الفهرس 
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Abstract
Lake Nasser is an enormous rock bounded water reservoir with a very irregular shoreline. It stores the Egyptian and Sudanese water share budget from the Nile River catchment. Since, 1960s the construction of High Aswan Dam, there is an increasing demand for understanding the sedimentation processes along Lake Nasser. The main objective of this thesis is to study the sedimentological and geomorphological processes in Lake Nasser using integrated modern approaches and techniques. In-situ sampling of bottom surface sediments, core sampling of deeper sediments and measurements of the hydrographic physico-chemical parameters were carried out along the lake between latitudes 21° 02’ 33’’ N and 23° 38’ 55’’ N and longitudes 30° 38’ 42’’E and 32° 54’23’’E.
Generally, the lake sediments are essentially controlled by the hydrographic physico-chemical parameters concerning the current velocity, temperature, turbidity, suspended sediment concentration, TDS, EC and pH. Therefore, there was a need to study the physico-chemical properties of the Lake water.
Air temperature ranged from 17°C to 31°C; whereas, water temperature ranged from 16.2°C to 24.6°C. The current velocity decreased northward from 45 to 2cm/sec, pH increased from 7.7 to 8.56, EC increased northward from 170 to about 260µmohs/cm, TDS concentration increased from 110 to 165 mg/l, turbidity decreased from 97 to 1.2 NTU, suspended sediments concentration decreased from about 107 to 3 mg/l. All of the hydrographic parameters showed the differentiation of the lake into its two main southern and northern geographic parts. Along the southern part of the lake, the northward increase of profile area accompanied with the decrease in each of the current velocity (from 41.4 to 16.9 cm/sec), suspended sediments concentration (from 99 to 68 mg/l) and turbidity (from 95 to 55 NTU) with nearly no change in TDS, EC and pH. Along the northern part at the south of Abu-Simbil (Arqeen Zone), the northward increase of profile area accompanied with the decrease in each of the current velocity (from 16.9 to 4.5 cm/sec), suspended sediments concentration (from 37 to 17 mg/l) and turbidity (from 25 to 10.15 NTU) and with the increase in each of TDS (from 115 to 134 mg/l) concentration, EC (from 187 to 209 µmohs/cm) and pH (from 8.25 to 8.45). North of Abu-Simbil, the northward increase of depth accompanied with the increase in each of the current velocity (from 4.5 to 16.18 cm/sec), TDS (from 134 to 163 mg/l), EC (from 209 to 255 µmohs/cm) and with the decreased in each of the suspended sediments concentration (from 17 to 4mg/l), Turbidity (from 10 to 1.4 NTU) and pH (from 8.45 to 8.25).
The hydrographic parameters were examined to be obtained from remotely sensed by satellite imaging, based on statistical correlation models. All of these parameters were strongly interrelate to the radiance values of the optical bands through polynomial correlation. It enabled to estimate and map the spatial distribution of each of the hydrographic parameters. This technique proven to provide value added information to decision makers and planners about the state of the lake on robust manner with minimum or no field observation.
In this study the surface layer of the bottom sediments was analyzed to determine its characteristics that are in a direct contact with the transporting and depositing agents. Recognizing the statistical parameters distribution, the lake was classified into a riverine and a lacustrine environment of deposition. The riverine environment extended between El-Daka and C-C, whereas, the lacustrine environment extended along the rest of the lake. Some statistical parameters were calculated to understand the variation in the sediments characteristics. These parameters included; median diameter (MdØ) ranges from 1.66Ø (medium sand) to 11.36Ø (clay) with an average of 8.14Ø (very fine silt), mean size (MzØ) ranged from 1.65Ø (medium sand) to 10.84Ø (clay) with an average of 7.97Ø (fine silt), inclusive sorting σI from 0.29Ø (very well sorted) to 3.64Ø (very poorly sorted) with an average of about 1.94Ø (poorly sorted), skewness SkI ranged from -0.76 (strongly coarse skewed) to 0.75 (strongly fine skewed) with an average of -0.10 (coarse skewed), and kurtosis (KG) ranged from 0.58 (very platykurtic) to 4.41 (extremely leptokurtic) with an average of about 1.28 (leptokurtic).
