Abdallah Alaoui

Dual-porosity and kinematic wave approaches to assess the degree of preferential flow in an unsaturated soil

Abstract The purpose of this study was to assess the degree of preferential flow in an unsaturated soil column using two different models: the dual-porosity model, MACRO, and the kinematic wave approach (KWA) based on boundary-layer flow theory. The soil column experiments consisted of six infiltrations with intensities varying from 15 to 101 mm h−1. Bromide solution was also infiltrated at an intensity of 79 mm h−1 and a concentration of 80 mg l−1. Both MACRO and the KWA indicated the absence of pure preferential flow. The KWA indicated intermediate flow with dispersion of the wetting front with depth, whereas MACRO indicated flow dominated by the diffusion of capillary potential. These results shed light on the transition between flows dominated by momentum dissipation and by diffusion of capillary potential. The absence of pure macropore flow in the structured sandy soil is mainly due to efficient lateral mass exchange in this material.

Land use change impacts on floods at the catchment scale : Challenges and opportunities for future research

Abstract Research gaps in understanding flood changes at the catchment scale caused by changes in forest management, agricultural practices, artificial drainage, and terracing are identified. Potential strategies in addressing these gaps are proposed, such as complex systems approaches to link processes across time scales, long‐term experiments on physical‐chemical‐biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology, and geomorphology.

Transport of iodide in structured clay-loam soil under maize during irrigation experiments analyzed using HYDRUS model

Transport of radioactive iodide 131I− in a structured clay loam soil under maize in a final growing phase was monitored during five consecutive irrigation experiments under ponding. Each time, 27 mm of water were applied. The water of the second experiment was spiked with 200 MBq of 131I− tracer. Its activity was monitored as functions of depth and time with Geiger-Müller (G-M) detectors in 11 vertically installed access tubes. The aim of the study was to widen our current knowledge of water and solute transport in unsaturated soil under different agriculturally cultivated settings. It was supposed that the change in 131I− activity (or counting rate) is proportional to the change in soil water content. Rapid increase followed by a gradual decrease in 131I− activity occurred at all depths and was attributed to preferential flow. The iodide transport through structured soil profile was simulated by the HYDRUS 1D model. The model predicted relatively deep percolation of iodide within a short time, in a good agreement with the observed vertical iodide distribution in soil. We found that the top 30 cm of the soil profile is the most vulnerable layer in terms of water and solute movement, which is the same depth where the root structure of maize can extend.

Assessment of promising agricultural management practices

iSQAPER project - Interactive Soil Quality Assessment in Europe and China for Agricultural Productivity and Environmental Resilience - aims to develop an app to advise farmers on selecting the best Agriculture Management Practice (AMPs) to improve soil quality. For this purpose, a soil quality index has to be developed to account for the changes in soil quality as impacted by the implementation of the AMPs. Some promising AMPs have been suggested over the time to prevent soil degradation. These practices have been randomly adopted by farmers but which practices are most used by farmers and where they are mostly adopted remains unclear. This study is part of the iSQAPER project with the specific aims: 1) map the current distribution of previously selected 18 promising AMPs in several pedo-climatic regions and farming systems located in ten and four study site areas (SSA) along Europe and China, respectively; and 2) identify the soil threats occurring in those areas. In each SSA, farmers using promising AMPs were identified and questionnaires were used to assess farmers perception on soil threats significance in the area. 138 plots/farms using 18 promising AMPs, were identified in Europe (112) and China (26).Results show that promising AMPs used in Europe are Crop rotation (15%), Manuring & Composting (15%) and Min-till (14%), whereas in China are Manuring & Composting (18%), Residue maintenance (18%) and Integrated pest and disease management (12%). In Europe, soil erosion is the main threat in agricultural Mediterranean areas while soil-borne pests and diseases is more frequent in the SSAs from France and The Netherlands. In China, soil erosion, SOM decline, compaction and poor soil structure are among the most significant. This work provides important information for policy makers and the development of strategies to support and promote agricultural management practices with benefits for soil quality.

