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Universität Tübingen (2013)

Application of GIS and remote sensing for water resource management in Arid area – Wadi Dahab Basin – South Eastern Sinai-Egypt (Case-study

Omran, Adel Fouad Abdou

Titre : Application of GIS and remote sensing for water resource management in Arid area – Wadi Dahab Basin – South Eastern Sinai-Egypt (Case-study)

Anwendung von GIS und Fernerkundung für die Bewirtschaftung der Wasserressourcen in Trockengebieten - Wadi Dahab Basin - Süd Ost Ägypten (Case-Study)

Auteur : Omran, Adel Fouad Abdou

Université de soutenance : Universität Tübingen

Grade : Dr. Rer. Nat. 2013

Résumé
The present work is conducted to estimate the flood risks areas in W. Dahab and to design a suitable management system to control its huge runoff quantities. Hydrogeological and -chemical investigations are necessary in order to define the water pollution and manage the available water resources in the study area. Moreover, Maps indicating the natural water resources should be drawn to show the future review of these resources and setting of the suggested tools to manage water resources in the study area. Many of investigations have been done for reaching the aim of this work. Geologically, Wadi Dahab catchments are covered mainly from Precambrian to Cretaceous rocks and Wadi deposits cover the valley floors of the main streams. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) has been used for lithological mapping in the study area. Band ratio and supervised classification were employed for the classification and discrimination of different rock types. The density lineament map shows that the high density area is recorded at the basement area especially in the eastern and southern parts of Dahab basin, while the low density area is located in the northern part of study area. Based on the Aster Digital Elevation Model, the drainage patterns of the Wadi’s sub-basins are delineated, the sub-basins are morphometrically analyzed to assess flash flood susceptibility. The parameters were computed using ESRI’s ArcGIS 9.3, enriched by some Visual Basic (VB) code to compute stream numbers according to Strahler Theory. The results of the study show that more than 35% of the sub-basins have high susceptibility of flooding. The unconfined aquifers in the study area could be differentiated into alluvial aquifer and fractured basement aquifer. Fractures play a vital role as conduits-fractures from the recharge zone to feed the production wells in the low-laying fault zones of the basement aquifer. Due to their wide spatial distribution, the hydraulic conductivities of fractured basement rocks have been estimated at some locations in W. Dahab using the remote sensing techniques and deterministic district fractured network (DFN). The results show that the hydraulic conductivities range between 2.3 × 10-7 to 6.1 × 10-7 m/s with an average of about 4 × 10-7 m/s (2 mm/hr). The chemical analyses show that most of the dissolved ions in groundwater originate mainly by weathering of rocks forming minerals. The analysis shows that some substances such as NO3, F, U, B and As affect human health directly and have concentrations above the limiting values of WHO. Those wells bearing groundwater of acceptable quality are specified in the study. Most of wells are suitable for drinking purposes, while wells in the downstream of Dahab basin, most wells in W. Saal and one well (R1) in W. Rimthy are unsuitable for drinking purposes. The study area has an arid to desertic climate with high rainfall intensity during storm events, high temperature and high evaporation rate. Occasional heavy rainfall storms cause dangerous flash floods. W.Dahab basin receives 66 Mm3 annually. During a maximum storm event, the rainfall enters at up to 76mm/day (150 Mm3/storm). Approximately 48% of the maximum rainfall contributes to dangerous runoff events. The results show that W. Zaghraa has the highest flooding risk in W. Dahab It can be seen that the wadi path W. Rimthy-W. Zaghraa Nasab – W. Zaghraa in the middle and southwestern part of Dahab basin is the most risky route for runoff which directly affects the downstream area of Dahab basin, while the northern part of Dahab basin is considered a low risk area for runoff especially in W. El Genah, W. Saal and northern part of W. El Ghaieb. A system of cisterns, detention and reservoir dams in addition to mitigation canals is proposed to control floods in risky basins. This system is very important to enhance recharging the existing aquifers in the wadis. This system is suggested at the risky subbasins such as W. Rimthy, W. Nasab, W. Saal and W. Abu Khshieb. The total storage capacity of the proposed design at W. Rimthy may store a maximum of 1.6 Mm3 of flood water with an efficiency of about 10.6% of the total runoff at maximum rainstorm. It is estimated that the proposed system for protection in W. Nasab can store as a maximum 7 Mm3 of runoff water with an efficiency of about 43% of the maximum rainstorm. Finally, an integrated approach using GIS and remote sensing was adopted to find new potential sites for groundwater exploration in the Dahab basin. Six different effective weighted parameters were included such as annual rainfall, lithology, lineament density, topography, slope and drainage density. The final map of groundwater potential shows that about 19.5% in W. Dahab is classified as high potential areas for groundwater exploration, concentrated in the northern part of study area and in some parts along the main stream of W. Nasab and W. Zaghraa.

Mots clés : Fernerkundung , Geoinformationssystem , Abfluss , Verschmutzung des Grundwassers , Ägypten , Trockengebiet ; Remote sensing , GIS , Runoff , Groundwater pollution

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Page publiée le 30 novembre 2013, mise à jour le 11 janvier 2019