Grand Ethiopian Renaissance Dam
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Grand Ethiopian Renaissance Dam
Rendition of the main dam
Location of Grand Ethiopian Renaissance Dam in Ethiopia
Country
Ethiopia
Location
Benishangul-Gumuz Region
Coordinates
11°12′55″N 35°05′35″ECoordinates:
11°12′55″N 35°05′35″E
Purpose
Power
Status
Under construction
Construction began
April 2011
Opening date
planned, no date[1]
Construction cost
$4 billion USD
Owner(s)
Ethiopian Electric Power
Dam and spillways
Type of dam
Gravity, roller-compacted concrete
Impounds
Blue Nile River
Height
155 m (509 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
Reservoir
Creates
Millennium Reservoir
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)
Power Station
Commission date
planned, no date[1]
Type
Conventional
Turbines
14 x 400 MW
2 x 375 MW
Francis turbines
Installed capacity
6.45 GW (max. planned)[2]
Capacity factor
28.6%
Annual generation
16,153 GWh(est., planned)[2]
Website
www.hidasse.gov.et
The Grand Ethiopian Renaissance Dam (GERD or Taehige; Amharic: ታታታ ታታታታታታ ታታታ
ታታታ Tālāqu ye-Ītyōppyā Hidāsē Gidib), formerly known as the Millennium Dam and sometimes
referred to as Hidase Dam, is a gravity dam on the Blue Nile River in Ethiopia that has been under
construction since 2011. It is in the Benishangul-Gumuz Region of Ethiopia, about 15 km (9 mi) east
of the border with Sudan.[3] At 6.45 gigawatts, the dam will be the largest hydroelectric power plant in
Africa when completed, as well as the 7th largest in the world.[4][5][6] As of August 2017, the work
stood at 60% completion.[7] Once completed, the reservoir will take from 5 to 15 years to fill with
water.[8]
Contents
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1Background
2Cost and financing
3Design
o 3.1Two dams
o 3.2Three spillways
o 3.3Power generation and distribution
o 3.4Early power generation
o 3.5Siltation, evaporation and irrigation
4Construction
o 4.1Major achievements
o 4.2Engineering questions
o 4.3Alleged over-sizing
5Benefits for Ethiopia
6Environmental and social impacts
o 6.1Impact on Ethiopia
o 6.2Impact on Sudan and Egypt
 6.2.1Reactions: cooperation and condemnation
7See also
8References
Background[edit]
The eventual site for the Grand Ethiopian Renaissance Dam was identified by the United States
Bureau of Reclamation during a Blue Nile survey conducted between 1956 and 1964. The Ethiopian
Government surveyed the site in October 2009 and August 2010. In November 2010, a design for
the dam was submitted.[9] On 31 March 2011, a day after the project was made public, a US$4.8
billion contract was awarded without competitive bidding to Salini Costruttori and the dam's
foundation stone was laid on 2 April 2011 by then Prime Minister Meles Zenawi.[10] A rock crushing
plant has been constructed along with a small air strip for fast transportation.[11] The first two
generators are expected to become operational after 44 months of construction.[12] Egypt, which lies
downstream, opposes the dam which it believes will reduce the amount of water that it gets from the
Nile.[13] Zenawi argued, based on an unnamed study, that the dam would not reduce water availability
downstream and would also regulate water for irrigation.[12] In May 2011, it was announced that
Ethiopia would share blueprints for the dam with Egypt so the downstream impact could be
examined.[14]
The dam was originally called "Project X", and after its contract was announced it was called the
Millennium Dam.[15] On 15 April 2011, the Council of Ministers renamed it Grand Ethiopian
Renaissance Dam.[16] Ethiopia has a potential for around 45 GW of hydropower.[17] The dam is being
funded by government bonds and private donations. It was slated for completion in July 2017.[9]
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 preconditions to negotiations, sought regional support
for its position, and some political leaders have discussed methods to sabotage it.[18] 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.[19] 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, which has accused Egypt of inflaming the situation.[20]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.[21] It has accused Egypt of being
unreasonable; Egypt is demanding to increase its share of the Nile's water flow from 66% to 90%.[21]
Cost and financing[edit]
The Ethiopian government has stated that it intends to fund the entire cost of the dam by itself. It has
issued a bond targeted at Ethiopians in the country and abroad to that end.[12] The turbines and
associated electrical equipment of the hydropower plants costing about US$1.8 billion are reportedly
financed by Chinese banks. This would leave US$3 billion to be financed by the Ethiopian
government through other means.[22] The estimated US$4.8 billion construction cost, apparently
excluding the cost of power transmission lines, corresponds to about 5% of Ethiopia’s gross
domestic product of US$87 billion in 2017.
