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See detailEfficiency of thermography in the study of hydrological connectivity
Cantreul, Vincent ULiege; Leemans, Vincent ULiege; Burgeon, Victor ULiege et al

Conference (2016, April)

Hydrologic connectivity is an emerging concept which permits deeper understanding of catchments behavior. However, the measurements of functional connectivity is complex and still needs new developments ... [more ▼]

Hydrologic connectivity is an emerging concept which permits deeper understanding of catchments behavior. However, the measurements of functional connectivity is complex and still needs new developments in order to approach the « dynamic » part of the story. This study aims at assessing the efficiency of thermography to analyze hydrologic connectivity in an agricultural catchment in Belgium (loamy soils). Tests have been performed on experimental tubs at first and on field at second. Under controlled conditions, hot milk was spread on an experimental tub with bare soil and grass. The hot milk permits to compare color tracer with thermic one. The results are quite good. The binarization of pictures from usual camera and from thermic one gives similar percentage of runoff coverage at same locations. The mean difference is about 8% for bare soils and 10% for planted grass. There is a slight overestimation with thermic camera because of time delay of soil cooling after milk passing. In the same time in the planted grass, there are some runoff pixels which are hidden by vegetation. On field, blue colored water was used to simulate a rainfall on a field covered with mustard and on the same field without any coverage. Where runoff flows, the soil appears warmer because of heat extracted by water in the soil. The results comparing visual and thermic pictures are more nuanced. The mean difference reaches 30% on bare soil. Indeed, (i) the rainfall drops seem to hide the runoff during the rain; (ii) the vegetation density (mustard) is quite a problem for runoff detection. However, the difference between successive time pictures permits to distinguish flow paths easily. In conclusion, thermography stands as a good alternative for connectivity study. It’s obviously a preliminary study which gives some indications of the possible use of thermography. At present, we are testing real rainfalls (different types) with different camera’s positions and different land use (different vegetation density). [less ▲]

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See detailEffect of DEM resolution and comparison between different weighting factors for hydrologic connectivity index
Cantreul, Vincent ULiege; Cavalli, Marco; Degré, Aurore ULiege

Poster (2016, April)

The emerging concept of hydrological connectivity is difficult to quantify. Some indices have been proposed. The most cited is Borselli’s one. It mainly uses the DEM as input. The pixel size may strongly ... [more ▼]

The emerging concept of hydrological connectivity is difficult to quantify. Some indices have been proposed. The most cited is Borselli’s one. It mainly uses the DEM as input. The pixel size may strongly impacts the result of the calculation. It has not been studied yet in silty areas. Another important aspect is the choice of the weighting factor which strongly influences the index value. The objective of this poster is so to compare 8 different DEM’s resolutions (12, 24, 48, 72, 96, 204, 504 and 996cm) and 3 different weighting factors (factor C of Wischmeier, Manning’s factor and rugosity index) in the Borselli’s index calculation. The IC was calculated in a 124ha catchment (Hevillers), in the loess belt, in Belgium. The DEM used is coming from a UAV with a maximum resolution of 12 cm. Permanent covered surfaces are not considered in order to avoid artefact due to the vegetation (2% of the surface). Regarding the DEM pixel size, the IC increases for a given pixel when the pixel size decreases. That confirms some results observed in the Alpine region by Cavalli (2014). The mean difference between 12 cm and 10 m resolution is 35% with higher values up to 100% for higher connectivity zones (flow paths). Another result is the lower impact of connections in the watershed (grass strips…) at lower pixel sizes. This is linked to the small width of some connections which are sometimes comparing to cell size. Furthermore, a great loss of precision is observed from the 500 cm pixel size and upper. That remark is quite intuitive. Finally, some very well disconnected zones appear for the highest resolutions. Regarding the weighting factor, IC values calculated using C factor are lower than with the rugosity index which is only a topographic factor. With very high resolution DEM, it permits to represent the fine topography. For the C factor, the zones up to very well disconnected areas (grass strips, wood…) are well represented with lower index values than downstream zones. On the contrary, areas up to very well connected zones (roads, paths…) are higher and much more connected than downstream areas. For the Manning’s factor, the values are very low and not very well contrasted. This factor is not enough discriminant for this study. In conclusion, high resolution DEM (1 meter or higher) is needed for the IC calculation (precison, impact of connections…). Very high resolution permits to identify very well disconnected areas but it multiplies the calculation time. For the weighting factor, rugosity index and C factor have each some advantages. It is planned to test other approaches for the IC calculation. [less ▲]

