Design flood estimation in ungauged catchments and statistical characterization using principal components analysis: application of Gradex method in Upper Moulouya     

Mahmoud Zemzami  Lahcen Benaabidate  Badr Layan  Abdallah Dridri 《水文研究》2013,27(2):186-195

Design flood estimation in ungauged catchments is of great importance in hydrologic practice especially where there is no available data about streamflow. Except the watershed of Anseghmir who is equipped with a gauge station, all the other watersheds are ungauged catchments. The use of frequency analysis of series of rainfall and streamflow is very important for the characterization of the hydrologic resources of the Upper Moulouya. The region has a semiarid climate that requires a good knowledge of the watershed's potential water to assist policy makers in forecasting extreme events, managing water resources and decision making. The frequency analysis was used to determine the design flood of different return periods. The results obtained are used in Gradex method to estimate the hydrologic variables of each subcatchment of the Upper Moulouya. Once the hydrologic study is completed, a principal components analysis was made to highlight the affinities between the different subcatchments and to deduce the hydrologic and hydrographic parameters that better characterize them. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Age assignment of a diatomaceous ooze deposited in the western Amundsen Sea Embayment after the Last Glacial Maximum     

Claus‐Dieter Hillenbrand  James A. Smith  Gerhard Kuhn  Oliver Esper  Rainer Gersonde  Rob D. Larter  Barbara Maher  Steven G. Moreton  Tracy M. Shimmield  Monika Korte 《第四纪科学杂志》2010,25(3):280-295

Reliable dating of glaciomarine sediments deposited on the Antarctic shelf since the Last Glacial Maximum (LGM) is challenging because of the rarity of calcareous (micro‐) fossils and the recycling of fossil organic matter. Consequently, radiocarbon (¹⁴C) ages of the acid‐insoluble organic fraction (AIO) of the sediments bear uncertainties that are difficult to quantify. Here we present the results of three different methods to date a sedimentary unit consisting of diatomaceous ooze and diatomaceous mud that was deposited following the last deglaciation at five core sites on the inner shelf in the western Amundsen Sea (West Antarctica). In three cores conventional ¹⁴C dating of the AIO in bulk samples yielded age reversals down‐core, but at all sites the AIO ¹⁴C ages obtained from diatomaceous ooze within the diatom‐rich unit yielded similar uncorrected ¹⁴C ages between 13 517 ± 56 and 11 543 ± 47 years before present (a BP). Correction of these ages by subtracting the core‐top ages, which probably reflect present‐day deposition (as indicated by ²¹⁰Pb dating of the sediment surface at one core site), yielded ages between ca. 10 500 and 8400 cal. a BP. Correction of the AIO ages of the diatomaceous ooze by only subtracting the marine reservoir effect (MRE) of 1300 a indicated deposition of the diatom‐rich sediments between 14 100 and 11 900 cal. a BP. Most of these ages are consistent with age constraints between 13.0 and 8.0 ka for the diatom‐rich unit, which we obtained by correlating the relative palaeomagnetic intensity (RPI) records of three of the sediment cores with global and regional reference curves. As a third dating technique we applied conventional radiocarbon dating of the AIO included in acid‐cleaned diatom hard parts extracted from the diatomaceous ooze. This method yielded uncorrected ¹⁴C ages of only 5111 ± 38 and 5106 ± 38 a BP, respectively. We reject these young ages, because they are likely to be overprinted by the adsorption of modern atmospheric carbon dioxide onto the surfaces of the diatom hard parts prior to sample graphitisation and combustion for ¹⁴C dating. The deposition of the diatom‐rich unit in the western Amundsen Sea suggests deglaciation of the inner shelf before ca. 13 ka BP. The deposition of diatomaceous oozes elsewhere on the Antarctic shelf around the same time, however, seems to be coincidental rather than directly related. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Delineation of saltwater intrusion zones using the time domain electromagnetic method: the Nabeul–Hammamet coastal aquifer case study (NE Tunisia)     

Fatma Trabelsi  Abdallah Ben Mammou  Jamila Tarhouni  Carlo Piga  Gaetano Ranieri 《水文研究》2013,27(14):2004-2020

