Lake Kivu
Template:Short description Template:Infobox body of water
Lake Kivu is one of the African Great Lakes.<ref name="readersnatural" /> It lies on the border between the Democratic Republic of the Congo and Rwanda, and is in the Albertine Rift, the western branch of the East African Rift.<ref>Template:Cite journal</ref> Lake Kivu empties into the Ruzizi River, which flows southwards into Lake Tanganyika.<ref name=":0" /> In 1894, German officer and colonial ruler Gustav Adolf von Götzen was the first recorded European to visit the lake.
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In the past, Lake Kivu drained toward the north, contributing to the White Nile. About 13,000 to 9,000 years ago, volcanic activity blocked Lake Kivu's outlet to the watershed of the Nile.<ref name="Danley">Template:Cite journal</ref> The volcanism produced mountains, including the Virungas, which rose between Lake Kivu and Lake Edward, to the north.<ref>Template:Cite book</ref> Water from Lake Kivu was then forced south down the Ruzizi. This, in turn, raised the level of Lake Tanganyika, which overflowed down the Lukuga River.<ref name="Danley"/>
Lake Kivu is one of three lakes in the world, along with Lake Nyos and Lake Monoun, that undergo limnic eruptions (where overturn of deepwater stratified layers releases dissolved carbon dioxide (Template:CO2)). The lake's bottom also contains methane (Template:CH4), meaning if a limnic eruption occurs, the lives of the two million people living nearby would be in danger.
Geography
Lake Kivu is approximately Template:Convert long and Template:Convert at its widest.<ref name="readersnatural">Template:Cite book</ref> Its irregular shape makes measuring its precise surface area difficult; it has been estimated to cover a total surface area of some Template:Convert, making it Africa's eighth largest lake.<ref name=":0">Template:Cite web</ref> The surface of the lake sits at a height of Template:Convert above sea level. This lake has a chance of suffering a limnic eruption every 1000 years.<ref name="readersnatural" /> The lake has a maximum depth of Template:Convert and a mean depth of Template:Convert, making it the world's twentieth deepest lake by maximum depth, and the thirteenth deepest by mean depth.<ref name="readersnatural" />
The lake bed sits upon a rift valley that is slowly being pulled apart, causing volcanic activity in the area.
The world's tenth-largest island in a lake, Idjwi, lies in Lake Kivu.
Human geography
Some Template:Convert or 58 percent of the lake's waters lie within DRC borders.<ref name=":0" />
Settlements on the lake's shore include Bukavu, Kabare, Kalehe, Sake and Goma in the Democratic Republic of the Congo, and Gisenyi, Kibuye, and Cyangugu in Rwanda.
In early 2025, during the M23 campaign, all settlements in the Congolese side of the lake's shores were occupied by the Rwandan military and the M23 Movement, with provincial capital Goma being captured in January and all settlements being under M23 control as of early March.<ref name=":015">Template:Cite web</ref> In 12 March, M23 landed on Idjwi island, occupying it without resistance.<ref>Template:Cite web</ref>
Chemistry
Lake Kivu is a meromictic lake containing a freshwater surface layer that becomes more saline with depth, with a salinity approaching 6g/kg near the bottom.<ref>Template:Cite journal</ref> Along with Cameroonian Lake Nyos and Lake Monoun, Lake Kivu is one of three that are known to undergo limnic eruptions (where overturn of deepwater stratified layers releases dissolved carbon dioxide). Around the lake, geologists<ref>Template:Cite web</ref>Template:Verify source found evidence of massive local extinctions about every thousand years, presumably caused by outgassing events. The trigger for lake overturns in Lake Kivu is unknown, but volcanic activity and changes in climate are both suspected.<ref>Template:Cite book</ref> The gaseous chemical composition of exploding lakes is unique to each lake. In Lake Kivu's case, it includes methane (Template:CH4) and carbon dioxide (Template:CO2), as a result of lake water interaction with volcanic hot springs.<ref name="Wenz">Template:Cite journal</ref>
