Misplaced Pages

#49950

57-573: The district lies on the shores of Lake Kivu , around the city of Gisenyi , and just across the border from the Congolese city of Goma . It is bordered in the east by Nyabihu District , west and north by the Democratic Republic of Congo and south by Rutsiro district and is 154.7 km from city of Kigali the capital of Rwanda which is 2 hours and 53 minutes drive. Its geographic location and related features such as Lake Kivu helps

114-405: A CO 2 concentration scale by taking air samples of the affected region. The Messel pit fossil deposits of Messel , Germany , show evidence of a limnic eruption there in the early Eocene . Among the victims are perfectly preserved insects , frogs , turtles , crocodiles , birds , anteaters , insectivores , early primates , and paleotheres . For a lake to undergo a limnic eruption,

171-505: A density of 1039 Inhabitants/Km2 , where 51.7 % of the total population are females and 48.3 % are male . Total population in urban areas is 149,209 which makes 37% of the total district's population whereas 254,453 (63%) reside in rural areas. The district's population represents 3.8% of the total country's population and 16.3 % of the Western Province population (2,471,239 inhabitants). The average house-hold size

228-637: A depth of 300 metres (1,000 ft). 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 . As far as large-scale exploitation of this resource is concerned, the Rwandan government has negotiated with a number of parties to produce methane from the lake. In 2011 ContourGlobal , a UK-based energy company focused on emerging markets, secured project financing to initiate

285-511: A far more densely populated area, with over two million people living along its shores. The part within the Democratic Republic of the Congo is a site of active armed conflict and low state capacity for the DRC government, which impedes both studies and any subsequent mitigating actions. Lake Kivu has not reached a high level of CO 2 saturation yet; if the water were to become heavily saturated,

342-577: A further 25 MW and are currently negotiating a PPA with the Rwanda Electricity Group which may see 8 MW of power despatched 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. In addition to managing gas extraction, KivuWatt will also manage the electrical generation plants and on-sell the electrical power to

399-470: 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 ). Among Rift Valley lakes , Lake Tanganyika and Lake Victoria are the only other with endemic freshwater crabs. In 2018, over 400 cases of potential illegal fishing were recorded on Lake Kivu. According to

456-413: 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 on-shore gas engines . Stage one of the project, powering three " gensets " along the lake shore and supplying 26 MW of electricity to

513-501: A limnic eruption would pose a great risk to human and animal life, potentially killing millions. Two significant changes in Lake Kivu's physical state have brought attention to a possible limnic eruption: the high rates of methane dissociation and a rising surface temperature. Research investigating historical and present-day temperatures show Lake Kivu's surface temperature is increasing by about 0.12 °C per decade. Lake Kivu

570-406: 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 of six Grand Coulee Dams operating at peak springtime power. The lake also holds an estimated 256 cubic kilometres (61 cu mi) of carbon dioxide which, if released in an eruption event, could suffocate all of the inhabitants of

627-448: A total surface area of some 2,700 km (1,040 sq mi), making it Africa's eighth largest lake. The surface of the lake sits at a height of 1,460 metres (4,790 ft) above sea level. This lake has a chance of suffering a limnic eruption every 1000 years. The lake has a maximum depth of 475 m (1,558 ft) and a mean depth of 220 m (722 ft), making it the world's twentieth deepest lake by maximum depth, and

SECTION 10

#1732782774050

684-507: Is 0.71 g C m d (≈ 260 g C m a ). 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. The elevation of the mountains west of the lake (which is currently the Kahuzi-Biega National Park , one of

741-486: Is 5.2 against 4.8 at national level, the population aged between 0-14 years old represented 43.8% and the population aged between 15 and 49 years old represented 47.8% while those above 50 years old represented 8.1%. 1°41′S 29°20′E  /  1.683°S 29.333°E  / -1.683; 29.333 Lake Kivu Lake Kivu is one of the African Great Lakes . It lies on the border between

798-724: Is also close to Mount Nyiragongo , an active volcano . On 2 May 2021, a new eruption started. Congo Nile is a 227 km trail along lake Kivu forming Kivu belt as it extends from Rubavu, continues through Rutsiro, then Karongi, up to Nyamasheke and ends at Rusizi District. The District of Rubavu is composed of 12 administrative sectors, 80 Cells and 525 Villages (Imidugudu). The 12 sectors ( imirenge ) are Bugeshi, Busasamana, Cyanzarwe, Gisenyi, Kanama, Kanzenze, Mudende, Nyakiliba, Nyamyumba, Nyundo , Rubavu and Rugerero. In 2012, The fourth Rwanda Population and Housing Census (PHC4), enumerated 403,662 residents in Rubavu District on

