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International audience; In Guadeloupe, the use between 1972 and 1993 of chlordecone, an organochlorine insecticide, has permanently contaminated the island’s soil, thus contaminating the food chain at its very beginning. There is today a strong societal requirement for an improved mapping of the contaminated zones. Given the extent of the areas to be covered, carrying out soil tests on each plot of the territory would be a long and expensive process. In this article, we explore a method of demarcating polluted areas. The approach adopted consists in carrying out, using surface water analyses, a hydrological delimitation that makes it possible to distinguish contaminated watersheds from uncontaminated ones. The selection of sampling points was based on the spatial analysis of the actual and potential contamination data existing at the beginning of the study. The approach was validated by soil analyses, after having compared the contamination data of the watersheds with the soil contamination data of the plots within them. The study thus made it possible to highlight new contaminated areas and also those at risk of contamination and to identify the plots to be targeted as a priority during future analysis campaigns by State services.

chap. 18; International audience

Operations at Westwood mine in Quebec, Canada, were temporary halted in May 2015 after three large-magnitude seismic events occurred over two days. The mechanisms leading to these events, which caused severe damage to several accesses, were not well understood at first. This was partly due to the complex geology at the site, where massive, unaltered, strong, brittle, and seismically active rock can alternate with highly altered, weak, foliated, and buckling-prone rock at the meter scale. Other ground behaviours such as the significant discrepancy in blasthole performance between secondary and primary stopes and the propagation of damage from stopes to haulage drives in some locations were also not well understood. In 2017, further geotechnical characterization of the rock mass was carried out and numerical back-analyses of several locations were completed using the continuum code FLAC3D. The objectives of the back analyses were to better understand the mechanisms controlling rock mass performance and to obtain a calibrated model for predictive stoping simulations. This paper presents the key aspects of the modelling, which include: (1) An anisotropic rock mass strength model with properties derived from field and lab strength testing, and (2) a scheme to account implicitly for the deconfinement that accompanies buckling around excavations.

Within the frame of the 2018 feasibility study of the Raglan Mine Mining Project 14 in northern Quebec, stability analyses of longhole stopes and the effects of cablebolting were conducted in the form of advanced three-dimensional discrete fracture network (DFN) simulations. DFN analyses examine, in an explicit manner, the potential for strata to loosen and unravel, and wedges to form and fall along various excavation surfaces due to local joint sets. A DFN model is a randomly generated explicit representation of a unique set of discrete fractures whose geometrical characteristics—in terms of orientation, spacing and persistence—honour the statistical description of the joint sets present in the local rock mass. The kinematic stability of that unique situation is then examined in a direct manner with the 3D discontinuum-based 3DEC numerical code. Since each DFN model, or ‘realisation’, is randomly generated and unique, multiple realisations are required to derive statistical confidence in the outcome. This paper describes the DFN methodology, discusses two means of populating a realisation (through the joint sets statistics or by ‘bootstrapping’ the characterisation data), introduces the velocity-based stability criterion retained for the analyses, and presents and compares results, with and without tendon ground support.

International audience; Increased soil erosion, pressure on agricultural land, and climate change highlight the need for new management methods to mitigate soil loss. Management strategies should utilize comparable data sets of long‐term soil erosion monitoring across multiple environments. Adaptive soil erosion management in regions with intense precipitation requires an understanding of inter‐annual variability in sediment yield (SY) at regional scales. Here, a novel approach is proposed for analysing regional SY. We aimed to (i) investigate factors controlling inter‐ and intra‐annual SY, (ii) combine seasonality and time compression analyses to explore SY variability and (iii) discuss management implications for different Mediterranean environments. Continuous SY measurements totalling 104 years for eight small catchments were used to describe SY variability, which ranged from 0 to 271 t/ha/year and 0 to 116 t/ha/month. Maximum SY occurs in spring to summer for catchments with oceanic climates, while semi‐arid or dry summer climates experience SY minimums. We identified three time compression patterns at each time scale. Time compression was most intense for catchments with minimum SY in spring to summer. Low time compression was linked to very high soil loss, low run‐off and sediment production thresholds, and high connectivity. Reforestation, grassland and terracing changed SY magnitudes and time compression, but failed to reduce SY for large storm events. Periods with a high probability of high SY were identified using a combination of intra‐annual SY variability, seasonality analysis, and time compression analysis. Focusing management practices on monthly flow events, which account for the majority of SY, will optimise returns in Mediterranean catchments.