The amount of methane contained at the bottom of the lake is estimated to be Template:Convert. If burned in a modern combined-cycle generating plant, that amount of methane would generate around 40,000 megawatts for an entire year, which is equivalent to the power output equivalent to six times that of the Grand Coulee Dam at peak springtime power. The lake also holds an estimated Template:Convert of carbon dioxide which, if released in an eruption event, could suffocate all of the inhabitants of the lakeshore.<ref>Template:Cite web</ref> The water temperature is Template:Convert, and the pH is about 7 in the anoxic region, and around 9 in the oxygenated waters.<ref>Template:Cite journal</ref> The methane is reported to be produced by microbial reduction of the volcanic Template:CO2.<ref>Template:Cite journal</ref> A future overturn and gas release from the deep waters of Lake Kivu would result in catastrophe, dwarfing the historically documented lake overturns at the much smaller Lakes Nyos and Monoun. The lives of the approximately two million people who live in the lake basin area would be threatened.<ref name="Wenz"/>
Cores from the Bukavu Bay area of the lake reveal that the bottom has layered deposits of the rare mineral monohydrocalcite interlaid with diatoms, on top of sapropelic sediments with high pyrite content. These are found at three different intervals. The sapropelic layers are believed to be related to hydrothermal discharge and the diatoms to a bloom which reduced the carbon dioxide levels low enough to precipitate monohydrocalcite.<ref>"Stoffers, P., and Fischbeck, R. (1974) Monohydrocalcite in the sediments of Lake Kivu (East Africa) Sedimentology, 21, 163–170.</ref>
Scientists hypothesize that sufficient volcanic interaction with the lake's bottom water that has high gas concentrations would heat water, force the methane out of the water, spark a methane explosion, and trigger a nearly simultaneous release of carbon dioxide, though the entry of 1 million cubic meters of lava during the January 2002 eruption had no effect.<ref>Template:Cite web</ref><ref name=solidarites> Template:Cite web mirror </ref> The carbon dioxide would then suffocate large numbers of people in the lake basin as the gases roll off the lake surface. It is also possible that the lake could spawn lake tsunamis as gas explodes out of it.<ref name="Rwanda and DRC Sign Agreement Over L. Kivu Methane Gas Exploration">Template:Cite web</ref><ref name="Killer Lakes">Template:Cite web</ref><ref>"In the Shadow of Doom" Template:Webarchive, The Walrus, May 2006</ref>
The risk posed by Lake Kivu began to be understood during the analysis of more recent events at Lake Nyos. Lake Kivu's methane was originally thought to be merely a cheap natural resource for export, and for the generation of cheap power. Once the mechanisms that caused lake overturns began to be understood, so did awareness of the risk the lake posed to the local population.
An experimental vent pipe was installed at Lake Nyos in 2001 to remove gas from the deep water, but such a solution for the much larger Lake Kivu would be considerably more expensive. The approximately Template:Convert of carbon dioxide in the lake is a little under 2 percent of the amount released annually by human fossil fuel burning. Therefore, the process of releasing it could potentially have costs beyond simply building and operating the system.
This problem associated with the prevalence of methane is that of mazuku, the Swahili term "evil wind" for the outgassing of methane and carbon dioxide that kills people and animals, and can even kill vegetation when in high enough concentration.
Methane extraction
Lake Kivu has recentlyTemplate:When been found to contain approximately Template:Convert of dissolved biogas at a depth of Template:Convert. Until 2004, extraction of the gas was done on a small scale, with the extracted gas being used to run boilers at the Bralirwa brewery in Gisenyi.<ref>"Case Studies : Recovery of Gas from Lake Kivu – The Goats of Rwanda" Template:Webarchive, Added Value Engineering Consultants, accessed 4 May 2007</ref><ref name=powerhouse>Template:Cite news</ref> As far as large-scale exploitation of this resource is concerned, the Rwandan government has negotiated with a number of parties to extract methane from the lake.
