Evaluation of the lnitial Filling Stage for Dams Case Study:Dam Complex of Upper Atbara and Setit Reservoir

Abstract

This research deals the initial filling stage of dams reservoir as the real test of the dam components (embankments, foundations, concrete bodies), as it gives a real assessment of the suitability of the theoretical design of the dam to the reality after construction and operation, and it expresses the extent of the dam for the purposes for which it was created (irrigation, hydropower generation, flood control and protection, etc.). The Dam Complex of Upper Atbara Project (DCUAP) is selected as a case study, because of the unique design of this giant project in terms of storing water from two different rivers having different hydrological and geological nature in one reservoir by constructing a connecting channel in the upstream between the two dams (Upper Atbara and Setit). The researcher developed a mathematical model on excel format basis on water balance calculations of upper Atbara and setit dams as described below:  The daily measured time series of inflow at Burdana hydrological station which is located on the downstream setit dam & Rumela hydrological station which is located on the downstream upper atbara dam had been used.  The statistical analysis erected on discharge measurements shows that 2011 data is representing a dry year (worst case), for the normal year the averaged inflow of the 5 years had been used.  The start of the filling is intended to be as late as possible in order to minimize the sedimentation in the reservoir.  The required storage volume is determined by the water requirements for irrigation, urban water supply, environmental flow and hydropower.  Various rates of filling are used to ensure the dam safety and to calculate the increase in water level and water content in the reservoir and to determine the period required to achieve targeted level. DCUAP initial filling stage had been planned to start in the flood season (2014) to reduce to the maximum operation level (521) ASL, however, due to some constraints the construction progress of the project was delayed, consequently the impounding also delayed. the initial filling took place between (15Augest to 19 October 2015) with final elevation of 514 m ASL .since, DCUAP is part of the national water resources management system, and due to unexpected demand (for v Evaluation of the initial Filling Stage for Dams October - 2017 power generation) in Merowe Dam, the filling was stopped at level 514.00 m ASL on 8 November 2018, with a total accumulative storage of 1.993 million cubic meters. Inflow was released in order to satisfy the demand in Merowe Dam. During and after filling a daily inspection program was carried out for all dam components to monitor and observe damages usually caused by the initial filling, it turns out that there is no signs of failure or any damage in the embankments, foundations. DCUAP first filling stage has achieved the target objectives from the point of view of the researcher, and it became clear after the evaluation and technical analysis of many data and information (design documents, construction methods, hydrological observations, and the engineer (LI) recommendations).