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See detailEfficiency of thermography in the study of hydrological connectivity
Cantreul, Vincent ULiege; Burgeon, Victor ULiege; Triquet, Johan ULiege et al

Poster (2016, March)

Hydrologic connectivity is an emerging concept which permits deeper understanding of catchments behavior. However, the measurements of functional connectivity is complex and still needs new developments ... [more ▼]

Hydrologic connectivity is an emerging concept which permits deeper understanding of catchments behavior. However, the measurements of functional connectivity is complex and still needs new developments in order to approach the « dynamic » part of the story. This study aims at assessing the efficiency of thermography to analyze hydrologic connectivity in an agricultural catchment in Belgium (loamy soils). Tests have been performed on experimental tubs at first and on field at second. Under controlled conditions, hot milk was spread on an experimental tub with bare soil and grass. The hot milk permits to compare color tracer with thermic one. The results are quite good. The binarization of pictures from usual camera and from thermic one gives similar percentage of runoff coverage at same locations. The mean difference is about 8% for bare soils and 10% for planted grass. There is a slight overestimation with thermic camera because of time delay of soil cooling after milk passing. In the same time in the planted grass, there are some runoff pixels which are hidden by vegetation. On field, blue colored water was used to simulate a rainfall on a field covered with mustard and on the same field without any coverage. Where runoff flows, the soil appears warmer because of heat extracted by water in the soil. The results comparing visual and thermic pictures are more nuanced. The mean difference reaches 30% on bare soil. Indeed, (i) the rainfall drops seem to hide the runoff during the rain; (ii) the vegetation density (mustard) is quite a problem for runoff detection. However, the difference between successive time pictures permits to distinguish flow paths easily. In conclusion, thermography stands as a good alternative for connectivity study. It’s obviously a preliminary study which gives some indications of the possible use of thermography. At present, we are testing real rainfalls (different types) with different camera’s positions and different land use (different vegetation density). [less ▲]

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Peer Reviewed
See detailSoil-specific calibration of capacitance sensors considering clay content and bulk density
Parvin, Nargish ULiege; Degré, Aurore ULiege

in Australian Journal of Soil Research (2016)

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See detailDélivrable D4.2. Modélisation agro-hydrologique
Sohier, Catherine ULiege; Degré, Aurore ULiege

Report (2016)

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See detailData
Touil, Sami ULiege; Degré, Aurore ULiege; Chabaca, Mohamed Nacer

Textual, factual or bibliographical database (2016)

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See detailCrop residue management in arable cropping systems under a temperate climate. Part 2: Soil physical properties and crop production. A review
Hiel, Marie-Pierre ULiege; Chelin, Marie ULiege; Parvin, Nargish ULiege et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (2016), 20(1), 245-256

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See detailSensitivity analysis of point and parametric pedotransfer functions for estimating water retention of soils in Algeria
Touil, Sami ULiege; Degré, Aurore ULiege; Chabaca, Mohamed Nacer

in SOIL (2016)

Improving the accuracy of pedotransfer functions (PTFs) requires studying how prediction uncertainty can be apportioned to different sources of uncertainty in inputs. In this study, the question addressed ... [more ▼]

Improving the accuracy of pedotransfer functions (PTFs) requires studying how prediction uncertainty can be apportioned to different sources of uncertainty in inputs. In this study, the question addressed was as follows: which variable input is the main or best complementary predictor of water retention, and at which water potential? Two approaches were adopted to generate PTFs: multiple linear regressions (MLRs) for point PTFs and multiple nonlinear regressions (MNLRs) for parametric PTFs. Reliability tests showed that point PTFs provided better estimates than parametric PTFs (root mean square error, RMSE: 0.0414 and 0.0444 cm3 cm-3, and 0.0613 and 0.0605 cm3 cm-3 at -33 and -1500 kPa, respectively). The local parametric PTFs provided better estimates than Rosetta PTFs at -33 kPa. No significant difference in accuracy, however, was found between the parametric PTFs and Rosetta H2 at -1500 kPa with RMSE values of 0.0605 cm3 cm-3 and 0.0636 cm 3 cm-3, respectively. The results of global sensitivity analyses (GSAs) showed that the mathematical formalism of PTFs and their input variables reacted differently in terms of point pressure and texture. The point and parametric PTFs were sensitive mainly to the sand fraction in the fine- and medium-textural classes. The use of clay percentage (C %) and bulk density (BD) as inputs in the medium-textural class improved the estimation of PTFs at -33 kPa. [less ▲]