International audience; no abstract

National audience; De la mise en place d’indicateurs pour la planification urbaine à la mesure des stocks de carbone, en passant par les instruments juridiques et économiques pour la protection des sols, cet ouvrage, issu du programme Gessol, synthétise les dernières connaissances biotechniques et sociétales sur le sujet. Il souligne l’importance d’une gestion durable des sols dans les enjeux globaux et identifie les leviers d’actions possibles.

The principal challenge in the parameterization of storm flow models for agricultural catchments with an artificial drainage network and fields with different degrees of tillage lies in the parsimonious definition of distributed model parameters in a way that reduces the number of calibration parameters to a justifiable minimum. This paper presents a comprehensive case study for the parameter estimation of a distributed storm flow model applied to an agricultural catchment (0.91 km2) in the Mediterranean region. Model parameterization was combined with procedures for multi-criteria, multi-storm calibration, where we automatically calibrated three parameters related to flow velocity and infiltration, and compared single and multi-storm criteria that are based on discharge volume, peak flow, and the Nash–Sutcliffe coefficient. Multi-storm calibration yielded a set of parameter values for the simulation batch with best multi-storm overall performance, which are close to the median values in the pre-calibration of individual storms. Our results suggest that flow velocities and proportionality of the channel infiltration rate do not vary significantly over the course of 11 years. Copyright © 2012 John Wiley & Sons, Ltd.

International audience; Due to their significant influence on infiltration/runoff partitioning and soil erosion, hydrological soil surface characteristics (SSC) have to be known in a spatially distributed manner. This paper proposes a new approach based on radiometric and spatial remotely sensed information, for the mapping of hydrological SSC classes according to a predefined typology based on infiltration rates. Traditional remote sensing approaches usually focus on single SSC attributes only, where the latter correspond to key structural properties such as micro topography, surface crusting and soil cover. The originality of the method proposed here is considering the composite nature of SSC classes, by combining the aforementioned single attributes. This method makes use of a multiscale image segmentation that allows extracting image objects at two spatial scales of interest. At the fine scale, each Homogeneous Unit (HU) is assigned to an SSC attribute. At the coarse scale, SSC classes are identified by combining HU of SSC attributes assigned at the fine scale. The method was applied on airborne images collected over a Mediterranean vineyard by a small Pixy drone, and validated using intensive ground-based observations. The results showed acceptable performances with an overall accuracy ranging from 63 to 84%, depending on SSC classes and surface conditions. However, unsystematic confusions still remained between SSC classes which significantly differ in terms of hydrological behaviours. Improvements are expected considering richer spectral information, and ancillary information about SSC evolution in the case of intensive temporal monitoring

Spatially distributed hydrological modelling is required to understand and predict erosion, flooding and pollution risks that affect the vine cultivated Mediterranean environment. Previous field studies have demonstrated the dominant influence of soil surface features on overland flow and they therefore constitute an essential input to the hydrological model. In this paper we propose a remote sensing based method to map vineyard soil surface features with a spatial and temporal resolution appropriate for integration into the model. Our goal was to classify each soil surface portion in accordance with a pre-established, field measured infiltration capacity based typology. The radiometric characteristics of the classes of this typology were measured in the field and their Bi-directional Reflectance Distribution Function (BRDF) was modelled. Vineyard sunlit soil surface pixels were automatically extracted from high spatial resolution scanned aerial colour photographs Wassenaar et al., 2001 , Wassenaar et al., 2002 . These pixels are radiometrically classified by comparison of their reflectance with BRDF-based reflectance predictions of each soil surface type for the specific illumination and viewing geometry of the pixel. The results show that most hydrological soil surface classes have distinct bi-directional radiometric properties. For one given geometric configuration however, the predicted reflectance ranges of some classes can considerably overlap (tilled soils and stone layers for example), while others can always unambiguously be identified (bare soil crusts, surfaces covered for more than 50% by weed or litter). We conclude that our fuzzy classification approach and the simple radiometric information used, allow us to identify the majority of the hydrological surface types. The method can easily be transposed in time and space. Its performance quite strongly depends on the radiometric and geometric accuracy of the input data. Significant improvements in soil surface classification precision are expected from considering spatial context information and monitoring the soil surface evolution.

