Something that We Need to Know about Our River’s Hydropower Potential

 

Lulseged Ayalew

Niigata University, Japan


Recently, we learned from government news media that the Electric Power Corporation launched the construction of “massive hydropower projects” in Tekezze and Gojeb rivers. The general manager of the same corporation was also quoted as saying that his institution “has been carrying out various activities aimed at facilitating conditions for the launching of the operation of three private companies, with which it signed memorandums of understanding to develop hydro and thermal power resources of the country.” These are good news coming too late. It would have been better if EEPCO and the government itself realize this a little earlier. Why I am saying this?

It is known that hydropower is the leading source of renewable energy. It provides 2.3% of the world’s energy and more than 97% of all electricity generated by renewable sources. The absence of polluting emissions during operations, its capability to respond quickly to utility load demands, and its very low operating costs makes hydropower the only energy source that needs to be exploited efficiently. The principal concept behind this energy source is that hydropower plants are designed and constructed to capture the kinetic energy of running water. A turbine and a generator convert the energy from the water to mechanical and then electrical energy. The turbines and generators are installed adjacent to dams or use penstocks (pipelines) that carry pressurized water from the dam or diversion-structure to the powerhouse. How is the power controlled?

The power capacity of a hydropower plant is primarily the function of two variables. The first is the amount of flow. More water flowing through the turbine will produce more power. The amount of water available depends on the amount of water flowing down the river. Big rivers have more flowing water and can produce more energy. Power is also directly proportional to the hydraulic head, which is the elevation difference the water falls in passing through the plant. The farther the water falls, the more power it has. This means that hilly or mountainous sites provide good locations for hydropower projects. What does this mean to Ethiopia?

Ethiopia is divided into three physio-graphic regions: the Northwestern Plateau, the Rift Valley and The Southeastern Plateau. There are places like Semein or Bale Mountains with an Elevation of more than 4000m. There are also places like the Afar and the Ogaden with less than 500 m elevation. Actually, it is not the maximum or minimum elevations in the country in general which matters whether hydraulic head is high or not. Rather, it is the elevation difference in areas where there is water which controls the magnitude of this parameter. This means, areas having constricted valleys with streams incised in sound bedrocks are ideal locations, especially for storage-mode hydropower projects. Do we have these locations?

Yes, we are really blessed that our country constitute highlands and lowlands, and some regions especially (the Blue Nile Basin for example) are mentioned as the best place for hydropower generation. Some countries with similar topographies such as Norway and Japan are using their hydropower potential almost fully, with the former generating 99% of its electricity from hydropower. As it is mentioned above, most hydropower projects use a dam and a reservoir to retain water from a river. This means we need to have access to flowing water, and the volume of this water must be above a given threshold. Are there rivers of this sort which can be used for hydropower in Ethiopia?

To my knowledge, there are at least 10 river basins in Ethiopia. I have hard evidences only on some of these basins, but from a general speculation, I believe that all of them can be used for hydropower generation. Or, I see no problem why they cannot be used for this purpose except the initial capital investment and the willingness of the government. Among these 10 river basins, work on Awash river started in the middle of the last century by the construction of Koka Dam. If I am not mistaken, this was the first major hydropower plant in the country built at the time when most African countries had none. It is a legacy of a good time, and is still providing energy although its service period has already been over. Currently, there are many geological, geotechnical and technical problems that will force the dam phasing out soon. Do we have replacements?   

There are a few, among which Melka Wakena, Finchewa and Tis Esat can be mentioned. Melka Wakena is located close to Bale Mountains. It was built during Mengistu Era mainly by Soviet specialists. The powerhouse suffered from flooding a couple of times, and in 1989 specially, the dam itself was on the brink of disaster. The reason was that while selecting a location for the powerhouse, the specialists underestimated the effect of a dry river present a few meters away from the latter. During rainy season, that river was flooded and came with boulders of rocks and inundated the powerhouse and the surrounding area. The boulders blocked the subsequent river flow and things were turned out to be worse for the dam itself. How about Finchewa?

