Flood evaluation and management after the high dam reservoir

The control of fluctuating river floods is not only achieved by building dams across water courses, but also by the optimum choice of the Dam site to utilize the geological and geographical nature of the dam site and the surrounding area to maximize the benefits from the dam construction and minimize the side effects along the water course from its sources to its debouchments, This achieves the following objectives: Flood management and flood control. Maximize water storage capacity upstream the dam. Dam safety. Improve the environment and maximize the benefits from valuable water resources. The River Nile is a good example for that, where its flood fluctuates from very high flood (150 milliard cubic meter per year) to high (120 milliard cubic meter per year) to medium (84 milliard cubic meter per year) and finally to low floods (40 milliard cubic meter per year). Moreover it is observed that high flood comes strong, giant in the peak months (August, September, October and November), weak in months (March, April, May, June) and narrowly cover the requirements. This nature of the River Nile has been subject for monitoring and evaluation by the Egyptians along the history. Since the Egyptians discovered the sources of The River Nile, they kept collecting hydrological and meteorological data. These include water levels, discharges, water depths, morphology and nature of the basin and the valleys, winds, precipitation, and the nature of the area around its course from the upper reaches in the Ethiopian and lake plateaus to its debouchments at the Mediterranean Sea. The River Nile became one of the most ideal rivers with this great amount of data with numerous studies and researches. Processing the available data, a great amount of information was deduced which helps the Egyptians to control the lower floods to maximize the benefits and avoid harmful effects. The High Aswan Dam was constructed during the years 1960-1970. It was provided with supplementary works such as Toshka spillway. Toshka spillway is a free canal spillway, 22 km long and connects Lake Nasser at khur Toshka with a group of four natural depressions in the western desert named (Toshka Depressions).The spillway canal lies at 250 km. south of the High Dam. The aim of this paper is to clear the importance of this spillway, and its role in the River Nile flood management.