Nature of the Distributed of the Bed Sediment within Mosul Dam Reservoir, Iraq

Mosul Dam is one of the biggest hydraulic structures in Iraq. It was constructed in 1986 on the Tigris River in the north of Iraq. The initial storage capacity and water surface area of its reservoir reaches 11.11 km 3 and 380 km 2 respectively at the maximum operation level 330 m a.s.l. The dam was operated in 1986. A total of 56 samples were collected from the bottom of Mosul reservoir covering most of the reservoir area. The results of the analysis of these samples revealed that they were composed of gravel (3.8%), sand (15%), silt (55.5%) and clay (25.7%). The distribution of these sediments indicates that the silt portion represents the highest followed by clay and then sand. However, sand percentages are the highest in the northern zone of the reservoir where the River Tigris enters the reservoir and decreases gradually toward the dam site. In the meantime, silt percentage decreases toward the dam site while the finer fraction (i.e. clay) increases. Keywords.Mosul dam, reservoir sedimentation, sediment size distribution, sediment characteristics.