An experimental study was conducted in a 91.4-ha Mediterranean vineyard catchment in southern France to characterize the fate and transport of oryzalin in runoff water and thus to assess the risk of contamination of surface waters. Oryzalin concentrations in soil were monitored on two fields, one no-till and one tilled from March 1998 to March 2000. Concentrations in solution and on solid phase of runoff water were measured at the outlets of both fields and the catchment. The droughts in the two summer periods reduced the dissipation of oryzalin and increased its field half-life up to 35 days. Consequently, oryzalin was detected throughout the year in runoff water, with maximum dissolved concentrations > 600 microg l(-1) at the field scale. Oryzalin transport essentially occurred in solution. At the no-till field, seasonal losses were 2.29% and 1.89% of the applied amount in 1998 and 1999, respectively. The corresponding values at the tilled field were 1.56% and 0.29%, since tillage reduced total losses by reducing surface runoff. At the catchment scale, oryzalin concentrations were smaller than those at the field scale, due to dilution effects and staggering of application. Large part of the overland flow from the fields reinfiltrated in the ditches before reaching the outlet of the catchment. As a result, seasonal oryzalin losses were

Modelling and predicting the hydrological processes associated with discontinuous, perennial crop growing areas, like the French vine-cultivated Mediterranean region, requires detailed quantitative information on spatial crop structure. A method was developed to provide such information by spatial frequency analysis on very high spatial resolution data. A simple crop geometry model, based on general knowledge and field observations was applied to the Fourier power spectrum of aerial colour imagery obtained over the La Peyne valley (Herault, France). This method, applied on a per-field basis, using a digital land register map, allowed the identification of vineyards and characterization of their crop spacing, orientation and training mode. Results showed good performances of this procedure under all conditions encountered, i.e. very variable soil surface optical properties and spatial structure. The main vineyard training modes, goblet and wire-trained, as well as orchards and continuous crop/fallow fields...

The contamination of soil and runoff water by two herbicides, diuron [N'-(3,4-dichlorphenyl)-N,N-dimethylurea] and simazine (6-chloro-N,N'-diethyl-1,3,5-triazine-2,4-diamine), were monitored on two fields, one no-till and one tilled. Experiments were carried out in a 91.4-ha watershed in southern France during the 1997 growing season in order to understand the patterns of pesticide transport from field to watershed. The persistence of the herbicides in soil was prolonged due to the climatic conditions. At the field scale, annual herbicide loads were due to overland flow and amounted to 65.6 and 6.3 g ha(-1) of diuron for the no-till and tilled field, respectively, and to 29.6 and 1.83 g ha(-1) of simazine. Maximum herbicide concentrations exceeded 580 microg L(-1) during the first storm event after application and decreased thereafter but remained for 8 mo above 0.1 microg L(-1). At the watershed outlet, estimated annual loads amounted to 4.12 g ha(-1) of diuron and 0.56 g ha(-1) of simazine. Among them, 96% of the losses in diuron and 83% of those in simazine were caused by the fast transmission through the network of ditches of the overland flow exiting the fields. For diuron, which was sprayed over most of the vineyards, its in-stream concentrations during storm flow were close to those at the outlet of the fields. The herbicide loads in baseflow were smaller than 0.2 g ha(-1). The patterns of the loads at the field and watershed scales suggested that a major part of the herbicides leaving the fields reinfiltrated to the ground water by seepage through the ditches, and was there degraded or adsorbed.

This study examines factors affecting the spatial variability of soil infiltration in cultivated fields in a Mediterranean environment. The study area is a wine growing catchment located near the town of Roujan (Herault) in the South of France. The steady state infiltration rate was measured in 1 m2 plots in a sample of eight untilled vineyards, using a rainfall simulator. Five measurements were made in each field in order to assess the between- and within-field variability of infiltration. The factors affecting variability of soil infiltration (field effect, slope, soil type, structure of the first few centimetres of the soil, roughness, texture, grass cover and surface water content) were analyzed. A simple classification of the topsoil structures is proposed. Analyses of variance were carried out as a first step, to test the effect of these factors on infiltration in all measurement plots. An attempt was made to simplify these results by grouping together fields with homogeneous characteristics. The results show that 40% of the total variance of observed infiltration rates can be explained either by differences between fields or by differences in local topsoil structure. The latter two criteria are easily observable and can therefore be used in practice for stratifying the spatial variability of infiltration rates.

