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International audience; This work analyzes the hydrological response characteristics at the event scale of catchments in Lebanon (eastern Mediterranean); and discusses the impact of climatic conditions and physiographic characteristics on the catchment response. Furthermore, the Lebanese catchments are compared throughout this work to catchments in other parts of the Mediterranean. The comparison was used not only to learn from similarities and differences but also to compensate the lack of high-resolution data. Hydro-meteorological data relative to 17 rainfall-runoff events (22 drainage basins ranging in area from 28.6 to 1432 km2) are collected and analysed across the country. Similar data are gathered from the literature for 137 events (137 drainage basins ranging in area from 3.8 to 4915 km2) all across the Mediterranean divided into the northwestern (NWM), eastern (EM) and southern Mediterranean (SM). All the chosen events are of at least a 10 years return period. The gathered information consist of the physiographic and climatic characteristics of the affected catchments, the date, duration and rainfall depth of the event, and the catchment response in term of peak flow, runoff depth and ratio. The analysis shows that the majority of the Lebanese catchments are mountainous with high relief ratio and drainage density which favors the rapid concentration of runoff along flow lines. Although under Mediterranean climate these catchments do not exhibit water-limited conditions, in fact annual runoff ratio/aridity index values are higher/lower than recorded in other EM catchments. Estimation of the unit peak flows are in the range of those recorded in other EM catchments however, events runoff ratios (mean = 0.39) are more in the range of the NWM catchments (mean runoff ratios are 0.4 for NWM, 0.35 for SM and only 0.12 in EM),. This could be attributed to the karstic nature of the Lebanese terrains. Finally, antecedent soil moisture conditions appear to have a major impact on the catchment response especially in term of event runoff ratio. This work shed some lights on the hydrological response characteristics of poorly-gauged Lebanese catchments at the event scale. Nevertheless, it does not omit the need for higher resolution data that permits more in-depth investigation of the mechanism that trigger Lebanese catchment response.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SYNERGIE [Axe_IRSTEA]TETIS-ATTOS; National audience; This work examines 140 hydrological studies conducted in the Mediterranean region. It identifies key characteristics of the hydrological responses of Mediterranean catchments at various time scales and compares different methods and modelling approaches used for individual-catchment studies. The study area is divided into the northwestern (NWM), eastern (EM) and southern (SM) Mediterranean. The analysis indicates regional discrepancies in which the NWM shows the most extreme rainfall regime. A tendency for reduced water resources driven by both anthropogenic and climatic pressures and a more extreme rainfall regime are also noticeable. Catchments show very heterogeneous responses over time and space, resulting in limitations in hydrological modelling and large uncertainties in predictions. However, few models have been developed to address these issues. Additional studies are necessary to improve the knowledge of Mediterranean hydrological features and to account for regional specificities.

