Estimation des coûts de l'épuration collective

peer reviewedThis paper contributes to a better understanding of costs for collective wastewater treatment in the Walloon Region (Belgium). Based on a large set of data, unit costs to population equivalents are modelled. Considering investment as well as exploitation costs, the model includes not only wastewater treatment plants but also collector and sewage networks in an integrated approach at the technical basin level. Beyond this modelling, each type of process is analyzed independently in order to explore the structure of investment costs and their variation factors. Then, the model was used to forecast the upcoming expenses for 36 areas which are not yet equipped with collective wastewater treatment facilities. In light of these results, strategic choices for decision makers are discussed

Exploration of strategies to improve irrigation management of alfalfa (Medicago sativa L.), berseem (Trifolium Alexandrinum L.) and silage maize (Zea mays L.) in Tadla – Morocco

The CropSyst model, an operative crop model, is used to explore irrigation scenarios for the main folder crops in Tadla irrigated area in Morocco. The calibration and validation of CropSyst model have been realized previously for alfalfa, silage maize and berseem. The model was run for a 40 year simulation with climatic data measured daily; using several scenarios involving a combination of irrigation times and water amounts. For alfalfa, the results obtained indicate that applying 1600 mm of irrigation water amount maximizes irrigation water efficiency (1.21 kg/m3) and achieve a yield of 23.1 t/ha (95% of the yield potential). In the case of maize, application of 648 mm through 2 irrigations in initial phase, 2 irrigations in linear and two in final phases allows to achieve high biomass yield and better water use. On berseem, the simulation results confirm that the adoption of the scenario that provides 625 mm allows obtaining 14.1 t/ha of dry matter which represents 94% of the yield potential. Finally, the coupling of the results of four years (2008 - 2012) experimentations with the simulations of scenarios by CropSyst has shown to be highly effective in order to improve the folder crops irrigation in the Tadla

Effet du déficit hydrique sur la croissance, le rendement et l'efficience d'utilisation de l'eau chez la luzerne (Medicago sativa L.) au Tadla

The study of crop response to water deficit is important in areas where water resources are limited. This study was conducted over the period 2009-2011 with the aim to study the effect of water deficit on alfalfa productivity in the irrigated perimeter of Tadla. Under flood irrigation, four water regimes (100%, 80%, 60% and 40% ETc) were compared. Under drip irrigation, the same regimes were associated with spacing between ramps (50 cm and 75 cm). Observations were made on the soil, root system and dry biomass at each cut. The results showed that the average maximum biomass yield was 23.2 T.ha-1. The contribution of the spring cycles to annual yield varies from 55% under 100% ETc to 65% under 40% ETc. In addition to amount of water, alfalfa productivity depend also on the moment when water is applied within a cycle. The water use efficiency varies from one cycle to another and between seasons. It is highest in spring and lowest in winter. Drip irrigation, in comparison with flood irrigation, allows similar biomass yield but with less water and more agronomic efficiency. Keywords: Alfalfa, Water deficit, Flood irrigation, Micro irrigation, Water use efficiency, Morocco.  L’étude de la réponse des cultures au déficit hydrique est importante dans les zones où les ressources en eau sont limitées. Cette étude a été réalisée sur la période 2009-2011 dans l’objectif d’étudier l’effet du déficit hydrique sur la productivité de la luzerne dans le périmètre de Tadla. Sous irrigation gravitaire, quatre régimes hydriques (100 %, 80 %, 60 % et 40 % ETc) ont été comparés. Sous irrigation localisée, ces mêmes régimes ont été associés à deux écartements entre rampes (50 cm et 75 cm). Les observations ont porté sur le sol, le système racinaire et la biomasse à chaque coupe. Les résultats ont montré que le rendement annuel maximal moyen obtenu est de 23,2 T.ha-1. La contribution des cycles de printemps au rendement annuel varie de 55% sous le régime 100% ETc à 65% sous 40% ETc. Les rendements de la luzerne dépendent, en plus des quantités d’eau apportées, de l’emplacement des apports à l’intérieur d’un cycle. L’efficience d’utilisation de l’eau varie d’un cycle à l’autre et d’une saison à l’autre. Elle est maximale au printemps et faible en hiver. L’irrigation localisée permet de réaliser des rendements similaires à l’irrigation gravitaire avec moins d’eau et plus d’efficience agronomique. Mots clés: Luzerne, Déficit hydrique, Irrigation gravitaire, Micro irrigation, Efficience d’utilisation de l’eau, Maroc. &nbsp

