Scenario analysis of pollutants loads to European regional seas for the year 2020. Part I: Policy options and alternative measures to mitigate land based emission of nutrients

A spatially explicit statistical approach (GREEN model) applied to continental Europe on a sub-catchment basis, is used to link input from anthropogenic activities and nutrient loads into European Seas (namely nitrogen and phosphorous). Effectiveness of environmental legislation is assessed at the horizon 2020, emphasizing the regional differences between European countries as well as the respective contribution of anthropogenic changes and hydrological fluctuation in nutrient exports. The set of scenarios analyzed includes a business as usual situation, a full implementation of on going policy options, a change in European diet based on a strong reduction of meat intake, and optimized management of agricultural practices. All prospective analyses are implemented for EU-27 and are discussed in terms of capacities to mitigate land based emissions of nutrient, and also according to their impacts on the loads of nutrient exported to European coastal areas.JRC.H.1-Water Resource

The community-centered freshwater biogeochemistry model unified RIVE v1.0: a unified version for water column

Research on mechanisms of organic matter degradation, bacterial activities, phytoplankton dynamics, and other processes has led to the development of numerous sophisticated water quality models. The earliest model, dating back to 1925, was based on first-order kinetics for organic matter degradation. The community-centered freshwater biogeochemistry model RIVE was initially developed in 1994 and has subsequently been integrated into several software programs such as Seneque-Riverstrahler, pyNuts-Riverstrahler, ProSe/ProSe-PA, and Barman. After 30 years of research, the use of different programming languages including QBasic, Visual Basic, Fortran, ANSI C, and Python, as well as parallel evolution and the addition of new formalisms, raises questions about their comparability. This paper presents a unified version of the RIVE model for the water column, including formalisms for bacterial communities (heterotrophic and nitrifying), primary producers, zooplankton, nutrients, inorganic carbon, and dissolved oxygen cycles. The unified RIVE model is open-source and implemented in Python 3 to create pyRIVE 1.0 and in ANSI C to create C-RIVE 0.32. The organic matter degradation module is validated by simulating batch experiments. The comparability of the pyRIVE 1.0 and C-RIVE 0.32 software is verified by modeling a river stretch case study. The case study considers the full biogeochemical cycles (microorganisms, nutrients, carbon, and oxygen) in the water column, as well as the effects of light and water temperature. The results show that the simulated concentrations of all state variables, including microorganisms and chemical species, are very similar for pyRIVE 1.0 and C-RIVE 0.32. This open-source project highly encourages contributions from the freshwater biogeochemistry community to further advance the project and achieve common objectives.</p

Nitrogen as a threat to European water quality

Anthropogenic increase of nitrogen in water poses direct threats to human health and aquatic ecosystems. High nitrogen concentrations in drinking water are dangerous for human health. In aquatic ecosystems the nitrogen enrichment contributes to eutrophication, which is responsible for toxic algal blooms, water anoxia, fish kills and habitat and biodiversity loss. Nitrogen concentrations in European rivers, lakes, aquifers and coastal waters are generally high in many regions. In addition, nitrogen is probably accumulating in groundwaters, reducing the future reliability of the resource. In Europe, nitrogen pressures on water are wide spread, resulting in elevated costs. About 40% of the European population would potentially be exposed to high nitrates values in drinking water if adequate treatment was not in place, and a large proportion of European aquatic ecosystems is eutrophicated or at risk of eutrophication. Even under favourable land use scenarios the nitrogen export to European waters and seas is likely to remain significant in the near future. The effects of climate change on nitrogen export to waters are still unsure. Policy tools are available within the European Union and under international conventions to mitigate against nitrogen pollution in water, but their full implementation has not yet been achieved throughout Europe. In many cases a delay in the water quality response to implementation of management measures have been observed, due to historical nitrogen accumulation in soils, sediments or aquifers or to inadequate design of the mitigation plans. The issue of pollution swapping between environmental compartments has appeared as an important element to be considered by both the scientific and policy prospective. To support the sustainable management of water resources, positive effects could be obtained implementing existing policy tools, improving the integration in sectoral policies and promoting the interactions between science and policy.JRC.DDG.H.5-Rural, water and ecosystem resource

