Options
Jeannin, Pierre-Yves
Nom
Jeannin, Pierre-Yves
Affiliation principale
Email
pierre-yves.jeannin@unine.ch
Identifiants
RĂ©sultat de la recherche
Voici les éléments 1 - 10 sur 11
- PublicationAccès libreThe VULK analytical transport model and mapping method(2004)
; ; ; ; - PublicationAccès libreVulnerability assessment in karstic areas: validation by field experiments(2004)
; Several methods have been developed for vulnerability mapping in karstic areas. These methods need additional validation by field experiments. Several tests have been carried out in the Swiss Jura with natural and artificial tracers. The protective role of some intrinsic properties of the system, such as glacial deposits covering karst, epikarst storage and system dilution effect, have been clearly demonstrated. Use of three tracers in parallel showed the reactivity of the epikarst: all tracers arrived at the same time, but their relative concentration stayed clearly different. A classification of contamination scenarios into four classes is proposed. It is shown that the relevance of some intrinsic properties depends on the considered scenario class. The hydrodynamic state of the aquifer influences greatly flow velocities and can strongly modify contaminant concentrations at the output of the system. The spatial repartition (point vs diffuse) and the quantity of contaminant entering the system will also influence the output response. Hence, results from tracing experiments cannot be used straightforward for obtaining a representative value of flow velocity, dispersion or recovery rate. - PublicationMétadonnées seulementA deterministic approach to the coupled analysis of karst springs' hydrographs and chemographs(2003)
; During the chemically based recession flow phase of karstic springs the carbonate (dissolved limestone) concentration can be expressed as negative power of the flow rate. The empirically determined Conc/Q relationship allows two parameters (alpha and A) to be defined, of which one (alpha) depends on the geometric dimensions of the saturated (submerged) karstic network. In this paper we present a deterministic model which simulates the concentration of carbonate at the outlet of a network of circular rectilinear conduits as a function of flow rate. This model, based on hydraulic principles and the calcite dissolution kinetics, allows the sensitivity of the alpha and A parameters to be studied under different chemical, physical and geometric scenarios. Simulation results show that A is a function of the calcite saturation concentration, whereas alpha depends on the spatial dimensions of the karstic network (void length and aperture). The deterministic model results were applied to real karstic systems to evaluate the geometric dimensions of submerged karstic networks. (C) 2002 Elsevier Science B.V. All rights reserved. - PublicationMétadonnées seulementEpikarst storage in a karst aquifer: a conceptual model based on isotopic data, Milandre test site, Switzerland(2003)
; The Milandre test site is a karst aquifer characterized by diffuse infiltration, a well developed conduit network, and several tributaries feeding an underground river. Field data include discharge rate measurements, stable isotopes, weekly rainfall and spring-water isotope sampling, and detailed isotope sampling during three flood events. Flood sampling was carried out at several tributaries corresponding to conduit flow, vadose flow and seepage flow. Weekly sampling showed a strong buffering of the rainfall isotopic signal at the spring. This attenuation suggests an important mixing reservoir in the system. Flood events showed highly peaking hydraulic responses but buffered rain isotope responses. These results indicate that the soil and epikarst sub-systems have an important storage capacity. A conceptual model of flow and transport in the soil and epikarst zone is proposed: Soil plays an important role in mixing due to the presence of capillary water storage. Consequently dampened concentrations reach the epikarst despite a rapid hydraulic response. The epikarst acts as the storage element and distributes water as either a base flow component or a quick flow component. When recharge exceeds a given threshold, excess infiltrated water bypasses the soil and epikarst and reaches the saturated zone as fresh flow. Based on this model, the significance of phreatic storage is thought to be limited, at least in Milandre test site. Hence the saturated zone is seen mainly as a transmissive zone through its well developed conduit network. (C) 2003 Elsevier B.V. All rights reserved. - PublicationAccès libreImplications of the spatial variability of infiltration-water chemistry for the investigation of a karst aquifer: a field study at Milandre test site, Swiss Jura(2003)
