Juba river is one of two perennial rivers in Somalia that accounts for majority of the country’s agricultural output. Juba river also known as Genale Dawa river in Ethiopia, originates from the Ethiopian highlands. Three tributaries in Ethiopia converge near the Somali border to form the Juba river. The three tributaries are Genale, Dawa and Gestro rivers. Approximately 70% of the basin area for the Juba river lies within Ethiopia. The Ethiopian highlands originate about 90% of the precipitation forming the Juba river in Somalia. The Ethiopian Ministry of Water Resources (MoWR) has been conducting several high level feasibility studies of the potential hydropower of the country in order to harness the energy and grow their economy. Some of those studies were completed and are currently at implementation stage while others are ongoing.
The studies that the MoWR has been conducting include Genale Dawa III (GD-3), Genale Dawa V (GD-5) and Genale Dawa VI (GD-6) as a cascading system. GD-3 is currently in construction and will be completed in March 2018; while GD-5 is still unknown whether it has been abandoned or is part of a long term vision. Two British firms were awarded the contract to design and construct GD-6 dam during the first quarter of 2017. Ethiopia has the rights to develop their country and deploy its available natural resources; however, there is an urgent need for transboundary coordination between the upstream and downstream bordering counties. Somalia which relies heavily on the Juba river could feel the devastating impacts of the water imbalances. It is also important to note that Ethiopia and Somalia are part of the African Convention on the Protection of Nature and Natural Resources. The convention requires the contracting States to coordinate the planning and development of water resources projects. Section V of the original convention from 1968 encourages setting up inter-states commissions to study and resolve problems arising from the joint use of these resources.
The attached whitepaper was prepared to assess the preliminary impacts of the proposed Ethiopian dams on Juba river. In particularly, it focuses on the impacts of the first completed hydropower project along the Genale Dawa river, GD-3. The GD-3 is expected to yield the total installed capacity (maximum output of all the generators combined under ideal conditions) of 254 MW. Based on historical streamflow data, the construction of GD-3 will have a significant impact on the Juba river in Somalia., the GD-3 dam will store a minimum of 260 million cubic meters of water to operate and has a capacity of 2.5 billion cubic meters (BCM). The annual runoff volume in Juba at the most upstream point of Luuq is 5.8 billion cubic meters. Historical streamflow data at Luuq from 1963 – 1990 were used as the baseline along with data from the feasibility study for GD-6 completed by the MoWR of Ethiopia. Detailed hydrologic and hydraulic study of the Genale/Juba basin is crucial to fully quantify and assess the impacts from GD-3 and GD-6.
Figure 1 below summarizes the reduction in the Juba river flow once the GD-3 is operational. The annual average flow at Luuq station in Somalia is the orange line and the red line is new average flow at Luuq with GD-3. Luuq flow is formed by the summation of average flows from Dawa river and Genale river. Historical studies indicate that flow from the Gastro river is negligible. Chenemasa gauging station is located upstream of GD-3 along the Genale river.
Figure 2 below compares the 90% probability graph (green) with the combined flow at Luuq post GD-3 (red). The average annual flow is a good indicator, but the results could also be skewed by several high values. The 90% probability corresponds to a total flow of 2.8 BCM annual flow at Luuq. GD-3 requires a minimum of 260 million cubic meters to maintain operations but for normal operations will store approximately 1 BCM.
Based on historical streamflow data and the assumption that the current streamflow matches data collected pre-civil war, the construction of GD-3 will have a significant impact on the Juba valley farmers and agro-pastoralists who depend on these resources for survival. A preliminary review of historical data indicated the following points:
- Genale River basin accounts for more than 50% of the flow in the Juba River downstream. This is supported by a review of historical streamflow data at Chenemasa gauging station (upstream of GD-3) where the annual average streamflow is 2.9 billion cubic meters. A review of the historical data for Helwei and Kole bridge stations is vital to support this assumption.
- Approximately 90% of the flow rate in Juba River originates from the Ethiopian portion of the Juba basin. Genale Dawa III regulates and impounds half of the total flow into Juba river. The available water in Juba River will be reduced from 5.8 BCM to 4.8 BCM due to this impoundment. Water balance for the Juba basin based on current and future needs is required to fully quantify the impacts to crop, livestock and domestic water demand.
- During draught periods, the flow rate at Luuq is equal to the streamflow at Chenemasa gaging station. This finding could be a coincidence, or it could mean that precipitation on the highlands of the Genale river solely contribute to the Juba river downstream. Further analysis of the hydrometric data for Dawa and Gastro rivers will shed some light into the seasonal precipitations to perform an accurate water balance.
- GD-3 estimated completion date is March 2018 and it will be crucial to determine the initial filling of the reservoir. Filling the reservoir immediately (as of February 20, 2018) will result in the extension of the draught season (Jilaal) to the Gu season to reach the minimum operating levels. If the reservoir filling has started in late 2017, current dry conditions in Luuq could be explained by this condition. During initial filling, entire rainfall from the Ethiopian highlands will be captured in the reservoir with no release.
- The construction of GD-3 results in a reduction of 24%-33% of the total streamflow at Juba River without taking the various other losses into account (i.e. evaporation, infiltration, transmission losses). Evaporation losses are amplified as one gets closer to the Somali national border. Therefore, the impoundment due to GD-3 could result (significantly more than the 24-33% estimate) in much higher impacts to the total volume of Juba river. A detailed hydrologic model will shed some light onto the total losses due to evaporation/transpiration and infiltration. It is also important to note that all the streamflow data summarized above is from 1963-1990 for Juba River, in other words recent irrigation project completed by the MoWR of Ethiopia along the Genale Dawa river are not considered. Recent streamflow data along Juba within Somalia is vital to make accurate predictions. Historical evaporation measurements or hydrometric data within Ethiopia will clarify the preliminary results.
- The construction of GD-3 along with the upcoming two projects (GD5 and GD6) in 2020 will likely diminishes the construction of Baardhere Dam in the future in Somalia and extension of exiting irrigation projects as included in Baardhere study. Similarly, GD-3 Dam will significantly decrease the water availability at Fanoole Barrage, Mogambo irrigation project, and Saakow Dam.
- The Draught Impact Needs Assessment (DINA) completed on October 2017 by the Somali government, various NGOs and the international partners has to be reevaluated based on the completion of GD-3. The framework and the long term solutions will have to incorporate the impacts of the dam on the agricultural communities along the Juba valley.
- New bathometry survey, cross sections and revised rating curves are a must for Juba and Shabelle rivers. The data currently generated by SWALIM/FAO is based on pre-war analysis that established the rating curves. During the last 28 years, the river profile and geometry has changed, and the pre-war rating curve data is no longer applicable.
For more details review the attached report.
Prepared By: Hussein Amiin and Guled (Wiliq) Ahmed
The views expressed in this article remain those of the authors, and do not necessarily reflect those of The Jamhuriyadda, its editorial board or staff.