In 2011 ContourGlobal, a UK-based energy company focused on emerging markets, secured project financing to initiate a large-scale methane extraction project. The project is run through a local Rwandan entity called KivuWatt, using an offshore barge platform to extract, separate, and clean the gasses obtained from the lake bed before pumping purified methane via an underwater pipeline to onshore gas engines. Stage one of the project, powering three "gensets" along the lake shore and supplying 26 MW of electricity to the local grid, has been completed. The next phase aims to deploy nine additional gensets at 75 MW to create a total capacity of 101 MW.<ref name="contourglobal">Template:Cite web</ref>
In addition, Symbion Power Lake Kivu Limited was awarded a Concession and Power Producing Agreement (PPA) in 2015, to produce 50 MW of power using Lake Kivu methane. The project was expected to commence construction in 2019, with first power (Phase 1 - 14 MW) to be produced in first quarter 2020. The plant was planned to be fully operational in 2021.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>Template:Update inline
Symbion Power has purchased another concession for a further 25 MW and are currently negotiating a PPA with the Rwanda Electricity Group which may see 8 MW of power dispatched to the Grid six months after the PPA has been signed. This concession is on the site of the original pilot plant known as KP1.Template:Update inline
In addition to managing gas extraction, KivuWatt will also manage the electrical generation plants and on-sell the electrical power to the Rwandan government under the terms of a long-term Power Purchase Agreement (PPA). This allows KivuWatt to control a vertically integrated energy offering from point of extraction to point of sale into the local grid. Extraction is said to be cost-effective and relatively simple because once the gas-rich water is pumped up, the dissolved gases (primarily carbon dioxide, hydrogen sulfide and methane) begin to bubble out as the water pressure gets lower. This project is expected to increase Rwanda's energy generation capability by as much as 20 times, and will enable Rwanda to sell electricity to neighbouring African countries.<ref name=powerhouse /> The firm was awarded the 2011 Africa Power deal of the year for innovation in the financing arrangements it obtained from various sources for the KivuWatt project.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> The $200 million power plant was operating at 26 MW in 2016.<ref>Template:Cite web</ref>
Biology and fisheries
The fish fauna in Lake Kivu is relatively poor with 28 described species, including four introduced species.<ref name=FishSnoeks>Template:Cite journal</ref> The natives are the Lake Rukwa minnow (Raiamas moorii), four species of barb (ripon barbel, Barbus altianalis, East African red-finned barb, Enteromius apleurogramma, redspot barb, E. kerstenii and Pellegrin's barb, E. pellegrini), an Amphilius catfish, two Clarias catfish (C. liocephalus and C. gariepinus), Nile tilapia (Oreochromis niloticus) and 15 endemic Haplochromis cichlids.<ref name=FishSnoeks/> Another Template:Circa possibly undescribed species of cichlids are known from the lake.<ref>Template:Cite journal</ref> The introduced species are three cichlids, the longfin tilapia (Oreochromis macrochir), blue-spotted tilapia (O. leucostictus) and redbreast tilapia (Coptodon rendalli), and a clupeid, the Lake Tanganyika sardine (Limnothrissa miodon)<ref name=FishSnoeks/><ref name="Collart">Template:Cite journal</ref><ref name="Capart">Template:Cite journal</ref> The sardine is referred to locally as 'Ndagala' or 'Isambaza'.<ref name="Collart 1989">Template:Cite book</ref>
The exploitable stock of the Lake Tanganyika sardine was estimated at Template:Convert per year.<ref>Template:Cite journal</ref> It was introduced to Lake Kivu in late 1959 by the Belgian agronomist Alphonse Collart.<ref name="Collart" /><ref name="Capart" /> An attempt to introduce the similar Lake Tanganyika sprat (Stolothrissa tanganicae) at the same time was unsuccessful.<ref name="Collart 1989" />
At present, Lake Kivu is the sole natural lake in which L. miodon, a sardine originally restricted to Lake Tanganyika, has been introduced initially to fill an empty niche. Prior to the introduction, no planktivorous fish was present in the pelagic waters of Lake Kivu. In the early 1990s, the number of fishers on the lake was 6,563, of which 3,027 were associated with the pelagic fishery and 3,536 with the traditional fishery. The widespread armed conflict in the surrounding region from the mid-1990s resulted in a decline in the fisheries harvest.<ref name="FAO">Template:Cite web</ref>
