References of "Degré, Aurore"
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See detailModélisation pré-normative de pratiques agricoles et agro-environnementales en vue des plans de gestion des eaux de surface et souterraines en Région wallonne à l’aide du modèle EPICgrid-Qualvados
Sohier, Catherine ULg; Degre, Aurore ULg

Report (2011)

Le présent Rapport synthétise et conclut les travaux réalisés dans le cadre de la Convention Qualvados 2 (Convention SPGE - ULg GxABT) : « Modélisation pré-normative de pratiques agricoles et agro ... [more ▼]

Le présent Rapport synthétise et conclut les travaux réalisés dans le cadre de la Convention Qualvados 2 (Convention SPGE - ULg GxABT) : « Modélisation pré-normative de pratiques agricoles et agro-environnementales en vue des plans de gestion des eaux de surface et souterraines en Région wallonne à l’aide du modèle EPICgrid-Qualvados ». [less ▲]

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See detailEffects of different spatial interpolators on the estimate of extreme precipitations
Ly, Sarann ULg; Beckers, Eléonore ULg; Charles, Catherine ULg et al

in Geophysical Research Abstracts (2011), 13

The design values of the areal precipitation are needed for engineer to manage vital elements of our infrastructure. The areal precipitation can be generated by different interpolation methods. The ... [more ▼]

The design values of the areal precipitation are needed for engineer to manage vital elements of our infrastructure. The areal precipitation can be generated by different interpolation methods. The problem involves choosing the interpolation method that we should use to estimate the extreme event. This work aimed at analyzing the effects of different interpolation methods on the estimate of extreme events of daily areal precipitations at catchment scale. The extreme rainfalls were estimated using areal daily rainfall interpolated by several interpolation methods (Thiessen polygon, Inverse Distance Weighting, Ordinary Kriging, Universal Kriging, Kriging with an External Drift and Ordinary Cokriging). We used thirty-years-long daily time series and different density of rain gages (from 4 to 70 rain gages). Our study is located in the Ourthe and Ambleve catchment area (2908 km²) in the southern part of Belgium). Spatial interpolation with the geostatistical and Inverse Distance Weighting algorithms outperformed considerably interpolation with the Thiessen polygon. Kriging with an External Drift and Ordinary Cokriging presented the highest Root Mean Square Error between the geostatistical and Inverse Distance Weighting methods. Ordinary Kriging and Inverse Distance Weighting were considered to be the best methods, as they provided smallest Root Mean Square Error for nearly all cases. However, it’s not really the case of extreme estimates for particular return period. The extreme daily rainfall, corresponding to return periods of 25, 50 and 100 years, were computed by fitting of a statistical model to the series of maximum annual precipitation. These estimates were conducted using HYFRAN which allows us to fit 16 different statistical models, in 2 or 3 parameters. The most known are the models of Gumbel, Gamma, Weibull, exponential, Pareto, lognormale, Pearson III and GEV. Our results showed that the behaviour of extreme daily areal rainfall in this area was best described via the Gumbel and lognormal distributions. Using 70 rain gages, little differences in extreme rainfall were observed between the interpolation methods. The estimates from these methods were in the area of 95% confidence intervals of the estimates using the Thiessen polygon. However, when the number of rain gages diminishes, the Universal Kriging and Kriging with External drift methods produced extreme estimates outside the area of 95% confidence intervals of the estimates using the Thiessen polygon with all available stations. The analysis described here provides a means to choose the interpolation method in view to calculate extreme events. It shows to engineers or hydrologists the need for a particular care when working in the regions of sparse data. [less ▲]

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See detailCiterne d’eau de pluie et effet sur le débit à l’exutoire du bassin versant de l’Orneau dans la région de Gembloux (Belgique
Xanthoulis, Dimitri ULg; Debauche, Olivier ULg; Fonder, Nathalie et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(2), 239-249

This study participates to the quantitative balance of rain water domestic use. It aims towards an optimal design of rain barrels volume, the feasibility of soil infiltration techniques with excess of ... [more ▼]

