Gibe Dams on the Omo River
Omo River Basin
Omo River Basin
Dean of Water Technology Institute, Addis Ababa University at Arba Minch
Semu Moges Moges
Dean of Graduate Studies, Addis Ababa University at Arba Minch, and National Coordinator for Nile Basin Initiative’s Operating Studies
Alison M. Jones
NWNL Director and Photographer
All images © Alison M. Jones. All rights reserved.
After a NWNL Omo River Expedition in Ethiopia, Alison Jones visited Arba Minch 1) to interview Water Technology Institute [WTI] scientists focused on Ethiopia’s water resources and hydrologic projects; and to discuss her 100-page Proposed Management Plan for Nech Sar National Park with the current manager of that park. (The Plan is online as 16 MB PDF — or 4 MB PDF). Dean Sine and Dean Moges, from Addis Ababa University in Arba Minch, were very helpful in explaining hydrologic issues in 2 NWNL case study watersheds: the Omo River Basin in southwestern Ethiopia and the Blue Nile River Basin in central and western Ethiopia. Prior to this interview, Dean Moges also spoke in a WTI interview with NWNL on the Blue Nile.
NWNL I appreciate both of you making time for this NWNL Interview. Dean Sine, please introduce yourself; and when Dean Moges arrives, we’ll have him do his introductions.
ABEBE SINE I work for the Addis Ababa University, at Arba Minch, as the Dean for the Water Technology Institute [WTI]. Our mission addresses Ethiopia’s great need for water professionals like hydrologic engineers, irrigation engineers, environmental engineers, and sanitary engineers to work on different sectors – especially in water sectors.
NWNL What is Ethiopia’s current main focus or goal concerning its fresh water issues?
ABEBE SINE Nowadays, Ethiopia is giving more attention to water as a basis for development. Thus, WTI’s focus is to produce a qualified resource of professionals who will create a water resource regimen that can solve Ethiopia’s problems.
NWNL I will ask about specific hydrologic plans for the Omo Basin; but first, in general, how do you compare water issues in the Omo River Basin in Ethiopia’s southwest with those the Blue Nile River Basin in the central and western part of Ethiopia? Your knowledge spans both watersheds.
ABEBE SINE The Blue Nile is the greatest river in the country. About 60% of our total water potential comes from that river. Thus, the population within Blue Nile River Basin is very large compared to other parts of the country. The government intends to utilize this huge amount of water resources. There are a number of projects being constructed in the Blue Nile River Basin, such as the Tana Beles Hydroelectric Power Plant and Dam. Yet, at the same time, we see problems related to shortage of water, food scarcity and so on. [Editor’s Note: The Tana Beles Dam is at the outlet of Lake Tana, source of the Blue Nile River, and upstream of Tissiat Falls.]
There are also other problems in the Blue Nile River Basin. This watershed primarily contains rivers with a flow that is full throughout the year. This huge of flow degrades our land. Already, much soil has been carried out to Sudan and Egypt. To address our sedimentation and erosion problems, we need watershed management as we simultaneously utilize these water resources.
NWNL In comparison, how would you describe the Omo River Basin hydrology and water usage?
ABEBE SINE In the Omo River Basin, many tributaries carrying monsoonal rains drop precipitously from Ethiopia’s highlands to join the Omo River. One of those tributaries is the Gibe River (also called the Gilgel Gibe River) which will soon be a great new source of energy for the country.
NWNL So, let’s jump right into discussing that cascade of dams being constructed on the Gibe River as it plunges down steep canyons to fertile Omo River plains.
ABEBE SINE A quick summary is that the first of this series of dams, Gibe 1, is complete and generating about 184 megawatts. Gibe 2 is under construction and may be completed after a year. It will generate about 400 megawatts. The Gibe 3 will have the capacity to generate about 1,800 megawatts when it’s finished in 2010.
NWNL These three Gibe Dams will generate much-needed hydropower for Ethiopia, but will there also be negative effects downstream?