Carbon Dynamics Along the Seine River Network: Insight From a Coupled Estuarine/River Modeling Approach

The Seine river discharges over 700 Gg of carbon (C) every year into the sea mostly under the form of dissolved inorganic carbon (DIC) and emits 445 Gg under the form of carbon dioxide (CO2) to the atmosphere over its entire river network. The watershed, which drains 76,000 km2, is heavily populated with 18 106 inhabitants and is thus submitted to large anthropic pressure. The offline coupling of two Reactive Transport Models is used to understand the complex spatial and temporal dynamics of carbon, oxygen and nutrients and quantify the CO2 exchange at the air-water interface along the main axis of the river. The estuarine section of the Seine is simulated by the generic estuarine model C-GEM (for Carbon Generic Estuarine Model), while the upstream part of the network, devoid of tidal influence is simulated by the pyNuts-Riverstrahler modeling platform which also includes an explicit representation of the drainage network ecological functioning. Our simulations provide a process-based representation of nutrients, oxygen, total organic carbon (TOC) and the carbonate system (DIC and alkalinity) over the entire year 2010. Our coupled modeling chain allows quantifying the respective contributions of the estuarine and freshwater sections of the system in the removal of carbon as well as following the fate of TOC and DIC along the river network. Our results also allow calculating an integrated carbon budget of the Seine river network for year 2010

Modélisation spatialisée des flux de nutriments (N, P, Si) des bassins de la Seine, de la Somme et de l'Escaut : impact sur l'eutrophisation de la Manche et de la Mer du Nord

The productivity of coastal ecosystems is linked to river nutrient sources, in particular nitrogen (N), phosphorous (P) and Silica (Si), three elements essential for their functioning. However, nutrient loading and their imbalance can result in the eutrophication of costal marine areas. In the continental coastal zone of the Channel and Southern Bight of the North Sea, enriched water inflows from the Seine, Somme and Scheldt rivers contribute to the massive development of harmful algae species. The adjacent and contrasted watersheds of these three rivers differ by their morphology, hydrology and anthropogenic activities, and offer a textbook example for in-depth analysis of nutrient fluxes in river basins and their impact at the coastal zone. This PhD thesis aimed to implement, at the scale of the 100,000 km² watershed drained by the aquatic continuum of the three rivers, a determinist modeling approach describing all basic processes involved in the transport, the retention and the transformation of nutrient (N, P, Si). The Seneque-Riverstrahler model implemented for that purpose, has been first validated for the recent period (1996-2001) and then used to establish a detailed budget of nutrient transfers. This latter was required to quantify the fluxes of nitrogen and phosphorus delivered in excess over silica at the French and Belgian coastal zone. Several mitigation measures have been designed and tested, including operational management options requested by the European Water Framework Directive (Eu-WFD) as well as long term scenarios of nutrient reduction. Assessment of these scenarios explores the ability to balance riverine exports with respect to the Redfield ratios, to improve nitrogen and phosphorous contamination within the drainage networks, and to limit the opening of biogeochemical cycles that has prevailed for more than 30 years. These results have been coupled with a marine model describing the ecological functioning coastal ecosystem, in the framework of an integrated “river – ocean” approach. The impact of the different watershed scenarios is thus finally expressed in terms of algal development at the costal zone.Les apports fluviaux en éléments nutritifs comme l'azote (N) le phosphore (P) et la Silice (Si) sont indispensables au fonctionnement des écosystèmes côtiers et en conditionnent la productivité. Cependant, l'intensité et le déséquilibre des flux de nutriments peuvent conduire à l'eutrophisation de ces zones de transition marines. En Manche – Mer du Nord cet enrichissement excessif se caractérise par des blooms phytoplanctoniques qui apparaissent sous l'influence des apports de la Seine, de la Somme et de l'Escaut. Ces trois hydrosystèmes, qui diffèrent largement par leur morphologie, leurs débits mais également les pressions anthropiques qui s'y exercent, offrent un cas d'étude exemplaire pour analyser les flux d'éléments nutritifs dans les bassins versants et leurs impacts à la zone côtière. L'objectif de cette thèse a été d'implémenter, pour ce continuum aquatique drainant plus de 100 000 km2 de surface continentale, une modélisation déterministe du fonctionnement des hydrosystèmes, s'attachant à décrire l'ensemble des processus microscopiques impliqués dans le transport, la rétention et la transformation des éléments N, P et Si. Validé sur la période récente (1996-2001), le modèle Sénèque-Riverstrahler a permis un calcul détaillé des transferts de nutriments, nécessaire pour quantifier le déséquilibre des flux d'azote et de phosphore exportés à la zone côtière franco-belge, par rapport à la silice. Différents scenarios, incluant des mesures de gestion concrètes, du type de celles préconisées par la directive Cadre Européenne sur l'eau (DCE), mais également des prospectives plus théoriques sur long terme, ont été élaborées et simulées. L'évaluation de ces scénarios porte sur la possibilité de rééquilibrer les apports fluviaux, en se basant sur les rapports de Redfield, de limiter la contamination azotée et phosphatée dans les réseaux hydrographiques et de réduire l'ouverture des cycles biogéochimiques qui a prévalu depuis plus de 30 ans. Dans le cadre d'une approche intégrée ‘rivière – zone côtière', ces résultats ont été couplés avec un modèle du fonctionnement des écosystèmes marins côtiers, permettant ainsi de traduire l'impact des mesures implémentées à l'échelle des bassins versants, en terme de développement algal atteint dans la zone côtière