Following this introduction, the sardine has gained substantial economic and nutritional importance for the lakeside human population but from an ecosystem standpoint, the introduction of planktivorous fish may result in important modifications of plankton community structure. Recent observations showed the disappearance during the last decades of a large grazer, Daphnia curvirostris, and the dominance of mesozooplankton community by three species of cyclopoid copepod: Thermocyclops consimilis, Mesocyclops aequatorialis and Tropocyclops confinis.<ref>Template:Cite book</ref><ref>Template:Cite journal</ref>
The first comprehensive phytoplankton survey was released in 2006.<ref name="Sarmento 2006">Template:Cite book</ref> With an annual average chlorophyll in the mixed layer of 2.2 mg m−3 and low nutrient levels in the euphotic zone, the lake is clearly oligotrophic. Diatoms are the dominant group in the lake, particularly during the dry season episodes of deep mixing. During the rainy season, the stratified water column, with high light and lower nutrient availability, favour dominance of cyanobacteria with high numbers of phototrophic picoplankton.<ref name="Sarmento 2006"/><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The actual primary production is 0.71 g C m−2 d−1 (≈ 260 g C m−2 a−1).<ref>Template:Cite journal</ref>
A study of evolutionary genetics showed that the cichlids from lakes in northern Virunga (e.g., Edward, George, Victoria) would have evolved in a "proto-lake Kivu", much older than the intense volcanic activity (20,000-25,000 years ago) which cut the connection.<ref>Template:Cite journal</ref> The elevation of the mountains west of the lake (which is currently the Kahuzi-Biega National Park, one of the largest reserves of eastern lowland (or Grauer's) gorillas in the world), combined with the elevation of the eastern rift (located in eastern Rwanda) would be responsible for the drainage of water from central Rwanda in the actual Lake Kivu. This concept of "proto-lake Kivu" was challenged by lack of consistent geological evidence,<ref>Template:Cite journal</ref> although the cichlid's molecular clock suggests the existence of a lake much older than the commonly cited 15,000 years.
Lake Kivu is the home of four species of freshwater crab, including two non-endemics (Potamonautes lirrangensis and P. mutandensis) and two endemics (P. bourgaultae and P. idjwiensis).<ref name=crabs>Cumberlidge, N., and Meyer, K. S. (2011). A revision of the freshwater crabs of Lake Kivu, East Africa. Journal Articles. Paper 30.</ref> Among Rift Valley lakes, Lake Tanganyika and Lake Victoria are the only other with endemic freshwater crabs.<ref name=crabs/><ref>Cumberlidge, N., and P.F. Clark (2017). Description of three new species of Potamonautes MacLeay, 1838 from the Lake Victoria region in southern Uganda, East Africa (Brachyura: Potamoidea: Potamonautidae). European Journal of Taxonomy 371: 1–19. Template:Doi</ref>
Illegal fishing
In 2018, over 400 cases of potential illegal fishing were recorded on Lake Kivu. According to the Animal Research and Technology Transfer at the Rwanda Agricultural Board, fish production in Kivu Lake dropped from 24,199 tonnes in the 2017–2018 fishing season to 16,194 tonnes in 2019–2020,<ref>Template:Cite web</ref> which Deputy Director Solange Uwituze attributed to fishing methods that affect fish reproduction. Between May and July 2020, Rwanda Police Marine Unit operations reported 27 cases including 10 arrested poachers for illegal fishing on the lake.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>
Gallery
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Lake Kivu from Sake, Goma, D R Congo
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Lake Kivu with Goma in the background, Congo
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Lake Kivu separating Bukavu (In the foreground) and Cyangugu (In the background) as seen from Tumbimbi.
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See also
References
Template:Commons category Template:African Great Lakes Template:Authority control
- Pages with broken file links
- Lake Kivu
- African Great Lakes
- Democratic Republic of the Congo–Rwanda border
- International lakes of Africa
- Lakes of the Great Rift Valley
- Lakes of the Democratic Republic of the Congo
- Lakes of Rwanda
- Meromictic lakes
- Limnically active lakes
- World Heritage Sites in the Democratic Republic of the Congo
- World Heritage Sites in Rwanda