Floodplains have been degraded in Central Europe for centuries, resulting in less dynamic and less diverse ecosystems than in the past. They provide essential ecosystem services like nutrient ...retention to improve overall water quality and thus fulfill naturally what EU legislation demands, but this service is impaired by reduced connectivity patterns. Along the second-longest river in Europe, the Danube, restoration measures have been carried out and are planned for the near future in the Austrian Danube Floodplain National Park in accordance with navigation purposes. We investigated nutrient retention capacity in seven currently differently connected side arms and the effects of proposed restoration measures using two complementary modeling approaches. We modelled nutrient retention capacity in two scenarios considering different hydrological conditions, as well as the consequences of planned restoration measures for side arm connectivity. With existing monitoring data on hydrology, nitrate and total phosphorus concentrations for three side arms, we applied a statistical model and compared these results to a semi-empirical retention model. The latter was originally developed for larger scales, based on transferable causalities of retention processes and set up for this floodplain with publicly available data. Both model outcomes are in a comparable range for NO3-N (77-198 kg ha-1 year-1) and TP (1.4- 5.7 kg ha-1 year-1) retention and agree in calculating higher retention in floodplains, where reconnection allows more frequent inundation events. However, the differences in the model results are significant for specific aspects especially during high flows, where the semi-empirical model complements the statistical model. On the other hand, the statistical model complements the semi-empirical model when taking into account nutrient retention at times of no connection between the remaining water bodies left in the floodplain. Overall, both models show clearly that nutrient retention in the Danube floodplains can be enhanced by restoring lateral hydrological reconnection and, for all planned measures, a positive effect on the overall water quality of the Danube River is expected. Still, a frequently hydrologically connected stretch of national park is insufficient to improve the water quality of the whole Upper Danube, and more functional floodplains are required.
Floodplains remove nitrate from rivers through denitrification and thus improve water quality. The Danube River Basin (DRB) has been affected by elevated nitrate concentrations and a massive loss of ...intact floodplains and the ecosystem services they provide. Restoration measures intend to secure and improve these valuable ecosystem services, including nitrate removal. Our study provides the first large-scale estimate of the function of large active floodplains in the DRB to remove riverine nitrate and assesses the contribution of reconnection measures. We applied a nutrient emission model in 6 river systems and coupled it with denitrification and flooding models which we adapted to floodplains. The floodplains have the capacity to eliminate about 33,200 t nitrate-N annually, which corresponds to 6.5 % of the total nitrogen emissions in the DRB. More nitrate is removed in-stream at regular flow conditions than in floodplain soils during floods. However, increasing frequently inundated floodplain areas reveals greater potential for improvement than increasing the channel network. In total, we estimate that 14.5 % more nitrate can be removed in reconnected floodplains. The largest share of nitrogen emissions is retained in the Yantra and Tisza floodplains, where reconnections are expected to have the greatest impact on water quality. In absolute numbers, the floodplains of the lower Danube convert the greatest quantities of nitrate, driven by the high input loads. These estimates are subject to uncertainties due to the heterogeneity of the available input data. Still, our results are within the range of similar studies. Reconnections of large floodplains in the DRB can, thus, make a distinct contribution to improving water quality. A better representation of the spatial configuration of water quality functions and the effect of floodplain reconnections may support the strategic planning of such to achieve multiple benefits and environmental targets.
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•A first estimate of the NO3 removal by large floodplains in the Danube River Basin.•We coupled a nutrient emission-, a denitrification-, and a flooding model.•Currently, active floodplains can remove ~33,200 t NO3-N (≙6.5 % of N emissions).•Reconnections could increase this by 9–32 %, besides other ecological improvements.•Assessing water quality functions supports the planning of floodplain restorations.