Exploration of strategies to improve irrigation management of alfalfa (Medicago sativa L.), berseem (Trifolium Alexandrinum L.) and silage maize (Zea mays L.) in Tadla – Morocco

Le modèle CropSyst a été utilisé pour explorer des scénarios d'irrigation des principales cultures fourragères au Tadla au Maroc. La calibration et la validation du modèle CropSyst ont été réalisées précédemment pour la luzerne, le maïs d'ensilage et le bersim. Des simulations de plusieurs scénarios impliquant une combinaison des moments d'irrigation et des quantités d'eau appliquées ont été réalisées sur 40 ans avec des données climatiques journalières. Pour la luzerne, les résultats indiquent que l'application de 1600 mm d’eau maximise l’efficience d’utilisation de l'eau  (1,21 kg/m3) et permet d’atteindre un rendement de 23,1 t / ha. Dans le cas du maïs, l'application de 648 mm à travers 2 irrigations en phase initiale, 2 irrigations en phase linéaire et deux en phase finale permet d'obtenir un rendement élevé en biomasse et une meilleure productivité de l'eau. Sur le bersim, les résultats de simulation confirment que l'adoption du scénario qui fournit 625 mm permet d'obtenir 14,1 t / ha de matière sèche qui représente 94 % du potentiel de rendement. Finalement, le couplage des résultats d’expérimentation de quatre ans (2008-2012) avec les simulations de scénarios par CropSyst s'est avéré très pratique pour améliorer l'irrigation des cultures fourragères au Tadla. Mots clés: Luzerne, maïs ensilage, modèle CropSyst, scenario d’irrigation, Tadla, Maroc.The CropSyst model, an operative crop model, is used to explore irrigation scenarios for the main folder crops in Tadla irrigated area in Morocco. The calibration and validation of CropSyst model have been realized previously for alfalfa, silage maize and berseem. The model was run for a 40 year simulation with climatic data measured daily; using several scenarios involving a combination of irrigation times and water amounts. For alfalfa, the results obtained indicate that applying 1600 mm of irrigation water amount maximizes irrigation water efficiency (1.21 kg/m3) and achieve a yield of 23.1 t/ha (95 % of the yield potential). In the case of maize, application of 648 mm through 2 irrigations in initial phase, 2 irrigations in linear and two in final phases allows to achieve high biomass yield and better water use. On berseem, the simulation results confirm that the adoption of the scenario that provides 625 mm allows obtaining 14.1 t/ha of dry matter which represents 94 % of the yield potential. Finally, the coupling of the results of four years (2008 - 2012) experimentations with the simulations of scenarios by CropSyst has shown to be highly effective in order to improve the folder crops irrigation in the Tadla. Keywords: alfalfa, berseem, silage maize, CropSyst model, irrigation scenarios, Tadla, Morocco

Does fertilization practices increase residual nitrate nitrogen in soil irrigated with treated wastewater? An experimental trial on maize

Treated wastewater has significantly improved DM yield compared to ground water. The form of nitrogen provided by the water was determinant in drawing yields. Irrigation with ground water (where nitrogen is as nitrate) induces a faster migration of nitrogen at depth. In contrast, using treated wastewater (where nitrogen is as ammonium), resulting in a relative distribution of the remaining nitric smaller in the lower profile and therefore higher in the surface, especially after the second year (2010). In addition, the relative distribution of nitrates in the soil surface is even more important in the presence of organic manure. All happens as if a certain amount of ammonium provided by treated wastewater is retained in the organic compounds of manure. Yields were significantly lower in irrigation with treated wastewater in the second year and especially when fertilization was given in additional. If the soil can be used for storage of the nitrogen supplied by the treated wastewater during the first year of irrigation (24 kg N-NO3/ha before irrigation to 115 kg N-NO3/ha after irrigation), to the second year the capacity drops (to 64 N-NO3/ha) and a significant increase in nitrate leaching occurs. Therefore, unlike the contribution of manure that seems enrich the topsoil nitrate nitrogen, at least during the first campaign, mineral fertilization unreasoning causes faster migration of nitrogen at depth