Finchewa contributes a significant amount of power to the central-grid. If it were not for the geology of the area, the topography of the region is quite suitable for the production of a lot of energy from streams draining in the area. But, because of the presence of moisture sensitive, low-bearing materials, this gorge in particular and the entire Blue Nile Basin in general is home for many pieces of landslides. The problem is that when the rainy season sets on, selective localities become unstable and the road to the powerhouse and several places within the project site become inaccessible. And Tis Esat?

I am not a champion of building hydropower plants around Tis Esat. One of the side effects of hydropower projects is that they completely change the appearance of the environment. Tis Esat 1 and 2 are not far from the natural waterfall commonly known as the Blue Nile Fall. The presence of these two projects around that area always frustrates tourists that one day the government may encroach the shoulders of the Fall in search of natural hydraulic head. I understand why the engineers and geologists are rotating around that area. But if it is not a question of money and determination, I believe that it is possible to produce an even higher amount of energy from tributaries coming from east and west of the main river. With Bahir Dar a little away from it, we can develop the Fall and its surroundings into a major sight of attraction. It is a symbol of our identity and we have to respect it. Can we say something about  ?

Yes, it is possible to say a lot about Gilgel Gibe hydropower project. The idea of building a dam, water pressure tunnel, and an underground powerhouse on Gilgel Gibe was conceived in the early 1980s. The first site investigation was completed in 1986 and excavation was commenced immediately. But, construction was interrupted shortly because of instability problems around powerhouses. After more than 10 years of delay, another design was worked out in 1996 and implemented, ironically on the basis of very limited additional information. What happened during this period?

The interruption of the work led to the worn out of equipment, removal of shotcrete and concrete covers and damage of tunnel supports. Currently, with a new design and operation strategy, it was needed to allocate new budget for these materials. Moreover, a complete staff set up by the government which includes drilling technicians, engineers and geologists was in the site since the beginning of the work in 1986. The idea of starting the work was always on the surface, so I guess it was not possible to dissolve the entire team and save unnecessary expenses. Moreover, it is true that the project site is located in an area where the total yearly agricultural production is known to be above average. When construction has started in 1986, almost all agricultural activities were stopped. The land was becoming nonproductive and local farmers lost a large amount of money. In general, it is assumed that the total sum of this income could allow the government to cover half of the project’s expenses, if the construction activities were delayed until the present time so that the people were allowed to use the land for their own purposes. Was there other unnecessary spending?  

Yes, in addition to the above expenditures, a lot of money was wasted because of lack of experience in underground works. For example during data collection in 1986, more vertical boreholes were drilled in the upstream section of the tunnel. Much unnecessary data was gathered just to fulfill standard procedures. But, a gap in some important engineering aspects was also found when the information was revised in the past three years which led to a sporadic new borehole drilling activity in 1997. The geological and geotechincal data were not properly interpreted before excavation and graphs and tables were ended up in appendices of a sequence of reports. Quite a lot of money was spent in this way and it seems that there was no good co-ordination, nor was there managerial responsibility. Now, the project is said to be on the final phase. If what the officials was saying is true, we will see more light (an additional 184MW) in 2004. But will the entire work be free from problems in the near future?

No, I do not think so. From what I have seen in the field, too much attention was given to the tunnel and the powerhouse. That is certainly ok, but when we see some of our old tunnels like Trama Ber, hard volcanic rocks found in Ethiopian plateaus, although not as sound as the theory says, do not create big problems at least for the first 20 to 25 years. Similar rocks in India’s Himalaya are usually known to be good for water tunnels. Our main problem actually is Siltation. What is then siltation?

Siltation is the process whereby fine particles of sand, mud and other material picked up by moving water are deposited to form a sediment. In engineering, siltation is generally considered as the most common problem and it largely determines the lifetime of a certain hydropower or water resource project. Its effect actually varies from area to area. Dams in tropical areas where rivers are rich in silt are more affected by siltation than those in temperate zones. The Nile River is among the most silt-laden rivers in the world. Silitation made Koka non-functional and Addis was blacked out in 2000 just in the middle of the rainy season. It reduced Borkena dam to a hide-and-seek field for children. Siltation also has a great effect on the life of Angereb and Melka Wakena. As if we learnt nothing from these happenings, once more there is neither a study on the silitation capacity of Gilgel Gibe nor a design for mitigation. The diversion channel that is now used for construction purposes is going to be closed after the work is finished. There is neither a total catchment policy nor soil conservation system in the area. So, I will not be surprised if we are told that the dam is silted up soon after it started giving services and de-electrification continues. We are late, but not too late actually. It is better to consider this problem now than to cry out later. It might be normal for our managers to allocate money for maintenance of newly finished projects to line their own pockets, but for the entire public it is embarrassing and unacceptable. And Tekezze?

