A bulk model for the atmospheric planetary boundary layer

The integrated momentum and thermodynamic equations through the planetary boundary layer (PBL) are solved numerically to predict the mean changes of wind and potential temperature from which surface fluxes are computed using bulk transfer coefficients of momentum and heat. The second part of the study involves a formulation and testing of a PBL height model based on the turbulent energy budget equation where turbulent fluxes of wind and heat are considered as the source of energy. The model exhibits capability of predicting the PBL height development for both stable and unstable regimes of observed conditions. Results of the model agree favourably with those of Deardorff's (1974a) and Tennekes' (1973) models in convective conditions.Contribution number 396.     

Plutonism in Pan-African belts and the geologic evolution of northeastern Africa

Plutonic igneous rocks of Pan-African belts (500–600 m.y. age) in Africa can be described in terms of three types of assemblages: (1) migmatites formed largely by remobilization of pre-existing sialic crust during Pan-African time; (2) calcalkaline batholithic suites formed in association with subduction of oceanic crust; and (3) alkali-rich, post-tectonic granites. Many suites cannot be placed precisely in one of these categories, either because of intermediate (gradational) characteristics or because of lack of adequate information. Distinction of rocks formed during Pan-African time from older ones whose radiometric clocks were reset at that time is also difficult.The rock suites are very unevenly distributed geographically. Migmatites formed by ensialic crustal remobilization occur mostly in southern and central Africa. Calcalkaline suites occur in north Africa, particularly the northeast. Alkali-rich granites are virtually restricted to the northeastern portion of the continent, the one major part of Africa not occupied by an Archean shield. Evidence for subduction of oceanic crust is also restricted to northeastern Africa.The geologic history proposed for northeastern Africa is as follows: During, and immediately preceding, Pan-African time an ocean basin of uncertain size and shape occurred between the West African and Nubian-Arabian shields. Subduction zones were active on the margins and within the basin. During, and at the end of, Pan-African time extensive development of alkali-rich granites was associated with cratonization of the basin. Paleozoic sediments were then deposited under platform conditions on the newly formed craton, which showed mild epeirogenic activity throughout the Phanerozoic.     

Recognition of the hydrogeological potential using electrical sounding in the Khemisset-Tiflet region,Morocco

The low recharge of reservoirs and the increasing demand for water limit the potential of mobilized resources, especially in arid to semi-arid areas like Morocco. Integrated management is essential to safeguard this resource. In respect with this perspective, this work provides the analysis of hydrogeological potential of Khemisset-Tiflet region, which falls within the action area of the Sebou Hydraulic Basin Agency. The basis of our studies was as follows:(1) The interpretation of the existing geoelectric data;(2) application of geophysical methods for non-destructive reconnaissance and their integration into a Geographic Information System(GIS). The analysis demonstrates that: The map of the isohypses and the geoelectric cross-section of the substratum of the superficial roof aquifer show clearly a plunge associated with development of the Paleozoic roof in the South and the direction of flow of the surface water is from south to north, from the upper zone to the north of the El Kansera dam. These conclusions constitute very useful contribution for any resource management projects in this area.     

TDR detection of nonaqueous phase liquids in sandy soils using the eigendecomposition method

In this study, the presence of nonaqueous phase liquids (NAPL) in sandy soils are detected using a TDR probe system and the eigendecomposition method of analysis. As a demonstration, five NAPLs with different physicochemical properties (acetone, benzene, heptane, trichloroethylene, and xylene; Table 1) were used. Samples were prepared in such a way that the soil pore fluid has different contents of deionized water and NAPLs. For each experiment, a pulse signal with known characteristics was used and reflected signals were captured by an oscilloscope and analyzed using the eigendecomposition method. Autoregressive modeling and singular value decomposition were used to calculate the eigenvalues. The most significant eigenvalues were identified based on their power spectrum. The relative eigenvalue of the first mode (Eow), which is a measure of the power carried by the signal, was calculated and correlated to NAPL type and content, and octanol water partition coefficient (log Kow). The results indicated that for the same NAPL content, as log Kow increases, Eow decreases due to increase of hydrophobicity. For the same log Kow, as the organic content in soil pore fluid increases, Eow increases due to decrease of dielectric properties of the pore fluids.     