This study participates to the quantitative balance of rain water domestic use. It aims towards an optimal design of rain barrels volume, the feasibility of soil infiltration techniques with excess of water and the impact assessment of rain barrel on the decrease of peak flow in a pilot rural watershed of 9 km², considering the chronology of precipitation events. The parameters that are considered are the roofs area, the number of inhabitants in the house, the average daily rainfall water consumption, and the local pluviometry. In order to design the infiltration structure associated with the rain barrel, the volume of rainfall excess from the rain barrel needs to be evaluated. Afterwards, the infiltration structure may be dimensioned according to the soil infiltration characteristics. We assume that 75 litres, out of the 115 litres daily consumed by each inhabitant, are coming from the rain barrel and the remainder (40 litres) is drawn from the drinking water distribution network. Calculations are carried out for roofs of 100, 135, 170 and 200 m², for a consumption of water ranging between 150 and 1150 L.day-1.house-1 and for rain barrels of 5, 10 and 20 m³. It appears that if correctly designed private rain barrel allow an opportune water use in households, the effect on flood reduction is, however, limited considering the relative low importance of the collecting surface (1.3% of the watershed surface). [less ▲]

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See detailSoil redistribution in rural catchment: how fifty years old soil survey can help model improvement
Legrain, Xavier ULg; Colard, François ULg; Colinet, Gilles ULg et al

in Geophysical Research Abstracts (2011), 13

In a context of high urbanization’s pressure in rural zones, landscape modelling of erosion opens interesting perspectives in land use planning. In most cases, validation data are the weak point. In this ... [more ▼]

In a context of high urbanization’s pressure in rural zones, landscape modelling of erosion opens interesting perspectives in land use planning. In most cases, validation data are the weak point. In this study, we present how fifty years old soil observations can help progressing towards a more accurate validation of such modelling in rural areas. As of 1947, a comprehensive systematic survey of the Belgian soil cover was initiated. Field observations were done every 75 meters by soil auger to a standard depth of 125cm (if possible). Map units were delineated on cadastral field survey maps at scale 1:5,000, based on auger observations and landscape context, then generalised on the 1:10,000 topographic base map for a publication at 1:20,000 scale. The legend of the map includes more than 6,000 different soil types and variants. More recently, the Walloon part of this map was digitalised to produce the Digital Soil Map of Wallonia (DSMW). A 10m resolution DEM was build up in 2009. Its RMSE is 0.8m. Soil erodibility and runoff production maps were derived at the same resolution. A land use map exists at 1:10,000 scale since 2005 and is updated yearly. We applied the USPED model (Unit Stream Power - based Erosion Deposition) (Moore and Burch, 1986) in a small watershed where first soil observations took place in 1956. New soil observations were done in 2010. The watershed is completely included in a cultivated area. The model was applied considering a transport capacity limitation proposed by Mitasova and Mitas (1996). Furthermore, we slightly modified it, in order to take into account recent advances in RUSLE factors computations like LS computation proposed by Desmet and Govers (1996) and Nearing (1997). The spatial distribution of erosion and deposition area produced by the model on the basis of the current DEM is consistent with a comparison between old and recent pedological observations. Furthermore, a comparison between horizons’ thickness in 1956 and 2010 gives spatially distributed quantitative information on erosion and deposition. Nevertheless, some uncertainties remain since the pedological descriptions are based on thickness classes, due to the variability of soil cartographical units, and since the current DEM is itself affected by an uncertainty on the elevation value. Future research will then focus on more accurate elevation data as starting point and then it will become conceivable to model the evolution of watershed elevation including land use and other local anthropogenic structures like hedgerows, ditches or grass strips. [less ▲]

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See detailHydrological response to climate change in the Lesse and the Vesdre catchments: contribution of a physically based model (Wallonia, Belgium)
Bauwens, Alexandra ULg; Sohier, Catherine ULg; Degre, Aurore ULg

in Hydrology & Earth System Sciences (2011), 15

The Meuse is an important rain-fed river in North-Western Europe. Nine million people live in its catchment, split over five countries. Projected changes in precipitation and temperature characteristics ... [more ▼]