Chapter 12 – Mapping Soil Vulnerability to Floods Under Varying Land Use and Climate

Floods may only last few hours and can cause considerable damage and a possible threat to life. Flood prediction requires quantitative knowledge about infiltration and runoff dynamics, which is generally gained at the local scale. When scaling up local measurements to the catchment scale, account needs to be taken off the catchment’s organization (connectivity and patchiness). For this purpose, we developed a new method to map soil vulnerability to floods based on two steps: (1) identification of the flow processes at the plot scale, and (2) up-scaling this knowledge to the catchment scale. Excess surface runoff was scaled up by means of terrain analysis using digital elevation models (TauDEMs) calibrated with in situ sprinkling experiments of three rainfall-simulation intensities carried out on 57 plots under grassland and forest that dominate in the investigated area. The marked differences in textural and structural porosities between forest and grassland plots appear to control runoff processes. On the one hand, forest soil has a higher storage capacity than grassland soil, probably caused by a high unsaturated hydraulic conductivity and root water uptake, and resulting in lower surface runoff. On the other hand, fine material in the topmost 10 cm of grassland soil helps to build a structure that impedes vertical downward percolation and thus enhances surface runoff. However, within each soil category, slope plays an important role in generating surface runoff. In addition, raising the rainfall-simulation intensity from 24 to 48 mm h−1 increases the risk of predisposition to surface runoff from middle to high in major parts of the catchment under grassland, whereas forest soils showed vertical percolation in all cases except on slopes steeper than 31.3 degrees. Scaling up runoff processes using TauDEM based on sprinkling experiments provided new quantitative insights into flow processes and enabled us to trace the hydrological connectivity between zones of various predispositions to excess surface runoff under different land uses. These promising results indicate that the approach is suited for mapping soil vulnerability to floods under varying land use and climate at any scale. Our study showed that the peak discharge can be significantly reduced if the succession and connectivity of land use are well planned.

Mapping Soil Vulnerability to Floods Under Varying Land Use and Climate

Floods may only last few hours and can cause considerable damage and a possible threat to life. Flood prediction requires quantitative knowledge about infiltration and runoff dynamics, which is generally gained at the local scale. When scaling up local measurements to the catchment scale, account needs to be taken off the catchment’s organization (connectivity and patchiness). For this purpose, we developed a new method to map soil vulnerability to floods based on two steps: (1) identification of the flow processes at the plot scale, and (2) up-scaling this knowledge to the catchment scale. Excess surface runoff was scaled up by means of terrain analysis using digital elevation models (TauDEMs) calibrated with in situ sprinkling experiments of three rainfall-simulation intensities carried out on 57 plots under grassland and forest that dominate in the investigated area. The marked differences in textural and structural porosities between forest and grassland plots appear to control runoff processes. On the one hand, forest soil has a higher storage capacity than grassland soil, probably caused by a high unsaturated hydraulic conductivity and root water uptake, and resulting in lower surface runoff. On the other hand, fine material in the topmost 10 cm of grassland soil helps to build a structure that impedes vertical downward percolation and thus enhances surface runoff. However, within each soil category, slope plays an important role in generating surface runoff. In addition, raising the rainfall-simulation intensity from 24 to 48 mm h−1 increases the risk of predisposition to surface runoff from middle to high in major parts of the catchment under grassland, whereas forest soils showed vertical percolation in all cases except on slopes steeper than 31.3 degrees. Scaling up runoff processes using TauDEM based on sprinkling experiments provided new quantitative insights into flow processes and enabled us to trace the hydrological connectivity between zones of various predispositions to excess surface runoff under different land uses. These promising results indicate that the approach is suited for mapping soil vulnerability to floods under varying land use and climate at any scale. Our study showed that the peak discharge can be significantly reduced if the succession and connectivity of land use are well planned.

Innovative Soil Management Practices (SMP) Assessment in Europe and China

(1) Instituto das Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), University of Évora, Núcleo da Mitra Apartado 94 7006-554 Évora, Portugal (lbarao@uevora.pt), (2) 2 Centre for Development and Environment (CDE), University of Bern, Hallerstrasse 10, 2012 Bern, Switzerland, (3) University of Pannonia (UP), Deák F. u. 16., H-8360 Keszthely, Hungary, (4) Wageningen University (WU), The Netherlands, (5) Stichting Dienst Landbouwkundig Onderzoek (DLO), The Netherlands, (6) Gaec de la Branchette (GB), France, (7) Research Centre for Natural Resources, Environment and Society (CERNAS), College of Agriculture, Polytechnic Institute of Coimbra, Coimbra, Portugal, (8) University of Miguel Hernández (UMH), Spain, (9) Agricultural University Athens (AUA), Greece, (10) University of Ljubljana, Biotechnical Faculty, Jamnikarjeva 101, 1000 Ljubljana, Slovenia, (11) Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó út. 15., H-1022 Budapest, Hungary, (12) National Research and Development Institute for Soil Science, Agrochemistry and Environmental Protection (ICPA), Romania, (13) Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland, (14) Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences, Estonia, (15) 15 Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences (IARRP, CAAS), China, (16) Soil and Fertilizer Institute of the Sichuan Academy of Agricultural Sciences (SFI), China, (17) Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources (ISWC), China