Design[edit]
Renaissance Dam and associated facilities
The design changed several times between 2011 and 2017. This affected both the electrical
parameters and the storage parameters.
Originally, in 2011, the hydropower plant was to receive 15 generating units with 350 MW nameplate
capacity each, resulting in a total installed capacity of 5,250 MW with an expected power generation
of 15,128 GWh per annum.[23] However, due to the upgrading made on the power plant, its
generation capacity was uplifted to 6,000 MW from 5,250 MW, with a power generation of
15,692 GWh per annum through 16 generating units with 375 MW nameplate capacity each. In
2017, the design has again been changed to add another 450 MW, with a power generation of
16,153 GWh per annum.[2][24] That was achieved by upgrading 14 of the 16 generating units from
375 MW to 400 MW without changing the nameplate capacity.[25]
Not only the electrical power parameters were to change over time, but also the storage parameters.
Originally, in 2011, the dam was considered to be 145 m (476 ft) tall with a volume of 10.1 million m3.
The reservoir was considered to have a volume of 66 km3 (54,000,000 acre⋅ft) and a surface area of
1,680 km2 (650 sq mi) at full supply level. The rock-filled saddle dam besides the main dam was
considered to have a height of 45 m (148 ft) meters and a length of 4,800 m (15,700 ft) and a
volume of 15 million m3.[9][26]
In 2013, an Independent Panel of Experts (IPoE) assessed the dam and its technological
parameters. At that time, the reservoir sizes were changed already. The size of the reservoir at full
supply level went up to 1,874 km2 (724 sq mi) (plus 194 km2). The storage volume at full supply level
had increased to 74 km3 (60,000,000 acre⋅ft) (plus 7 km3).[27]These numbers did not change anymore
after 2013.
After the IPoE made its recommendations, in 2013, the dam parameters were changed to account
for higher flow volumes in case of extreme floods: a main dam height of 155 m (509 ft) (plus 10
meters) with a length of 1,780 m (5,840 ft) (no change) and a dam volume of 10.2 million m3 (plus
0.1 million m3). The outlet parameters did not change, only the crest of the main dam was raised.
The rock saddle dam went up to a height of 50 m (160 ft) (plus 5 meters) with a length of 5,200 m
(17,100 ft) (plus 400 meters). The volume of the rock saddle dam increased to 16.5 million m3 (plus
1.5 million m3).[27][28]
The design parameters as of August 2017 are as follows, given the changes as outlined above:
Two dams[edit]
The zero level of the main dam, the ground level, will be at a height of almost exactly 500 m
(1,600 ft) above sea level, corresponding roughly to the level of the river bed of the Blue Nile.
Counting from the ground level, the main gravity dam will be 155 m (509 ft) tall, 1,780 m (5,840 ft)
long and composed of roller-compacted concrete. The crest of the dam will be at a height of 655 m
(2,149 ft) above sea level. The outlets of the two powerhouses are below the ground level, the total
height of the dam will therefore be slightly higher than that of the given height of the dam. In some
publications, the main contractor constructing the dam puts forward a number of 170 m (560 ft) for
the dam height, which might account for the additional depth of the dam below ground level, which
would mean 15 m (49 ft) of excavations from the basement before filling the dam. The structural
volume of the dam will be 10,200,000 m3 (13,300,000 cu yd). The main dam will be 15 km (9 mi)
from the border with Sudan.
Supporting the main dam and reservoir will be a curved and 5.2 km (3 mi) long and 50 m (164 ft)
high rock-fill saddle dam. The ground level of the saddle dam is at an elevation of about 600 m
(2,000 ft) above sea level. The surface of the saddle dam has a bituminous finish, to keep the
interior of the dam dry. The saddle dam will be just 3.3–3.5 km (2–2 mi) away from the border with
Sudan, it is much closer to the border than the main dam.
The reservoir behind both dams will have a storage capacity of 74 km3 (60,000,000 acre⋅ft) and a
surface area of 1,874 km2 (724 sq mi) when at full supply level of 640 m (2,100 ft) above sea level.