International audience; Soil surface characteristics (SSC) constitute an important land surface property that drives the partitioning between infiltration and runoff. Therefore, knowledge of SSC is crucial for runoff-forecasting in hydrology. However, the difficulties in measuring spatial variabilities and temporal dynamics of SSC have limited the use of this property in operational hydrology at the catchment extent. Recent progresses have permitted to characterize hydrological SSC classes (H-SSC) with distinct infiltration rates, by implementing monotemporal classifications along with aerial photos. However, when dealing with Mediterranean vineyards, some classes still are difficult to discriminate on the basis of remotely sensed spectral and spatial information only. The objective of the current study was to propose a multitemporal classification that integrates a priori information about possible H-SSC evolutions, such as it is possible improving their characterization. H-SSC evolutions could be either natural, depending on rainfall events, or anthropogenic, driven by soil management practices. Knowledge of possible H-SSC evolutions was translated in the form of decision rules. It was applied to a time series of H-SSC class maps derived from a monotemporal classification of monthly aerial photos. As compared to the monotemporal classification, the multitemporal classification had two advantages for the identification of H-SSC classes. First, it allowed improving the discrimination of classes related to crusting processes, with increased performances between 35 and 48% relative. Second, it was able to detect H-SSC temporal evolutions in relation to soil management practices. (C) 2012 Elsevier B.V. All rights reserved.

Contact: pare@supagro.inra.fr; International audience; Soil surface characteristics (SSC) influence strongly hydrological processes and are known to vary largely in space and time according to soil characteristics and soil management. Because tillage is a main source of variation, the goal of this study was to present and evaluate a prediction model of the temporal variation of the SSC after tillage at the catchment level. The study focused on bare soils prevailing in spring and summer. A logistic regression approach was used to predict the evolution along three stages, starting from the fresh tillage stage to the crusted soil stage. This method provides the probabilities of occurrence of each stage. The predictor candidates tested were a rainfall characteristic, namely cumulative rainfall depth or cumulative kinetic energy, basic soil properties and tillage features. The results showed that a model based on cumulative kinetic energy since tillage and soil stoniness accurately predicts the dynamics of SSC: the rate of well classified SSC was 91%. However, no significant difference in the prediction performance was found using as predictor either cumulative kinetic energy or cumulative rainfall amount since tillage. In the prediction model, the rainfall characteristic was the most significant predictor for the SSC evolution and the only one during the first stages of crust development since tillage. Stoniness was also shown to influence SSC evolution but only during the last stages of crust development: high stone cover speeds up soil surface evolution. The same approach using logistic regression can be applied elsewhere but will require a re-examination of the most relevant predicting variables. Finally, to be able to predict the soil surface characteristic evolution on an annual scale, weed growth characteristics must be considered in the list of predictor candidates.

Correspondance auteur: Raclot D. raclot@supagro.inra.fr; International audience; Soil erosion surveys and modeling approaches often rely on datasets collected from small experimental plots or fields. Therefore, one important issue is to assess to what extent reference data collected on small areas can be affected by soil tillage practices and extrapolated to larger areas. The objectives of this paper are to discuss: (i) the impact of superficial tillage on the erosion rates at field scale and (ii) the impact of the scale on the erosion rates for areas ranging from small fields to 1 km(2) catchments. We analyzed a dataset of 18 rainfall events including runoff and erosion data from fields of approximately 1200 m(2) and 3200 m(2) consisting of vineyards with two contrasting weeding practices - either superficial tillage or notillage with chemical weeding - and from the outlet of a 0.91 km(2) catchment that was 70% vineyard. Results showed that superficial tillage significantly reduced (4.5 times) soil losses as compared to notillage, with a large event-to-event variability. Considering the natural conditions studied by the authors, no-tillage with chemical weeding is not recommended for the study area. Erosion rates observed at catchment scale were significantly lower than those observed at the scale of individual fields. This trend, which has already been observed by many researchers, confirms that catchment soil loss cannot be estimated by the sum of individual field soil losses. In this context, the scaling transition between the field and the 1 km(2) catchment can be analyzed in terms of the spatial variability of soil management and connectivity between the sediment-producing and deposition areas