Lebanon is a small mountainous country with a typical Mediterranean climate and a high spatial variability of precipitation with a substantial amount occurring as snow. Moreover, the majority of Lebanese terrains are karstic. It is a heavily urbanized country with increasing anthropogenic pressure on water resources. Furthermore, the Lebanese catchments are poorly-gauged due mainly to a large gap of data (1975 - 2000) caused by the civil war (1975 - 1990). However, previous studies on regionalization suggested that across Lebanon when physical characteristics are not changing, hydrologic parameters shows a remarkable degree of spatial coherence. Thus, with an integration of more physical and functional characteristics, a regionalization procedure could be considered as a framework for defining the physical and hydrological characteristics of the Lebanese catchments.Consequently, this work aims to understand the hydrological response characteristics of Lebanese catchments in the Mediterranean context and to classify these catchments according to their physical and hydrological properties. It is structured into three parts: (i) a review on Mediterranean catchments hydrology, (ii) a datal analysis of the Lebanese catchments and comparison to the Mediterranean context, and finally (iii) a classification and modeling of the Lebanese catchments.The first part reviews 152 hydrological studies conducted in the Mediterranean region at various time scales (paper accepted in Hydrological Sciences Journal). This study also compares methods and modeling approaches used for individual-catchment or regionalization studies. The study area is divided into the northwestern (NWM), eastern (EM) and southern (SM) Mediterranean. The analysis indicates regional discrepancies in which the NWM shows the most extreme rainfall regime. A tendency for reduced water resources driven by both anthropogenic and climatic pressures and a more extreme rainfall regime are also noticeable. Catchments show very heterogeneous responses over time and space, resulting in limitations in hydrological modelling and large uncertainties in predictions. However, few models have been developed to address these issues. Regionalization studies are scarce and inconsistent in the Mediterranean. Additional studies are necessary to improve the knowledge of Mediterranean hydrological features and to account for regional specificities.In the second part, an inventory of the available spatial and temporal data was carried out and followed by a detailed data analysis of twenty eight Lebanese catchments through extracting the physical and hydrological response characteristics for the period 2001 – 2011. The spatial data concerns the morphometry, drainage system, geology, karst, soils and land cover. The temporal data concerns the precipitation (32 stations at a daily –when available- and monthly time step), evapotranspiration (remote sensing data at a monthly time step) and discharge data (24 gauging stations at a daily time step and 4 at a monthly time step). Gathering the available temporal data was a real challenge since these data are not always available for the same period and precipitation data is expensive. The 2001 - 2011 temporal data was analyzed and compared with a database from the pre-war period. Afterwards, the hydrological responses of the Lebanese catchments are compared with other Mediterranean catchments at different time scales. At the annual water balance level, runoff ratio values are found to be high across the country. At the event scale, the amount of rainfall in a given event represents a substantial amount of the total annual rainfall. Moreover, unit peak flow [maximum daily discharge] decreases with the catchment area and is not correlated with the rainfall depth of an event. Event runoff ratio is high; in fact it is much higher than values recorded in the EM and is the range of the NWM catchments. The third part concludes with a new clustering of the Lebanese catchments according to their physical and hydrological characteristics. The variables defined from the data analysis were used for the classification. Three classifications were carried out using catchments physical descriptors and runoff signatures separately. Catchments holding simultaneously the same physical and hydrological similarities were grouped together forming five “physically and hydrologically similar” catchments’ classes. Finally, a simple modeling approach at a monthly time step was tested using GR2M model. Different regionalization approaches were also compared. The discussion focuses on the analysis of the hydrological functioning of each basin and each class of basins.; Le Liban est un petit pays montagneux à climat typiquement méditerranéen avec une grande variabilité spatiale des précipitations dont une quantité substantielle est sous forme de neige. La majorité des terrains libanais sont karstiques. En plus, le pays est fortement urbanisé avec une grande pression anthropique sur les ressources en eau. En outre, les