AbstractsEngineering

Reservoir sedimentation is the main problem that directly affects the performance of dams due to the reduction in the storage capacity of their reservoirs. Monitoring the storage capacity of reservoirs is an important issue for the planners, designers and operators of the dams. Iraq mainly depends on the rivers Tigris and Euphrates for its water resources. Until the 1970s, Iraq was regarded as a rich country with regard to its water resources, due to the presence of the Tigris and Euphrates rivers. Recently, its water resources have decreased significantly due to an increased water demand and global climate changes. In view of this situation, it became necessary to know about Iraq’s water resource trends to adopt prudent water resource management strategies. Among these strategies is the assessment of the sedimentation rates in its reservoirs to determine their actual storage capacities and reduction rates of storage capacity through time. Mosul Dam Reservoir (MDR) is the biggest and one of the most important strategic projects in Iraq. It is a multipurpose project constructed to store water and to handle flood control and hydropower generation but the main purpose was to provide water for three irrigation projects that cover 2,500 km2 of agricultural areas. The dam is located on the River Tigris in northern Iraq, 60 km north-west of the city of Mosul. The project was designed to store 11.11 km3 with water surface area of about 380 km2 at the maximum operation level 330 m a.s.l. It is noteworthy to mention that MDR has operated since 1986, and no detailed studies have been carried out to determine the sedimentation characteristics in its reservoir since that time. In the present work, the storage capacity, sedimentation rates, area-storage capacity (ASC) curves, sediment nature and their grain size distribution and bottom morphology of its reservoir were studied. Direct and indirect methods were used to achieve these goals. In the direct methods, two topographic maps for MDR’s area were established in a triangular irregular network (TIN) format using Arc/GIS software. One of them before dam construction from pre-construction topographic map scale 1:50000 and other from bathymetric survey that was conducted in 2011. These maps were used; to calculate the volume of deposited sediment, to develop and evaluate ASC curves, to determine the bed morphology and to estimate the useful life of MDR. The results of the two surveys indicated that 1.143 km3 of sediment were deposited in MDR during the 25 years of its operation. This implies that the reduction in its original storage capacity was 10.29% with an annual reduction rate of 0.441% which is less than the sedimentation rates in the worldwide and Middle East. Furthermore, the results showed that 0.563 km3 and 0.58 km3 of sediment were deposited in live storage and dead storage zones respectively. This indicates that the live and dead storage zones lost 6.9% and 19.66% of their storage capacity till 2011 respectively. According to these results, MDR’s useful life will be…