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See detailContraintes Socio-économiques de Répartition des Terres et Impacts sur la Conservation des Sols dans les Hauts Plateaux de l’Ouest du Cameroun
Djoukeng, Henri Grisseur ULiege; Dogot, Thomas ULiege; Tankou, Christopher Mubeteneh et al

in Tropicultura (2016), 34(3), 231-241

This article combines the social survey data on access to land and those of the adoption of tied ridging as soil conservation technique to help better understand the management of erosion and runoff by ... [more ▼]

This article combines the social survey data on access to land and those of the adoption of tied ridging as soil conservation technique to help better understand the management of erosion and runoff by farmers in the Western Highlands of Cameroon, specifically in the hills of Fongo-Tongo villages’ group. The study focused on 230 plots owned by 157 respondents on 158 people inventoried. Five main modes of access to land were listed as: inheritance, purchase, temporary transfers, donations and rental. The owners and operators of the hills of gentle slopes (between11% and 17%) and steepest slopes (between 22% and 29%) were inventoried. Two main social ranks were identified: the dignitaries (Chiefs, Notables, Elites and heirs) and other (non-heirs son and women). The study showed that the agronomic abilities of plots as recognized by farmers are a key factor in the implementation of soil conservation techniques. The peasant approach of soil fertility has been scientifically proven by the physicochemical analysis of soil samples taken under plant species used locally as indicator of soil fertility (Pennisetum spp on fertile soils and Imperata cylindrica and Melinis minutiflora on poor soils). The study showed that access to land, adoption of tied ridging and slope exploitation were significantly influenced by the socio-economic status of farmers (p <0.05). [less ▲]

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See detailImproving Farmers’ Profitability, Soil and Water Conservation through an Adapted Tillage Technique: Experiences from the Cultivation of Potatoes in Bamiléké’s Hills, Cameroon
Djoukeng, Henri Grisseur ULiege; Brostaux, Yves ULiege; Tankou, Christopher Mubeteneh et al

in International Journal of Agriculture Innovations and Research (2016), 4(4), 708-716

On farms situated on slopes, such as those in the Western Highlands of Cameroon, the implementation of soil and water conservation techniques remains a major concern. The land preparation methods commonly ... [more ▼]

On farms situated on slopes, such as those in the Western Highlands of Cameroon, the implementation of soil and water conservation techniques remains a major concern. The land preparation methods commonly practiced in the Western Highlands agro-ecological zone of Cameroon are ridging along the steepest slopes (RASS) and the flatbed (FB). Field observations showed FB and RASS promote erosion by runoff, thereby compromising some agriculture functions (environmental function, production function and even social function). In order to ensure soil stability and maintain good water quality for rivers, a new land preparation method, tied ridging (TR), was tested. Erosion by runoff tests were conducted with four blocks of three plots on each of the most commonly exploited slopes, namely 11% and 29% gradient. With the main crop in the area (potato, Solanum tuberosum L.), the performance of RASS, FB, and TR were compared during crop years 2013 and 2014. The water runoff and sediments were collected per plot and per block after every rainfall. The results showed a significant difference between the FB or RASS and TR in terms of soil loss (Fmin(2, 2) = 322.7, p = 0.003), yields (F(2, 2) = 287.7, p = 0.003), and runoff water (Fmin(2, 12) = 2.4x106, p < 0.001). The TR technique generated a 7% increase in seedlings density, a 41% increase in the workforce, and an 81% and 100% increase in yields compared to FB in 11% and 29% slopes, respectively. The TR increased farmer’s profitability by 686 US$.ha-1 and 1420 US$.ha-1 over RASS in 11% and 29% slopes, respectively. The TR showed undeniable advantages: for the producer, the stress of additional work was offset by the gain in yields while creating additional job opportunities and improving the conservation of soil and water. Although the technique has several advantages, the provision of financial means for its implementation could be a negative point. Twelve farmers were involved in the experiment. The test results convinced the participants and other curious farmers who adopted the technology during the second experiment. [less ▲]

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See detailHow to measure connectivity?
Cantreul, Vincent ULiege; Pineux, Nathalie ULiege; Swerts, Gilles ULiege et al

Poster (2015, September)

Erosion is a major threat to European soil. Consequences can be very important both on-site and off-site. Belgian loamy soils are highly vulnerable to this threat because of their natural sensitivity to ... [more ▼]