bassins versants libanais manquent de longues séries de données à cause de l’arrêt des mesures durant la guerre civile (1975-1990) et l’après guerre (1990-2000).Ce travail vise à comprendre les caractéristiques de la réponse hydrologique des bassins versants libanais dans le contexte méditerranéen et à classer ces bassins en fonction de leurs propriétés physiques et hydrologiques. La thèse est structurée en trois parties : une revue bibliographique de l’hydrologie méditerranéenne, une analyse des données hydrologiques du Liban et la comparaison au contexte méditerranéen, et finalement un essai de classification et de modélisation des bassins versants Libanais. La première partie concerne une synthèse bibliographique basée sur 152 articles portant sur l’hydrologie méditerranéenne (article accepté dans Hydrological Sciences Journal). Les études ont été classées selon trois catégories d’objectifs : étude du bilan hydrologique, les crues et la sécheresse. La méthodologie adoptée porte aussi bien sur l’étude des processus hydrologiques à l’échelle d’un bassin versant particulier que des études de régionalisation sur plusieurs bassins versants. La zone d'étude est divisée en trois parties : nord-ouest (NWM), est (EM) et sud (SM) Méditerranée. L'analyse montre les disparités régionales : fortes intensités des pluies et des crues dans la région NWM, faibles écoulements et longues périodes de sécheresse en SM, et une situation intermédiaire pour EM. Une tendance à la réduction des ressources en eau entraînées par les pressions anthropiques et climatiques et un régime de précipitations plus extrêmes sont également perceptibles. Les bassins versants montrent des réponses hydrologiques très hétérogènes dans le temps et l'espace. La modalisation du fonctionnement hydrologique de ces bassins est souvent difficile accompagnée de grandes incertitudes dans les prévisions. Cependant, peu de modèles ont été développés pour répondre aux spécificités des bassins méditerranéens. Les études de régionalisation sont rares et les résultats des différentes études difficilement transposables d’une zone à une autre. Des études supplémentaires sont nécessaires pour améliorer la compréhension des processus hydrologiques en milieu méditerranéen et pour tenir compte des spécificités régionales.La deuxième partie porte sur l’analyse des données cartographiques et pluie/débit des bassins libanais et la comparaison de ces bassins aux bassins méditerranéens étudiés précédemment. Vingt huit bassins versants libanais sont étudiés sur la période 2001-2011. Une base de données cartographique et hydrologique a été constituée. Les données cartographiques concernent le relief, les cours d’eau, le sol, la géologie, la présence du karst, et l’occupation du sol. Les données pluie/débit concernent l’analyse des données pluviométriques (32 stations à pas de temps mensuel et journalier quand disponible), les données du couvert neigeux, l’évapotranspiration (à partir des images satellites MODIS à pas de temps mensuel) et les débits (vingt quatre stations à pas de temps journalier et quatre stations à pas de temps mensuel). Ces données pluie/débit sont comparées à une base de données de la période précédant la guerre civile. L’acquisition de données pluie/débit était un véritable défi. Ces données ne sont pas toujours disponibles pour la même période et une partie étant payante (données pluviométriques). A partir de ces données, nous avons établis des indicateurs pour décrire les caractéristiques physiques des bassins versants et les caractéristiques de la réponse hydrologique. Ensuite, les réponses hydrologiques des bassins versants libanais sont comparées à celles des autres bassins versants méditerranéens. A l’échelle du bilan annuel, les valeurs du coefficient de ruissellement sont élevées à travers tout le pays. À l'échelle de l'événement de crue, comme pour les autres régions méditerranéennes, les précipitations pendant un seul événement peut représenter jusqu'à 40 % du total annuel des précipitations. Le débit de pointe spécifique diminue avec la surface du bassin versant. Le coefficient de ruissellement à l’échelle de l’événement de crue est beaucoup plus élevé que les valeurs observées enregistrées dans l’EM et est dans la gamme des bassins versants NWM.La troisième partie présente un essai de classification et de modélisation des bassins versants libanais en fonction de leurs caractéristiques physiographiques et hydrologiques. Les variables définies à partir de l'analyse des données ont été utilisées pour la classification. Trois classifications ont été menées sur la base des indicateurs physiques, hydrologiques et physiques et hydrologiques. Cinq classes de bassins physiquement et hydrologiquement similaires ont été identifiées. Enfin, un essai de modélisation au pas de temps mensuel en utilisant le modèle GR2M a été entrepris. Plusieurs approches de régionalisation ont été comparées. La discussion porte sur l'analyse du fonctionnement hydrologique de chaque bassin versant et de chaque classe de bassins.