; Le site test de Milandre est un aquifère karstique idĂ©al pour Ă©tudier lhĂ©tĂ©rogĂ©nĂ©itĂ© spatiale des Ă©lĂ©ments chimiques majeurs car de nombreux points dobservation sont accessibles : source, rivière souterraine et affluents, forages Ă diffĂ©rentes profondeurs. Les principales causes de la variabilitĂ© spatiale des paramètres chimiques sont : nature et localisation des intrants, la structure de la zone dinfiltration, la rĂ©activitĂ© des paramètres (temps de transit vs. cinĂ©tique de rĂ©action) et le mĂ©lange des eaux. Les chimiogrammes observĂ©s Ă la source du système karstique reprĂ©sentent la somme de cette hĂ©tĂ©rogĂ©nĂ©itĂ© spatiale. Il est de fait difficile, pour un tel aquifère, dinterprĂ©ter la rĂ©ponse chimique globale en termes de mĂ©langes deau des diffĂ©rents sous-systèmes de laquifère (ruissellement, rĂ©servoir matriciel, Ă©pikarst). Les Ă©lĂ©ments chimiques correspondant aux intrants agricoles montrent des variations saisonnières relativement importantes (Coefficient de variation denviron 15%) alors que les paramètres liĂ©s Ă la pluie (δ18O) et Ă laquifère (Ca2+, HCO3–) prĂ©sentent des variations de quelques pour cents. Un tel rĂ©sultat indique un stockage deau dau minimum quelques mois dans lĂ©pikarst., The Milandre test site is an ideal karstic aquifer for studying the spatial heterogeneity of groundwater chemistry. Numerous observation points can be sampled: the spring, the underground river and its tributaries, and boreholes at different depths. The main causes of the spatial variability of the chemical parameters are: nature and localisation of the input, the structure of the infiltration zone, chemical reactions (transit time vs. reaction kinetics) and mixing of different waters. Physico-chemical data on springs discharging from the karstic system represent the sum of this spatial heterogeneity. Therefore, it is difficult to interpret the global-chemical response with a simple mixing model of the aquifer subsystems (runoff, matrix reservoir, epikarst). Chemical constituents related to agricultural inputs show important seasonal variations (coefficient of variation approximately 15%) and parameters linked to rainfall (δ18O) and to the aquifer (Ca2+, HCO3–) present variations of less than 5%. This result indicates the importance of water storage in the epikarstic aquifer for periods of a few months., La zona de ensayos de Milandre (Suiza) es un acuĂfero kárstico ideal para estudiar la heterogeneidad especial de la quĂmica de las aguas subterráneas. Se puede muestrear numerosos puntos de observaciĂłn, incluyendo manantiales, rĂos subterráneos y sus tributarios, y sondeos a diferentes profundidades. Las causas principales de la variabilidad espacial de los parámetros quĂmicos son las siguientes: naturaleza y localizaciĂłn de la entrada, estructura de la zona de infiltraciĂłn, reacciones quĂmicas (tiempo de tránsito versus la cinĂ©tica de las reacciones), y mezcla de aguas diferentes. Los gráficos hidroquĂmicos de los manantiales en el sistema kárstico representan la suma de esta heterogeneidad espacial. Por tanto, es difĂcil interpretar la respuesta quĂmica global con un modelo de mezcla simple de los subsistemas acuĂferos (escorrentĂa, reservorio de la matriz, epikarst). Los parámetros asociados a aportaciones de origen agrĂcola muestran variaciones estacionales importantes, con un coeficiente de variaciĂłn en torno al 5%, mientras que los parámetros vinculados a la precipitaciĂłn (δ18O) y al acuĂfero (calcio, bicarbonato) presentan variaciones inferiores al 5%. Este resultado indica que se produce un almacenamiento importante de agua durante un par de meses en el acuĂfero epikárstico. - PublicationMĂ©tadonnĂ©es seulement
- PublicationMétadonnées seulementEvaluation and validation of vulnerability concepts using a physically based approach(2001)
; - PublicationMétadonnées seulementSpatial variability of groundwater chemistry within a karst aquifer(2000)
; - PublicationMétadonnées seulement
- PublicationMétadonnées seulementFrom a conceptual model of karst hydrological systems to water-vulnerability mapping(1999)
; ;