The full supply level is therefore 140 m (460 ft) above the ground level of the main dam. Hydropower
generation can happen between reservoir levels of 590 m (1,940 ft), the so-called minimum
operating level, and 640 m (2,100 ft), the full supply level. The live storage volume, usable for power
generation between both levels is then 59.2 km3 (48,000,000 acre⋅ft). The first 90 m (300 ft) of the
height of the dam will be a dead height for the reservoir, leading to a dead storage volume of the
reservoir of 14.8 km3(12,000,000 acre⋅ft).[27]
Three spillways[edit]
The dams will have three spillways. All three spillways together are designed for a flood of up to
38,500 m3/s (1,360,000 cu ft/s), an event not considered to happen at all, as this discharge volume is
the so-called 'Probable Maximum Flood'. All waters from the three spillways are designed to
discharge into the Blue Nile before the river enters Sudanese territory.
The main and gated spillway is located to the left of the main dam and will be controlled by
six floodgates and have a design discharge of 14,700 m3/s (520,000 cu ft/s) in total. The spillway will
be 84 m (276 ft) wide at the outflow gates. The base level of the spillway will be at 624.9 m
(2,050 ft), well below the full supply level.
An ungated spillway, the auxiliary spillway, sits at the center of the main dam with an open width of
about 205 m (673 ft). This spillway has a base-level at 640 m (2,100 ft), which is exactly the full
supply level of the reservoir. The dam crest is 15 m (49 ft) higher to the left and to the right of the
spillway. This ungated spillway is only expected to be used, if the reservoir is both full and the flow
exceeds 14,700 m3/s (520,000 cu ft/s), a flow value, that is expected to be exceeded once every ten
years.
A third spillway, an emergency spillway, is located to the right of the curved saddle dam, with a base
level at 642 m (2,106 ft). This emergency spillway has an open space of about 1,200 m (3,900 ft)
along its rim. This third spillway will carry water only if the conditions for a flood of more than around
30,000 m3/s (1,100,000 cu ft/s) are given, corresponding to a flood to occur only once every 10,000
years.
Power generation and distribution[edit]
Flanking either side of the auxiliary ungated spillway at the center of the dam will be two power
houses. The right will contain 10 x 375 MW Francis turbine-generators, the left power house will
house 6 x 375 MW of the same turbine-generators. 14 of the 16 turbine-generators have been
upgraded to 400 MW without changing the nameplate capacity (which is still at 375 MW), while two
turbine-generators remained at 375 MW.[28][25] The total installed capacity with all turbine-generators
will be 6,450 MW. The average annual flow of the Blue Nile being available for power generation is
expected to be 1,547 m3/s (54,600 cu ft/s),[27] which gives rise to an annual expectation for power
generation of 16,153 GWh, corresponding to a plant load factor (or capacity factor) of 28.6%.
The Francis turbines inside the power houses are installed in a vertical manner, raising 7 m (23 ft)
above the ground level. For the foreseen operation between the minimum operating level and the full
supply level, the head waters for the turbines will be 83–133 m (272–436 ft) high. A switching
station will be located close to the main dam, where the generated power will be delivered to the
national grid. Completed have been four 500 kV main power transmission lines in August 2017, all
going to Holeta and then with several 400 kV lines to the metropolitan area of Addis Ababa.[29] Two
400 kV lines are running from the dam to the Beles Hydroelectric Power Plant. Also planned are
500 kV high-voltage direct current lines.
Early power generation[edit]
Two non-upgraded turbine-generators with 375 MW each are considered to be the first to go into
operation with 750 MW delivered to the national power grid, possibly 2018. This early power
generation will start well before the completion of the dam, when the filling of the reservoir
commences. The two units are sitting within the 10 unit powerhouse to the right side of the dam at
the auxiliary spillway. They are fed by two special intakes within the dam structure that are located at
a height of 540 m (1,770 ft) above sea level. It is foreseen, that power generation can start at a water
level of 560 m (1,840 ft), 30 m (98 ft) below the minimum operating level of the other 14 turbinegenerators. At that level, the reservoir has been filled with roughly 5.5 km3 (1.3 cu mi) of water, which
corresponds to roughly 11% of the annual inflow of 48.8 km3 (11.7 cu mi). During the rainy season,
this is expected to happen within days to weeks. The two early power generating units probably will
be the only units in operation for several years as the filling of the reservoir will take from 5–15
years.
Siltation, evaporation and irrigation[edit]
Two "bottom" outlets at 542 m (1,778 ft), 42 m (138 ft) above ground level are available for delivering
water to Sudan and Egypt under special circumstances, in particular for irrigation purposes
downstream, if the level of the reservoir falls below the minimum operating level of 590 m (1,940 ft)
but also during the initial filling process of the reservoir.