Duration Magnitude Scale and Site Residuals for Northern Morocco

— The first empirical duration magnitude (M_D) formula is developed and tested for the Northern Morocco Seismic Network (NMSNET). This relationship is obtained by relating the IGN (Instituto Geografico National, Madrid) body-waves mbLg^IGN to the duration (), and the epicentral distance (), at 25 analogue stations of the NMSNET for 479 earthquakes with 2.5 mb 5.4, from March 1992 to February 2001. M_D estimates are significantly more precise while introducing a correction term for each of these stations, cSta_j. The magnitude for the i^th event (M_D)_i is the mean value of individual M_Dij=–0.14+1.63log₁₀(_ij)+0.031(_ij)+cSta_j. The cSta_j corrections reduce considerably the local site effects which influence the recorded durations and cause stations to either overestimate, or underestimate M_D up to 0.5 magnitude units. Average station M_D residuals (–cSta_j) are found to be independent of the distance from the epicenter to at least 10 degrees. It seems evident that regional geological features in the immediate behavior of stations have a systematic effect on the corresponding obtained residuals: older well-consolidated Precambrian crystalline rocks produce high negative residuals (shorter durations), younger unconsolidated sediments produce high positive residuals (longer durations), whereas, intermediate M_D site residuals appear to be the result of the effect of various factors, principally age and state of consolidation of the bedrock, combined with the local tectonic.     

Assessment of hydraulic properties of sedimentary and volcanic aquifer systems under arid conditions in the Republic of Djibouti (Horn of Africa)

The Republic of Djibouti (23,000 km²; 500,000 inhabitants), located within the Horn of Africa, undergoes an arid climate with an average annual rainfall less than 150 mm. Water resources are provided up to 98% by groundwater. Two types of aquifers are encountered: volcanic and sedimentary aquifers. This paper focuses on the assessment of their hydraulic properties, which is necessary for future tasks regarding the management of these aquifers. To this end, a data base consisting of all available pumping test data obtained since the 1960s was compiled. Pumping tests have been interpreted to determine transmissivity. Solely for volcanic aquifers, transmissivity also has been estimated through an empirical relationship using specific capacity corrected for turbulent well losses. The transmissivity of each type of aquifer can span up to four orders of magnitude, pointing out their strong heterogeneity. For the various volcanic rocks, the younger the rock, the higher the transmissivity. The transmissivity of volcanic rocks has therefore decreased in the course of geological time. At present, a much better understanding of the hydraulic properties of these complex aquifers has been obtained, which should enable optimal management of their groundwater resources through the use of numerical modeling.

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Resumen La República de Yibuti (23.000 km², 500.000 habitantes) está situada en el Cuerno de África, donde se han formado diversas unidades volcánicas—basaltos y riolitas—y rocas sedimentarias desde la expansión de los continentes acaecida al inicio de la deriva continental (hace 30 millones de años). La precipitación media anual es inferior a 150 mm. Las rocas volcánicas y sedimentarias, con dimensión inferior a 2.000 km², constituyen acuíferos locales. Los basaltos estratificados forman un acuífero regional que se extiende a más de 9.000 km². La multitud de datos existente ha sido almacenada desde los años 1960 en una base de datos. La transmisividad de estos acuíferos ha sido determinada mediante datos de ensayos de bombeo y una relación empírica que usa la capacidad específica corregida con las pérdidas turbulentas en el pozo. La transmisividad de estos acuíferos se comporta como una variable lognormal, hecho importante para los trabajos previstos de modelación con métodos estadísticos. La transmisividad de cada acuífero puede variar hasta en cuatro órdenes de magnitud, manifestando su gran heterogeneidad. Para los materiales volcánicos, la transmisividad es mayor cuanto más joven es la roca. La permeabilidad de las rocas volcánicas ha evolucionado por tanto con el tiempo geológico. Actualmente, se posee un mayor conocimiento sobre las propiedades hidráulicas de estos acuíferos complejos, de manera que se puede hacer una gestión óptima de sus recursos hídricos subterráneos con la utilización de modelos numéricos.

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Résumé La République de Djibouti (23,000 km²; 500,000 habitants), située dans la Corne de lAfrique, subit un climat aride avec une pluviométrie moyenne annuelle inférieure à 150 mm. Les ressources en eau sont fournies à plus de 98% par les eaux souterraines contenues dans des aquifères sédimentaires ou volcaniques. Cet article a pour objectif lévaluation des propriétés hydrauliques de ces aquifères, étape indispensable pour entreprendre par la suite des études en vue de la gestion de ces aquifères. Une base rassemblant les données dessais par pompage disponibles depuis les années Soixante a dabord été établie. Les essais par pompage ont été interprétés pour déduire la transmissivité. Concernant les aquifères volcaniques, la transmissivité a également été estimée à laide dune relation empirique reliant la transmissivité et le débit spécifique corrigé des pertes de charge anormales. La transmissivité pour chaque aquifère couvre jusquà quatre ordres de grandeur, montrant la forte hétérogénéité de ces milieux. Pour les roches volcaniques, on observe que la transmissivité est dautant meilleure que la roche est plus jeune. Leur transmissivité a ainsi diminué durant les temps géologiques. La compréhension des propriétés hydrauliques de ces aquifères complexes est à présent bien meilleure, ce qui permet denvisager une gestion optimale de leurs ressources à laide de modèles numériques.

