Developed by Angola’s Ministry of Energy and Water (MINEA), the Caculo Cabbala hydropower plant project is a 2,172 megawatt run-of-the-river hydroelectric facility under construction in Kwanza Norte Province of the Southern Africa country, approximately 19 kilometers upstream of the Lauca hydropower station and 270 kilometers east of Angola’s capital city Luanda.
The project comprises the construction of a 103m-high concrete dam with a crest length of 553 meters. The maximum length of the reservoir will be 16.3 kilometers and an area of 16.6 km2 will be inundated. The dams’ storage capacity of 440 million cubic meters.
The dam’s hydraulic structure includes a controlled frontal spillway with five radial gates and a flow rate of 10.02m3/s. The bottom outlet of the structure is formed by two-lined tunnels while its central body comprises 2 saddle dams, closed by concrete weirs, 525m and 192m long, and 36m and 4m wide respectively.
The water intake structure for the Caculo Cabaca hydropower plant will be located about 2.4 kilometers upstream of the dam’s left abutment.
The project also involves the construction of an underground powerhouse equipped with 4 530 megawatt turbine-generator units, as well as a 52 megawatt ecological power plant situated adjacent to the dam. The underground powerhouse, whose cavern measures 221m-long, 26.5m-wide, and 68m-high, will receive the water supply through four 300m-long concrete-lined headrace tunnels with an inner diameter of 9m each.
The turbines inside the powerhouse will operate with a design water flow rate of 1100m3/s, while the water operating head between the reservoir and the power plant is 215m. The water from the powerhouse will be released back to the river through two 16m-diameter, and approximately 5.1km-long concrete-lined tailrace tunnels.
Noteworthy, the 52 megawatt ecological power plant will also have its water intake, headrace tunnel, and tailwater canal facilities. Its turbine will be designed to operate at a water flow rate of 60m3/s.