The Meuse is an important rain-fed river in North-Western Europe. Nine million people live in its catchment, split over five countries. Projected changes in precipitation and temperature characteristics due to climate change would have a significant impact on the Meuse River and its tributaries. In this study, we focused on the impacts of climate change on the hydrology of two sub-catchments of the Meuse in Belgium, the Lesse and the Vesdre, placing the emphasis on the water-soil-plant continuum in order to highlight the effects of climate change on plant growth, and water uptake on the hydrology of two sub-catchments. These effects were studied using two climate scenarios and a physically based distributed model, which reflects the water-soil-plant continuum. Our results show that the vegetation will evapotranspirate between 10 and 17% less at the end of the century because of water scarcity in summer, even if the root development is better under climate change conditions. In the low scenario, the mean minimal 7 days discharge value could decrease between 19 and 24% for a two year return period, and between 20 and 35% for a fifty year return period. It will lead to rare but severe drought in rivers, with potentially huge consequences on water quality. [less ▲]

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See detailEssai de cartographie des classes d'infiltrabilité des sols de Wallonie
Demarcin, Pierre ULg; Sohier, Catherine ULg; Mokadem, Abdel Ilah et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(1), 119-128

On the basis of the digital soil map of Wallonia (1/20000), a decision tree is proposed for attributing infiltration class to each soil type. The proposition takes into account soil texture, drainage ... [more ▼]

On the basis of the digital soil map of Wallonia (1/20000), a decision tree is proposed for attributing infiltration class to each soil type. The proposition takes into account soil texture, drainage characteristics, substratum and, when appropriate, percentage of stoniness. The so defined infiltration classes are coherent with SCS methodology for abstraction computation (continuous or event based modelling). There are four groups named A, B, C and D from higher to lower basic infiltration rate. The map produced is a raster with a ground resolution of 10 meters, covering Wallonia (16900 km²), readily usable in hydrological distributed models. The paper deals with the classification and its inherent limitations. [less ▲]

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See detailRevue bibliographique : la prise en compte des transferts horizontaux dans les modèles hydrologiques
Beckers, Eléonore ULg; Degre, Aurore ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(1), 143-151

This bibliographical review sums up the different schemes in hydrological modelling. Moreover, it underlines how the interflows are taken into account and draws the first lines to improve their physically ... [more ▼]

This bibliographical review sums up the different schemes in hydrological modelling. Moreover, it underlines how the interflows are taken into account and draws the first lines to improve their physically based representation. In the mood of the change in agricultural practices, especially concerning the conventional tillage reduction in support of conservational tillage, it seems to be necessary to propose a better description of decisive parameters like horizontal hydraulic conductivity. More precisely, the dependence of this parameter with the water retention curve has to be described in order to represent fluxes at the plot scale and at the watershed scale. Under these circumstances, an approach with in situ measurements and physically based modelling is suggested. [less ▲]

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See detailImpact of thresholding techniques on X-ray soil microtomogram analyses
Beckers, Eléonore ULg; Léonard, Angélique ULg; Beekkerk van Ruth, Jöran ULg et al

in Geophysical Research Abstracts (2011), 13

Using X-ray microtomography, 3D soil structure can be visualised and analysed through useful factors like pore size distribution, shape, connectivity, orientation, etc. X-ray scans yield grey-level 2D ... [more ▼]