Effet du déficit hydrique sur la croissance, le rendement et l'efficience d'utilisation de l'eau chez le bersim (Trifolium alexandrinum) au Tadla

The study of crop response to water deficit is important in areas where water resources are limited. This study was carried out over the period 2008-2011 in order to study the effect of water deficit on the productivity of berseem in the Tadla region. Four water regimes (100 %, 80 %, 60 % and 40 % ETc) were compared under both flood and drip irrigation techniques. Observations were made on the soil, biomass at each cut and root system. The results showed that the average annual maximum yield obtained was 16.2 t.ha-1. Reductions in yields by applying 60 % of water inputs are 40 % and 42 % in 2009/10 and 2010/11, respectively. The contribution of cycles without irrigation to annual biomass yield varies from 35 % under 100 % ETc to 52% under 40 % ETc. Water use efficiency of berseem over the over the entire crop period is 3.37 kg.m-3. The maximum average yield obtained under drip irrigation was 15.7 t / ha. It was obtained with a water supply of 411 mm which allowed a saving of 57 % of water supply versus flood irrigation technique.  Key words:  Berseem, water stress, flood irrigation, drip irrigation, water use efficiency, Morocco.L’étude de la réponse des cultures au déficit hydrique est importante dans les zones où les ressources en eau sont limitées. Cette étude a été réalisée sur la période 2008-2011 dans l’objectif d’étudier l’effet du déficit hydrique sur la productivité du bersim dans le périmètre de Tadla. Quatre régimes hydriques (100 %, 80 %, 60 % et 40 % ETc) ont été comparés sous les deux techniques d’irrigation gravitaire et localisée. Les observations ont porté sur le sol, la biomasse à chaque coupe et le système racinaire. Les résultats ont montré que le rendement annuel maximal moyen obtenu est de 16,2 t.ha-1. Les réductions de rendements en appliquant 60% des apports en eau sont de 40 et 42 % en 2009/10 et 2010/11 respectivement. La contribution des cycles sans irrigation au rendement annuel varie de 35 % sous le régime 100 % ETc à 52 % sous 40 % ETc. L’efficience d’utilisation de l’eau du bersim sur toute la période de culture est de 3,37 kg.m-3. Le rendement moyen maximal obtenu sous le goutte à goutte est de 15,7 t/ha. Il a été obtenu avec un apport en eau de 411 mm, ce qui a permis une économie d’eau de 57 % par rapport au gravitaire. Mots clé : Bersim, déficit hydrique, irrigation gravitaire, micro irrigation, efficience d’utilisation de l’eau, Maroc.&nbsp

Influence of the media granular size of small pilot subsurface flow wetlands on axial dispersion and the hydraulic behaviour

peer reviewedThe objective of this paper is to evaluate using tracer tests, the role of the granular media size on the hydraulic behaviour of small -scale pilot horizontal subsurface flow (HSSF) gravel beds. The non-ideal flow was modelled by the tank-in-series model (TIS) using the moment analysis and Gamma distribution fitting using the Solver™ routine in Microsoft Excel™; the Plug Flow with Dispersion (PFD) model was also assessed. Tests were performed under a greenhouse in four identical pilot-scale gravel beds of 9:1:1 ratio, which received an equal, inflow of clear water. The influent flow rate was 40 L/day and the surface area of the pilot cells was 0.8 m². The pea gravel media used in the four beds were as follows: 3-5 mm, 6-8 mm, 8-10 mm and 10-12 mm. The tracer used was Potassium Bromide (KBr) with a concentration of 1 g Br/L, using a single-shot injection into the inlet distribution tubes. Tests were repeated three times, with identical materials and methods. Statistical differences were observed between replications. Water loss by evaporation of the unplanted gravel beds was of 11% for the smaller media size (3-5 mm) which is significantly different than the 4 to 5% obtained for the other media sizes. Tracer detention time, tracer peak time, volumetric and hydraulic efficiencies show all the same tendency which is a significant reduction with larger particles sizes. The two methods of calculation for the number NTIS by moment analysis and Gamma distribution fitting (using Solver™) are significantly different. The Gamma model increases the number of TIS with significantly higher values for smaller media sizes