The Grand Ethiopian Renaissance Dam (GERD) Amharic: ታላቁ የኢትዮጵያ ሕዳሴ ግድብ, romanized: Tālāqu ye-Ītyōppyā Hidāsē Gidib), formerly known as the Millennium Dam and sometimes referred to as Hidase Dam (Amharic: ሕዳሴ ግድብ, romanized: Hidāsē Gidib), is a gravity dam on the Blue Nile River in Ethiopia under construction since 2011. The dam is in the Benishangul-Gumuz Region of Ethiopia, about 45 km (28 mi) east of the border with Sudan.
The Grand Ethiopian Renaissance Dam is designed to trap 100 years of sediment inflow. Lack of sediment data and rapid land degradation may result in higher sediment yields than expected. Reduction of sediment inflow through watershed management is key to achieving long-term sustainability. Debre Yakob watershed demonstrates a successful example of economically self-supporting watershed management.
|Grand Ethiopian Renaissance Dam|
|Construction began||April 2011|
|Opening date||July 2020|
|Construction cost||$5 billion USD|
|Owner(s)||Ethiopian Electric Power|
|Dam and spillways|
|Type of dam||Gravity, roller-compacted concrete|
|Impounds||Blue Nile River|
|Height||145 m (476 ft)|
|Length||1,780 m (5,840 ft)|
|Elevation at crest||655 m (2,149 ft)|
|Dam volume||10,200,000 m3 (13,300,000 cu yd)|
|Spillways||1 gated, 2 ungated|
|Spillway type||6 sector gates for the gated spillway|
|Spillway capacity||14,700 m3/s (520,000 cu ft/s) for the gated spillway|
|Total capacity||74×109 m3 (60,000,000 acre⋅ft)|
|Active capacity||59.2×109 m3 (48,000,000 acre⋅ft)|
|Inactive capacity||14.8×109 m3 (12,000,000 acre⋅ft)|
|Catchment area||172,250 km2 (66,510 sq mi)|
|Surface area||1,874 km2 (724 sq mi)|
|Maximum length||246 km (153 mi)|
|Maximum water depth||140 m (460 ft)|
|Normal elevation||640 m (2,100 ft)|
|Turbines||14 x 400 MW|
2 x 375 MW
|Installed capacity||6.35 GW (max. planned)|
|Annual generation||16,153 GWh (est., planned)|
The primary purpose of the dam is electricity production to relieve Ethiopia’s acute energy shortage and for electricity export to neighboring countries. With a planned installed capacity of 6.45 gigawatts, the dam will be the largest hydroelectric power plant in Africa when completed, as well as the seventh largest in the world.
Filling the reservoir began in July 2020. It will take between 4 and 7 years to fill with water, depending on hydrologic conditions during the filling period and agreements reached between Ethiopia, Sudan, and Egypt.
The name that the Blue Nile river takes in Ethiopia ("Abay") is derived from the Ge'ez word for 'great' to imply its being 'the river of rivers'. The word Abay still exists in Ethiopian major languages to refer to anything or anyone considered to be superior.
The eventual site for the Grand Ethiopian Renaissance Dam was identified by the United States Bureau of Reclamation in the course of the Blue Nile survey, which was conducted between 1956 and 1964 during the reign of Emperor Haile Selassie. Due to the coup d'état of 1974, however, the project failed to progress. The Ethiopian Government surveyed the site in October 2009 and August 2010. In November 2010, a design for the dam was submitted by James Kelston.
On 31 March 2011, a day after the project was made public, a US$4.8 billion contract was awarded without competitive bidding to Italian company Salini Impregilo, and the dam's foundation stone was laid on 2 April 2011 by the Prime Minister Meles Zenawi. A rock-crushing plant was constructed, along with a small air strip for fast transportation. The expectation was for the first two power-generation turbines to become operational after 44 months of construction, or early 2015.
Egypt, located over 2,500 kilometres downstream of the site, opposes the dam, which it believes will reduce the amount of water available from the Nile. Zenawi argued, based on an unnamed study, that the dam would not reduce water availability downstream and would also regulate water for irrigation. In May 2011, it was announced that Ethiopia would share blueprints for the dam with Egypt so that the downstream impact could be examined.