     

Participatory groundwater management in Jordan: Development and analysis of options

Groundwater over-exploitation has been on the rise in Jordan. Competing demands have grown in the face of perennial water shortages, a situation which has been exacerbated by drought conditions in the past decade. This paper reports findings of a project in which management options to address over-exploitation were developed for one of Jordans principal aquifer systems, the Amman-Zarqa Basin. Options for addressing the situation were developed through a participatory approach that involved government officials and various public and private sector interest groups. Particular efforts were made to involve well irrigators, who are likely to be heavily impacted by the changes required to reduce groundwater pumping to a sustainable level. With information obtained from a rapid appraisal survey as well as from interviews with farmers, community groups, government officials, and technical experts, an extensive set of options was identified for evaluation. Based on integrated hydrogeologic, social, and economic analysis, five complementary management options were recommended for implementation. These included the establishment of an Irrigation Advisory Service, buying out farm wells, placing firm limits on well abstraction and irrigated crop areas, exchanging treated wastewater for groundwater, and measures to increase the efficiency of municipal and industrial water use. Various combinations and levels of these options were grouped in scenarios, representing possible implementation strategies. The scenarios were designed to assist decision makers, well owners and other stakeholders in moving gradually towards a sustainable abstraction regime. Social and economic aspects of each option and scenario were analyzed and presented to stakeholders, together with a summary of legal, institutional and environmental ramifications. Combining scientific analysis with a participatory approach in the Amman Zarqa Basin groundwater management was devised as a prototype to be used in the management of other groundwater basins in Jordan. This participatory management approach would also be useful in other parts of the world that are experiencing similar groundwater over-exploitation problems.Résumé La surexploitation des eaux souterraines prend de limportance en Jordanie. Les demandes en concurrence ont augmenté face à des déficits permanents deau, situation qui a été exacerbée par la sécheresse de la dernière décennie. Cet article rend compte de laboutissement dun projet dans lequel des options de gestion portant sur la surexploitation ont été développées pour lun des principaux systèmes aquifères de Jordanie, le bassin dAmman Zarqa. Des options pour aborder cette situation ont été développées grâce à une approche participative qui implique des fonctionnaires du gouvernement et des groupes dintérêts variés des secteurs public et privé. Des efforts particuliers ont été faits pour impliquer les irrigants utilisant des puits, qui sont probablement ceux qui ont le plus fort impact sur les changements attendus permettant de remettre le système en équilibre. À partir des informations obtenues de campagnes rapides dévaluation, telles que des réunions de communautés et des entrevues avec des experts techniques du gouvernement, un large jeu doptions a été identifié pour lévaluation. Basées sur une analyse hydrogéologique, sociale et économique, cinq options complémentaires de gestion ont été recommandées pour la réalisation. Ce sont la création dun Service Consultatif dIrrigation, achetant les puits agricoles, fixant des limites fermes aux prélèvements des puits et aux zones irriguées, échangeant les eaux usées traitées avec des eaux souterraines, et la mise en place de mesures pour accroître lefficacité des usages collectifs et industriels. Des combinaisons et des niveaux variés de ces options ont été regroupés en scénarios, présentant les stratégies possibles de mise en uvre. Les scénarios ont été mis au point pour assister les décideurs, les propriétaires de puits et les autres acteurs pour atteindre progressivement un régime de prélèvement durable. Les aspects sociaux et économiques de chaque option et de chaque scénario ont été analysés et présentés aux acteurs, en même temps quun résumé des ramifications légales, institutionnelles et environnementales. En combinant une analyse scientifique à une approche participative du bassin dAmman Zarqa, la gestion des eaux souterraines a été imaginée comme un prototype pouvant être utilisé pour la gestion dautres bassins aquifères de Jordanie. Il peut également être utile à dautres régions du monde qui sont concernées par des problèmes similaires de surexploitation des eaux souterraines.Resumen La sobreexplotación de las aguas subterráneas ha ido en aumento en Jordania, donde las demandas en competición han crecido frente a una escasez perenne de agua, situación que ha sido agravada por el estado de sequía de la última década. Este artículo presenta los hallazgos de un proyecto en el que se han desarrollado opciones de gestión para hacer frente a la sobreexplotación en uno de los principales sistemas acuíferos de Jordania: la cuenca de Ammán-Zarga. Se ha elaborado opciones para afrontar la situación mediante un enfoque participativo que incluye a personal del gobierno y a diversos grupos de interés de los sectores público y privado. En particular, se ha intentado involucrar a los regantes que se sirven de aguas subterráneas, quienes tienen más probabilidad de ser directamente afectados por los cambios requeridos para devolver el sistema a un balance equilibrado. A partir de la información obtenida en rápidas campañas de valoración, así como de encuentros con la comunidad y entrevistas con los expertos técnicos del gobierno, se ha identificado un amplio conjunto de opciones para su evaluación. Basándose en un análisis integrado de los aspectos hidrogeológicos, sociales y económicos, se ha recomendado la implementación de cinco opciones complementarias de gestión: establecimiento de un Servicio Asesor de Riego; adquisición de pozos de granjas; imposición de límites estrictos en las extracciones de pozos y superficies de riego; substitución de las aguas subterráneas con aguas residuales depuradas; y medidas para incrementar la eficiencia de los usos municipales e industriales del agua. Se ha agrupado varias combinaciones y niveles de dichas opciones en escenarios, representando estrategias posibles de implementación. Los escenarios han sido diseñados para ayudar a los gestores en la toma de decisiones, a los propietarios de pozos y a otros agentes para que se vaya consiguiendo de forma gradual un régimen de extracciones sustentable. Se ha analizado los aspectos sociales y económicos de cada opción y de cada escenario, presentándolos a los diversos agentes, además de generar un resumen de ramificaciones legales, institucionales y medioambientales. Se ha concebido la combinación de un análisis científico con un enfoque participativo en la cuenca de Ammán-Zarga como un prototipo de gestión de las aguas subterráneas que puede ser aplicado a la gestión de otras cuencas en Jordania. También sería útil en otros lugares del mundo que estén experimentando problemas similares de sobreexplotación de los recursos hídricos subterráneos.Abbreviations and acronyms AED Academy for Educational Development - ARD Associates in Rural Development - AZB Amman–Zarqa Basin - ECC Economic Consultative Council - GMCC Groundwater Management Consultative Committee - GMF Groundwater Management Fund - GIS Geographic Information System - HDH Hashmiya–Dulayl–Hallabat - IAS Irrigation Advisory Service - JICA Japanese International Cooperation Agency - M&I Municipal and Industrial - MOA Ministry of Agriculture - MWI Ministry of Water and Irrigation - NCARTT National Center for Agricultural Research and Technology Transfer - NGO Non-governmental Organization - O&M Operations and Maintenance - RA Rapid Appraisal - RS Remote Sensing - UFW Unaccounted for Water - USAID United States Agency for International Development - WAJ Water Authority of Jordan - WEPIA Water Education & Public Information Activity - WRPS Water Resource Policy Support     