The paper describes the results obtained from the monitoring activities carried out during the 2012–2013 water year in the T. Ciciriello catchment, located in the terrigenous, hilly, forested area of the Cilento, Vallo di Diano and Alburni National Park-European and Global Geopark. Using rainfall, discharge and electrical conductivity data collected in the catchment stations at daily and 10 min time intervals, hydro-chemical time series analysis were performed in the perspective of hydro-geomorphological regionalization of the headwaters and mountainous catchments. Analysis of the data collected during this first monitoring year allowed us to compute reliable rating curves at selected stream flow stations, perform a good fit of the stream flow discharge-electrical conductivity relationship, apply an useful mixing model for hydrograph separation. This last was based on the water end-members referred to the specific runoff sources and flow paths, previously defined and mapped by hydro-geomorphological surveys and finally detected by the monitoring activity.

Karst catchments frequently exhibit complex exchanges between surface and subterranean flow. While the swing between surface flood and underground flood is complex, the ability to predict such behavior would be of great interest for flood forecasting and water recharge assessment. To this end an innovative methodology is proposed to visualize internal variables of a neural network model. It proves to be efficient to extract internal variables highly correlated to measured signals previously identified as proxy of the karst-river exchanges. The study focuses on a small Mediterranean catchment where karst/river interactions control the dynamic and genesis of surface floods. But the methodology is generic and can be applied to any catchment provided the availability of a sufficient database.

Terrestrial sedimentation buries large amounts of organic carbon (OC) annually, contributing to the terrestrial carbon sink. The temporal significance of this sink will strongly depend on the attributes of the depositional environment, but also on the characteristics of the OC reaching these sites and its stability upon deposition. The goal of this study was to characterise the OC during transport and stored in the depositional settings of a medium sized catchment (111 km2) in SE Spain, to better understand how soil erosion and sediment transport processes determine catchment scale OC redistribution. Total Organic Carbon (TOC), Mineral-Associated Organic Carbon (MOC), Particulate Organic Carbon (POC), Total Nitrogen (N) and particle size distributions were determined for soils (i), suspended sediments (ii) and sediments stored in a variety of sinks such as sediment wedges behind check-dams (iii), channel bars (iv), a small delta in the conjunction of the channel and a reservoir downstream (v) and the reservoir at the outlet of the catchment (vi). The data show that the OC content of sediments was approximately half of that in soils (9.42 ± 9.01 g kg−1 vs. 20.45 ± 7.71 g kg−1, respectively) with important variation between sediment deposits. Selectivity of mineral and organic material during transport and deposition increased in a downstream direction. The OC mineralisation, burial or formation occurred in sediments depending on their transport process and on the post-sedimentary conditions. Upstream sediments showed low OC contents because they were partially mobilised by non-selective erosion processes affecting deeper soil layers. We hypothesise that the relatively short transport distances, the effective preservation of OC in micro-aggregates and the burial of sediments in the alluvial wedges give rise to low OC mineralisation, with C : N ratios similar to those in soils. Deposits in middle stream areas (fluvial bars) were enriched in sand, selected upon deposition and had low OC concentrations. Downstream, sediment transported over longer distances was more selected, dominated by silt and clay fractions and associated with OC. Overall, the study shows that OC redistribution in the studied catchment is highly complex, and that transport and deposition processes have a strong effect on the concentration and quality of OC found at the different depositional settings, with important consequences for the temporal stability of the buried OC and in turn for the OC budget.

International audience; This article addresses the critical need for a better quantitative understanding of how water resources from the Hérault River catchment in France have been influenced by climate variability and the increasing pressure of human activity over the last 50 years. A method is proposed for assessing the relative impacts of climate and growing water demand on the decrease in discharge observed at various gauging stations in the periods 1961–1980 and 1981–2010. An annual water balance at the basin scale was calculated first, taking into account precipitation, actual evapotranspiration, water withdrawals and water discharge. Next, the evolution of the seasonal variability in hydroclimatic conditions and water withdrawals was studied. The catchment was then divided into zones according to the main geographical characteristics to investigate the heterogeneity of the climatic and human dynamics. This delimitation took into account the distribution of climate, topography, lithology, land cover and water uses, as well as the availability of discharge series. At the area scale, annual water balances were calculated to understand the internal changes that occurred in the catchment between both past periods. The decrease in runoff can be explained by the decrease in winter precipitation in the upstream areas and by the increase during summer in both water withdrawals and evapotranspiration in the downstream areas, mainly due to the increase in temperature. Thus, water stress increased in summer by 35%. This work is the first step of a larger research project to assess possible future changes in the capacity to satisfy water demand in the Hérault River catchment, using a model that combines hydrological processes and water demand.

