A method to assess annual average renewable groundwater reserves for large regions in Spain

This paper proposes a method for assessing the groundwater renewable reserves of large regions for an average year, based on the integration of the recession curves for their basins springs or the natural base flow of their rivers. In this method, the hydrodynamic volume (or renewable reserves), were estimated from the baseflow equation. It was assumed that the flow was the same as the natural recharge, and that the recession coefficients were derived by the hydrogeological parameters and geometrical characteristics of aquifers, and adjusted to fit the recession curves at gauging stations. The method was applied to all the aquifers of Spain, which have a total groundwater renewable reserve of 86,895 hm3 four times the mean annual recharge. However, the distribution of these reserves is very variable; 18.6% of the country aquifers contain 94.7% of the entire reserve

Estimation of High Floods by Three Rainfall-Runoff Models with Short Rainfall-Runoff Series (Alzette River Basin, Luxembourg)

This paper presents a comparison of hourly high runoff simulations using short discharge series for three parsimonious rainfall-runoff models that differ substantially in their conceptualisation (two reservoir models and one physically-based model). The models were applied to eight monitored sub-basins characterised by different physiographical properties and hydrological behaviour, located in the experimental Alzette river basin (Luxembourg). The model calibration procedure consists in selecting only rainfall-runoff events with highest peak flows and highest runoff production that occurred during the available measurement period (1997-2001). Simulated extreme values of peak flow and stormflow volumes were analysed and compared to observed runoff series. Results show that the models are able to provide good fits to the rainfall-runoff event’s hydrographs. Nevertheless, the physically-based MHM model gives the best results in terms of predictive accuracy

Geological and Hydrogeological Characterization of Springs in a DSGSD Context (Rodoretto Valley – NW Italian Alps)

As continuous groundwater monitoring in the upper sector of Rodoretto Valley (Germanasca Valley, Italian Western Alps) is hampered by logistical problem of data collection during winter and spring months, the only tools currently available to derive hydrogeological information are non-continuous and non-long-term dataset of spring discharge (Q), temperature (T) and electrical conductivity (EC). In order to quantity aquifer groundwater reserve, available Q dataset of a small mountain spring (Spring 1 CB) was investigated by applying the analytical solutions developed by Boussinesq (J Math Pure Appl 10:5–78, 1904) and Maillet (Essais dı’hydraulique souterraine et fluviale, vol 1. Herman et Cie, Paris, 1905); T and EC datasets were also used to provide qualitative information about the nature of the aquifer that supplies the spring. The outcomes of the elaborations highlighted the limits of applicability of these methods in the presence of a non-continuous Q dataset: both Boussinesq (J Math Pure Appl 10:5–78, 1904) and Maillet (Essais dı’hydraulique souterraine et fluviale, vol 1. Herman et Cie, Paris, 1905) estimated that discharge values as a function of recession time were found to be consistently lower than the available discharge ones and the estimated groundwater volumes stored over time above the spring level turned out to be underestimated. Continuous (hourly value) and long-term Q, EC and T values are, therefore, needful to correctly quantify and to make a proper management of groundwater resources in mountain areas

Comment introduire de la "bonne incertitude" dans les projections climatiques ? Vers la construction d'un "stress-test" climatique dans le bassin transnational de la Meuse.

International audiencePast analysis of climate variability is useful to maximize the good uncertainty when producing future climate projections. This paper presents the application of a simple method linking atmospheric circulation and surface climatic variables with the aim to extrapolate knowledge of climate in the past (until the Maunder minimum) and in the near future (21st century). This allows building a lot of plausible climatic scenarios, which form the basis of a climate “stress-test”. Its objective is to assess the hydrologic vulnerability of a catchment to the climate change. Calculated on the whole period of interest (1659-2100), monthly precipitation and temperature anomalies show that the knowledge of past climate has a high informative value, which is not enough taken into account in the climate change impact studies.L’étude rétrospective de la variabilité climatique contribue à maximiser la bonne incertitude dans l’exercice de scénarisation climatique. Cet article présente l’application d’une méthode simple liant la circulation atmosphérique et les variables climatiques de surface dans le but l’extrapoler la connaissance du climat dans le passé (jusqu’au minimum de Maunder) et dans un futur proche (XXIe siècle). Ceci permet de produire un grand nombre de scénarios climatiques vraisemblables formant le socle d’un « stress-test » climatique, dont l’objectif est d’évaluer la vulnérabilité hydrologique d’un bassin au changement climatique. Le calcul, sur toute la période d’étude (1659-2100) des anomalies mensuelles de précipitations et de température de l’air, montre que la connaissance du climat passé a une grande valeur informative, trop souvent négligée dans les études d’impact du changement climatique futur