Using X-ray microtomography, 3D soil structure can be visualised and analysed through useful factors like pore size distribution, shape, connectivity, orientation, etc. X-ray scans yield grey-level 2D images, which can be recombined to form 3D structures. Treatments of the grey-level images can consist of either a binarization -distinguishing soil and pores- or a permeability level attribution directly linked to the grey-level values. The latter leads to problems in order to assign a permeability for each point (in soil a same grey level value can be assigned to points with a different permeability), as well as to analyse the 3D structure. On the other hand, treatment of black and white 3D structures is well-handled. However, the impact of the choice of one thresholding technique on the resulting images has already been demonstrated. Moreover, thresholding methods are various and numerous. Many of them are based on the image histogram analysis. But because of the soil complexity, the relevance of these techniques becomes debatable, with a risk of producing non reliable images. We propose to palliate this with a simple new algorithm based on physical measurements: it uses a loop fixing the threshold value in order to match the measured porosity for each sample. In this communication, our point is to highlight the impact of different thresholding techniques on the analysis and interpretation of our soil microtomograms. The underlying questions could be: Does the thresholding method influence our conclusions? Are the results depending on the sample itself or on the methodology? In order to answer these questions we tested the Otsu technique and our physically based algorithm. Soils samples were removed from the upper layer (Ap horizon) of a silty soil (Gentinnes, Brabant Walloon, Belgium) in plots with different management practices. In fact, since 2004, the field has been cultivated in conventional tillage (CT) or reduced tillage (RT). In order to empty the meso- and macroporosity, samples were placed under a 1.5 MPa pressure (Richards apparatus). Samples were then scanned by X-ray microtomography using a Skyscan-1172 high-resolution desktop micro-CT system (Skyscan, Kontich, Belgium). The cone beam source operated at 100 kV, using an aluminium filter. The detector configuration, i.e. 1048x2000 pixels with a 16-bit X-ray camera, and the distance source-object-camera were adjusted to produce images with a pixel size of 17 µm. Porosity was measured for each scanned sample. Then the threshold methods -the Otsu technique on one hand and our developed algorithm on the other - were applied, and morphological factors were calculated for both methods. A comparison of the first results shows a threshold influence on average porosity and number of pores, but also on connectivity factors and size distribution. The apparent porosity of the images, as well as connectivity, is underestimated with the Otsu technique. Despite the fact that the changes induced by thresholding are more important for RT than CT, global conclusions about the comparison of these agricultural practices are approximately the same in this case. However, differences between tillage systems are less important with the Otsu method, confirming the impact of choosing the adapted threshold method. [less ▲]

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See detailStatistical analysis of low-flow based on short time series. The case of Wallonia
Verstraete, Arnaud ULg; Gailliez, Sébastien; Degre, Aurore ULg

in Geophysical Research Abstracts (2011), 13

The floods have always been the main concern resulting of extreme weather conditions. Now droughts and low flows are more and more recognized as risk situations due to the huge consequences of water ... [more ▼]

The floods have always been the main concern resulting of extreme weather conditions. Now droughts and low flows are more and more recognized as risk situations due to the huge consequences of water shortage. Furthermore, the changing climate context constitutes a new threat even if the uncertainty in low-flows evolution remains high. In Wallonia (Southern part of Belgium), a knowledge gap remains on statistical analysis of low-flows. In this paper, we present a study of historical data in Walloon Region and the first steps of their statistical analysis. Wallonia is one of the three regions of Belgian federal state. It covers an area of 17000 km² and spreads on 4 districts (Meuse, Escaut, Rhin, Senne). The watercourses are divided in navigable watercourses (700km), not navigable watercourses that are listed in 3 categories (14300km) and streams that are not navigable and not listed (4000km). Hydrological monitoring has a short history in Wallonia. The first monitoring site was installed in 1960. It consisted in a limnimetric scale and daily manual readings. Since 1974, hourly data are recorded. The number of measurement sites reached 244 stations in 2011. About 60 % of the monitoring sites have less than 20 years of hourly data. A qualitative analysis of monitoring stations led us to disregard 184 stations. The main quality problems were important discharge rating curve extrapolation, algae development in summer or low flow inferior to 5l/s. In preparation for a statistical analysis of low-flows, the old manual daily readings were analyzed. Unusable in high flow situations, they still hold practical and usable information during drought. This analysis allowed us to extend the registration period up of 7 stations and to recover 16 stations. There were lots of missing data during the 1960-1994 period, due to a poor management of the monitoring network. A yearly hydrograph analysis leads us to keep years of partial measurement when the gaps were found to be out of the low-flow period. The monitoring sites presenting more than 20 years of readings were selected for the statistical analysis. A homogeneity test was performed. Finally 64 out of 244 monitoring sites are kept for the frequency analysis. The indicators used to characterize low-flows are the popular Q95 and MAM7. Five below bounded distributions are tested with the HYFRAN software: Weibull (2 parameters), log-normal 2 parameters and 3 parameters, Gamma and Pearson type III. The parameters of the laws are estimated by the maximum likelihood estimation. The selection of the three best laws is performed for each site thanks to three Bayesian criterions proposed by HYFRAN. Then the distribution that fits the best the data is visually chosen. The results of the adjustment method are the same for the two indicators. The Gamma distribution is the most used followed by the lognormal with 2 parameters. However in some cases a law of three parameters is more appropriate. This preliminary work gives a first analysis of low-flows statistics in Wallonia. Yet a lot of missing data or short recording duration still limits our knowledge, this analysis allows us to progress towards best management practices in rivers and watersheds. [less ▲]