International audience; During the last decades, the European loess belt has been confronted with a significant increase in environmental problems due to erosion on agricultural land. Spatially distributed runoff and erosion models operating at the catchment scale are therefore needed to evaluate the impact of potential mitigation measures. Expert-based models offer an alternative solution to process-based and empiricalmodels, but their decision rules are only valid for the local conditions forwhich they have beenderived. The STREAMmodel,whichwas developed inNormandy (France), has been applied in two Belgian catchments having a similar soil texture, as well as in a catchment of southern France differing by soil, land use and climate characteristics. The performance of hydrological models can be assessed for instance by calculating the Nash–Sutcliffe efficiency criterion (ENS).When applied to Belgium, the model results are satisfactory to good after an adaptation of the decision rules (0.90bENSb0.93 for runoff predictions and 0.85bENSb0.89 for erosionpredictions).Given the important environmental differences between Normandy and southern France, the model rules were also adapted for application in the latter environment. Unfortunately, the quality of runoff predictions was insufficient to simulate erosion in southern France. In conclusion, STREAMis a reliablemodel providing satisfactory runoff and erosion predictions in the regionswhere hortonian overland flowdominates.Nevertheless, an adaptation of decision rules based on localmulti-scale (plot, field, catchment) data is needed, before running themodel. STREAMcan then serve as a decision support tool to design for instance flood control measures.

International audience; Spatial patterns of soil surface characteristics (SSC) are important factors for heterogeneity in runoff and infiltration processes in row-cropped fields. The objective of this paper is to analyse the spatial heterogeneity of SSC in the case of a vineyard in order to propose an adequate sampling strategy. A preliminary field survey was carried out to obtain a quantitative assessment of SSC. The experimental layout consisted of 3 wire-trained vine subplots with 3 different soil treatment. 60 observations per subplot were conducted using the line transect method. Their locations were determined according to a stratified sampling design conceived in accordance with the geometric structure of the vineyard system, defined by the alignment of vine rows and the direction of the main slope. The spatial heterogeneity of SSC was analysed at intra-transect and inter-transect levels using measurements of structural crust, sedimentary crust, grass and organic litter. The characterization of intra-transect heterogeneity, using join-count statistics, allowed patches of homogeneous units of attributes to be detected and hence an appropriate sampling resolution and an adequate transect length to be determined. A sampling resolution of 10 cm on a 1.25 m length transect was found to be appropriate for the observation of homogeneous units of attributes. Analysis of inter-transect heterogeneity, using non-spatial statistics, revealed considerable variability between rows and inter-rows that must be accounted for during field surveys. The role of site topography on spatial patterning of SSC attributes across the plot and the need to stratify the plot into areas with homogeneous slope were also demonstrated. Finally, the t-test procedure indicated that the minimum sample size was found to be 200 transect/ha for a minimum precision rate of 80% in the values of SSC attributes. The proposed sampling protocol is described as a step-by-step procedure and could be applied in sampling designs relevant to SSC monitoring in row-cropped fields.

With the current trend of exploiting mines at increasing depths comes the challenge of managing increasingly high stress conditions. One tool at the disposal of mine engineers and designers is the numerical simulation of the stresses and deformations likely to be encountered ahead of the mining fronts for various mining scenarios. Although the benefits of numerical modelling are by now well accepted throughout the industry, the applicability of the various types of numerical modelling approaches is not always well understood and still the subject of much debate. This paper endeavours to explain the basic differences between the elastic and inelastic approaches, as well as provide practical guidelines concerning which one to use for various sets of circumstances. Case studies of high stress situations are provided that show where the simpler elastic approach was adequate, and where implementing an inelastic approach was unavoidable. Some insight is also provided into the type of practical information that can be extracted from advanced failure analyses (the exclusive domain of inelastic techniques), such as determining the degree of failure of a rock mass by examining the stress state of its failed zones, which indicates their position along the strain-softening post-peak response typical of hard rock masses.