Modélisation spatialisée des flux de nutriments (N, P, Si) des bassins de la Seine, de la Somme et de l Escaut (impact sur l eutrophisation de la Manche et de la Mer du Nord)

Les apports fluviaux en éléments nutritifs comme l azote (N) le phosphore (P) et la Silice (Si) sont indispensables au fonctionnement des écosystèmes côtiers et en conditionnent la productivité. Cependant, l intensité et le déséquilibre des flux de nutriments peuvent conduire à l eutrophisation de ces zones de transition marines. En Manche Mer du Nord cet enrichissement excessif se caractérise par des blooms phytoplanctoniques qui apparaissent sous l influence des apports de la Seine, de la Somme et de l Escaut. Ces trois hydrosystèmes, qui diffèrent largement par leur morphologie, leurs débits mais également les pressions anthropiques qui s y exercent, offrent un cas d étude exemplaire pour analyser les flux d éléments nutritifs dans les bassins versants et leurs impacts à la zone côtière.L objectif de cette thèse a été d implémenter, pour ce continuum aquatique drainant plus de 100 000 km2 de surface continentale, une modélisation déterministe du fonctionnement des hydrosystèmes, s attachant à décrire l ensemble des processus microscopiques impliqués dans le transport, la rétention et la transformation des éléments N, P et Si. Validé sur la période récente (1996-2001), le modèle Sénèque-Riverstrahler a permis un calcul détaillé des transferts de nutriments, nécessaire pour quantifier le déséquilibre des flux d azote et de phosphore exportés à la zone côtière franco-belge, par rapport à la silice. Différents scenarios, incluant des mesures de gestion concrètes, du type de celles préconisées par la directive Cadre Européenne sur l eau (DCE), mais également des prospectives plus théoriques sur long terme, ont été élaborées et simulées. L évaluation de ces scénarios porte sur la possibilité de rééquilibrer les apports fluviaux, en se basant sur les rapports de Redfield, de limiter la contamination azotée et phosphatée dans les réseaux hydrographiques et de réduire l ouverture des cycles biogéochimiques qui a prévalu depuis plus de 30 ans.Dans le cadre d une approche intégrée rivière zone côtière , ces résultats ont été couplés avec un modèle du fonctionnement des écosystèmes marins côtiers, permettant ainsi de traduire l impact des mesures implémentées à l échelle des bassins versants, en terme de développement algal atteint dans la zone côtière.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Long-Term Evolution of Greenhouse Gas Emissions From Global Reservoirs