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See detailErosion and rainfall erosivity under climate change: rainfall simulation and soil losses measurement at field scale
Kummert, Nora ULg; Beckers, Eléonore ULg; Degre, Aurore ULg

in Geophysical Research Abstracts (2011), 13

Soil and water conservation is a big issue of this century. The soil is a non renewable resource. As we know, the change in climate brings more short erosive rainfall with a high capacity to take away the ... [more ▼]

Soil and water conservation is a big issue of this century. The soil is a non renewable resource. As we know, the change in climate brings more short erosive rainfall with a high capacity to take away the topsoil. Moreover, topsoil contains all the nutrients the plants needs. It is now essential that we found a new balance between productivity and durability. Impacts of new agricultural techniques on soil structure are already studied in different countries (i.e. Beckers et al., 2010; Walh et al., 2004; Malone et al., 2003). But what are the impacts on erosion? That is a question with few answers. And this is where our experiment comes, in order to link erosion and future erosion with management practices. Two ways exist to act against soil losses: enhancing soil structure or increasing vegetation cover. Our study aims at measuring soil losses and runoff under different practices and for a future scenario of climate change. This study explores new practices and measures their effects on erosion and runoff under a future rainfall. We focus on two cultures: sugar beet and maize. Each is tested under three different systems. For sugar beet soil structure impact is monitored: three tillage systems are tested: winter ploughing, fall ploughing and fall topsoiling. For maize vegetation cover impact is monitored: three seeding systems are studied: classical seeding (75 cm interrow), classical seeding with Ray-grass seeding in the interrows, and distributed seeding (obtained with a grains seeder). Rainfall simulation has been chosen for the study so the impacts of climate change can also be tested. A future rainfall was calculated based on a climate change scenario for Belgium (CCI-HYDR project, Willems, 2006-2010). A basic current rainfall of 100 years return period and 30 minutes duration (correspondent intensity: 70 mm/h) entered into the model gives the new rainfall. After the application of the scenario, the new rainfall has an intensity of 80 mm/h. This is our future rainfall used in this experiment. The simulations of this rainfall were carried on during the main crop season (between June and August). Three simulations were performed on sugar beet and two on maize on plots with the dimensions: 3 m length and 90 cm and 120 cm width respectively for sugar beet and maize (corresponding to two rows of the main culture). During each simulation soil losses and runoff quantities were measured. From the first year experiment, some tendencies can be observed. The topsoiling on sugar beet culture seems to produce less soil losses when the winter ploughing gives the lower quantities of runoff. The distributed seeding for the maize culture gives the lower rates for both soil losses and runoff quantities. Our experiment will be repeated at least for the next two years with new future rainfall to be tested. The climatic conditions are an important factor which can modify the behavior of soil response under rainfall event. More research has to be done in order to improve our knowledge of runoff and erosion phenomenon at smaller scale. [less ▲]

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See detailA methodology to assess the exactness of Stream Network modeling process on agricultural watersheds
Ouedraogo, Mohamar ULg; Degre, Aurore ULg; Beckers, Eléonore ULg et al

in Geophysical Research Abstracts (2011)