The dam was originally called "Project X", and after its contract was announced it was called the Millennium Dam. On 15 April 2011, the Council of Ministers renamed it Grand Ethiopian Renaissance Dam. Ethiopia has a potential for about 45 GW of hydropower. The dam is being funded by government bonds and private donations. It was slated for completion in July 2017.
The potential impacts of the dam have been the source of severe regional controversy. The Government of Egypt, a country which relies heavily on the waters of the Nile, has demanded that Ethiopia cease construction on the dam as a precondition to negotiations, has sought regional support for its position, and some political leaders have discussed methods to sabotage it.Egypt has planned a diplomatic initiative to undermine support for the dam in the region as well as in other countries supporting the project such as China and Italy. However, other nations in the Nile Basin Initiative have expressed support for the dam, including Sudan, the only other nation downstream of the Blue Nile, although Sudan's position towards the dam has varied over time. In 2014, Sudan accused Egypt of inflaming the situation.
Ethiopia denies that the dam will have a negative impact on downstream water flows and contends that the dam will, in fact, increase water flows to Egypt by reducing evaporation on Lake Nasser. Ethiopia has accused Egypt of being unreasonable; In October 2019, Egypt stated that talks with Sudan and Ethiopia over the operation of a $4 billion hydropower dam that Ethiopia is building on the Nile have reached a deadlock. Beginning in November 2019, U.S. Secretary of the Treasury Steven T. Mnuchin began facilitating negotiations between the three countries.
Hydrology and sediment
The basin of the upper Blue Nile tributary to the dam drains the Ethiopian highlands. The Blue Nile has a single wet season and flow is highly seasonal, as shown in figure 1. The Ethiopian highlands range from about 500 to 4,533 m in elevation, with average rainfall varying regionally from 600 to 2,200 mm/year.
Sediment concentration peaks one month prior to the discharge peak. Trend analysis at the El Diem gage showed a 61 per cent increase in sediment load, from 91 Mt/yr for the 1980-1992 period to 147 Mt/yr for the 1993-2009 period, and was associated with a significant increase in suspended sediment concentration, especially during the rising limb of the wet season (Gebremicael et al. 2013). The recent sediment yield is 835 t/km2/yr across the 176,000 km2 watershed tributary to the El Diem gage. A recent study by the Water and Land Resource Centre (WLRC) using a very detailed modelling approach indicates that sediment entering GERD will be in the order of 287 million M3/year (WLRC, 2017 unpublished), much higher than previous predictions.
About 83 per cent of Ethiopia's population lives in rural areas and many derive their livelihoods from agricultural and environmental resources, primarily rain-fed agriculture and cattle grazing. Over 90 per cent of the cropland consists of small scale rain-fed household production systems. Ethiopia’s dramatic population expansion over the last 50 years, and future predictions of a growing population (see figure 2), has placed extreme pressure on the land, resulting in accelerated erosion, soil degradation, and rural impoverishment. Land degradation occurred because the production system was based on continuously expanding land for cultivation, rather than increasing the production per unit area, as described in the Abbay basin (Zeleke and Hurni 2001):
As cultivated land was expanded at the expense of other land use and land cover units, grassland declined, resulting in less available fodder and a decrease in the number and quality of livestock. This led to a shortage of animals required for plowing and transport, as well as to a reduction of income and food from animals and their products. This series of related impacts indirectly affected the traditional land management system. When livestock and fodder was plentiful (in the 1950s), manuring was an important practice in the area. It increased soil fertility and hence production without extra cost to the farmer except for labor. After fodder availability and livestock had decreased, manuring (traditionally called hura) was gradually reduced. Moreover, manure is now in greater demand than ever not only because of the lower number of livestock but also because its use as a source of fuel has increased due to reduction of fuelwood.