International audience; The Euro-Mediterranean area has experienced widespread land cover change since 1950, but few studies of land cover change explicitly explore spatial constraints on land cover change patterns. The main objective of this study was to analyze the spatial dynamics of land cover change from 1950 to 2008 in a French Mediterranean catchment. Aerial photographs (1950, 1982, and 2008) were screen digitized, and surfaces were classified into five categories: forest, vineyard, grassland, urban, and suburban. Land cover changes were concentrated mainly in the alluvial plain. Although forest remained the dominant land cover in the catchment (>85.0%), it underwent significant swapping with vineyard and grassland. Vineyard decreased (34% of initial loss) while grassland increased (43% of initial). Urban and suburban areas remained minor in the catchment (0.2% in 1950 and 3.0% in 2008), but showed a dramatic relative increase (about 20×). Changes occurred mainly at low altitudes and slopes. Vineyard located near streams was converted mainly to grassland. Built areas were dependent on roads and former built areas for expansion but expanded little near streams due to flooding risks. The rate of change was greater during the latter part of the study (1982-2008) than in the earlier phase (1950-1982).

Land cover has been changing rapidly throughout the world, and this issue is important to researchers, urban planners, and ecologists for sustainable land cover planning for the future. Many modeling tools have been developed to explore and evaluate possible land cover scenarios in future and time scales vary greatly from one study to another. The main objective of this study is to test land cover change prediction at different time scales in a Mediterranean catchment in SE France. Land cover maps were created from aerial photographs (1950, 1982, 2003, 2008, and 2011) of the Giscle catchment (235 Km2) and surfaces were classified into four land cover categories: forest, vineyard, grassland, and built area. Explanatory variables were selected through Cramer’s coefficient. Different time scales were tested in the study: short (2003-2008), intermediate (1982-2003), and long (1950-1982). To test the model’s accuracy, Land Change Modeler (LCM) of IDRISI was used to predict land cover in 2011 and predicted images were compared to a real 2011 map. Kappa index and confusion matrix were used to evaluate the model’s accuracy. Altitude, slope, and distance from roads had the greatest impact on land cover changes among all variables tested. Good to perfect level of spatial and perfect level of quantitative agreement were observed in long to short time scale simulations. Kappa indices (Kquantity = 0.99and Klocation = 0.90) and confusion matrices were good for intermediate and best for short time scale. The results indicate that shorter time scales produce better predictions. Time scale effects have strong interactions with specific land cover dynamics, in which stable land covers are easier to predict than cases of rapid change and quantity is easier to predict than location for longer time periods.

11 páginas, 3 tablas, 5 figuras., The aim of this study was to gain insights on the potential hydrological and biogeochemical mechanisms controlling the response of two nested Mediterranean catchments to long-term changes in atmospheric inorganic nitrogen and sulphate deposition. One catchment was steep and fully forested (TM9, 5.9 ha) and the other one had gentler slopes and heathlands in the upper part while side slopes were steep and forested (TM0, 205 ha). Both catchments were highly responsive to the 45% decline in sulphate concentration measured in atmospheric deposition during the 1980s and 1990s, with stream concentrations decreasing by 1.4 to 3.4 μeq L−1 y−1. Long-term changes in inorganic nitrogen in both, atmospheric deposition and stream water were small compared to sulphate. The quick response to changes in atmospheric inputs could be explained by the small residence time of water (4–5 months) in these catchments (inferred from chloride time series variance analysis), which was attributed to steep slopes and the role of macropore flow bypassing the soil matrix during wet periods. The estimated residence time for sulphate (1.5–3 months) was substantially lower than for chloride suggesting unaccounted sources of sulphate (i.e., dry deposition, or depletion of soil adsorbed sulphate). In both catchments, inorganic nitrogen concentration in stream water was strongly damped compared to precipitation and its residence time was of the order of decades, indicating that this essential nutrient was strongly retained in these catchments. Inorganic nitrogen concentration tended to be higher at TM0 than at TM9 which was attributed to the presence of nitrogen fixing species in the heathlands. Our results indicate that these Mediterranean catchments react rapidly to environmental changes, which make them especially vulnerable to changes in atmospheric deposition., S.B. work was funded by the Spanish Research Council (JAE-DOC027) and the Spanish CICT (Juan de la Cierva contract JCI-2008-177). The financial support from the Spanish Government projects CGL2009-13188-C03-01, MED_FORESTREAM (CGL2011-30590) and MONTES-Consolider (CSD-2008-00040) is fully acknowledged.

