments. Overall, as the relevance of Fyw in TTD modeling is not yet well established, our aim is to investigate whether additional indicators such as Fyw are useful for TTD modeling and thus allow improving the description of flow and transport in catchment areas, especially in situations where a high-resolution tracer data are lacking.

Understanding catchment controls on catchment solute export is a prerequisite for water quality management. StorAge Selection (SAS) functions encapsulate essential information about catchment functioning in terms of discharge selection preference and solute export dynamics. However, they lack information on the spatial origin of solutes when applied at the catchment scale, thereby limiting our understanding of the internal (subcatchment) functioning. Here, we parameterized SAS functions in a spatially explicit way to understand the internal catchment responses and transport dynamics of reactive dissolved nitrate (N-NO3). The model was applied in a nested mesoscale catchment (457 km²), consisting of a mountainous partly forested, partly agricultural subcatchment, a middle-reach forested subcatchment, and a lowland agricultural subcatchment. The model captured flow and nitrate concentration dynamics not only at the catchment outlet but also at internal gauging stations. Results reveal disparate subsurface mixing dynamics and nitrate export among headwater and lowland subcatchments. The headwater subcatchment has high seasonal variation in subsurface mixing schemes and younger water in discharge, while the lowland subcatchment has less pronounced seasonality in subsurface mixing and much older water in discharge. Consequently, nitrate concentration in discharge from the headwater subcatchment shows strong seasonality, whereas that from the lowland subcatchment is stable in time. The temporally varying responses of headwater and lowland subcatchments alternates the dominant contribution to nitrate export in high and low-flow periods between subcatchments. Overall, our results demonstrate that the spatially explicit SAS modeling provides useful information about internal catchment functioning, helping to develop or evaluate spatial management practices.