Characteristics of the delta formation resulting from sediment deposition in Lake Nasser, Egypt: Approach to tracing lake delta formation

摘要

A major problem encountered by managers of large reservoirs, such as Lake Nasser (located in the south of Egypt), is the continuous deposition of sediments, resulting in a bed-level increase, a decrease in lake capacity, and the creation of a new delta that might eventually hinder navigation. To investigate the sedimentation problem in Lake Nasser, a series of surveyed cross-sections were reviewed and samples of suspended sediment and bed material collected. These sets of data were analysed to investigate the progress of the delta formation, the change in its properties in all directions and the corresponding patterns of suspended and deposited sediment particles. Results showed that deposited sediments, characterized by a variable pattern of particle composition, are building up at the lake entrance. Although the expansion of the delta is multidirectional, its accelerated advance towards the High Aswan Dam would depend on the frequent occurrence of high floods following extended drought periods. Based on the calculated deposited sediment volume in Lake Nasser during the period 1964–1998, the lifetime of the dead storage zone allocated for sediment deposition (31 × 109 m3) is estimated at a minimum of 310 years.