855-650: Is estimated only one meromictic lake exists for every 1,000 holomictic lakes. Finally, a lake must be very deep in order to have sufficiently pressurized water that can dissolve large amounts of CO 2 . Once an eruption occurs, a large CO 2 cloud forms above the lake and expands to the surrounding region. Because CO 2 is denser than air, it has a tendency to sink to the ground, simultaneously displacing breathable air, resulting in asphyxia . CO 2 can make human bodily fluids highly acidic and potentially cause CO 2 poisoning . As victims gasp for air, they actually accelerate asphyxia by inhaling CO 2 . At Lake Nyos,

912-517: Is in close proximity to potential triggers: Mount Nyiragongo (an active volcano which erupted in January 2002 and May 2021), an active earthquake zone, and other active volcanoes. While the lake could be degassed in a manner similar to Lake Monoun and Lake Nyos, due to the size of Lake Kivu and the volume of gas it contains, such an operation would be expensive, running into the millions of dollars. A scheme initiated in 2010 to use methane trapped in

969-572: 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 (CO 2 )). The lake's bottom also contains methane ( CH 4 ), meaning if a limnic eruption occurs, the lives of the two million people living nearby would be in danger. Lake Kivu is approximately 42 km (26 mi) long and 50 km (31 mi) at its widest. Its irregular shape makes measuring its precise surface area difficult; it has been estimated to cover

1026-442: Is unknown, but volcanic activity and changes in climate are both suspected. The gaseous chemical composition of exploding lakes is unique to each lake. In Lake Kivu's case, it includes methane ( CH 4 ) and carbon dioxide (CO 2 ), as a result of lake water interaction with volcanic hot springs. The amount of methane contained at the bottom of the lake is estimated to be 65 cubic kilometres (16 cu mi). If burned in

1083-594: The Democratic Republic of the Congo and Rwanda , and is in the Albertine Rift , the western branch of the East African Rift . Lake Kivu empties into the Ruzizi River , which flows southwards into Lake Tanganyika . In 1894, German officer and colonial ruler Gustav Adolf von Götzen was the first European to discover the lake. In the past, Lake Kivu drained toward the north, contributing to

1140-695: The White Nile . About 13,000 to 9,000 years ago, volcanic activity blocked Lake Kivu's outlet to the watershed of the Nile. The volcanism produced mountains, including the Virungas , which rose between Lake Kivu and Lake Edward, to the north. 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 . Lake Kivu

1197-639: 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, 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

SECTION 20

#1732782774050

1254-456: The CO 2 comes out of solution and forms bubbles. The natural buoyancy of the bubbles draws the water up the pipe at high velocity resulting in a fountain at the surface. The degassifying water acts like a pump, drawing more water into the bottom of the pipe, and creating a self-sustaining flow. This is the same process which leads to a natural eruption, but in this case it is controlled by the size of

1311-495: The CO 2 is dissolved in the water. In both lakes and soft drinks, CO 2 dissolves much more readily at higher pressure due to Henry's law . When the pressure is released, the CO 2 comes out of solution as bubbles of gas, which rise to the surface. CO 2 also dissolves more readily in cooler water, so very deep lakes can dissolve very large amounts of CO 2 since pressure increases, and temperature decreases, with depth. A small increase in water temperature can lead to

1368-639: The Democratic Republic of the Congo, and Gisenyi , Kibuye , and Cyangugu in Rwanda. Lake Kivu is a fresh water lake and, along with Cameroonian Lake Nyos and Lake Monoun , 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 found evidence of massive local extinctions about every thousand years, presumably caused by outgassing events. The trigger for lake overturns in Lake Kivu

1425-429: 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 sulphide and methane) begin to bubble out as

1482-504: The carbon dioxide levels low enough to precipitate monohydrocalcite. Scientists hypothesise 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. The carbon dioxide would then suffocate large numbers of people in