Floodplains provide an extraordinary quantity and quality of ecosystem services (ES) but are among the most threatened ecosystems worldwide. The uses and transformations of floodplains differ widely ...within and between regions. In recent decades, the diverse pressures and requirements for flood protection, drinking water resource protection, biodiversity, and adaptation to climate change have shown that multi-functional floodplain management is necessary. Such an integrative approach has been hampered by the various interests of different sectors of society, as represented by multiple stakeholders and legal principles. We present an innovative framework for integrated floodplain management building up on ES multi-functionality and stakeholder involvement, forming a scientifically based decision-support to prioritize adaptive management measures responding at the basin and local scales. To demonstrate its potential and limitations, we applied this cross-scaled approach in the world's most international and culturally diverse basin, the Danube River Basin in Europe. We conducted large-scale evaluations of anthropogenic pressures and ES capacities on the one hand and participatory modelling of the local socio-ecohydrological systems on the other hand. Based on our assessments of 14 ES and 8 pressures, we recommend conservation measures along the lower and middle Danube, restoration measures along the upper-middle Danube and Sava, and mitigation measures in wide parts of the Yantra, Tisza and upper Danube rivers. In three case study areas across the basin, stakeholder perceptions were generally in line with the large-scale evaluations on ES and pressures. The positive outcomes of jointly modelled local measures and large-scale synergistic ES relationships suggest that multi-functionality can be enhanced across scales. Trade-offs were mainly present with terrestrial provisioning ES at the basin scale and locally with recreational activities. Utilizing the commonalities between top-down prioritizations and bottom-up participatory approaches and learning from their discrepancies could make ecosystem-based management more effective and inclusive.
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•A first cross-scaled DPSIR assessment of floodplains in the Danube River Basin.•We provide a spatial prioritization scheme based on floodplain multi-functionality.•Synergies dominate across scales, supporting ecosystem-based management.•A few discrepancies between scales offer opportunities for mutual learning.
River floodplains are hotspots of productivity and biodiversity and recognized to fulfil vital ecosystem functions and services. Restoration measures of the decoupled Danube floodplains east of ...Vienna aim to re‐establish multi‐functionality, that is, ensure navigation, preserve and restore unique fluvial and riparian habitats and re‐establish natural processes and service provisioning. Side‐channels are proposed for reconnection combined with the removal of embankments and groins. We evaluated how a programme of measures influences the diversity and quantity of specific ecosystem services (ES) and therefore, the overall multi‐functionality of the floodplain compared to the current situation. Therefore, regulating ecosystem services (RES), such as nutrient retention and habitat provisioning, were modelled and predicted using multivariate regression models. Also, the potential of cultural ecosystem services (CES) was assessed based on mapping of recreational activities. The impact of proposed measures on ES quantity, that is, quantitative spatial representation, and quality, that is, biodiversity and nature experience, as well as potential synergies and trade‐offs were analysed. Our results show clear synergies especially for RES (habitat for the rheotopic community and nutrient retention) and the CES of nature experience. Those services have a weak and local trade‐off with the quantitative availability of opportunities for recreation. This pattern could only be detected by considering both, quantitative as well as qualitative aspects of ES. Overall, our results show that the restoration measures have a high potential to increase the multi‐functionality of the floodplain system by supporting the provisioning of RES including habitat for endangered species and selected CES.
Excess nitrogen (N) from agricultural sources is a major contributor to the water pollution of rivers in Europe. Floodplains are of tremendous importance as they can permanently remove nitrate (NO3) ...from the environment by releasing reactive N to the atmosphere in its gaseous forms (N2O, N2) during denitrification. However, the quantitative assessment of this ecosystem function is still challenging, particularly on the national level. In this study, we modeled the potential of NO3-N removal through microbial denitrification in soils of the active floodplains of the river Elbe and river Rhine in Germany. We combined laboratory measurements of soil denitrification potentials with straightforward modelling data, covering the average inundation duration from six study areas, to improve an existing Germany-wide proxy-based approach (PBAe) on NO3-N retention potential. The PBAe estimates this potential to be 30–150 kg NO3-N ha−1 yr−1. However, with soil pH and Floodplain Status Category identified as essential parameters for the proxies, the improved PBA (PBAi) yields a removal potential of 5–480 kg N ha−1 yr−1. To account for these parameters, we applied scaling factors using a bonus-malus system with a base value of 10–120 N ha−1 yr−1. Upscaling the determined proxies of the PBAi to the entire active floodplains of the river Elbe and river Rhine results in similarly high NO3-N retention sums of ~7000 t yr−1 in spite of very different retention area sizes, strengthening the argument for area availability as the primary objective of restoration efforts. Although PBAs are always subject to uncertainty, the PBAi enables a more differentiated spatial quantification of denitrification because local key controlling parameters are included. Hence, the PBAi is an innovative and robust approach to quantify denitrification in floodplain soils, supporting a better assessment of ecosystem services for decision-making on floodplain restoration.