Bare lands were used as grazing land. Livestock were forced to stay on these land units, especially during the cropping season, although there was little for them to feed on. This is one of the practices adopted by farmers when the population grows and land becomes scarce. The farming system remains traditional while most of the grasslands are converted to cultivated lands. In this case, both livestock and cultivation took over marginal lands, eventually leading to even more severe land degradation.
The Ethiopian highlands within the GERD watershed are considered to be one of the severest cases of watershed degradation in the world. Sediment yields in the Lake Tana sub-basin, where the Debre Yakob site is located, average about 2,500 t/km2/yr, and in the areas of highest erosion, hazard sediment yield may be as high as 6,500 t/km2/yr. Areas with the highest erosion potential have been analysed and identified using the SWAT model, together with climatic time series and GIS spatial databases of soil characteristics (Setegn 2008).
Thus, much more is at stake than the issue of reservoir sedimentation, because the degraded soil conditions result in rural poverty and food insecurity. It is essential to maintain this soil on the farms to support productive and sustainable agriculture, just as it is necessary to keep it out of the reservoir to sustain long-term hydropower production.
Sediment management strategies
The Debre Yakob watershed encompasses about 325 ha, and is located at 11º 16’ 59" N latitude and 37º 13’ 45" E longitude. Rainfall averages about 2,300 mm/year. It was selected as a ‘learning watershed’ by WLRC in 2012 to serve as a demonstration site for a variety of interventions aimed at improving land management practices in a way that would substantially improve the economic circumstances for farmers, while simultaneously reducing soil erosion. Typical of the region, the Debre Yakob watershed was severely degraded by overgrazing, resulting in soil denudation and gullying. To transform the local watershed, the first order of business, and the greatest challenge, was to achieve a shift from free grazing across the entire landscape, to the use of enclosures and cut-and-carry feeding of the livestock (figure 3). Without relieving the continuous grazing pressure, it would not be possible to achieve re-vegetation needed to control erosion.
There was considerable initial scepticism in the Debre Yakob community, which had no prior experience with a cut-and-carry livestock management system. Many believed it would not work. However, by working closely with cooperating farmers in one area of the watershed, and by providing the initial funds to build check dams and plant vegetation to stabilise gullies, it was possible to demonstrate that the check dams would accumulate eroding soil and grow luxuriant vegetation (figure 4). By the end of the first wet season, the amount of forage production was exceeding the needs of the livestock that, previously, had barely survived when grazing freely. Feeding in one of the livestock enclosures is shown in figure 5.
The key to long-term success in watershed management lies not in the building of erosion control structures, but in changing the economic activities of the community to embrace sustainable production systems."
With grazing pressure removed, re-vegetation occurred rapidly in the moist soil held by the check dams. Vegetation also began to recover on the upland soils once the livestock was confined and young plants were not immediately consumed by wandering animals. Vegetative growth enhanced soil infiltration capacity and improved soil structure, leading to higher soil moisture levels and, in turn, more vegetation, establishing a positive feedback loop of land restoration.
By eliminating free grazing and producing sufficient forage to support the livestock, the community saw the benefits of changing their production systems. Attention then turned to enhancing the value of farm production through multiple avenues. The most important management strategies employed at Debre Yakob are:
- Gulley rehabilitation coupled with community agreements for livestock management incorporating a zero/controlled grazing system linked to cut-and-carry forage production on closed areas, gullies, farm terraces, and around homesteads.
- Area closures to rehabilitate degraded hills that used to serve as grazing lands even though they were not productive. This requires protecting the land against free grazing (animal exclusion areas as part of the zero-grazing arrangement) but cut-and-carry is allowed through agreements among the communities.
- Homestead development interventions are designed to enhance household income and empower women as well as households. It incorporates sub-components such as: home garden, an improved fruit tree agroforestry system, forage plantings around the household compound, introduction of new crops (papaya, avocado which has a good export market, hops for beer which has a good local market, etc.), bee-keeping, small-scale poultry, dairy and animal production, compost-making, fuel saving stove (figure 6) and improved water sources (shallow well or pond).
- Permanently vegetated soil and water conservation terraces were established between fields and planted with fruit trees and forage bushes to make these ‘conservation’ features economically productive (see figure 7 and 8).
