Lake Kivu and Rusizi River Basin Water Quality Management Project

Together with the Ruzizi River Basin, Lake Kivu is a sub-basin of the Lake Tanganyika Basin which is itself a sub-Basin of the Congo River Basin. Lake Kivu has a surface area of 2,370 km2, a shoreline of 860 km, a length of 97 km and width of 48 km, an average depth of 240 m, a maximum depth of 485 m, water volume of 500 km3, a water residence period of 193 years, and a basin of 5,097 km2. Rwanda and Democratic Most of the water input is through rainfall (3.3 km3/year), numerous small rivers (2.0 km3/year), and groundwater (1.3 km3/year), and water loss is through evaporation (3.6 km3/year) and the Ruzizi River into Lake Tanganyika (3.0 km3/year). The area receives long rainy periods from February to May and short rains from October to December, and the lake’s surface temperature varies between 22 and 24oC. The basin is characterised by a great range of vegetation cover from grasses interspersed with trees, deciduous forest, savannah mosaics and woodland in some areas, and a high susceptibility to changes in land use. The region has experienced in the past decade political instability, refugee migration and civil war, large-scale land clearance to satisfy energy demand, construction and timber harvesting from neighbouring countries and from within, and most especially for agricultural purpose (Majaliwa et al., 2009); exacerbating therefore soil erosion and pollution related loadings into the fresh surface waters and lake Kivu in particular (Jorgensen et al., 2004).

The Lake Kivu-Ruzizi basin is uniquely valuable, rich in biodiversity, and a catalyst for economic growth with high potential to improve the quality of life in Lake Basin communities. The basin is also very important for biodiversity and for ecosystem services that they provide and covers parts of at least 15 Key Biodiversity Areas (KBAs) of which 12 are terrestrial and 3 freshwater KBAs, hosting 55 Red-Listed species. The Virunga National Park, a World Heritage site, is located on the DR Congo side of the basin.

Environmental problems
Lake Kivu basin is among the most fragile and highly sensitive ecosystems in the region. The lake is being affected by atmospheric pollution, sedimentary, anthropogenic and climate change threats (Bootsma et al., 1999; Hecky et al., 2006). In the southern part of the Lake the demographic pressure and associated anthropogenic activities coupled with the micro-catchment topography contribute to increased degradation of land and water resources. The excessive growth of human populations in the Lake Kivu basin, land use, urbanisation, deforestation, intensive agriculture and climate warming prompt changes in the water quality of the lake. The major sources of nitrogen and phosphorus appears to be rivers and the atmosphere. The increase in sediment and nutrients loading pose a threat to biodiversity. Karamage (2016) argues that deforestation and natural grassland conversion to agricultural land use constitute a major threat to soil and water conservation and postulate that mean erosion rates approximate 41 t·ha−1·year−1 for settlement, 31 t·ha−1·year−1 for cropland, 28t·ha−1·year−1 for forest land, and 20t·ha−1·year−1 for grassland.

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