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Context and necessity
Lake Kivu, one of the African Great Lakes, and the Ruzizi River are connected watercourses that lie along the border of Burundi, the Democratic Republic of the Congo (DRC) and Rwanda. Lake Kivu is connected to Lake Tanganyika by the Ruzizi River and is part of the Congo River Basin. Lake Kivu and the Ruzizi River provide the foundation for the everyday activities and livelihoods of more than 11 million people.
Soil erosion is of growing concern in the area and is further exacerbated by the negative effects of climate change. Soil erosion can lead to loss of fertile land, increased flooding, soil degradation, increased pollution and sedimentation in rivers which can in turn cause a decline in fish and other species. As such, soil erosion has a great impact on local communities whose livelihood is dependent upon the basin. The study conducted by the German Aerospace Centre (DLR) offers an assessment and monitoring of soil erosion parameters in the transboundary Lake Kivu and Ruzizi River Basin.
Results of the study
The DLR team presented their findings through a hybrid online and in-person workshop, facilitated in both English and French with a total number of 34 participants. The study sought to quantify the erosion risk from an Earth Observation perspective using the following parameters: precipitation, vegetation dynamics, land use and urbanisation and population development. The analysis was split into four key Work Packages (WP).
- WP1 > analysed long term and seasonal vegetation dynamics, concluding that there are regions with seasonally repeating low vegetation cover regularly found in the Ruzizi plain and the southern slopes of the volcanos in the north of the study area, where the main agricultural fields are found.
- WP2 > analysed extreme precipitation events, the findings suggest not a single hot-spot month or region could be determined. However, an increase in the number of extreme events is detected for the months April or May, August and November or December in most years.
- WP1 & WP2 > were combined to form an Erosion Risk Index highlighting regions particularly threatened by soil erosion. The following areas have been identified as erosion risk hotspots: The Ruzizi plain, the area between the city of Goma and the northern volcanic region, the city agglomerations of Goma and Bukavu and the grasslands east of lake Kivu.
- WP3 > analysed the turbidity of lake Kivu, finding that turbidity is lower during the dry season and increased in March/April and October to December. Nonetheless, only a low connection between erosion risk and lake turbidity could be identified.
- WP4 > analyses population growth, showing only a small increase in predicted urban growth in the city agglomeration for Bukavu (includes Bukavu in DRC and Rusizi in Rwanda), likely to be a result of the steep slopes and rugged terrain around the city agglomeration. For Goma agglomeration (includes Goma in DRC and Rubavu in Rwanda), a stronger growth is predicted, especially along the road network on the Rwandan side of the agglomeration. Urban growth is likely to further increase the pressure on the soils in the study area and can provoke more intense soil erosion and soil degradation.
Key points of discussion and next steps
After the presentation, the participants engaged in a fruitful discussion with the DLR team about the results of the study. Suggestions and remarks were made, notably regarding the turbidity in the river and along the plain requiring further analysis. When analysing rivers, satellite data can prove insufficient; in-situ data is best suited to assess water quality and turbidity. Another point raised was the impact of extractive activities and in particular (gold) mining was noted as an erosion risk and a major factor leading to turbidity and sedimentation. In addition to this, participants noted the correlation between erosion and demographic growth, whereby the latter increases pressure on land and vegetation. Further erosion drivers include human activity, land management systems and urban growth. Concluding the session, the DLR team suggested possibilities for further research, seeing this study combined with the ABAKIR report: Baseline Study for the Basin of Lake Kivu and Ruzizi River. Combined, these two studies could be used to develop mitigation and adaptation strategies and to help decision makers to identify and implement solutions.
Recording of the session
Download the full report here.
- Report // Assessment and Monitoring of Soil Erosion Parameters in theTransboundary Lake Kivu and Ruzizi River Basin
- Nexus Interview Series // Kristine Herbomel, Advisor Support to the integrated management of water resources of lake Kivu and Ruzizi river
- Lake Kivu and Ruzizi River Project // Validation Workshop of the Extended Basin Baseline Study of the Lake Kivu and Ruzizi River
- Report // Summary of Lake Kivu and Ruzizi/Rusizi River Basin
- Support to the Integrated Management of Water Resources of Lake Kivu and the Ruzizi River