1539-544: The district to be a business and tourism hub (especially through cross border trade with DRC). Geography of the District Rainfall in Rubavu District varies between 1200 mm and 1500 mm per year. The Land of Northwest part of the District has a very rich soil, but shallow, volcanic ash and lava decomposed, while land in the south east has deep soils but poor, often acidic, sandy clay and leached by high erosion, It

1596-545: The gas cloud descended into a nearby village where it settled, killing nearly everyone; casualties as far as 25 km (16 mi) were reported. A change in skin color on some bodies led scientists to hypothesize the gas cloud may have contained dissolved acid such as hydrogen chloride , though this hypothesis is disputed. Many victims were found with blisters on their skin, thought to have been caused by pressure ulcers , which were likely caused by low blood oxygen levels in those asphyxiated by carbon dioxide. Nearby vegetation

1653-425: The gas into the air and can displace enough water to form a tsunami . Limnic eruptions are exceptionally rare for several reasons. First, a CO 2 source must exist; regions with volcanic activity are most at risk. Second, the vast majority of lakes are holomictic (their layers mix regularly), preventing a buildup of dissolved gases. Only meromictic lakes are stratified , allowing CO 2 to remain dissolved. It

1710-477: The lake basin area would be threatened. 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

1767-478: 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. 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

Rubavu District - Misplaced Pages Continue

1824-428: The lake. Limnic eruption A limnic eruption , also known as a lake overturn , is a very rare type of natural hazard in which dissolved carbon dioxide (CO 2 ) suddenly erupts from deep lake waters, forming a gas cloud capable of asphyxiating wildlife , livestock , and humans . Scientists believe earthquakes , volcanic activity , and other explosive events can serve as triggers for limnic eruptions as

1881-593: The lake. 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 ) The sardine is referred to locally as ' Ndagala ' or 'Isambaza'. The exploitable stock of the Lake Tanganyika sardine was estimated at 2,000–4,000 metric tons (2,000–3,900 long tons) per year. It

1938-435: The lakeshore. The water temperature is 24 °C (75 °F), and the pH is about 8.6. The methane is reported to be produced by microbial reduction of the volcanic CO 2 . 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

1995-515: 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 . The first comprehensive phytoplankton survey

2052-483: The largely invisible nature of the underlying cause (CO 2 gas) behind limnic eruptions, it is difficult to determine to what extent, and when, eruptions have occurred in the past. The Roman historian Plutarch reports that in 406   BC, Lake Albano surged over the surrounding hills, despite there being no rain nor tributaries flowing into the lake to account for the rise in water level. The ensuing flood destroyed fields and vineyards before eventually pouring into

2109-403: 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, although the cichlid's molecular clock suggests the existence of

2166-554: The local grid, has since been completed. The next phase aims to deploy nine additional gensets at 75 MW to create a total capacity of 101 MW. 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 is expected to commence construction in 2019, with first power (Phase 1 - 14 MW) to be produced in first quarter 2020. The plant will be fully operational in 2021. Symbion Power has purchased another concession for

2223-401: The much larger Lake Kivu , rests on the border between the Democratic Republic of the Congo and Rwanda , and contains massive amounts of dissolved CO 2 . Sediment samples taken from the lake showed an event caused living creatures in the lake to go extinct around every 1,000 years, and caused nearby vegetation to be swept back into the lake. Limnic eruptions can be detected and quantified on

2280-423: The pipe. Each pipe has a limited pumping capacity and several would be required for both Lake Monoun and Lake Nyos to degas a significant fraction of the deep lake water and render the lakes safe. The deep lake waters are slightly acidic due to the dissolved CO 2 which causes corrosion to the pipes and electronics, necessitating ongoing maintenance. There is some concern that CO 2 from the pipes could settle on

2337-560: 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. Lake Kivu has recently been found to contain approximately 55 billion m (1.9 trillion cu ft) of dissolved biogas at

Rubavu District - Misplaced Pages Continue

2394-524: The release of a large amount of CO 2 . Once a lake is saturated, it is very unstable and it gives off a smell of rotten eggs and gunpowder, but a trigger is needed to set off an eruption. In the case of the 1986 Lake Nyos eruption, landslides were the suspected triggers, but a volcanic eruption, an earthquake , or even wind and rain storms can be potential triggers. Limnic eruptions can also be caused by gradual gas saturation at specific depths triggering spontaneous gas development. Regardless of cause,