ABEBE SINE As we construct these dams, there’ll be no negative effects downstream; but there will be upstream, especially in the reservoir areas. Gibe 1’s reservoir displaced 115,000 families. Thus, a development project compensated them by constructing a village with churches, mosques, infrastructure like schools, clinics, hospitals and so on. It also provided agricultural lands for irrigation.
NWNL Are the communities displaced by Gibe 1 content with these arrangements?
ABEBE SINE Actually, they are happy. They were working with traditional practices; but since they’ve resettled in their new village, the government established some modernized agriculture, like using tractors to cultivate the land. This makes the people willing to accept displacement.
NWNL Addressing the Gibe 2 diversion, what is its purpose and benefits?
ABEBE SINE The problem of Gibe 2 is downstream on the Omo River itself. When Gibe 2’s diversion is complete, that water will go directly into the Omo River. But previously, the Gibe River joined other tributaries at a confluence point before flowing into the Omo River. Soon the Gibe River will completely bypasses about 15.5 miles [25 kms] of its final stretch. So that area may be really affected; but downstream demand there is small. Some water will be released downstream for ecologic purposes, but not as much as previous flows.
NWNL Will there be any mitigation or compensation for ecological losses when this stream diversion is complete?
ABEBE SINE Construction is underway for Gibe 2’s powerhouse and tunnel. When completed, the final downstream stretch of the Gibe River will be blocked and all water diverted through a tunnel. Obviously, this lower stretch of the Gibe’s riverbed will be affected when it is left dry. While negative effects of Gibe 1 are on its surrounding environment and fertile lands upstream, Gibe 2’s negative impacts are on what has been its downstream course.
NWNL Turning to the much larger Gibe 3 Dam, I’ve just seen from the air that there’s much more construction to be done on that. What do you know about its impacts?
ABEBE SINE As you saw, the Gibe 3 is not actually started yet; and so it’s difficult for me to say what its environmental effects will be. They are just constructing access now.
NWNL Yes, I saw that. As we know, there can be unintended consequences of building reservoirs. A year and a half ago, there were unusually heavy rains. The Gibe 1 reservoir was very full, so they had to suddenly release water downstream, causing problems particularly in the Omo Delta. Some local Dassanech people were killed, as were many of their cattle. Why weren’t the Dassanech warned about the release of that water that flooded the Delta? Do you feel the Dassanech deaths were caused by that lack of communication?
ABEBE SINE That was not the problem. The flooding was not caused by the release from Gibe 1. Last year there was very high rainfall, due to this climate change. The rainfall pattern is very different now. We receive very high rainfalls due to climate change, not only in Omo, but also other parts of the country.
NWNL So, the deadly flooding wasn’t due to a sudden release of water from the dam?
ABEBE SINE No, it was not.
NWNL As residents in the Omo watershed face new challenges from climate change, what are the best ways to address them?
ABEBE SINE Again, there’s a difference between the Omo and Blue Nile River Basins. The Blue Nile River Basin has a large population, whereas the Omo’s population and its population density are lower. Consequently, the Omo has less stress on its water resources than the Blue Nile River.
Additionally, the Omo has such very low land. Thus, the steep flow from its tributaries is highly concentrated onto its downstream plains. So, especially during rainfall time during wet seasons, there are serious flood problems, as we observed last year.
NWNL That brings my questions back to the Gibe Dams. As the growing cascade of Gibe dams stabilizes the Omo’s water levels, how will that affect riverside residents – given that these dams will provide a new source for substantial income for Ethiopia?
ABEBE SINE The Gibe Dam projects will have a positive impact related to flood control, since the flow from these hydropower plants can be regulated. But maybe the missing part is just that there is no flood warning system. For instance, in the coming seasons, if there is a huge rainfall, there should be some system developed to relieve the amount of water in the reservoirs so that there will be no downstream flood problems. That is the only missing part. We also need to develop an early flood-warning system.
NWNL Ah, Dean Semu Mogasa is now joining us. Please introduce yourself before we discuss your thoughts on hydrology in the Omo River Basin.