The goal of our study is to evaluate the exactness of stream network modeling process on agricultural watersheds. Agricultural watersheds topography is always changing, making it difficult to be modeled ... [more ▼]

The goal of our study is to evaluate the exactness of stream network modeling process on agricultural watersheds. Agricultural watersheds topography is always changing, making it difficult to be modeled. According to the standard ISO-7078 (ISO-7078, 1985) of the Inernational Organization of Standardization, the exactness of a measurement process or a modeled process can be defined as the difference between results obtained from the measurement process and a reference accepted as the «true value». A small watershed of a dozen hectares size has been surveyed by terrestrial LiDAR (Light Detecting And Ranging) scanner and photogrammetrical techniques to produce a row data of 30 cm resolution. Three interpolation techniques i.e. natural neighbourg, multiquadratic radial basis function and inverse distance weighted have been applied on the original data to create original digital elevation models (DEM) of 1 m resolution. RTK (Real Time Kinematics) GPS (Global Positionning System) ground control points have been surveyed on the watershed to evaluate DEM errors and fit a variogram that is used by a conditional sequencial gaussian simulation model to generate error maps. However, ground control point’s elevations accuracy is depending on the microtopography of parcels in an agricultural watershed. Depending on the crop that is planned by the farmer, the soil tillage will be different, and soil structure and roughness can considerably influence ground control point’s elevation. Analysis of variance and geostatistical methods have been applied on total station and RTK GPS data to estimate intervals in which, ground control points elevations vary. These intervals have been estimated for two parcels that soils are tilled in different ways. These errors are added to the generated errors maps to create final error maps. The final errors maps are added to the original DEM to create likely DEM realizations for the watershed (Temme and al., 2007). Then, two spurious sinks filtering methods (Colson 2006; Lindsay and Creed, 2005) and one flat area treatment method (Jenson and Domingue, 1988) are applied on each DEM realization for preprocessing. Finally, the three common flow direction extraction methods (D8, D-infity and Multiple Flow Direction) are applied on each preprocessed DEM to extract stream Network. The extracted stream network is overlapped with RTK GPS field positioned stream network i.e. a polyline format data. To estimate the exactness of the stream extraction methods, the polyline format is converted in raster format. That allows to compute for each pixel of the observed stream network, the distance to the extracted stream network. Then, for each pixel the mean distance can be calculated, and can be represented through the stream network. LiDAR technology is becoming useful for environment modeling because of his accuracy. Such quantity of data is not free of errors. This research will allow us to estimate the uncertainty of stream network modeled from agricultural watersheds by considering the main sources of errors that are propagated through computing processes. [less ▲]

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See detailL’hydrologie, une partenaire de la géomorphopédologie pour une gestion transéchelle des grands enjeux environnementaux
Degre, Aurore ULg; Sohier, Catherine ULg; Colard, François ULg et al

Conference (2010, November 24)

La zone insaturée du sol et du sous-sol est souvent qualifiée de zone critique, étant donné son rôle d’interfaçage entre les compartiments aérien et souterrain de notre environnement. Dans les thématiques ... [more ▼]