The time domain electromagnetic method (TDEM) is applied to monitor, to delineate and to map the saltwater intrusion zones in the Mediterranean Plio‐Quaternary aquifer. Forty‐two TDEM soundings were carried out in the coastal plain of Nabeul–Hammamet region (NE Tunisia). TDEM resistivity data were correlated with the existing borehole logging data to assign them to a particular lithology and to provide information about the position of the freshwater–seawater transition zone. The geoelectric sections showing the vertical configuration of seawater intrusion, with the brackish‐salty‐saturated zones, have a resistivity ranging from ~0.1 to 5 Ω?m and are detected at a depth lower than 1.5 m. The salinized zones are located at Nabeul (Sidi Moussa, Sidi El Mahrsi, Al Gasba and Mrazgua) and at Hammamet (Touristic zone of Hammamet north and south, Baraket Essahel) and reached a distance of 4 km from the coastline, indicating a severe state for the aquifer in these zones. These TDEM results are confirmed by the increase of chloride concentration content in the analysed water samples of monitoring wells. Moreover, in the northeastern part, the presence of a saltwater front located far from the coast and along the NW–SE major surface fault can be explained by two hypothesis: (i) this fault seems to provide a conduit for seawater to move readily towards the water wells and (ii) the clay and gypsum infiltration of marine Messinian deposits through the fault plane leads to low resistivities. Finally, it comes out from this study that TDEM survey has successfully depicted salinized zones of this coastal aquifer. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Geochemical exploration for gold in the Nile Valley Block (A) area,Wadi Allaqi,South Egypt     

Mohamed Abdallah Gad Darwish  Herbert Poellmann 《Chemie der Erde / Geochemistry》2010,70(4):353-362

The present work aims to estimate Au-anomalous distribution patterns, the optimum grain size fraction and pathfinder elements for gold placer. The obtained data of analyzed elements (Au, Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Ga, Hg, Li, Mn. Mo, Ni, Pb, Rb, Sb, Se, Sr, Te, Ti, V, Y and Zn) in both the fine (?0.25 mm) and coarse (?1 mm+0.25 mm) grain size fractions of 32 dry stream sediment samples, which have been derived from metamorphosed Island Arc volcanic rocks of Late Proterozoic age, revealed that most of the analyzed elements in both grain size fractions are asymmetrically distributed and did not pass the tests of normality. The coarse grain size fraction appears to be the better size fraction for Au detection and can be considered as the optimum grain size fraction for future application in regional stream sediment surveys. The presence of Au anomalies in the upper part of the stream and beside the mine is either sourced by the main Au-mineralization or new potential extension of the mineralization in the study area. Silver, Cd, Se, Zn and Te can be considered as useful pathfinder elements for Au in the coarse grain size fraction, and they may be used for future geochemical exploration for Au in the area. Recommendation of the authors is pointing to perform lithogeochemical survey in the eastern and western parts of the mine.  相似文献   

Piezometric levels as possible indicator of aquifer structure: analysis of the data from Maknassy basin aquifer system (Central Tunisia)     

Ismail Chenini  Abdallah Ben Mammou  Mohamed Moncef Turki  Eric Mercier 《Arabian Journal of Geosciences》2010,3(1):41-47

The knowledge of piezometric data is of vast interest in many applications, such as assessing groundwater flow direction and identifying recharge zone of the aquifer. In this paper, a methodology is presented as a complementary approach to characterize multilayered aquifer system structure and functioning using piezometric data and the cartography of the hydraulic charge difference. The methodology is presented to gradually discriminate the aquifer system levels and to evaluate the spatial distribution of hydraulic heads. The hydraulic charge difference mapping permits to track spatial evolution of the impermeable levels. The methodology has been applied over the Maknassy basin aquifer system, located in central Tunisia. The obtained results, showing the multilayered aquifer structure, are validated using hydrochemical approach and piezometric data not considered in the reasoning.  相似文献   

Palaeomagnetic correlation and dating of Plio/Pleistocene sediments at the southern margins of the North Sea Basin     

B. A. Maher  D. F. Hallam 《第四纪科学杂志》2005,20(1):67-77

A series of discontinuous sediment sequences, of Plio/Pleistocene age, occur onshore around the southern North Sea margins, notably in the East Anglian region of Britain. Intensive lithological and palaeontological analyses of these sediments have shown that they record both major and minor oscillations in climate, sea level and environmental conditions. However, significant uncertainties exist regarding the absolute and relative chronostratigraphies of many of these sequences, hindering understanding of the relative impacts of climatic, eustatic and tectonic changes on the palaeogeographic development of the southern North Sea basin. Here, a number of key East Anglian Plio/Pleistocene sites are subjected to robust palaeomagnetic and mineralogical examination, in order to determine those sediments which display reliable, syn‐depositional magnetic polarities, which are thus of use in ascribing a palaeomagnetically determined age from comparison with the Geomagnetic Polarity Timescale (GPTS). Based on a range of palaeomagnetic and complementary mineralogical methods, reliable palaeomagnetic directions were obtained from eight sites, with reversed polarities displayed by sediments from three sites. These polarity determinations can be used to infer absolute ages and test published, between‐site correlations. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Support vector regression to predict asphalt mix performance     