Test de la résilience climatique aux inondations sur l'Ourthe, Belgique

International audienceObjectivesClimate changes are now recognized as one of the main issue of the societies and are expected to bring disturbances in many fields including floods. However, as future is unknown, and climate models projections still own a wide range of uncertainties, adaptation measures are confronted to large uncertainties, that can lead decision-makers to inaction due to the high risk to mistake when designing. Furthermore, adaptation measures usually yield from deterministic, or top-down climate change impact studies, which restricts them to only few potential climate scenarios. The position of this study is to follow an alternative approach to assess the potential impacts of climate change on floods in the Ourthe catchment, Belgium. Grelier et al (2016) elaborated a transfer function method to assess long-term climate risk from mesoscale atmospheric circulation using a paleoclimate reconstruction and many climate models projections. They produced more than 2000 monthly anomalies with which they perturbed a baseline series to run a hydrological model. Based on these results we propose to use the hydraulic modelling to assess the impact of climate change on floods.MethodsIn a first step, a statistical sampling aims at selecting climate change reference scenarios (and corresponding hydrological scenarios) considered as representative of different atmospheric conditions. A 1D bin hydraulic model is calibrated and used to simulate the hydrological scenarios (of 30 years each) on a reach of the Ourthe river in order to detect sequences of overflowing at each bin. Two parameters have been retained: the firstdischarge and the duration of the overflowing sequences, which are then examined via a frequency analysis procedure to assess the impacts of climate change on floods.Finally, a simple planning measure is tested with the hydraulic model: implementation of hedge in the flood plain. Results will provide information of the flood resilient nature of such a “soft” measure.ConclusionsTo summarize, our approach can contribute to consider the unexpected in the flood assessment and management: as climate change uncertainties still remains large, the resilience concept represents a promising way to better consider the potential climate change impacts on flood risk. Our work fits into this frame of resilience and besides testing a simple river planning measure, it may serve for example the elaboration of climate security margins or impulse the integration of a climate change component in the flood risk management documents and plans

L'amélioration de la qualité du cacao équatorien comme facteur de compétitivité

International audienceLe cacao "Nacional" équatorien fait partie de ce que nous appelons les cacaos fins et d'arôme. Mais il est aussi unique au monde pour sa saveur florale très particulière. Pendant longtemps, il fut, pour cette raison, un produit très demandé par les chocolatiers du monde entier. Cependant depuis quelques années, le cacao équatorien souffre d'une mauvaise image auprès de ses clients parce qu'il ne répond pas aux exigences de qualité des acheteurs internationaux. Cette perte de la qualité du cacao "Nacional" équatorien a comme conséquence directe une perte de compétitivité face aux autres cacaos fins et d'arôme qui répondent à ces exigences. La qualité du cacao "Nacional" équatorien dépend de deux types de critères : les critères objectifs comme la taille des fèves, le degré de fermentation ou le contenu en beurre et des critères plus subjectifs comme la qualité organoleptique. Ce dernier critère est essentiel dans le cas du cacao "Nacional" d'Equateur. Sur la base de ces critères, les auteurs ont cherché à voir comment l'amélioration de la qualité du cacao "Nacional" permettrait de restaurer sa compétitivité sur le marché international. Trois facteurs principaux participent à l'amélioration de la qualité : le facteur génétique, les itinéraires techniques et un traitement post-récolte adéquat. Ils montrent comment ces facteurs interagissent dans l'optimisation des critères cités plus haut. Il apparaît que la faible compétitivité du cacao équatorien n'est pas liée à son prix et qu'en améliorant la qualité à chaque échelon de la chaîne agroalimentaire, on augmente la valeur ajoutée mais également les coûts de production ou de commercialisation