Koysha: The 2,160 MW Hydroelectric Power Project

Koysha hydropower project, located in the southern part of Ethiopia, has a capacity of generating 2, 160 MW of electricity and it is the biggest hydropower project in Ethiopia next to the Grand Ethiopian Renaissance Dam (GERD).

As per the ten-year strategic plan of the ministry, Ethiopia needs some 20,000 MW electric power for its national economic development aspired to be realized after 12 years, Eng. Seleshi said.

The ministry has also planned to provide electric services to all parts of the country over the coming five years, he stated.

Hence, the government of Ethiopia is making efforts to complete the construction of the Koysha hydropower project in three years, the minister pointed out.

According to the minister, the construction of the power plant will be carried out with a capacity to hold only 6 billion cubic liters of water as the project is expected to use water from the nearby Gibe 3 hydropower, and this expedites the completion of the construction within the stated period.

The speedy completion of the project will also contribute a lot to the efforts being made to make the area one of Ethiopia’s key tourist destinations, Seleshi added.

The construction work of the Koysha hydropower project, whose agreement was signed some four years ago, has now reached 39 percent and created 4,000 jobs.

Koysha is one of the new tourist destination development projects in the Southern Nations, Nationalities, and Peoples’ Region along with Gorgora and Wonchi located in Amhara and Oromia regional states, respectively.

The Koysha hydropower project is a 2.16GW hydroelectric facility under construction on the Omo River in the Oromia region of Ethiopia.

State-owned public utility enterprise Ethiopian Electric Power (EEP) is developing the project with an estimated investment of approximately £1.93bn ($2.80bn). The civil construction works on the project were started in October 2016.

Once completed, the Koysha hydropower project is expected to generate up to 6,460 Giga watt-hours (GWh) of electricity while offsetting approximately one million tonnes (Mt) of CO₂ annually.

The Koysha hydroelectric power project is located on the Omo River, approximately 370km southwest of the capital city Addis Ababa. The other hydroelectric facilities built on the Omo River include the Gigel Gibe (200MW), the Gibe II (420MW), and the Gibe III (1,870MW) power stations.

Koysha hydroelectric power plant make-up

The Koysha hydroelectric power project comprises a 180m-high, roller-compacted concrete (RCC) gravity dam, and a 250m-long, 41m-wide, and 60m-high surface powerhouse equipped with eight Francis turbine units of 270MW rated capacity each.

The RCC gravity dam with a crest length of 990m will create a reservoir capacity of nine billion cubic meters (bcm). The project also features a 330m-long and 42m-high cofferdam.

The main dam will have six spillway gates, 20m-wide and 17m-high, with a discharge capacity of 13,100m³/s. The project also involves the construction of a diversion canal and two 6m-diameter middle-level outlets embedded in the dam body to control the reservoir level.

The power station will utilize three 650m-long steel penstocks, one of which will be lowered to facilitate early power generation using the first two units during the first impounding.

The other electrical component of the power station includes a total of 24 transformers, including three single-phase 400kV transformers and a switchyard.

Ancillary infrastructure facilities

The ancillary infrastructure facilities for the Koysha hydropower project will include a bridge over the Omo River, temporary and permanent camps, access roads, a landing strip, as well as crushing and batching plants.

Power evacuation

The electricity generated by the Koysha hydroelectric power station will be evacuated into the grid through a 400kV overhead power transmission line.

Financing

Italian export credit agency Servizi Assicurativi del Commercio Estero (SACE) agreed to provide £1.15bn ($1.68bn) of financing for the Koysha hydroelectric power project in April 2016.

Contractors involved

Italian construction and civil engineering company Salini Impregilo (now Webuild) signed an engineering, procurement, and construction (EPC) contract for the Koysha hydropower project in May 2016.

Studio Peitrangeli Consulting Engineers were subcontracted by Salini Impregilo for the engineering services and technical supervision of the project. The scope included pre-feasibility and feasibility studies, as well as the basic design of the power project.

Pizzi Instruments was subcontracted by Salini Impregilo for the supply of monitoring instruments, including vibrating wire piezometer, CUM3000 datalogger, and meteorological devices in July 2016.

Tractebel Engie was selected as the project consultant by EEP for the Koysha power station, while VAW was subcontracted to perform physical model tests on the middle-level outlets, along with the jet trajectories and scour formation in the downstream section.

Stantec was selected for the contract management services for the Koysha hydroelectric power project