Abstract
According to the agreement between Egypt and Sudan in 1959 for the full utilization of Nile water arriving Aswan, both countries agreed to build the High Aswan Dam (HAD) in 1964 to get benefits from the water which was flowing to the Mediterranean Sea. Therefore, Lake Nasser, the greatest artificial lake in the world, was created with large areas of shallow depths adjacent to the edges of the lake on both sides according to the topography of the surrounding area namely (khores). These khores increased the surface area; consequently, the estimated evaporation losses reach about 10 BCM/year in average. Reducing evaporation losses from HAD Lake is an option to increase the Egyptian available water resources. Many studies were done in order to partially or completely closure of the Khores, where the surface area of the khores of Lake Nasser is about one third of the total area of the lake, which indicates the effectiveness of its closure in decreasing the evaporation. The objectives of the research are studying the Lake Nasser’s large area khores, evaluating the idea of closing these khores using different types of dams such as earthfill, rockfill and rubber dams, and the consequent saved water. Meanwhile, a preliminary cost study for the different types of dams was done to determine the most suitable dam type. This research used the land sat 4 & 5 at years 1988 and 1999 in order to identify the surface area of the lake for the lowest and highest levels respectively. Also it gets benefit from the data available at Ministry of water Resources and Irrigation (MWRI), such as the Khores bathymetric maps and the evaporation rates of Lake Nasser. The results of the study show that Kalabsha khore is the most optimum for dam closure as its entrance is suitable for dam construction, and at high water levels it has the greatest area thus, reducing the evaporation. It is highly appreciated to use rubber dam either economically or environmentally. The amount of saved water reach about 1.0 Milliard m3 representing 11.11% of the annual total evaporation losses from Lake Nasser, the water saved may reach 1.53 Milliard m3 if the water level reaches 181.52 m for considerable time span.
Highlights
The water losses of the High Aswan Dam (HAD) lake due to evaporation are one of the major problems facing the management of Egyptian water resources, where increasing the surface area of the lake at high levels and high temperature is the main raison for increasing the rate of evaporation.The designed value for annual average water losses from Lake Nasser was assumed to be 10 km3, 90% of it covering evaporation from its water surface and 10% for percolation and seepage along its soil surface
After supervised classification of the satellite images, it was analyzed to calculate the surface area of the large Khores, at the highest and lowest water levels occurred in the lake, which expected to affect the amount of evaporation losses from the Lake and the shape of connection
Comparing the surface area of the lake with satellite images at the lowest and highest water levels, it can be concluded that there are three Khores characterized by large surface area which are (Toshka - Allaqei - Kalabsha) khores, as summarized in Table II and “Fig. 4”
Summary
The designed value for annual average water losses from Lake Nasser was assumed to be 10 km3, 90% of it covering evaporation from its water surface and 10% for percolation and seepage along its soil surface. The latest study was by [2] for complete khore closure through integration of remote sensing, (GIS), aerodynamic principles, and Landsat images to determine the best khore that should be disconnected to reduce evaporation losses. It was based on many approximations as it assumed average depth for all water body through the khore deduced from the satellite images, which isn't suitable to rely on it in the design of suggested dams. In the present work the water depths get from bathymetric maps
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