Chapitre 2.3; International audience

Correspondance: fax: +33 4 6763 2614. E-mail address: moussa@ensam.inra.fr; International audience; Tillage operations are known to greatly influence local overland flow, infiltration and depressional storage by altering soil hydraulic properties and soil surface roughness. The calibration of runoff models for tilled fields is not identical to that of unfilled fields, as it has to take into consideration the temporal variability of parameters due to the transient nature of surface crusts. In this paper, we seek the application of a rainfall-runoff model and the development of a calibration methodology to take into account the impact of tillage on overland flow simulation at the scale of a tilled plot (3240 m(2)) located in southern France. The selected model couples the (Morel-Seytoux, H.J., 1978. Derivation of equations for variable rainfall infiltration. Water Resources Research. 14(4), 561-568). Infiltration equation to a transfer function based on the diffusive wave equation. The parameters to be calibrated are the hydraulic conductivity at natural saturation K-s, the surface detention S-d and the lag time omega. A two-step calibration procedure is presented. First, eleven rainfall-runoff events are calibrated individually and the variability of the calibrated parameters are analysed. The individually calibrated K-s values decrease monotonously according to the total amount of rainfall since tillage. No clear relationship is observed between the two parameters S-d and omega, and the date of tillage. However, the lag time omega increases inversely with the peakflow of the events. Fairly good agreement is observed between the simulated and measured hydrographs of the calibration set. Simple mathematical laws describing the evolution of K-s and omega are selected, while S-d is considered constant. The second step involves the collective calibration of the law of evolution of each parameter on the whole calibration set. This procedure is calibrated on 11 events and validated on ten runoff inducing and four non-runoff inducing rainfall events. The suggested calibration methodology seems robust and can be transposed to other gauged sites.

Correspondance: voltz@ensam.inra.fr; International audience; Observation and interpretation of spatial soil surface moisture patterns are fundamental to spatially distributed modelling of runoff generation, soil evaporation, and plant transpiration. Compared to natural basins, man-made managements in farmed basins, such as field limits, agricultural practices and the networks of ditches, Lead to great spatial heterogeneity in hydrological processes at the catchment scale. The aim of this study was to identify the factors controlling the spatio-temporal variability of the surface soil moisture in the farmed Mediterranean catchment of Roujan (0.91 km(2)) located in southern France. Intensive measurements of soil moisture patterns were recorded during two drying sequences, respectively, in dry and wet seasons. Results show that the soil surface characteristics (SSC), which result in part from the agricultural practices such as soil tillage, chemical weed control or grass covering, are the main factors controlling the spatio-temporal distribution of the soil surface moisture during both the wet and dry drying sequences. However, in this study, none of the local factors such as the soil insolation (sunlight reaching soil surface through the plant canopy if there is one), the slope, the aspect and the soil texture is correlated to the soil moisture spatial variability. Only local factors control the spatio-temporal variability of soil surface moisture because agricultural operations like tillage influence greatly the local surface runoff by altering soil hydrologic properties. Also, the ditch networks influence the water transfer from the fields to the catchment outlet by routing runoff directly to the catchment outlet without modifying the soil surface moistures of downslope fields. Consequently, in farmed catchments the agricultural managements and practices strongly modify the spatio-temporal soil moisture distribution and must be taken into account in the understanding and in the modelling of hydrological processes

Most runoff simulation and infiltration models have been developed at the global-catchment scale or the local-soil column scale. Few models have been specifically developed at the scale of agricultural fields and there are no guidelines to help modellers choose an adequate model to simulate overland flow and hence analyse the impact of different soil management practices on flood generation. A comparison is undertaken to select and calibrate models that simulate Hortonian overland flow at the field or small plot scale. The proposed methodology couples a runoff production model to a unit hydrograph transfer function. Four different models were tested: Philip, Morel-Seytoux, Horton and SCS. These models differ by their mathematical structure and the parameters to be calibrated while input hydrologic data are the same site data: rainfall/runoff and initial water content. The models are calibrated on 14 events and validated on 14 others. The results of both the calibration and validation phases are compared on the basis of their performance with regards to six objective criteria, three global criteria and three relative criteria representing volume, peakflow, and the root mean square error. The first type of criteria gives more weight to strong events whereas the second considers all events to be of equal weight. The results show that the calibrated parameter values are dependent on the type of objective criteria used. Furthermore, when analysing the performance of the six objective criteria used, it can be seen that the global volume, global RMSE and relative peakflow criteria give the best compromise between bias and precision. Within the selected modelling framework, Morel-Seytoux's model performed better than the other three and the SCS gave the worst results. Horton's model showed to be more consistent in overall performance than Philip's model. Results also highlight problems related to the simulation of low flow events and intermittent rainfall events.