Validation methods commonly used to test catchment models are not capable of demonstrating a model's fitness for making predictions for catchments where the catchment response is not known (including hypothetical catchments, and future conditions of existing catchments which are subject to land-use or climate change). This paper describes the first use of a new method of validation (Ewen and Parkin, 1996. J. Hydrol., 175: 583–594) designed to address these types of application; the method involves making ‘blind’ predictions of selected hydrological responses which are considered important for a particular application. SHETRAN (a physically based, distributed catchment modelling system) is tested on a small Mediterranean catchment. The test involves quantification of the uncertainty in four predicted features of the catchment response (continuous hydrograph, peak discharge rates, monthly runoff, and total runoff), and comparison of observations with the predicted ranges for these features. The results of this test are considered encouraging.

This paper concerns the problem of extending the lead-time of flood forecasts on small catchments when using a lumped rainfall-runoff model. It shows how a stochastic rainfall generator, based on renewal processes, has been linked to a rainfall-runoff model for the Mediterranean catchment of the Gardon d'Anduze (545 km2). This linked system provides future scenarios conditioned by past observed rainfalls and includes a confidence interval calculation for the flood forecasts. It is reliable 4 h ahead, but could be useful for decisionmaking beyond this period. Although already operational, the proposed system could be improved if better rainfall forecasts were available.

28 páginas, 11 figuras, 4 tablas., This study investigates the geomorphological dynamics of badland areas in the Araguás catchment (0.45 km2) in the Central Pyrenees. The genesis and development of badlands in the Central Pyrenees is favoured by the presence of Eocene marls and a markedly seasonal climate. The Araguás catchment has been monitored since 2004. Analysis of weathering processes and regolith dynamics showed that alternating freeze-thaw and wetting-drying cycles are the main causes of regolith development and weathering, and effectiveness and intensity of these processes is maximum in winter and summer. Evolution of the badland surfaces is related to regolith moisture level and temperature, closely associated with the season and slope exposure, which cause cyclical variations in regolith physical conditions. The most important effect associated with regolith dynamics is the temporal delay between maximum rainfall erosivity and variation in maximum surface runoff generation, reflected in seasonal differences in sediment transport. The dynamics of weathering and erosion processes affecting badland areas are the principal factors controlling geomorphological development, and the extreme hydrological and sedimentological responses of badlands are the main effects of such morphologies. From a hydrological point of view, badlands increase water production, and flood frequency relative to neighbouring areas; from a sedimentological point of view, suspended sediment transport from badland areas can reach amounts two or three orders of magnitude higher than other nearby environments. Given these results, possible responses of badland dynamics to altered hydroclimatic regime are briefly discussed., This research was financially supported by projects CGL2006–11619/HID (Processes and sediment balances at different spatial scales in Mediterranean environments: effects of climate fluctuations and land use changes) and CGL2007-66644-C04-01 (Space-temporary behaviour and models of the sediment transfer on different land uses), funded by the CICYT, Spanish Ministry of Education and Science; and PI032/08, financed by the Aragon Government. Monitoring of the badland catchment was also funded by a consortium of the CSIC and the Spanish Ministry of Environment (RESEL Project). The first author benefited from a research contract (Human resources mobility, National Programme I-DþI 2008-2011) funded by the Spanish Ministry of Education and Science.

Ce papier presente une analyse frequentielle des crues basee sur un echantillon de crues collecte sur une periode systematique et sur une periode historique. Elle est appliquee sur plusieurs petits bassins versants mediterraneens. Apres le recensement et la collecte des donnees sur les crues historiques, plusieurs modeles hydrauliques ont ete construits pour prendre en compte l'evolution geomorphologique des cours d'eau. Des courbes de tarage pour les periodes recentes et historiques ont ete construites et utilisees pour estimer les debits de crues avec leurs incertitudes. Ces incertitudes prennent en compte deux types d'erreurs: (a) une erreur aleatoire liee a la lecture de la hauteur d'eau, et (b) une erreur systematique liee a une sur ou sous estimation de la courbe de tarage. Un modele bayesien d'analyse frequentielle est developpe pour prendre en compte ces deux sources d'incertitudes. Il est montre que les incertitudes affectant les debits doivent etre prise en compte dans l'analyse frequentielle des crues car elles peuvent significativement modifier les intervalles de confiance des quantiles. Les quantiles de crues obtenus semblent concordant avec les estimations de formules empiriques pour deux des quatre bassins etudies.