The space below the "bottom" outlets is the primary buffer space
for alluvium through siltation and sedimentation. For the Roseires Reservoir just downstream from
the GERD site, the average siltation / sedimentation volume (without GERD in place) amounts to
around 0.035 km3 (28,000 acre⋅ft) per year. Due to the large size of the GERD reservoir, the siltation
/ sedimentation volume is expected to be much higher in this case, expected are
0.21 km3 (170,000 acre⋅ft) per annum.[27][30] The GERD reservoir will foreseeable take away the
siltation threat from the Roseires reservoir almost entirely.
The ground level of the GERD dam is at around 500 m (1,600 ft) above sea level. Water flowing out
of the dam will be released into the Blue Nile again which will flow for only around 30 km (19 mi),
before joining the Roseires reservoir, which – if at full supply level – will be at 490 m (1,610 ft) above
sea level. There is only a 10 m (33 ft) elevation difference between both projects. The two reservoirs
and accompanied hydropower projects could – if coordinated properly across the border between
Ethiopia and Sudan – become a cascaded system for more efficient hydropower generation and
better irrigation (in Sudan in particular). Water from the 140 m (460 ft) column of the water storage of
the GERD reservoir could be diverted through tunnels to facilitate new irrigation schemes in Sudan
close to the border with South Sudan. In Ethiopia itself, no irrigation schemes are planned due to the
proximity of the dam to the downstream border with Sudan.
Evaporation of water from the reservoir is expected to be at 3% of the annual inflow volume of
48.8 km3 (11.7 cu mi), which corresponds to an average volume lost through evaporation of around
1.5 km3 (0.36 cu mi) annually. This was considered neglectable by the IPoE.[27] For comparison, Lake
Nasser in Egypt loses between 10–16 km3 (2.4–3.8 cu mi) annually through evaporation.[31]
Construction[edit]
Major achievements[edit]
The main contractor is the Italian company Salini Costruttori, which also served as primary
contractor for the Gilgel Gibe II, Gilgel Gibe III, and Tana Beles dams. Simegnew Bekelewas the
project manager of GERD from the start of construction in 2011 up to his death on July 26, 2018.
The dam is expected to consume 10 million metric tons of concrete. The government has pledged to
use only domestically produced concrete. In March 2012, Salini awarded the Italian firm Tratos Cavi
SPA a contract to supply low- and high-voltage cable for the dam.[28][32] Alstom will provide the eight
375 MW Francis turbines for the project's first phase, at a cost of €250 million.[33] As of April 2013,
nearly 32 percent of the project was complete. Site excavation and some concrete placement was
underway. One concrete batch plant has been completed with another under
construction.[34] Diversion of the Blue Nile was completed on 28 May 2013 and marked by a
ceremony the same day.[35] By January 2016 the dam had 4 million cubic meters of concrete poured,
and the installation of the first two turbines was imminent. The first power production of 750 MW was
slated for sometime later that year.[36]
Engineering questions[edit]
Dam construction in 2014
In 2012, the International Panel of Experts was formed with experts from Egypt, Sudan, Ethiopia,
and other independent entities to discuss mainly engineering and partially impact related questions.