Maher Maalouf  Naji Khoury  Theodore B. Trafalis 《国际地质力学数值与分析法杂志》2008,32(16):1989-1996

Material properties are essential in the design and evaluation of pavements. In this paper, the potential of support vector regression (SVR) algorithm is explored to predict the resilient modulus (M_R), which is an essential property in designing and evaluating pavement materials, particularly hot mix asphalt typically used in Oklahoma. SVR is a statistical learning algorithm that is applied to regression problems; in our study, SVR was shown to be superior to the least squares (LS). Compared with the widely used LS method, the results of this study show that SVR significantly reduces the mean‐squared error and improves the correlation coefficient. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Geochemical reconnaissance survey and environmental assessment for stream sediments of Wadi Um Gier,Southeastern Desert,Egypt     

Mohamed Abdallah Gad Darwish 《Environmental Earth Sciences》2011,62(3):657-672

The purposes of this study were to assess the influence of old mining activities on the geochemistry and quality of sediments and to identify the sites of economic elements. Thirty sites of stream sediment were sampled in the study area covered by granitic, metarhyodacitic and meta-andesitic rocks and related tuffs-hosted abandoned Au mine. The suite of chemical elements, Ag, Bi, Cd, Cu, Fe, Ga, Hg, Mn, Nb, Pb, Rb, Sb, Se, Sn, Te, Th, U, Y, Zn and Zr, pH value and total organic carbon were determined, and univariate, bivariate and multivariate statistical methods were applied. The results show that the enrichment factor (EF) is very high in the case of Te and significant also with respect to Ag, Bi, Cu, Sb, Se, Sn and Zn. Likewise, geoaccumulation indices (Igeos) varied from very highly polluted with Sn and Te, strongly to very strongly polluted with Bi and Se, and moderately polluted with Sb. The polluted sites of Ag, Bi, Sb, Se, Sn and Te were outlined using Igeos maps, and economic sites of Ag and Sn were identified by geochemical maps leading to their sources, which are likely to be mining activities and lithogenic processes. The pollutant elements may cause toxicity in stream sediments, or surface or underground water, as well as plants and animals in the area. This investigation provides an environmental baseline for future monitoring of possible human/anthropogenic, industrial and agricultural impacts on the study area and considers an attempt at re-mining Ag and Sn.  相似文献   

Evaluation of archaeological site potential on the Tall al-Kharrar area (Jordan) using magnetic and resistivity methods     

Awni Batayneh  Abdallah Al-Zoubi  Ula Tobasi  George Haddadin 《Environmental Geology》2001,41(1-2):54-61

  相似文献   

Contribution de la gravimétrie à l'étude de la structure de la plaine de Mornag (nord est de la Tunisie): implications hydrogéologiques     

Boutheina Farhat  Ramdhane Benassi  Chokri Jallouli  Abdallah Ben Mammou 《水文科学杂志》2013,58(8):1396-1404

Résumé

Cette étude est basée sur l'analyse des données gravimétriques; elle a pour but d'améliorer la connaissance de la structure de la plaine de Mornag. La carte de l'anomalie résiduelle a d'abord été calculée à partir de la carte de l'anomalie de Bouguer en enlevant un gradient régional. La résiduelle calculée fournit des informations sur la variation de la densité dans le bassin de Mornag. Afin de mettre en évidence les différentes structures dans le bassin, nous avons calculé la magnitude du gradient horizontal (MGH). Cette technique a permis de déterminer des linéaments gravimétriques représentant l'emplacement des contrastes de densité, et de déduire une carte structurale de la zone d'étude. Cette carte constitue un document très utile pour orienter l'exploration des ressources en eau dans la plaine de Mornag.

Citation Farhat, B., Benassi, R., Jallouli, C. & Ben Mammou, A. (2010) Contribution de la gravimétrie à l'étude de la structure de la plaine de Mornag (nord est de la Tunisie): implications hydrogéologiques. Hydrol. Sci. J. 55(8), 1396–1404.  相似文献