Structuration profonde des dépôts de l'Albien–Maastrichtien en Tunisie centrale : nouvelle limite de l'archipel de Kasserine et implications géodynamiques

The Albian–Maastrichtian seismic horizon analysis in central Tunisia (Gafsa–Sidi Bouzid area) using the reflection seismic sections calibrated to the well data, shows buried structures with deposit distributions and sedimentation geometries varying from the depressive to uplifted zones. Pinch outs, unconformities and hiatuses recognized on the folded high structures are caused by reactivation of the bordering faults. The Turonian–Maastrichtian unconformities correspond to the palaeogeographic limits that outline the Kasserine Islets and correspond to the N120, N180 major wrench-salt-intruded corridors and associated N90, N60 strike-slip faults. Formation of the different structures and evolution of the basins and platforms were controlled by conjugate dextral and sinistral strike-slip movements. These structures allow new palaeogeographic limits of the Kasserine Islets to be identified. To cite this article: T. Zouaghi et al., C. R. Geoscience 337 (2005).     

Estimation of frequency dependent coda wave attenuation structure at the vicinity of Cairo Metropolitan Area

Estimation of seismic wave attenuation in the shallow crust in terms of coda wave Q structure previously investigated in the vicinity of Cairo Metropolitan Area was improved using seismograms of local earthquakes recorded by the Egyptian National Seismic Network. The seismic wave attenuation was measured from the time decay of coda wave amplitudes on narrow bandpass filtered seismograms based on the single scattering theory. The frequency bands of interest are from 1.5 to 18 Hz. In general, the values obtained for various events recorded at El-Fayoum and Wadi Hagul stations are very similar for all frequency bands. A regional attenuation law Q _c = 85.66 f ^0.79 was obtained.     

Contents of Volume 54

Volume Contents

Contents of Volume 54