Erosion is a major threat to European soil. Consequences can be very important both on-site and off-site. Belgian loamy soils are highly vulnerable to this threat because of their natural sensitivity to erosion on the one hand, and because the land is mainly used for intensive agricultural practices on the other hand. Over the last few decades, rising erosion has even been observed in our regions. This shows the importance of a deeper understanding of the coupled phenomena of runoff and erosion in order to manage soils at catchment scale. Plenty of research have already studied this but all agree to say that it seems to have a non-linear relationship between rainfall and discharge, as well as between rainfall and erosion. For that reason, a new concept has been developed a few years ago: the hydrological connectivity. Several research have focused on connectivity but up to now, each there are as much definition as papers. In this thesis, it will be important firstly to resume all these definitions to clarify this concept. Secondly, a methodology using various transects on the watershed and some pertinent field measurements will be used. These measurements include spatial distribution of particle size, surface states and perhaps soil moisture. A new approach of photogrammetry using an UAV will be used to observe erosion and deposition zones on the watershed. In addition to that, infrared camera will be installed on different positions in the catchment. This permits to detect when and where variably saturated areas are active and so when connectivity is active between hillslopes and stream. In this framework, several time scales will be studied from the event scale to the annual scale passing by monthly and seasonal scales. All this will serve to progress toward a better understanding of the concept of hydrological connectivity in order to study erosion at catchment scale. The final goal of this study is to describe hydrologically each different part of the catchment and to generalize these behaviors to other catchments with similar properties if possible. Afterwards, this research will be integrated in an existing (or not) model to improve the modelling of discharge and erosion in the catchment. Thanks to that, a scenario of hydraulic mitigation measures could be proposed in order to reduce runoff and erosion in the catchment. This scenario will include hydraulic, hydrologic but also ecological, landscape and economical points of view. [less ▲]

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See detailEvaluation of soil structural changes through macroscopic and microscopic measurement
Parvin, Nargish ULiege; Degré, Aurore ULiege; Chelin, Marie ULiege et al

Poster (2015, April 16)

The heterogeneity of soil structure and pore size distribution are highly influenced by external factors like tillage systems and other agricultural management practices. However, changes in soil ... [more ▼]

The heterogeneity of soil structure and pore size distribution are highly influenced by external factors like tillage systems and other agricultural management practices. However, changes in soil hydrodynamic behavior are not fully understood and are still under research. Also, researchers have explained the impact of tillage practices on soil hydraulic properties related to pore size distribution, connectivity and orientation are involved but the characterization of these modifications and consequences remains a challenge. Furthermore, the relation between macroscopic measurements and microscopic investigation of the soil structure remains scarce. Recently, X-ray tomography (X- μCT) has been used in order to characterize changes in soil pore size distribution in various contexts and the method is able to link microtomography information to hydrodynamic measurement. In our study, X-μCT has been used in order to characterize changes in soil pore system. Since, tomography does not count most of the micropores, Richards’ pressure plate and evaporation method was also combined to get complete range of pore size distribution. We found good match between evaporation data with X-μCT at the macropore scale and evaporation data with pressure plate method at micropore scale. X-μCT data refines retention and hydraulic curves near saturation where Richards’ data alone can lead to numerous sets of fitted parameters. On the otherhand, evaporation data (Hyprop apparatus ©) provide comparable datasets with X-μCT. Combining micro and macroscopic measurements allows us to validate X-μCT information, which is otherwise not so obvious. [less ▲]

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See detailSoil porosity in agricultural context: A review of measurement techniques at various scales
Garré, Sarah ULiege; Chelin, Marie ULiege; Luong, Jeanne ULiege et al

Poster (2015, April 13)

Soil compaction was identified by European Commission as one of the eight main threats for agricultural soils. In order to address this issue, measurements of soil porosity are critical. However, there ... [more ▼]

Soil compaction was identified by European Commission as one of the eight main threats for agricultural soils. In order to address this issue, measurements of soil porosity are critical. However, there are as many techniques to measure as there are definitions of porosity. A single method is not sufficient to obtain a complete image of the soil porosity at various scales and encompassing different levels of complexity. Each existing method is characterized by a unique combination of a specific level of complexity, resolution and scale of measurement. In this review, we started by defining the basic terms linked to soil porosity in an agricultural context. Then we give an overview of relevant measurement techniques, from classical methods to recent advances. We present their advantages and disadvantages, the scales of measurement, the resolution, the expected accuracy and the susceptibility to errors. This work aims at guiding the choice for the best (combination of) technique(s) to answer questions related to agricultural soil porosity, categorizing techniques according to the parameters they focus on: from total porosity over pore size distribution, structure and connectivity up to the quantification of spatio-temporal dynamics. [less ▲]

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See detailCan spatial study of hydrological connectivity explain some non-linear behaviors of catchments?
Cantreul, Vincent ULiege; Pineux, Nathalie ULiege; Swerts, Gilles ULiege et al

