Lake Kivu is one of the African Great Lakes. 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. Lake Kivu empties into the Ruzizi River, which flows southwards into Lake Tanganyika.
Lake Kivu is approximately 90 km (56 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 a total surface area of some 2,700 km2 (1,040 sq mi), making it Africa’s eighth largest lake. The surface of the lake sits at a height of 1,460 meters (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 eighteenth deepest lake by maximum depth, and the ninth deepest by mean depth.
Some 1,370 km2 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 on a lake, Idjwi, lies in Lake Kivu, within the boundaries of Virunga National Park. Settlements on the lake’s shore include Bukavu, Kabare, Kalehe, Sake, and Goma in Congo, and Gisenyi, Kibuye, and Cyangugu in Rwanda.
Lake Kivu is a freshwater lake and, along with Cameroonian Lake Nyos and Lake Monoun, is one of three that are known to undergo limnic eruptions. Around the lake, geologists found evidence of massive local extinctions about every thousand years, presumably caused by outgassing events. The trigger for lake overturns is unknown in Lake Kivu’s case, but volcanic activity is suspected. The gaseous chemical composition of exploding lakes is unique to each lake. In Lake Kivu’s case, it includes methane and carbon dioxide, as a result of lake water interaction with a volcano.
Lake Kivu has recently been found to contain approximately 55 billion cubic meters (1.94 trillion cubic feet) of dissolved biogas at a depth of 300 meters (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 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.
The fish fauna in Lake Kivu is relatively poor with 28 described species, including four introduced species. The natives are the Lake Rukwa minnow, four species of barb (Ripon barbel, East African red-finned barb, redspot barb, and Pellegrin’s barb, an Amphilius catfish, two Clarias catfish (C. leptocephalus and C. gariepinus), Nile tilapia and 15 endemic Haplochromis cichlids. The introduced species are three cichlids, the longfin tilapia, blue-spotted tilapia and redbreast tilapia, and a clupeid, the Lake Tanganyika sardine.
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.