2451-467: The rising CO 2 displaces water. Lakes in which such activity occurs are referred to as limnically active lakes or exploding lakes . Some features of limnically active lakes include: Investigations of the Lake Monoun and Lake Nyos casualties led scientists to classify limnic eruptions as a distinct type of hazard event, even though they can be indirectly linked to volcanic eruptions. Due to

2508-443: 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 510 million metric tons (500 × 10 ^ long tons) of carbon dioxide in the lake is a little under 2 percent of the amount released annually by human fossil fuel burning. Therefore,

2565-466: The same amount of gas that naturally enters at the lake bed. In January 2003, an 18-month project was approved to fully degas Lake Monoun, and the lake has since been rendered safe. There is some evidence that Lake Michigan in the United States spontaneously degasses on a much smaller scale each fall. Lake Kivu is not only about 1,700 times larger than Lake Nyos , but is also located in

2622-669: The sea. This event is thought to have been caused by volcanic gases, trapped in sediment at the bottom of the lake and gradually building up until suddenly releasing, causing the water to overflow. In recent history, this phenomenon has been observed twice. The first recorded limnic eruption occurred in Cameroon at Lake Monoun in 1984, causing asphyxiation and death of 37 people living nearby. A second, deadlier eruption happened at neighboring Lake Nyos in 1986, releasing over 80 million m of CO 2 , killing around 1,700 people and 3,000 livestock, again by asphyxiation. A third lake,

2679-674: The surface of the lake forming a thin layer of unbreathable air and thus potentially causing problems for wildlife. In January 2001, a single pipe was installed by the French-Cameroonian team on Lake Nyos, and two more pipes were installed in 2011 with funding support from the United Nations Development Programme . A pipe was installed at Lake Monoun in 2003 and two more were added in 2006. These three pipes are thought to be sufficient to prevent an increase in CO 2 levels, removing approximately

2736-485: The thirteenth deepest by mean depth. Some 1,370 square kilometres (529 sq mi) or 58 percent of the lake's waters lie within DRC borders. 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. Settlements on the lake's shore include Bukavu , Kabare , Kalehe , Sake and Goma in

2793-399: The trigger pushes gas-saturated water higher in the lake, where the reduced pressure is insufficient to keep gas in solution. The buoyancy from the resulting bubbles lifts the water even higher, releasing yet more bubbles. This process forms a column of gas, at which point the water at the bottom is pulled up by suction , and it too loses CO 2 in a runaway process. This eruption discharges

2850-478: The water must be nearly saturated with gas. CO 2 was the primary component in the two observed cases, Lake Nyos and Lake Monoun. In Lake Kivu's case, scientists, including lake physicist Alfred Johny Wüest, were also concerned about the concentrations of methane . CO 2 may originate from volcanic gas emitted from under the lake, or from decomposition of organic material. Before a lake becomes saturated, it behaves like an unopened carbonated soft drink :

2907-459: 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. 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. The $ 200 million power plant

SECTION 50

#1732782774050

2964-428: The waters of these lakes in a controlled manner. The team positioned a pipe vertically in the lake with its upper end above the water surface. Water saturated with CO 2 enters the bottom of the pipe and rises to the top. The lower pressure at the surface allows the gas to come out of solution. Only a small amount of water must be mechanically pumped initially through the pipe to start the flow. As saturated water rises,

3021-493: Was introduced to Lake Kivu in late 1959 by the Belgian agronomist Alphonse Collart. An attempt to introduce the similar Lake Tanganyika sprat ( Stolothrissa tanganicae ) at the same time was unsuccessful. 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

3078-476: Was largely unaffected, except any growing immediately adjacent to the lake. There, vegetation was damaged or destroyed by a 24 m (79 ft) high tsunami caused by the violent eruption. Efforts are underway to develop a solution for removing the gas from these lakes and to prevent a build-up which could lead to another disaster. A team led by French scientist Michel Halbwachs began experimenting at Lake Monoun and Lake Nyos in 1990 using siphons to degas

3135-706: Was operating at 26 MW in 2016. The fish fauna in Lake Kivu is relatively poor with 28 described species, including four introduced species . 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. Another c. 20 possibly undescribed species of cichlids are known from

3192-438: 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. Following this introduction, the sardine has gained substantial economic and nutritional importance for

3249-501: Was released in 2006. With an annual average chlorophyll a in the mixed layer of 2.2 mg m 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. The actual primary production

#49950