The aim of this study was to assess the toxicity of runoff waters in an agricultural multipollution context through an in-depth assessment of copper bioavailability and toxicity. Runoff waters were screened for major ions, metals and diuron. The potential environmental impact of these runoff waters was evaluated using the conventional 72-h growth inhibition test with the green alga Pseudokirchneriella subcapitata. The results suggested that the toxicity detected in the calcareous vineyard field was due to the presence of diuron, whereas the non-calcareous runoff waters were non-toxic. Chemical speciation modelling by MINEQL revealed that most of the copper present in the non-toxic natural runoff waters was complexed by organic matter. These samples were spiked with copper, and then the toxicity and the electrochemically bioavailable copper fraction were measured. Differential pulse anodic stripping voltammetry (DPASV) was used to detect labile complexes and free copper. This combined approach highlighted the presence of some labile copper complexes in samples reaching the EC10—these could have contributed to the copper toxicity. D 2005 Elsevier B.V. All rights reserved.

Field limits, tillage practices and ditch networks constitute man-made hydrological discontinuities in farmed catchments, and are expected to influence hydrological response during flood events. The purpose of this study is to assess the role of human impact, especially the existence of tillage practices and ditch network, on flood events. The study area is the farmed catchment of Roujan (0.91 km 2 ) located in Southern France for which a spatially distributed hydrological model, MHYDAS, was developed and tested. The model considers the catchment as a series of interconnected field parts linked to the ditch network. Descriptions are provided for the main model procedures: computation of Hortonian excess rainfall on fields using the Green and Ampt approach, conversion of excess rainfall to surface runoff, interaction between ditch network and groundwater using a simple Darcian model and flood routing through the ditch network using the diffusive wave model. To analyse the role of both tillage practices and the ditch network, two sets of sensitivity analysis of the model were applied. The first set studied the role of tillage practices by comparing the actual spatial distribution of tillage practices on the catchment with three hypothetical scenarios. The second set studied the role of the ditch network by comparing the actual man-made ditch network with a hypothetical drainage network automatically extracted from a digital elevation model. Results show the importance of the role of tillage and the ditch network on the form of the hydrograph, the lag time, the runoff volume and the peak discharge. This technique could also be applied to study the impact of land use change on the hydrological behaviour of the catchment.

International audience; In the Mediterranean wine producing region, soil surface remote sensing for hydrological modelling is hampered by the discontinuous canopy of the perennial vine stocks. Very high spatial resolution imagery allows the recording of ground resolution elements that comprise only soil in between vine stocks. To enable the comparison of the resolution element's spectral properties with known bi-directional properties of different types of soil surface, pixels representing the pure and sunlit soil surface have first to be extracted from the imagery. Multi-scale analysis proved to provide a robust and satisfactory segmentation method. Conditional per-field adjustment of a multi-scale image mask allows the extraction of the image segments corresponding to the sunlit soil surface, whatever its state or composition. Moreover, the vegetation cover can be estimated with an error of at most 10% if the geometric configuration is taken into account.; Extraction de la surface du sol éclairée dans des images de télédétection de cultures pérennes et discontinues ; le cas du vignoble méditerranéen. En région méditerranéenne viticole, l'estimation des états de surface du sol par télédétection est perturbée par la présence d'un couvert végétal pérenne et discontinu. L'imagerie à très haute résolution spatiale permet d'obtenir des pixels constitués uniquement de la surface du sol. Pour comparer la radiométrie de ces pixels aux propriétés bidirectionnelles connues de différents types de surface, on cherche à isoler les pixels correspondant à la surface du sol éclairée. L'analyse multi-échelle fournit une approche de segmentation robuste et satisfaisante. L'ajustement conditionnel par parcelle d'un masque obtenu par analyse multi-échelle permet d'accéder à la surface du sol éclairée, indépendamment de son état ou de sa composition. De plus on peut estimer le couvert végétal de la vigne avec une marge d'erreur de 10 % si la configuration géométrique est prise en compte.