SEMU MOGES I am Dean of the School of Graduate studies at this University. My specialization is hydrology and water resource management. I’m also the National Coordinator for Operating Studies at the Nile Basin Initiative [Editor’s Note: The Nile Basin Initiative is one of the recent initiatives that has been established with the nine countries politically involved in water rights of the Nile River Basin.]
NWNL We have just discussed the benefits of the Gibe Dams regulating the Omo River’s levels. Between my visits in September to January this year the Omo seems to have dropped about 45ft (13.7m).
Do you have figures from past years on the range of the Omo’s changing volume and its annual rise and fall? With the Gibe Dams, the Omo’s wide fluctuation will stop. Indigenous tribes have farmed the banks of the river as eons of flood waters have receded. That tradition will stop.
SEMU MOGES Well, I think those water-level numbers are reasonably uncertain. I know in the lowland area, the people are always affected during dry seasons due to the Omo River recessions. Also, during the floods, they pay a price in life and their property.
The fact is that this Gibe Dam project enhances the Omo’s flow during dry seasons. It enhances water availability because extra water is released to achieve maximum hydropower. That means Omo farmers will receive enhanced flows during the dry season.
During the wet season, if there are extraordinary flows like last year, the dams have a huge storage capacity for water. If extra storage is needed, there is a spillway that releases water. This storage ensures there will be enough water for agriculture during the dry season.
Therefore, in my view, there will be advantages in two ways. First, hydropower does not consume any water. It just puts the water in the turbine and releases it. Then, during dry season, downstream residents get enhanced supplies of water. During flood season, they get some control
Another point is these dams are not constructed close to the lowlands. They are in the highlands where their construction doesn’t have much of a deterring effect because the dams only control less than one third of the total country upstream. Whereas if you place a dam close to the outlet to the lowland, that might have an effect.
NWNL I understand some of the Omo’s water comes from the west, as well as the eastern highlands….
SEMU MOGES Yes, there are huge rivers below the proposed dams that have no control. So, I think all in all it the Gibe Dams have little negative impact. In fact, they have some positive impact by enhancing water supplies. But when there are extreme wet seasons, like last year, even the Gibe Dams might not be enough because of those torrential rivers below the dam site.
NWNL What about Gibe 4?
SEMU MOGES I cannot answer that question because I don’t know the exact location.
NWNL Its location has not been established yet?
SEMU MOGES Right, it is not yet certain. Perhaps that still has to be investigated.
NWNL Do your students work on these hydro-projects?
SEMU MOGES Yes, they’ve worked on many projects and they’re all highly technical of course. We have many projects on the Nile. And we have projects to establish an early flood warning system for Omo. For this, we’ve tried to establish the lag time that would predict the amount of time it takes for a highland flood to reach the lowland.
Even if our research thus far is somewhat preliminary, we now understand we want a flood warning; and we have an understanding of what it takes to develop a flood warning. We developed a model that can predict the amount of floods that can reach the lowlands, as well as the period of time that it takes.We found that a concentrated flood might take from six to ten days to reach from highlands to lowlands. That is not yet a perfect estimate, thus we have to do more research hydrologic research to establish what exactly it takes to reach it.
We’re studying how to avoid flood water reaching downstream. Another part of the warning is to establish a communication mechanism. If we see a flood could reach a certain place, we have to have a communication mechanism to inform the community, to issue warnings so that they have to evacuate within an amount of days.
NWNL And, yet in these days of satellite phones and mobile phones such communications are easier than they would have been fifty years ago. So, modern technology does help – and such communications are indeed of life-and-death importance.
Thank you both so much for your time. I look forward to continuing these conversations while I am in Arba Minch.
Posted by NWNL on February 3, 2020.
Transcription edited and condensed for clarity by Alison M. Jones.
Interview Guidelines describe the NWNL protocol for editing raw transcripts.
All images © Alison M. Jones. All rights reserved.