- Techniques to improve soil moisture capacity and fertility through the use of mulches, composting, etc.
- Small nurseries to produce biological materials such as tree, forage bushes, grass, fruit and other seedlings for transplanting.
At Debre Yakob, the economic benefits to farmers provided by the technology package are clearly evident, not only in terms of increased production, but also in purchasing power. Among the earliest signs of improved living standard is the replacement of thatched roof with corrugated iron sheets. As development proceeds, financing structures to facilitate productive investment become more important, for example, to allow the purchase of a communal truck to transport products to market instead of selling to a middleman at depressed prices.
While many of these activities do not directly influence soil management, they are all part of a farming technology package that makes responsible land management self-sustaining. The key to long-term success in watershed management lies not in the building of erosion control structures, but in changing the economic activities of the community to embrace sustainable production systems. To be productive and sustainable these systems must retain topsoil on the farm. As a result, erosion control occurs as a natural and self-sustaining product of a successful farming system, as opposed to a top-down programme aimed at benefiting a downstream hydropower reservoir and sustained by costly subsidies. The importance of focusing on the household economic unit is underscored by the differences between unsuccessful and successful long-term interventions in Ethiopia (Zeleke 2015):
In the past focus was given only to rehabilitation of watersheds and less was done on activities that enhance income at household level. This was proved wrong over time as rehabilitation intervention alone didn’t enhance income within a short time and as a result many watershed development interventions fell back to previous situations. Over the years we have learned that any watershed development intervention should have economic development interventions as a major component of the watershed development plan and this was best organised in the form of homestead development intervention. We have seen that many households graduated from food insecurity through the combination of rehabilitation and economic development interventions.
The key underlying strategy is to greatly enhance productivity and economic value through optimal management of the best soils, while converting the poorer and steeper soils to woodlands (eg firewood, building materials), pasture, or tree crops. Multiple avenues need to be pursued to enable the farmer to enjoy higher income and enhanced economic security, providing self-sustaining economic incentives derived from the land itself which guides farmers to maintain and improve soils and sustain vegetative cover without additional external incentives.
Reducing sediment yield by changing land use requires a significant and sustained effort, potentially requiring the intervention with tens of thousands of small farmers. Realistically, an intervention on this scale can only be achieved through the participation of multiple entities including government, NGOs, and the private sector. In some cases, with small watersheds and known erosion hot-spots, there may be the opportunity for effective unilateral action by the dam owner. However, more typically a watershed management project is not a go-it-alone project for the dam owner, but may involve many organizations at multiple levels, from the local community up to the national government level. For example, to address land management issues in the North Fork of the Feather River (California, USA), hydropower owner PGE joined in a formal memorandum of understanding with 17 other organisations (Morris and Fan 1998).
Hydropower producers can play key roles in this process by using their available funds to help develop and demonstrate viable technology packages, and to sustain work at demonstration sites which can then be copied and disseminated throughout the watershed by others through both formal workshops and informal means. An economically successful system is likely to be adopted by others, on their own, given access to the information and provided learning opportunities. This is already happening at Debre Yakob Learning Watershed.
In selecting project areas for intervention, it is essential to understand the natural background rates of erosion and sediment yield, and to select for intervention those areas where the erosion rate has been greatly accelerated by poor land use practices, and where interventions can be applied successfully and sustainably. Tools such as the SWAT model coupled to GIS databases can be extremely helpful in preparing a sediment budget and identifying areas of greatly accelerated erosion. Equally important is the development of locally-relevant technology packages that are economically self-sustaining.
Watershed management programmes are not always successful. Key factors that point to long-term success at Debre Yakob include the development of technology packages that are economically self-supporting because they increase on-farm income, and a climate with sufficient moisture to achieve rapid re-vegetation. Establishment of such learning watersheds in different parts of hydropower catchments help to educate and change the attitude of local communities, experts and policy-makers. This facilitates expansion of successful technology packages into other areas.
Graphs and figures
Sources: Wikipedia.org, The Hydropower.org