International audienceThe contribution of artificial reservoirs to greenhouse gas (GHG) emissions has been emphasized in previous studies. In the present study, we collected and updated data on GHG emission rates from reservoirs at the global scale, and applied a new classification method based on the hydrobelt concept. Our results showed that CH 4 and CO 2 emissions were significantly different in the hydrobelt groups (p < 0.01), while no significant difference was found for N 2 O emissions, possibly due to their limited measurements. We found that annual GHG emissions (calculated as C or N) from global reservoirs amounted to 12.9 Tg CH 4-C, 50.8 Tg CO 2-C, and 0.04 Tg N 2 ON. Furthermore, GHG emissions (calculated as CO 2 equivalents) were also estimated for the 1950-2017 period based on the cumulative number and surface area of global reservoirs in the different hydrobelts. The highest increase rate in both the number of reservoirs and their surface area, which occurred from 1950 to the 1980s, led to an increase in GHG emissions from reservoirs. Since then, the increase rate of reservoir construction, and hence GHG emissions, has slowed down. Moreover, we also examined the potential impact of reservoir eutrophication on GHG emissions and found that GHG emissions from reservoirs could increase by 40% under conditions in which total phosphorus would double. In addition, we showed that the characteristics of reservoirs (e.g., geographical location) and their catchments (e.g., surrounding terrestrial net primary production, and precipitation) may influence GHG emissions. Overall, a major finding of our study was to provide an estimate of the impact of large reservoirs during the 1950-2017 period, in terms of GHG emissions. This should help anticipate future GHG emissions from reservoirs considering all reservoirs being planned worldwide. Besides using the classification per hydrobelt and thus reconnecting reservoirs to their watersheds, our study further emphasized the efforts to be made regarding the measurement of GHG emissions in some hydrobelts and in considering the growing number of reservoirs

Long-term assessment of nutrient budgets for the four reservoirs of the Seine Basin (France)

International audienc

Carbon dioxide, methane and nitrous oxide emissions from the human-impacted Seine watershed in France

International audienceGreenhouse gas (GHG) emissions from rivers and lakes have been shown to contribute significantly to global carbon and nitrogen cycling. In temperate and human-impacted regions, simultaneous carbon dioxide, methane and nitrous oxide emissions from aquatic systems are poorly documented. We estimated carbon dioxide (CO2) concentrations in the Seine hydrosystem (71,730 km2, France) using direct measurements, and calculations of CO2 partial pressures from 14 field campaigns conducted between 2010 and 2017, and compared them to methane (CH4) and nitrous oxide (N2O) concentrations.In the main stem of the Seine River, CO2 showed the same spatial gradient as N2O and CH4 with peaks in concentration downstream from the arrival of effluents from wastewater treatment plants enriched in organic matter, thus favoring mineralization. It is likely that high CO2 concentrations upstream were due to organic carbon inputs from soils and enriched CO2 groundwater discharges, whereas high N2O and CH4 upstream values were likely due to denitrification in riparian wet areas and anoxic decomposition of organic matter-rich wetlands, respectively. In addition, seasonal variations in all three GHGs were observed with higher concentrations in summer when higher temperatures promote mineralization and low water reduces the dilution of organic matter mainly originating from WWTP effluents.GHG emissions were calculated and compared with agricultural and nonagricultural (urban, transport) fluxes in the basin. In the Seine River network, CO2 emissions dominated riverine GHG emissions, reaching 95.3%, while N2O and CH4 emissions accounted for 4.4% and 0.3%, respectively. These indirect emissions from the hydrosystem were estimated to account for 3.7% of the total GHG emissions from the basin that amounted to 61,284 Gg CO2eq yr−1. Comparatively, direct agricultural and nonagricultural GHG emissions were estimated at 23.3% and 73.0%., respectively

22. Les eaux stagnantes

Les eaux dites « stagnantes » sont celles des lacs, des réservoirs, des étangs, des sablières et des canaux. Il existe une convergence entre les systèmes courants et stagnants des points de vue de l’hydrologie. En effet, le temps de séjour des lacs (systèmes stagnants) peut atteindre plusieurs siècles, mais aussi se limiter à quelques semaines, comme c’est le cas de certaines rivières (systèmes courants) en période de basses eaux. Les systèmes stagnants sont très diversifiés (cf. III.8) : ils..