LAKE KIVU EXPEDITION
Lake Kivu is a fascinating lake. An exceptional amount of methane and carbon dioxide has accumulated in its deep waters.
Age: ~ 1 to 5 million years old
Surface area: 2370 km2
Maximum depth: 485 m
Volume: 560 km3
Location: East African Rift Valley
Riparian countries: Democratic Republic of Congo, Government of Rwanda
Altitude: 1463 m above sea level
Uniqueness: more methane than any other lake
Gases in Lake Kivu
Carbon dioxide: ~300 km3 STP, 80% of the gases volume, only 20% of the total gas pressure
Methane: ~60 km3 STP, 20% of the gases volume, but 80% of the total gas pressure.
These gases are dissolved (like in a bottle of Coke) and trapped below 260 m depth, where they accumulated over ~800 years. This unusual accumulation can be explained by the lake’s permanent stratification and the input of carbon dioxide from the surrounding volcanoes.
CO2 has a magmatic origin. CH4 is generated biologically by the reduction of magmatic CO2 (~65%) and the mineralization of organic carbon (~35%). CH4 concentrations seemed to have increased by 15% in the last 30 years.
Structure of Lake Kivu
The water column is characterized by increasing temperature, salinity and gas concentrations with depth and by several sharp gradients resulting from sub aquatic springs.
The annual deep mixing occurs during the dry season (June to September). The mixing depth varies annually but is limited to a maximum depth of 63 m. Below this oxygenated zone, the different layers are homogenous and stable. Lake Kivu is therefore permanently stratified.
Catchment area: 5097 km2 (excluding the lake), relatively small compared to the lake surface.
5 Basins around Idjwi Island: Main Basin, Kalehe Basin, Ishungu Basin, Bukavu Bay and Kabuno Bay.
Rivers: ~200 small inflowing rivers, but no surface water in the volcanic region of Goma Internal sub-aquatic springs: in the north, at different depths mainly at 180 and 250 m.
Annual lake level fluctuations: 0.17 to 1.17 m
Biology of Lake Kivu
Only 31 fishes live in Lake Kivu. The Tanganika sardine (Isambaza) was introduced in the 1960s, to fill the empty pelagic zone. The Isambaza sustain traditional fisheries and is an important source of protein for the local population.
The food web of Lake Kivu is simple: phytoplanktons are eaten by zooplankton, which are fed by Isambaza fish.
An estimated 2 million inhabitants live in the catchment basin of Lake Kivu. Their activities are:
- Marine and terrestrial transport of passengers and goods
- Tea plantations: Gisovu, Gisakura, Pfunda and Shagasha Tea Factories (www.ocir-the.co.rw)
- 12 coffee washing stations: in Kinunu
- Subsistence agriculture: kidney beans, potatoes, sorghum, maize, rice, tomatoes, cabbages and other vegetables, sweet potatoes, cassava, green and yellow bananas…
- Cattle farming: cows, goats, sheep and pork
- Production of milk and cheese
- honey harvesting
- Fishing: isambaza, indugu and tilapia
- Brewery Bralirwa in Bukavu and Nyamyumba
- Small hydropower plants: in Gisenyi, Nkora, Cyimbiri and Kaya
- Tertiary activities in the main cities: Goma, Bukavu, Gisenyi, Kibuye, Cyangugu
- Mining and quarries
- Methane extraction in Lake Kivu
- Markets all along the coast: in Nkora, Kirambo, Kamemebe Market places
- Boat building
- Construction work: sand collecting and bricks
- Medical care in hospitals and health centers
Leisure – Tourism activities
Lake Kivu is probably one of the unique lakes in Africa, where you can safely swim:
-Pleasant surface temperatures throughout the year from 23°C to 27°C
-No gas outburst: the methane is trapped below 260 m and far away from the shores
Kayaking, wind surfing, catamaran and jet-ski. The equipment can be hired at Kivu Serena in Gisenyi. Kayaks can also be hired in Moriah Hills in Kibuye.
Visit one of the beautiful islands
-Visit Napoleon Island near Kibuye, home to thousands of bats
-Sleep or eat on Amahoro Island near Kibuye
-Relax on the island from Paradis Malahide Hotel in Gisenyi
-Visit the inhabitants of Bugarama and Nkomo Islands
The isambaza are attracted by the petrol lights from the fishermen at night. During full moon, fishing is therefore not possible.
-Join the fishermen for an evening on their boat to learn more about their traditional techniques
-Listen to the fishermen singing as they paddled in and out their landing sites
-Watch the isambaza fishing boats with their beams and telescopic poles during the day along the shores.
-Taste the isambaza and tilapia fishes in local restaurants
-Hire the speed boat “Munezero” from Rwanda Development Board in Gisenyi
-Hire local pirogues
-Use the pirogues from the public transport
The Congo-Nile Trail
Cycling, hiking or driving along the Congo-Nile Trail. This 227 km long trail runs from Gisenyi to Kamembe along the scenic shores of Lake Kivu.
-Hire or buy bicycles in Gisenyi
-Cycle with bicycle guides and porters along the Congo-Nile trail
Nyiragongo Volcano – the world largest lava lake
-Hike on the Niyragongo Volcano (1500 m of denivellation)
-Camp in the bandas at the top (3500 m) and admire the lava lake
-The smoke from the volcano during the day and its glow at night can be observed in Gisenyi, Kibuye and as far as Nyungwe Forest
-Track Mountain Gorillas either in Ruhengeri Rwanda or in DRC
-Track Lowland Gorillas near Bukavu
Montane Rain Forests
-Hike in Nyungwe Forest and experience its new canopy walk
-Hike in the Giswati Forest, a new conservation area
-Track the chimpanzees
Other points of interests in Rwanda
-Hot springs: in Nyambyumba and Bugarama
-Bisesero Resistance Hill and memorial site
-L'Espérance Orphanage, based on the principle of being self-sufficient.
-King Musinga memorial tree
-Visit pigmy communities