E-mail Addresses: dages@supagro.inra.fr; International audience; Farmed catchments in the Mediterranean area often exhibit dense networks of ditches which are also preferential zones of water table recharge, and thereby of groundwater contamination. This study presents an experimental analysis of seepage losses and related groundwater recharge patterns during a typical Mediterranean runoff event at the scale of a ditch located above a shallow water table. The objectives were (i) to evaluate the patterns of water table recharge by seepage in a ditch, (ii) to study the main flow processes occurring during recharge, and (iii) to estimate solute propagation in case of contaminated flow in the ditch. The field observation indicated three major points. Firstly, they showed that seepage losses during a runoff event in a ditch can rapidly lead to a significant recharge of a shallow water table. Secondly, the recharge induces a groundwater mound much larger than the event plume. The infiltrated water and the accompanying solutes remained in the vicinity of the ditch. The patterns of groundwater recharge and contamination appeared very different. Lastly, both unsaturated and saturated-piston flow processes were observed which suggests that a variably-saturated flow modelling approach ought to be used to simulate the ditch-water shallow table interaction. Finally, the study indicates that the patterns of water table recharge and contamination in Mediterranean catchments with dense ditches network vary largely in space and time, and will require dense monitoring networks to estimate the evolution of the average contamination levels..

16 páginas, 9 figuras, 3 tablas., This paper analyses the temporal patterns of suspended sediment yield in the Araguás catchment, Central Spanish Pyrenees, a small experimental catchment with extensive badlands. The catchment has been monitored since 2004 to study weathering, erosion, and hydrological and sediment responses to understand the superficial dynamics of a badland area in a relatively humid environment. The development of badlands in the Central Spanish Pyrenees is favoured by the presence of marls and a markedly seasonal climate. The continuous observation of selected physical parameters and environmental variables enables us to establish seasonal patterns of weathering processes and identify those factors that control regolith development. Freeze–thaw cycles in winter and wetting–drying in spring–summer are the main processes involved in regolith weathering, thereby controlling slope development in combination with rainfall-related erosion processes. The 64 floods recorded during the study period (December 2005 to January 2007) were used for a hydrosedimentological analysis. The main observed features indicate that the Araguás catchment reacts to all rainfall events, resulting in steep rising and recession limbs on the hydrograph and a very short time lag. Floods show high suspended sediment concentrations and a heterogeneous temporal distribution related to seasonal variations in surface runoff production. These differences increase the degree of complexity involved in studying sediment response. Suspended sediment concentration and transport mainly depend on rainfall volume, maximum rainfall intensity, peak flow, and runoff occurrence. Finally, the similarities among the obtained hydrographs, sedigraphs, and hyetographs, in combination with the rapid response of most of the floods, suggest a large contribution of overland flow, derived mainly from infiltration excess runoff upon badland areas. Accordingly, the significant correlations obtained between rainfall intensity and sediment concentration (mainly during the dry season), which suggest a single source area for both runoff and sediment, also support the hypothesis of Hortonian hydrological response within badland areas., This research was financially supported by the following projects: “Characterization and modelling of hydrological processes and regimes in gauged basins for prediction in non-gauged basins” (CANOA, CGL 2004- 04919-C02-01) and “Processes and sediment balances at different spatial scales in Mediterranean environments: Effects of climate fluctuations and land use changes” (CGL2006-11619/HID), both funded by the CICYT, Spanish Ministry of Education and Science, and “Validation of a coupled model for the simulation of hydrological and hydraulic processes using data from experimental catchments in a Mediterranean mountain” (PM088/2006), funded by the DGA. Monitoring of the badland catchment was also funded by a consortium between the CSIC and the Spanish Ministry of Environment (RESEL Project). The first author is grateful to the CSIC for financial support within the framework of an I3 Ph.D. grant. J. Latron has benefited from a research contract (Juan de La Cierva programme) funded by the Spanish Ministry of Education and Science.