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•A robust nitrate removal estimate denitrification in large floodplains•Linking measurements with a flooding model for improved NO3-N removal proxies•Active floodplains of Elbe and Rhine are both capable of removing ~7000 t NO3-N yr−1.•Improved proxy-based approach for decision-making on floodplain restoration
Abstract
The access to an adequate quantity and quality of water is vital to sustain healthy ecosystems and human socioeconomic development. However, the shift from an agrarian, solar energy based to ...an industrialized, fossil fuel‐based socio‐metabolic regime has put natural water resources under stress and led to dramatic transformations of riverine landscapes in the Anthropocene. Thus, we need interdisciplinary research approaches that integrate the knowledge and methods from ecology, humanities, and engineering. The Doctoral School “Human River Systems in the 21st Century” (HR21) studies riverine landscapes as coupled socio‐ecohydrological systems (SEHS) within four research clusters, that is, connectivity, metabolism, vulnerability, and governance. HR21 analyzes the transformation processes and coevolution of nature and society in rivers and their response to future environmental, social, cultural, and economic drivers of change. HR21 aims to improve the understanding of the coupling of the socioeconomic, ecological, and hydrological systems within industrialized riverine landscapes to support their urgent, more sustainable transformation. To discuss how this agenda can be implemented, five different HR21 PhD projects are presented, clearly routed in one scientific domain, applying a combination of the research clusters and addressing various topics: (i) hydropower effects in high alpine river ecosystems, (ii) wastewater impacts on carbon storage and greenhouse gas fluxes in tropical wetlands, (iii) the nutrient retention and ecosystem service potential of floodplains in large river catchments, and the influence of hydrometeorological variables on (iv) the runoff response and on (v) the transit time distribution of runoff, both impacting water resource management at the basin level. These examples highlight how disciplinary PhD research can be framed within an interdisciplinary research agenda to coupled SEHS.
River systems have undergone a massive transformation since the Anthropocene. The natural properties of river systems have been drastically altered and reshaped, limiting the use of management ...frameworks, their scientific knowledge base and their ability to provide adequate solutions for current problems and those of the future, such as climate change, biodiversity crisis and increased demands for water resources. To address these challenges, a socioecologically driven research agenda for river systems that complements current approaches is needed and proposed. The implementation of the concepts of social metabolism and the colonisation of natural systems into existing concepts can provide a new basis to analyse the coevolutionary coupling of social systems with ecological and hydrological (i.e., ‘socio-ecohydrological’) systems within rivers. To operationalize this research agenda, we highlight four initial core topics defined as research clusters (RCs) to address specific system properties in an integrative manner. The colonisation of natural systems by social systems is seen as a significant driver of the transformation processes in river systems. These transformation processes are influenced by connectivity (RC 1), which primarily addresses biophysical aspects and governance (RC 2), which focuses on the changes in social systems. The metabolism (RC 3) and vulnerability (RC 4) of the social and natural systems are significant aspects of the coupling of social systems and ecohydrological systems with investments, energy, resources, services and associated risks and impacts. This socio-ecohydrological research agenda complements other recent approaches, such as ‘socio-ecological’, ‘socio-hydrological’ or ‘socio-geomorphological’ systems, by focusing on the coupling of social systems with natural systems in rivers and thus, by viewing the socioeconomic features of river systems as being just as important as their natural characteristics. The proposed research agenda builds on interdisciplinarity and transdisciplinarity and requires the implementation of such programmes into the education of a new generation of river system scientists, managers and engineers who are aware of the transformation processes and the coupling between systems.
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•River systems have been massively transformed and are socio-ecohydrological systems.•A socio-ecohydrologically driven approach provides insights into coevolutionary processes.•Social metabolism and the colonisation of natural systems are underlying concepts.•Four research clusters analyse the transformation and coupling of society and nature.•Interdisciplinary and transdisciplinary approaches support the operationalization of the research agenda.
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