Preserving the Omo Valley – Tapping into what Gibe III offers

Partial view of the dam under construction from upstream (pictured, above)

Chisha Chinesho, 25, joined the Gibe III dam construction crew inside the hot Omo River valley two years ago. He says the commencement of the dam construction project, more than seven years ago has created job opportunities for hundreds youth from his homeland, Wolayta. Chisha, who completed secondary school a few years before, has managed to pay the fee and attend the night school at Wolayta University during the hours after his work and the income he got has also helped him to biuld a house for him and his families. Many youth, drawn from different corners of the country are persevering day and night, to make the plan to start generating power from the first turbine of Gibe III dam a reality.

This dam is the third scheme in the Gibe-Omo Cascade, located along the lower course of the Omo River,155-kms downstream of Gilgel Gibe II power plant. The installed capacity of the plant is 1870MW with annual energy production of 6,500GWh This is expected to double the present installed capacity of the country. Salini Constructtori, the globally renowned Italian firm in dam construction, is granted with the civil works while the Chinese Dongfang is responsible for the electro-mechanical work. As it started completion of the project was scheduled to be on 2014, however, the unexpected geological and other factors have contributed for its delay. Abayneh Getnet, Civil works supervisor with the project, says amid all the natural and other challenges, major tasks that could transform the process of the construction into a key level have been successfully undertaken. The boring of two tunnels, each with one kilometer length, to divert the river and that of the third tunnel, that is used to take the water from the dam to the powerhouse to hit the turbines and generate power is fully completed.

The first unit is scheduled to start generating power during the first few months of next year, Abayneh noted. At present the construction of the dam itself is consuming about 20 MW power everyday, most of which is generated from diesel generators. To meet the plan ahead, the task to finish the 246 meters long roller compacted dam, which will be one of the highest of its kind in the world, is well underway that more than 250 thousand meter cube of concrete is compacted every month. The artificial dam, that will be expected to cover about 150 kilometers long land upstream, is to create a good opportunity for fishing and irrigation to thousands dwellers nearby the dam.

According to Abayneh, the Roller Compacted Concrete (RCC) technology has helped the project not only to undertake its task at a faster rate than before, but also to reduce its amount of cement use by one third. The Italian and French companies are engaged in joint consultancy the project expected to cost more than 1.74 billion euros. Eyuel Solomon, Civil Works Supervisor at the site, says to make the dam fully operational via its ten turbines after the start of power generation by the first turbine, it might take a year. The power produced by the 1,870 MW powerhouse at Gibe III will be delivered to Interconnected System (ICS) through a four double circuit 400 kV overhead transmission line, whose installation is already completed, that connects the Gibe III to a new substation at Sodo, and will be

65-kms long, Eyuel noted. Its from this substation that the power is planned to be exported to Kenya and transmitted to the main grid at Addis.

The dam’s reservoir is expected to submerge a considerable length of road and a bridge over Omo River that connects Dawro and Wolayta zones and the project has already constructed 130 meter long new bridge and 78 kilometer long new road as replacement. According to Eyuel, about 2 million meter cube material is excavated to prepare the basement for the dam and it was a trying as the slope was very steep and hence made access to heavy machines very difficult. As the work has reached the optimum level at present, more than 7 thousand workers are engaged in different sections of the work 24 hours everyday. “there is gap in capacity of both the contractor and the consultant. The main thing is to secure the financial expenses needed for the project. To fill this gap, I think the government is making relentless efforts.” Eyuel said.

As it is the case for almost all similar projects, the dam’s construction was started with a feasibility study. But the result of these kinds of studies may not be fully reliable. Abayneh told this reporter that as the right side of the foundation wall was not as strong as predicted, it has increased the amount of material to be excavated and in turn compelled amount concrete to be compacted to be increased from 5.6 million meter cube to 6.1 million meter cube. This unexpected geological scenario has taken more time and cost from the amount scheduled based on the feasibility study. The amount of rainy days in the site every year unfolds with also has its own effect. The project expected to face 80 rainy days on average per year, Abayneh noted. “But this may vary. You can not be sure of the natural events and the geological scenarios,” he added.

The environmental and social impact assessment undertaken of the site of the dam indicates there is no significant effect both in down and up stream areas. Ethiopia also has issued a number of regulations aimed to conserve and protect the remaining natural ecosystems of the country in National Parks, Wildlife Sanctuaries, National Priority Forest Areas and Controlled Hunting Areas. However, the reservoir area of this dam is neither contiguous with nor in close proximity with any of these nationally protected areas. As the result of the less favourable rainfall, Tsetse fly infestation and the consequent occurrence of cattle disease, trypanosomiasis, there is very little farming activity around the Omo valley bottom lands. The steepness of the slope on either side of the valley appears to be another important factor which has discouraged the use of the valley for agricultural purposes. This makes is almost with no significant effect on the farmers and other settlers in the area as the valley is an ideal place for the dam to be situated.

What is more, The importance of the Gibe III reservoir area and the immediate surrounding has been investigated in terms of religious and cultural site relics and archaeological importance. Based on this investigation the historical sites known as King Ejajo (in Wolayta Zone) and King Halala (in Dawro Zone) walls were found on both sides of the Omo River. According to the research, The dam’s reservoir will not totally have any effect on King Halala Wall while only 2 per cent of King Ijajo Wall may be covered by it.

Although the lower valley of the Omo River (downstream of the Gibe III dam) was designated a UNESCO World Heritage Site (because of geological and archaeological importance), the proposed dam and the reservoir areas are not in close proximity to this UNESCO designated heritage site. No visible archaeological remains, which have scientific, cultural, public, economic, ethnic and historic significances, have been observed in the area and dam sites. The sites have no archaeological importance.

Sourced here:  http://www.ethpress.gov.et/herald/index.php/herald/development/4549-persevering-the-omo-valley-tapping-into-what-gibe-iii-offers

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