La zone insaturée du sol et du sous-sol est souvent qualifiée de zone critique, étant donné son rôle d’interfaçage entre les compartiments aérien et souterrain de notre environnement. Dans les thématiques du transfert des solutés ou de la conservation des eaux et des sols, les recherches d’hydrologie et d’hydraulique agricole s’appuient sur les informations pédologiques et ce depuis une échelle extrêmement locale jusqu’à la vision régionale de la gestion environnementale. Le rôle des descriptions pédologiques dans la gestion et la protection des ressources naturelles est donc majeur. La dérivation des paramètres hydrodynamiques depuis les descriptions pédologiques des sols permet à l’hydrologue de quantifier et de représenter spatialement la dynamique des échanges eau-sol-végétation-atmosphère, les déplacements de l’eau dans le sol et la vadose ainsi que les déplacements et les transformations des solutés. L’hydrologue en retire des indicateurs de pression sur les ressources hydriques de surface et souterraine. Il calcule des flux d’eau, de nutriments et de sédiments à un pas de temps très fin et durant de longues périodes (plus de 30 années). Les recherches présentées ici couvrent la modélisation hydrologique physiquement basée à l’échelle régionale qui vise l’analyse prospective (au-delà de 2020) des mesures envisagées pour limiter les pollutions diffuses d’origine agricole, tout comme des modélisations physiques détaillées en sites expérimentaux. L’érosion hydrique des sols est un autre un enjeu majeur de gestion environnementale. Le sol étant une ressource peu renouvelable, les techniques de conservation des sols et l’aménagement hydraulique des bassins versants ruraux nécessitent la plus grande considération. Elles sont un outil supplémentaire de limitation des apports au cours d’eau (tant en termes de sédiments qu’en termes de nutriments). Là encore, les descriptions pédologiques permettent de cibler les sols les plus sensibles. De plus, les cartes des sols qui incluent une interprétation géomorphologique permettent de confronter les modèles d’arrachement, de transport et de dépôt de sédiments aux observations des pédologues faites lors des premiers levés et actuellement en cours. Ces observations de terrain, réalisées à plusieurs dizaines d’années d’intervalle, constituent un gisement de données précieux et quasiment unique pour la validation des modèles hydrologiques de perte en sol et de dépôt et en vue de l’étude morphodynamique des bassins versants. Il reste actuellement des besoins en termes de description pédologique. Ils ont trait à la caractérisation plus fine de certains sigles, où l’introduction d’éléments relatifs à la dynamique des flux pourrait s’avérer pertinente. Toutefois, on peut constater que dans le contexte actuel et crucial de préservation des ressources eau et sol, l’hydrologie et la science du sol sont réaffirmées comme des partenaires forts de gestion des grands enjeux environnementaux. [less ▲]

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See detailMicro-catchments classification: a tool for mud flow mitigation
Degre, Aurore ULg; Mokadem, Abdel Ilah; Cordonnier, Hélène et al

Poster (2010, November)

Hydrologic similarities between catchments can be of use in the context of overland flood and mud flow hazards management. In Wallonia, upstream micro-catchments were mapped for each runoff concentration ... [more ▼]

Hydrologic similarities between catchments can be of use in the context of overland flood and mud flow hazards management. In Wallonia, upstream micro-catchments were mapped for each runoff concentration axis. The outlets of these catchments are considered at the point where water reaches the permanent river stream. No less than 145 547 micro catchments were mapped in Wallonia (16900 km²). Their area varies between 1 and 1233 ha (mean area: 7.8 ha). A data base was built up to synthesize their major characteristics like e.g. area, shape and mean slope. No clear classification appeared. At this stage, it became obvious that the major components of these catchments had to be handled simultaneously from a hydrological point of view in order to produce a clear classification. The main hydrologic significant data are available in Wallonia: the digital soil map at 1/20 000 scale, the DTM (raster file of 10 meters resolution), digital land use at 1/10 000 scale and spatial statistics for rain (IDF curves for each commune). A hydrologic model was developed using the python programming language in the ArcGis 9.3 environment. This model is based on the NRCS – USDA method. Rain abstraction is calculated on the basis of a CN (curve number) which integrates the soil type, the land use and the slope. Water transfer is computed using a convolution based on triangular unit hydrogrammes. This calculation includes the concentration time which integrates the catchment morphology (shape and slope) and the land use (roughness). The MUSLE equation is also computed in order to handle the sediment problem. The results consist in a full project hydrograph, peak flow value, flood water volume and sediment quantification in response to a project rainfall. The CN and MUSLE semi-empirical methods are validated at larger scale in Wallonia but have still to demonstrate their efficiency at the micro-catchment scale. Nevertheless, the aforementioned variables can be considered as integration factors of the whole hydrological context of the micro-catchments. It allows us to build advice on overland flow and mud flow mitigation at watershed scale. This approach can also be of help to compare ungauged micro-catchments between each other and possibly transpose the soil conservation practices from a site to another. [less ▲]

