Towards long-term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems : a review

Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.Peer reviewe

Indirect N2O emissions from shallow groundwater in an agricultural catchment (Seine Basin, France)

International audienceProduction and accumulation of nitrous oxide (N2O), a major greenhouse gas, in shallow groundwater might contribute to indirect N2O emissions to the atmosphere (e.g., when groundwater flows into a stream or a river). The Intergovernmental Panel on Climate Change (IPCC) has attributed an emission factor (EF5g) for N2O, associated with nitrate leaching in groundwater and drainage ditches-0.0025 (corresponding to 0.25% of N leached which is emitted as N2O)-although this is the subject of considerable uncertainty. We investigated and quantified the transport and fate of nitrate (NO3 (-)) and dissolved nitrous oxide from crop fields to groundwater and surface water over a 2-year period (monitoring from April 2008 to April 2010) in a transect from a plateau to the river with three piezometers. In groundwater, nitrate concentrations ranged from 1.0 to 22.7 mg NO3 (-)-N l(-1) (from 2.8 to 37.5 mg NO3 (-)-N l(-1) in the river) and dissolved N2O from 0.2 to 101.0 mu g N2O-N l(-1) (and from 0.2 to 2.9 mu g N2O-N l(-1) in the river). From these measurements, we estimated an emission factor of EF5g = 0.0026 (similar to the value currently used by the IPCC) and an annual indirect N2O flux from groundwater of 0.035 kg N2O-N ha(-1) year(-1), i.e., 1.8% of the previously measured direct N2O flux from agricultural soils

Technical note: A two-sided affine power scaling relationship to represent the concentration-discharge relationship

This technical note deals with the mathematical representation of concentration-discharge relationships. We propose a two-sided affine power scaling relationship (2S-APS) as an alternative to the classic one-sided power scaling relationship (commonly known as "power law"). We also discuss the identification of the parameters of the proposed relationship , using an appropriate numerical criterion. The application of 2S-APS to the high-frequency chemical time series of the Orgeval-ORACLE observatory is presented here (in calibration and validation mode): it yields better results for several solutes and for electrical conductivity in comparison with the power law relationship

A combined mixing model for high-frequency concentration–discharge relationships

International audienceStreamflow is the major factor influencing the evolution of solute concentration in river water and different modelling approaches exist to characterize the dependency of ion concentration to discharge: the simplest are based on measurable quantities (stream discharge and stream ion concentration) but do not allow for an explicit, physical, flow-path interpretation; the more complex are based on mixing assumptions with different end-members sources, but require the knowledge of (unmeasurable) flow components. We present here a new concentration–discharge model, which associates a classical concentration–discharge relationship with a classical two-component mixing equation. The originality of our approach lies in the fact that we do not proceed in the usual way to perform the hydrograph separation: we use an a priori assumption of the baseflow-quickflow separation to infer the source concentration values, contrarily to the usual (inverse) approach. The other notable originality is that all the parameters of this model depend on the temporal variation of the stream discharge. This combined model was tested on high-frequency ion concentration series from the ORACLE-Orgeval observatory (France). This work demonstrates that high temporal resolution data allows for explicit testing of model performance across different hydrologic scales. Results show that the combined mixing model allows a better estimation of streamflow solute concentration series for most ions tested at inter-annual scale, except for nitrate (which do not exhibit a clear C-Q relationship). Our results also confirm the advantage of coupling a time dynamic hydrological model with static C-Q relations for each of the flow components

Validation des données haute fréquence sur l'observatoire ORACLE. Réseau des bassins versants

International audienc

How to integrate scientific models in order to switch from flood control river management to multifunctional river management?

International audienceSince 2000, the European Water Framework Directive has required managers to restore water bodies to good ecological status, including rivers that have been substantially anthropomorphized, i.e. the vast majority of rivers in France. This obligation creates situations, such as removal of mill sluice gates and strong resistance from local stakeholders that must be addressed by governmental agencies and local elected officials. Seine watershed researchers have suggested using a hydraulic model to give river managers an overall vision of structure function (including sluice gates) and the water elevation adjustments between the upstream and downstream reaches with adjustments to the structures. Scientists adapted their model with the collaboration of the local actors in charge of the river management. This simulation of the management of river structures was achieved by constructing an interactive platform and using it to simulate annual flow scenarios for the river and management objective scenarios for all types of use, both recreational and high- and low-water scenarios. Model construction and simulation reunited scientists; State services agents, elected officials but also mill owners and members of local associations. The objective of this collective use was to allow managers to appreciate the current knowledge on the effects that removing a structure would have, around a multifunctional approach to the river, to consider removal of certain structures depending on the locally expected results

How should agricultural practices be integrated to understand and simulate long-term pesticide contamination in the Seine river basin?

International audienceModelling long term pesticide transfer to river at the catchment scale is still difficult due to a lack of knowledge about agricultural practices and non-adapted field observation. The Orgeval experimental catchment was first investigated to validate a modeling approach. Beside pesticide practices investigated over 20 years, directly collected from farmers, monthly integrated river samples were ana-lyzed for 10 years. To explicitly integrate agricultural practices and crop rotation, the crop model STICS was adapted to simulate pesticide transfer in soil. Annual load simulations were compared to observed pesticide fluxes in river. In order to simulate the contamination of groundwater, STICS-Pest model was coupled to the hydrogeological model MODCOU. Results are discussed at the sub-basin scale in relation to available data. To upscale the approach at the Seine river basin scale, other strategies need to be developed

How to integrate agricultural practices to understand and simulate long term contamination of pesticides in the Seine basin ?

International audienceModelling long term pesticide transfer to river at the catchment scale is still difficult due to a lack of knowledge about agricultural practices and non-adapted field observation. The Orgeval experimental catchment was first investigated to validate a modeling approach. Beside pesticide practices investigated over 20 years, directly collected from farmers, monthly integrated river samples were ana-lyzed for 10 years. To explicitly integrate agricultural practices and crop rotation, the crop model STICS was adapted to simulate pesticide transfer in soil. Annual load simulations were compared to observed pesticide fluxes in river. In order to simulate the contamination of groundwater, STICS-Pest model was coupled to the hydrogeological model MODCOU. Results are discussed at the sub-basin scale in relation to available data. To upscale the approach at the Seine river basin scale, other strategies need to be developed

La valse des pesticides : de l’analyse des données à la modélisation des transferts

International audienc

La valse des pesticides : de l’analyse des données à la modélisation des transferts

International audienc