Little work has up to now been done on the mechanisms of storm flow generation in Mediterranean cultivated environments. The present work analysed such mechanisms by natural chemical tracing in a small Mediterranean wine-growing catchment (0.91 km 2 ): Roujan, Herault, France. Two autumn runoff events with very different characteristics were studied. The first, a minor one (specific peak flow=28 l/s/km 2 ), was used to evaluate the sensitivity of the environment to low intensity rainfall. The second was significantly larger (specific peak flow=944 l/s/km 2 ) and was used to analyse the response of the catchment to heavy downpours. Tracer concentrations at the catchment outlet, for the groundwater of two distinct geomorphological units (depression and plateau) and in an experimental plot are presented. A mixing model involving three reservoirs and two tracers (chloride and nitrate) is then used to estimate the contributions of the three main storm flow components: (a) the pre-event water deriving from the depression groundwater; (b) the event water of the precipitations; and (c) the pre-event water of the plateau groundwater. The event water end member basically corresponds to infiltration-excess overland flow plus direct precipitation on saturated areas. The imprecision of the calculations was estimated by the Monte Carlo method. During both runoff events, there was little variation in the rate at which the stream was fed by pre-existing water deriving from the groundwater, although the water tables rose rapidly. Overland flow dominated in the rapid storm flow. Its contribution varied between 12 and 82% according to the importance of the event. When the water level rose, particularly in the case of the heavy runoff event, the overland flows concentrated in the man-made network of ditches running down towards the main ditch. This wave of overland flow spread, expelling the pre-event water into the ditches located downstream, which were initially fed by the groundwater. With the rapid rise in the level of water in the ditches, ditchwater infiltrated into the groundwater, and the latter then ceased to contribute to the flow in the ditch network.

Regulation of herbicide pollution in vineyard: a simulation in a mediterranean area - We investigate in a hydrologic-economic integrated model framework, how different incentive instruments aiming at regulating the emission of no-point source pollutants (herbicides) do heva an impact on cultural practices. Based on multiparametric programming techniques, two combined tools are considered by the decision model: (i) positive and negative quality-based differentiation of the price of the products and (ii) positive differentiation and tax on the polluting inputs. Non-linear responses are observed, with a favorable environmental effect at the farm level when positive différenciation of the price is noticeable. However, this favorable response at the farm level results into poor performances at the watershed level, because the described incentive design does not include location-based devices., Cet article expose une approche des possibilités de gestion des pollutions par herbicides en milieu viticole méditerranéen à l'aide des outils de la programmation multiparamétrique. Deux hypothèses de politique de limitation de la pollution sont proposées, par bonification et pénalisation des produits et en associant une taxation des intrants et une bonification des produits. Les résultats montrent que, séparément, bonification et taxation ont un effet environnemental favorable. Leur combinaison entraîne des réponses profondément nonlinéaires pouvant conduire, localement, à des résultats environnementaux contreproductifs. De plus, l'effet positif au niveau de l'exploitation correspond à de médiocres performances sur le Bassin versant proprement dit, les mesures envisagées par les scénarios n'étant pas localisées., Rio Patrick, Causeret François, Andrieux Patrick, Dejean Cyril, Frot Elisabeth, Louchart Xavier. Gérer la pollution par les herbicides: une simulation en milieu viticole méditerranéen. L'émission de polluants vue comme problème de décision. In: Économie rurale. N°259, 2000. pp. 33-49.

The variation in the availability of diuron to transport by overland flow was studied in a vineyard field under a Mediterranean climate during three years. The availability of diuron decreased with time due to the dissipation of diuron in the topsoil and the decrease of its accessibility by runoff water, which is not represented in pesticide transfer modelling. Thus, calculated concentrations of diuron with simple and actual relations are always greater than those measured in the overland flow.

The Mediterranean climate is characterized by a hot and dry summer where occasional storm events induce erosion and runoff. The high leaching potential of pesticides to surface waters under such climate conditions are not in relation to the main body of data that originated from summer-rain row-crop scenarios. In this 2-yr study we monitored runoff discharge and concentrations of the two soil applied herbicides diuron [3-(3,4-dichlorphenyl)-1,1-dimethylureal and simazine [6-chloro-N 2 ,N 4 -diethyl-1,3,5-triazine-2,4-diamine] from two field sites-one tilled and one no-till-cropped with grapevine (Vitis vinifera L.; Cinsault and Aramon, respectively). Despite a time lag of 140 d in 1994 between chemical application and first runoff event, diuron concentrations in overland flow exceeded 200 μg L -1 at the no-till site. In 1995 the first strong rainfall-runoff event following application carried >87 and 60% of the respective seasonal simazine and diuron loss at both sites, although it accounted for

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