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See detailEvolution des structures de sols sous itinéraires techniques contrastés : relations entre courbes de rétention et analyse par microtomographie à rayons X
Beckers, Eléonore ULg; Roisin, Christian; Léonard, Angélique ULg et al

in Milieux Poreux et Transferts Hydriques (2010, November), 56

Tillage reduction seems to affect porosity distribution, orientation and connectivity. Soil samples were removed from plots under conventional tillage or reduced tillage. Their water retention curves were ... [more ▼]

Tillage reduction seems to affect porosity distribution, orientation and connectivity. Soil samples were removed from plots under conventional tillage or reduced tillage. Their water retention curves were measured, and the characterization of soils porosity was made using x-ray microtomography measurements. Results show differences in the meso as well as in the macroporosity. [less ▲]

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See detailEvolution des structures de sols sous itinéraires techniques contrastés : relation entre courbes de rétention et analyse par microtomographie aux rayons X
Beckers, Eléonore ULg; Roisin, Christian; Léonard, Angélique ULg et al

Poster (2010, November)

Tillage reduction seems to affect porosity distribution, orientation and connectivity. Soil samples were removed from plots under conventional tillage or reduced tillage. Their water retention curves were ... [more ▼]

Tillage reduction seems to affect porosity distribution, orientation and connectivity. Soil samples were removed from plots under conventional tillage or reduced tillage. Their water retention curves were measured, and the characterization of soils porosity was made using x-ray microtomography measurements. Results show differences in the meso as well as in the macroporosity. [less ▲]

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See detailModélisation de la pollution agricole diffuse vers les eaux de surface et souterraines: le projet QualVados
Degre, Aurore ULg; Sohier, Catherine ULg

Scientific conference (2010, October 21)

La pollution diffuse issue de l’agriculture est une donnée majeure de la gestion durable des ressources en eau. Elle doit prendre en compte tant les variables environnementales (Sol, sous-sol, relief ... [more ▼]

La pollution diffuse issue de l’agriculture est une donnée majeure de la gestion durable des ressources en eau. Elle doit prendre en compte tant les variables environnementales (Sol, sous-sol, relief, météo) que les modes de gestion de l’espace (occupation du sol, pratiques agricoles). Le modèle EPICgrid est un modèle hydrologique distribué et physiquement basé qui a été développé à cette fin par l’unité d’Hydrologie et Hydraulique agricole de Gembloux Agro-Bio Tech. Il permet la quantification des pertes d’azote tant vers les eaux de surface que vers les eaux souterraines et couvre toute la Wallonie. Depuis 2006, le projet QualVados (qualité de la zone vadose) a permis d’importants développements visant à prendre en compte notamment les nouvelles réglementations (PGDA et MAE) et les nouvelles données disponibles (COSW et campagnes APL). Des simulations prospectives de la qualité des ressources en eau ont été menées jusqu’aux différentes échéances de la Directive cadre sur l’eau. L’exposé synthétisera les nouveaux développements et les enseignements issus de ces modélisations. [less ▲]

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See detailProjet GISER - Elaboration d'un module de calcul des écoulements par la méthode SCS
Colard, François ULg; Mokadem, Abdel Ilah; Cordonnier, Hélène et al

Poster (2010, October 20)

Le projet GISER (gestion intégrée sol érosion ruissellement) consiste en différents axes de travail. Le poster présente un des outils opérationnels de calcul du ruissellement et des rendements en ... [more ▼]

Le projet GISER (gestion intégrée sol érosion ruissellement) consiste en différents axes de travail. Le poster présente un des outils opérationnels de calcul du ruissellement et des rendements en sédiments qui a été développé sur base des informations cartographiques existantes. Il utilise la carte d'occupation des sols mais également le MNT, la carte des sols, et les produits du projet ERRUISSOL. [less ▲]

Detailed reference viewed: 106 (33 ULg)