This panel concluded at a number of engineering modifications, that were proposed to Ethiopia and
the main contractor constructing the dam. One of the two main engineering questions, dealing with
the size of flood events and the constructive response against them, was later addressed by the
contractor. The emergency spillway located near the rock saddle dam saw an increase of the rim
length from 300 m to 1,200 m to account even for the largest possible flood of the river. The second
main recommendation of the panel however found no immediate resonance. This second
recommendation dealt with the structural integrity of the dam in context with the underlying rock
basement as to avoid the danger of a sliding dam due to an unstable basement. It was argued by
the panel, that the original structural investigations were done with considering only a generic rock
mass without taking special conditions like faults and sliding planes in the rock basement (gneiss)
into account. The panel noted, that there was indeed an exposed sliding plane in the rock basement,
this plane potentially allowing a sliding process downstream. The panel didn't argue that a
catastrophic dam failure with a release of dozens of cubic kilometers of water would be possible,
probable or even likely, but the panel argued, that the given safety factor to avoid such a
catastrophic failure might be non-optimal in the case of the Grand Ethiopian Renaissance Dam.[27] It
was later revealed that the underlying basement of the dam was completely different from all
expectations and did not fit the geological studies as the needed excavation works exposed the
underlying gneiss. The engineering works then had to be adjusted, with digging and excavating
deeper than originally planned, which took extra time and capacity and also required more
concrete.[1]
Alleged over-sizing[edit]
Originally, in 2011, the hydropower plant was to receive 15 generating units with 350 MW nameplate
capacity each, resulting in a total installed capacity of 5,250 MW with an expected power generation
of 15,128 GWh per annum.[23] The capacity factor of the planned hydropower plant – the expected
electricity production divided by the potential production if the power plant was utilized permanently
at full capacity – was only 32.9% compared to 45–60% for other, smaller hydropower plants in
Ethiopia. Critics concluded that a smaller dam would have been more cost-effective.[23]
Soon after, in 2012, the hydropower plant was upgraded to receive 16 generating units with 375 MW
nameplate capacity each, increasing the total installed capacity to 6,000 MW, with the expected
power generation going up only slightly to 15,692 GWh per annum. Consequently, the capacity
factor shrank to 29.9%. According to Asfaw Beyene, a Professor of Mechanical Engineering at San
Diego State University (California), the dam and its hydropower plant are massively oversized:
"GERD’s available power output, based on the average of river flow throughout the year and the
dam height, is about 2,000 megawatts, not 6,000. There is little doubt that the system has been
designed for a peak flow rate that only happens during the 2–3 months of the rainy season.
Targeting near peak or peak flow rate makes no economic sense."[37][38]
In 2017, the total installed capacity was moved to 6,450 MW, without changing the number and
nameplate capacity of the generating units (which then remained at 6,000 MW in total). This was
thought to arrive from enhancements made to the generators.[4] The expected power generation per
annum went up to 16,153 GWh,[2] the capacity factor shrank again and reached 28.6%. This time
nobody publicly voiced concern. Such an optimization of the Francis turbines used at the dam site is
indeed possible and is usually done by the provider of the turbines taking into account site-specific
conditions.
Considering the critics voiced about the alleged over-sizing of the possible power output, now of
6,450 MW. Ethiopia is relying heavily on hydropower, but the country is often affected
by droughts (see e.g. 2011 East Africa drought). The water reservoirs used for power generation in
Ethiopia have a limited size. For example, the Gilgel Gibe I reservoir, that feeds both the Gilgel Gibe
I powerplant and the Gilgel Gibe II Power Station, has a capacity of 0.7 km3. In times of drought,
there is no water left to generate electrical power. This heavily affected Ethiopia in the drought years
2015/16 and it was only the Gilgel Gibe III powerplant, that in 2016 just started to run in trial service
on a 14 km3 well-filled reservoir, that saved the economy of Ethiopia.[1] The GERD-reservoir, once it
has filled, has a total water volume of 74 km3, 3 times the volume of Ethiopia's largest lake, Lake
Tana. Filling it takes 5–15 years and even by using all generating units at maximum capacity will not
drain it within a few months. The installed power of 6.450 MW in combination with the size of the
reservoir will help managing the side effects of the next severe drought, when other hydropower
plants have to stop their operations.
Benefits for Ethiopia[edit]
This section will only cover the benefits for Ethiopia, but there are also transboundary benefits
expected.
A major benefit of the dam will be hydropower production. All the energy generated by GERD will be
going into the national grid of Ethiopia to fully support the development of the whole country, both in
rural and urban areas. The role of GERD will be to act as a stabilizing backbone of the Ethiopian
national grid. There will be exports, but only if there is a total surplus of energy generated in
Ethiopia. This is mainly expected to happen during rainy seasons, when there is plenty of water for
hydropower generation.[1]
The eventual surplus electricity of GERD which does not fit the demand inside Ethiopia, is then to be
sold and exported to neighboring countries including Sudan and possibly Egypt, but also Djibouti.
Revenues in US$ or in € are to be expected. Exporting the electricity from the dam would require the
construction of massive transmission lines to major consumption centers such as Sudan’s
capital Khartoum, located more than 400 km away from the dam. These export sales would come on
top of electricity that is expected to be sold from other large hydropower plants. Powerplants that
have been readied or are under construction in Ethiopia, such as Gilgel Gibe III or Koysha, whose
exports (if given surplus energy) will mainly be going to Kenya through a 500 kV HVDC line.
The volume of the reservoir will be two to three times that of Lake Tana which allows to expect
abundant fish. Expected are up to 7,000 tonnes of fish annually as well as the reservoir becoming a
hotspot for tourism.[39]