Aerating weir at Lom Pangar dam

Lom Pangar is a new dam under construction in Cameroun. Its aim is mainly flow regulation of the Sanaga River in order to improve and secure hydropower production of downstream facilities. To reduce impact on water quality and especially on dissolved oxygen for 25 to 100 m3/s discharge, an aerating weir is going to be implemented downstream of the dam for at least the 10 first years of the dam exploitation. After site selection, preliminary studies have conducted to chose a rockfill stepped weir for technical reasons including availability of materials on the dam work site and asier
decommissioning. According to literature, nappe flow is the flow regime providing most effective aeration for this type of structure and application of formulae to the discharge range and geometry of the project leads to choose 50 cm high steps to create this flow regime. The proposed solution has been tested using a 1:1 scale physical model, with the following geometry: 3 m high and 15° downstream slope. Dissolved oxygen concentration has been measured in the upstream reservoir, in the downstream collecting channel and on several steps. Aeration efficiency has been measured
and the physical model has been able to validate and optimize the weir design in order to reach the water aeration objectives and limit hydraulic impacts. The works are planned beginning 2017 and water aeration will be monitored.