Poster (2015, April)

Erosion is a major threat to European soil. Consequences can be very important both on-site and off-site. Belgian loamy soils are highly vulnerable to this threat because of their natural sensitivity to ... [more ▼]

Erosion is a major threat to European soil. Consequences can be very important both on-site and off-site. Belgian loamy soils are highly vulnerable to this threat because of their natural sensitivity to erosion on the one hand, and because the land is mainly used for intensive agricultural practices on the other hand. Over the last few decades, rising erosion has even been observed in our regions. This shows the importance of a deeper understanding of the coupled phenomena of runoff and erosion in order to manage soils at catchment scale. Plenty of research have already studied this but all agree to say that it seems to have a non-linear relationship between rainfall and discharge, as well as between rainfall and erosion. For that reason, a new concept has been developed a few years ago: the hydrological connectivity. Several research have focused on connectivity but up to now, each there are as much definition as papers. In this thesis, it will be important firstly to resume all these definitions to clarify this concept. Secondly, a methodology using various transects on the watershed and some pertinent field measurements will be used. These measurements include spatial distribution of particle size, surface states and soil moisture. A new approach of photogrammetry using an UAV will be used to observe erosion and deposition zones on the watershed. In this framework, several time scales will be studied from the event scale to the annual scale passing by monthly and seasonal scales. All this will serve to progress toward a better understanding of the concept of hydrological connectivity in order to study erosion at catchment scale. The final goal of this study is to describe hydrologically each different part of the catchment and to generalize these behaviors to other catchments with similar properties if possible. Afterwards, this research will be integrated in an existing (or not) model to improve the modelling of discharge and erosion in the catchment. Thanks to that, a scenario of hydraulic mitigation measures could be proposed in order to reduce runoff and erosion in the catchment. This scenario will include hydraulic, hydrologic but also ecological, landscape and economical points of view. [less ▲]

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See detailGISER- Gestion intégrée Sol Erosion Ruissellement - rapport d'activités année 4
Demarcin, Pierre ULiege; Dewez, Arnaud; Maugnard, Alexandre et al

Report (2015)

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See detailDétection de l'érosion dans un bassin versant agricole par comparaison d'images multidates acquises par drone
Lisein, Jonathan ULiege; Pineux, Nathalie ULiege; Pierrot-Deseilligny, marc et al

Scientific conference (2015, March 26)

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See detailSiltation and Pollution of Rivers in the Western Highlands of Cameroon: a Consequence of Farmland Erosion and Runoff
Djoukeng, Henri Grisseur ULiege; Tankou, Christopher Mubeteneh; Degré, Aurore ULiege

in International Journal of Agricultural Research and Reviews (2015), 3(3), 206-212

In the Western Highlands agro-ecological zone of Cameroon, rivers are constantly silted and polluted with eroded sediment and waste from cultivated land. This study characterizes and quantifies the amount ... [more ▼]

In the Western Highlands agro-ecological zone of Cameroon, rivers are constantly silted and polluted with eroded sediment and waste from cultivated land. This study characterizes and quantifies the amount of material coming from plots cultivated in the Méloh Watershed. In a natural rocky-bottomed well measuring 0.90 m deep, 3 m long, and 2.5 m wide, for a period of three years we performed the collection, differentiation, and measurement of trapped sediment in the cultivated part of river that runs through the watershed. Both cultivated sides of the watershed had fairly regular slopes of 14% on one side and 17% on the other side. The material retrieved consisted of soil, plant residues, chemical packages, and plastic casing used for irrigation. During the years 2012 and 2013, farmers practiced both flatbed cultivation and ridging along the steepest slopes. These two methods of land preparation are inefficient in terms of water conservation, as evidenced by the collection of 10.429 t.ha-1 average total sediment per year during this period. Tied ridging cultivation method was experimented during the 2013 crop year and adopted on 75% of plots in 2014. We subsequently collected 3.586 t.ha-1 total sediment, a decrease of 65.61% compared to the average of previous years. The tied ridging cultivation method significantly reduced siltation of the Méloh River (p<0.05). This study showed that traditional agricultural practices are a principal cause of siltation and pollution of the Méloh River. By extrapolation, we can state that the problem must occur in almost all rivers in the study area with similar topography and agricultural practices [less ▲]

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See detailGiser: formation à destination des communes
Dewez, Arnaud; Bielders, Charles; Degré, Aurore ULiege et al

Learning material (2015)

Detailed reference viewed: 36 (3 ULiège)