17 research outputs found
De lâeau pour un dĂ©veloppement durable : enjeux et stratĂ©gies
Le dĂ©veloppement socio-Ă©conomique dâun pays, dâune rĂ©gion, est un objectif principal de tout gouvernant; hĂ©las, cela affecte inĂ©vitablement les ressources dâeau tant sur la qualitĂ© du fait de la pollution domestique et industrielle que sur la quantitĂ© puisque la consommation augmente de façon vertigineuse.Il est dĂ©sormais largement admis que la mise en place dâun dĂ©veloppement durable exige de mettre en Ă©quation des prĂ©occupations sociales et Ă©conomiques avec des prĂ©occupations environnementales en tenant compte du facteur essentiel et limite, Ă savoir lâeau.LâAlgĂ©rie est un des pays du Nord du bassin mĂ©diterranĂ©en qui souffre de la pĂ©nurie dâeau. Les Ă©coulements en eau y sont caractĂ©risĂ©s par une irrĂ©gularitĂ© saisonniĂšre et interannuelle importante et par une violence et une rapiditĂ© des crues. En effet, la connaissance des conditions climatiques joue un rĂŽle important dans les Ă©tudes de planification Ă©conomique; elle permet de mieux maĂźtriser les apports non contrĂŽlĂ©s qui engendrent le bon fonctionnement du systĂšme de prĂ©vision et de gestion des ressources hydriques Ă court, moyen et long termes.Le dĂ©veloppement durable consiste entre autres Ă mettre au point des systĂšmes dâinformation, de gestion des risques et de prĂ©vision des catastrophes naturelles et Ă mettre en place des systĂšmes de dĂ©tection prĂ©coce et de contrĂŽle, ainsi que des plans dâintervention en cas dâurgence dans les zones prĂ©dĂ©terminĂ©es.Nous dĂ©velopperons dans cet article les points suivants :Une sĂ©rie de recommandations sont exposĂ©es pour rĂ©soudre le problĂšme de crise de lâeau et pour un dĂ©veloppement durable.The socio-economical development of a country or a region is the main objective of all managers; however, this affects inevitably the water resources in terms of quality related to domestic and industrial pollution, and also quantity due to increasing consumption use.Henceforth, a sustainable development requires taking into consideration the social and the economical as well as environmental factors.Algeria is one of the northern countries of the Mediterranean basin which suffers from water shortage. The river flows are characterized by important seasonal and inter-year irregularities, especially in flood periods. Indeed, the knowledge of the climatic conditions has an important role in the economical planning: it permits the best management of the uncontrolled flows for short, mean, and long term.The sustainable development requires taking a number of steps, among others, development of information system, management and prediction of the risks, forecasting natural disasters, implementation of systems of early detection, as well as plans of intervening in case of emergency. We develop in this article:A set of recommendations is given in order to solve the problem of crisis of the water and for sustainable development
On modeling chronic detachment of periphyton in artificial rough, open channel flow
Periphyton communities, which are native to river beds, serve as a functional indicator of river health but remain one of the least-studied communities despite the significant increase in the examination of aquatic microbial communities in recent years. In this study, we tested the relevance of three formulations of the chronic detachment term in a simple model for the biomass dynamics of periphyton. Numerical simulations of the periphyton biomass dynamics were performed by using three different descriptors for the flow conditions: the discharge Q, the friction velocity uâ, and the roughness Reynolds number k+ = uâks/m (where m is water kinetic viscosity and ks is the Nikuradse equivalent sand roughness). Comparisons of numerical simulation results with experimental data from literature revealed chronic detachment to be better simulated by taking the roughness Reynolds number as the external variable of detachment. These results support the idea that transport phenomena that occur in the nearbed layer, e.g. chronic detachment of periphyton matter or vertical transport of nutrients and pollutants in submerged aquatic canopies, are not related to a single turbulence descriptor such as the friction velocity uâ. Its description requires at least two descriptors, here the friction velocity uâ and the Nikuradse equivalent sand roughness ks, which depend on the initial form and dimensions of the colonized substratum, and its changes owing to the thickness, resistance, and composition of the epilithic matter
Risque de pollution nitratée des zones semi-arides : cas de la vallée du moyen Cheliff occidental (Nord Algérien)