Along the riverine environment the river processes were the prevailing. Therefore, the bottom sediments are composed mainly of sand (87 to 100%) mixed with small ratios of silt (zero to 10%). MzØ of the bottom sediments mainly exceeded MdØ influencing with its skewness towards the fine fraction. The distribution of each of MdØ and MzØ described the capability of the sedimentation processes to deposit sediments grains as coarse as medium and fine sand. In addition, the well sorting, the fine skewness and the leptokurtic grain size distribution represent a high degree of texture maturity along this part. Along the southern part of the lacustrine environment (south of the 2nd Cataract), the influence of river processes rapidly decreased giving rise to the slow deposition from quite water to operate. Accordingly, north of Atiry, sand formed no more than 5% of the bottom sediments, silt 36 to 58% as average values, whereas clay 18 to 59%. Along the northern part of the lacustrine environment, the slow deposition from quite water prevailed; therefore, the bottom sediments were sand free. Along this segment of the lacustrine environment, the bottom sediments composed mainly of clay (57 to 84%) and silt (14 to 37%).
Further comprehensive understanding of the sediment of the lake, the core samples were collected and analyzed along the mid-line of the lake between Atiry (30° 58’ 31.64’’E & 21° 27’ 42.07’’N) and Adendan (31° 26’ 25.10’’E & 22° 10’ 15.11’’N). The collected core samples were employed in determining the mineralogical composition. The values of its statistical parameters were widely varied; MdØ ranged from 2.62Ø (fine sand) to10.12Ø (clay) with an average of 7.76Ø (fine silt), MzØ from 3.57Ø (very fine sand) to 9.94Ø (clay) with an average of 7.86 Ø (fine silt), σI from 1.78Ø (poorly sorted) to 2.96Ø (very poorly sorted) with an average of 2.25Ø (very poorly sorted), SkI from -0.44 (strongly coarse skewed) to 0.58 (strongly fine skewed) with an average of 0.09 (nearly symmetrical), KG from 0.74 (platykurtic) to 1.60 (very leptokurtic) with an average of 1.03 (mesokurtic). They composed of; about zero to 71% sand, 24 to 82% silt and 3 to 75% clay. So, Silt and clay sized particles were the main component.
To determine the mineralogical composition, the sediments were examined using the X-Ray diffraction. The pattern of X-Rays proven that the sediments composed mainly of montmorillonite, kaolinite and illite as clay minerals in addition to quartz, feldspar and calcite as non clay minerals. The abundance of the bulk non clay minerals was estimated to increase with the increase of the grain size. Quartz was estimated as the most abundant non clay mineral (0.35 to 0.77 parts of the unit) followed by feldspar (0.18 to 0.53) then calcite (0.12 to 0.29). With the decrease of grain size, the abundance of quartz found to decrease, calcite increased, whereas, feldspar increased south of Gomay and decreased north of Gomay.
Montmorillonite, was estimated as the main clay mineral constituent (0.685 to 0.917 parts of the unit) followed by kaolinite (0.040 to 0.142) and illite (0.025 to 0.207). Along the southern part of lacustrine environment, the core average montmorillonite content increased northward, relative to the other clay mineral constituents, from 0.838 at Atiry to 0.876 at the Second Cataract, whereas, kaolinite fluctuated between 0.053 and 0.093 and illite between 0.030 and 0.096. North of Gomay, the core average montmorillonite and kaolinite proportions decreased northward to 0.724 and 0.079 respectively by Adendan, whereas, illite increased to reach 0.147 by Arqeen and nearly did not change further north. However, the quantitative estimation of the clay minerals percentage content in the core sampled sediments explained that montmorillonite ranged from 2.8 to 65 %, kaolinite from 0.14 to 7.72 %, illite from 0.33 to 14.02 %.
For more realistic representation of all of the sediment parameters and analysis, they were mapped and presented using GIS to spatially show the distribution of the sediment characteristics along the lake. When spatially presented it more aligned with the sedimentological process of lacustrine and riverine environment. It enabled for understanding the controlling factors of such sedimentation process.