Braided channels of Tekezze river with a significant 
amount of sediments in the middle portion of the valley

Tekezze is not different from other major rivers in Ethiopia. Actually siltation in the north is even much worse than in the south.  Tekezze starts in Wello and Gonder highlands and drains northward before it turns to the west. These areas are used for agriculture, and soil materials are largely loose and can easily be taken by the river. There is no forest which can protect this. There is little study on the geomorphology of Tekezze and no know-how on where erosion stops and deposition starts. Of course the question of looking for natural hydraulic head may make this study irrelevant, but not impossible. It is useful at least to determine the life of the dam and the reservoir. The senior engineer of the Ministry of Water Resources, Dr. Mohammed Ahmed, has told us once that it will take about 50 years before half of the Tekezze dam is silted up. But, given the location of the structure, this seems to be a guesstimate from the office and if we use the “one design for all” approach, it might even be difficult to serve Mekele let alone Sudan. Tekezze even has treats from landslides and active and passive faults. Anything about Gojeb? 

Gojeb is not that much different from Gilgel Gibe. Of course, it is silt laden. But, the area where it drains is naturally well vegetated and the dam may serve a little better than others if the appropriate design is in place. Actually, we have many rivers of Gojeb size, and I would suggest damming these unknown, small rivers. Why?

It is mainly for financial, political, social, environmental, engineering and management reasons. Hydropower plants range in size from "micro-hydro" that power only a few homes to giant dams that provide electricity for millions of people. In the middle, there are “mini- and small-hydro”. There is no a universally accepted definition for these terms, but commonly small-hydro can generate up to 20-25MW and projects in the 100 KW to 1 MW range are referred to as "mini-hydro" whereas those under 100 KW are known as "micro-hydro." In almost all corners of the country, we have streams which can allow us realize one of these hydropower plants. So, unless it is for a show off, I do not see the reason why we beg IMF and World Bank to build big dams. These are projects which can easily be executed by private investors with a modest capital investment. The development of small hydropower projects typically takes two to three years. They require little maintenance over their useful life, which is well over 50 years and do not necessarily need dams or reservoirs. They can easily be up-graded or even totally closed so that the old environment can reestablish itself. I think we are better off with these projects. Only the government starts to understand this now, of course galvanized by a series of cries and requests. And recently we saw some encouraging beginnings, and studies are conducted on couple of rivers (Jemma River, Muger and Guder Falls for example). But more cannot be said about these projects because they are not yet implemented. What should be done in general?

I do not like saying we have this and that in Ethiopia. The government papers are more than enough for that. They always tell us things like we have an iron here, a gold over there, oil in this corner and energy in that section. Or of the type like water project is executed there, another is completed here, a road is opened in the east and one more is renovated in the west. In reality, the deposits might be non-exploitable and the projects are usually ineffective, and the reports are simply sheer political ineptitude introduced to boost psychological relieves among the society. I believe that it is always good to talk and think about what we do not have. It gives us energy, strength and determination. That means, rather than saying we have this amount of rivers with this much hydropower potential, it is better to start an ever greater investment in power generation today in order to exploit the potential lying untapped in various rivers. It is time to act! The government must understand this and change its policy in the way this can be accomplished easily. We are in the middle of a sea. We can still float but to sail, we need to be in the right direction. If we are not able to find that direction, a time may come that we cannot anymore float. We will then sink miserably.

I will come with more writings on our water resource and irrigation projects and roads some time in the near future. Till then, I wish you all a happy Ethiopian new year.


Dr. Lulseged Ayalew is a research scientist currently working in the Faculty of Science of the Niigata University in Japan. He earned his Doctor of Geological Engineering degree from the Technical University of Claustal in Germany in 2000. He may be contacted at: ayalew@env.sc.niigata-u.ac.jp

 

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