Lâagriculture est lâactivitĂ© dominante dans la vallĂ©e du moyen Cheliff occidental (Nord algĂ©rien). Les cultures principales sont lâarboriculture et le maraĂźchage, ce dernier est un grand consommateur de fertilisants minĂ©raux de type azotĂ©.La prĂ©sente Ă©tude montre, dans une premiĂšre Ă©tape, lâĂ©volution spatiale des nitrates Ă travers une carte Ă©tablie par krigeage ordinaire pour lâannĂ©e 2004 en pĂ©riode de hautes eaux. Il apparaĂźt, dâaprĂšs cette carte, que les zones les plus affectĂ©es sont celles pour lesquelles le niveau dâintensification de la fertilisation azotĂ©e (zones de maraĂźchage) est le plus fort sous les sols les plus permĂ©ables situĂ©s sur les bordures de la vallĂ©e. Ces mĂȘmes zones sont reconnues par des pratiques dâĂ©levage importantes. Au contraire, les teneurs sont plus faibles sous les sols de texture fine couvrant la partie centrale de la vallĂ©e. Lâinfiltration assez faible, caractĂ©risant en gĂ©nĂ©ral les zones semi-arides, semble aussi jouer un rĂŽle important dans ce sens.Dans une seconde Ă©tape, cette Ă©tude permet dâestimer, pour lâannĂ©e 2004, lâapport total en azote sur les sols de la vallĂ©e. Lâapport par lâagriculture constitue 86 % du total, dont 97 % est attribuĂ© aux fertilisants azotĂ©s utilisĂ©s dâune maniĂšre intensive dans les cultures maraĂźchĂšres, la pomme de terre en particulier. RapportĂ© Ă la surface totale irriguĂ©e, cet apport est Ă©valuĂ© Ă 238 kgâąhaâ1 pour cette annĂ©e.Les conditions pĂ©doclimatiques semblent favoriser des pertes dâazote par volatilisation et par dĂ©nitrification en parallĂšle avec un apport faible dâazote naturel par minĂ©ralisation. Au contraire, les pertes par lessivage en profondeur sont trĂšs faibles.Agriculture is the most important activity in the Western Mid-Cheliff valley (North Algeria). This activity consists of two major types: tree plantations and horticulture. Horticulture requires large amounts of mineral fertilizers, such as nitrogen. This study shows, firstly, the spatial variation of nitrate concentrations for the year 2004 in periods of high water using a map prepared by simple kriging. It is apparent from this map that the areas most affected are those for which the level of intensification of nitrogen fertilization (areas of horticulture) is the strongest. These areas have a more porous soil and are located on the edges of the valley. These same areas are known for intensive farming practices. In contrast, the pollution levels are lower in the fine-textured soil covering the central part of the valley. The lower pollution level is also due to low water infiltration, a feature of semi-arid areas.Secondly, this study was able to estimate, for the year 2004, the total amount of nitrogen present in soils in the valley: 86% of the nitrogen present is due to agricultural activities, most of which, 97%, is attributed to nitrogen fertilizer used extensively in horticulture, for potatoes in particular. Extrapolated to the total irrigated area, this contribution is estimated at 238 kgâąhaâ1 for the year 2004. Pedo-climatic conditions seem to encourage the loss of nitrogen through denitrification and evaporation, together with a low rate of natural nitrogen mineralization. In contrast, the losses by leaching at depth appear very low
Analysis, in a free surface steady flow, of the interstitial velocity field inside a sedimentary bed
Pollution parameters and identification of performance indicators for wastewater treatment plant of medea (Algeria)
Specification of sewage sludge arising from a domestic wastewater treatment plant for agricultural uses
Effect of nearâbed turbulence on chronic detachment of epilithic biofilm: Experimental and modeling approaches.
The biomass dynamics of epilithic biofilm, a collective term for a complex microorganism community that grows on gravel bed rivers, was investigated by coupling experimental and numerical approaches focusing on epilithic biofilmâflow interactions. The experiment was conducted during 65 days in an artificial rough openâchannel flow, where filtered river water circulated at a constant discharge. To characterize the effect of nearâbed turbulence on the chronic detachment process in the dynamics of epilithic biofilm, local hydrodynamic conditions were measured by laser Doppler anemometry and turbulent boundary layer parameters inferred from doubleâaveraged quantities. Numerical simulations of the EB biomass dynamics were performed using three different models of chronic detachment based upon three different descriptors for the flow conditions: Discharge Q, friction velocity u*, and roughness Reynolds number k+. Comparisons of numerical simulation results with experimental data revealed chronic detachment to be better simulated by taking the roughness Reynolds number as the external physical variable forcing chronic detachment. Indeed, the loss of epilithic matter through the chronic detachment process is related not only to hydrodynamic conditions, but also to change in bottom roughness. This suggests that changes in the behavior and dimensions of river bed roughness must be considered when checking the dynamics of epilithic biofilm in running waters
Ressources en eau : quelles stratégies? quelles solutions? quelles politiques? quelles perspectives?
Réunion: NEPAD Science and Technology Regional Workshop for Northern Africa, 25-28 Jan. 2004, Algiers, DZPrésentation PowerPoin
NEPAD water crisis
Réunion: NEPAD Science and Technology Regional Workshop for Northern Africa, 25-28 Jan. 2005, Algiers, DZTexte en françaisPrésentation PowerPoin