[Departement_IRSTEA]DS [TR1_IRSTEA]51 - METHODO / GEOSYSTEMES; International audience; Distributed modelling in hydrology assess catchment subdivision to take into account physic characteristics. In this paper, we testthe effect of land use aggregation scheme on catchment hydrological response. Evolution of intra-subcatchment land use is studiedusing statistic and entropy methods. The SCS-CN method is used to calculate effective rainfall which is here assimilated to hydrologicalresponse. Our purpose is to determine the existence of a critical threshold-area appropriate for the application of hydrologicalmodelling. Land use aggregation effects on effective rainfall is assessed on small mediterranean catchment. The resultsshow that land use aggregation and land use classification type have significant effects on hydrological modelling and in particularon effective rainfall modelling.

8 páginas, 8 figuras, [EN]Fluvial systems in Mediterranean areas are subject to strong precipitation seasonality, characterized by a low flow period, and, in severe conditions, the complete disruption of surface flow continuum. The Fuirosos is a Mediterranean intermittent stream that has been monitored since 1998. It is located near Barcelona (Spain) in a catchment almost untouched by anthropic activity. Thus it has become a target for many studies on biogeochemistry and fluvial ecology. Some of these studies especially emphasize the role of the dry-wet cycling and its influence on other aspects of fluvial processes. This text provides a wide overview of the research conducted in Fuirosos catchment and highlights the relevance of the alternation of hydrological periods in Mediterranean systems. [DE]Die Abflusssysteme mediterraner Einzugsgebiete sind in starkem Maße von der Saisonalität der Niederschläge beeinflusst und zeigen daher Perioden mit Niederwasserführung bzw. gänzlich fehlendem Oberflächenabfluss. Der Fuirosos- Fluss zeigt intermittierende Verhältnisse, die seit 1998 beobachtet werden. Er liegt nahe Barcelona (Spanien) und ist nahezu anthropogen unbeeinflusst. Daher wird er oft als Testgebiet für biogeochemische und flussökologische Untersuchungen herangezogen. Diese konzentrieren sich oft auf den Einfluss von Trocken-Feuchte-Zyklen auf andere fluviatile Prozesse. Der Beitrag bietet einen Überblick über die Forschungsaktivitäten am Fuirosos-Fluss und unterstreicht die Wichtigkeit der Unterscheidung zwischen Feucht- und Trockenperioden in mediterranen Einzugsgebieten., This contribution has been partially founded by Ministerio de Economia y Competitividad (project CGL2011-30151- C02).

L’estudi de la hidrologia de les àrees Mediterrànies de muntanya és especialment important ja que les regions Mediterrànies es caracteritzen per una forta variabilitat intra i interanual de la precipitació, una forta estacionalitat climàtica, importants pertorbacions humanes i una distribució desigual dels recursos hídrics que depenen principalment de l’aportació de l’aigua de les àrees de muntanya. A més, hi ha pocs estudis hidrològics centrats en aquestes regions. Durant el període 2011-2013 s’estan recollint dades hidrològiques de la conca d’investigació de Can Vila, monitoritzada des de 1996, per tal de millorar la caracterització dels processos hidrològics en conques Mediterrànies de muntanya. Les dades inclouen mesures hidrològiques distribuïdes i de traçadors ambientals (geoquímics i isotòpics) a diferents escales temporals (estacional i a escala d’esdeveniment). S’utilitzaran diferents metodologies (anàlisis de la relació precipitació-escolament, separació d’hidrogrames, índex d’humitat...) per tal d’analitzar: la dinàmica del nivell freàtic i del seu efecte sobre la relació precipitació-escolament; les dinàmiques dels diferents traçadors ambientals a escala estacional i d’esdeveniments; la contribució de l’aigua del sòl i del freàtic al torrent durant i entre els esdeveniments de pluja.

Μη διαθέσιμη περίληψη Not available summarization Παρουσιάστηκε στο: 21st Century Watershed Technology Conference and Workshop Improving Water Quality and the Environment