Using sediment fingerprinting to identify erosion hotspots in a sub-catchment of Lake Kivu, Rwanda
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
Environmental Monitoring and Assessment
Abstract
Sedimentation of water bodies affects water quality and biotic communities of aquatic ecosystems. Understanding the causes and origin of sediments is crucial for planning watershed management activities and safeguarding aquatic biodiversity and critical ecosystem services. Rwanda, as a hilly country, experiences increased sedimentation due to unsustainable land use practices in
upstream catchment areas which negatively affects irrigation, fishing and hydropower generation. We used a sediment
fingerprinting technique to determine sources of sedimentation and identifying hotspots of soil erosion in Sebeya River Catchment (area of 357 km2), a subcatchment of Lake Kivu located in Northwest Rwanda. Five soil samples were collected from each of the six geological classes, and 34 suspended sediment samples were taken within key locations of the hydrological network
in the catchment. X-Ray Spectrometry was used to determine the geochemical composition of suspended sediments
and soil. A multi-step statistical procedure with a Bayesian mixing model was used to determine the contribution of each geologic group and sub-catchment to the suspended sediments in the river. Erosion hotspots were classified based on the underlying land use and their contribution to the suspended sediments. The resulting erosion hotspot map shows that about 70.9% of the Sebeya
Catchment area contributes at least 50% of sediment load in the river and currently experiences unsustainable land use and land cover. The erosion hotspots identified and culpable factors should be used to guide best land use practices, prioritizing the areas with high contribution to the river sedimentation in Sebeya Catchment.
Description
Keywords
Sebeya River, Erosion hotspots, Sediment fingerprinting, Rwanda
Citation
Akayezu, P., Musinguzi, L., Natugonza, V., Ogutu-Ohwayo, R., Mwathe, K., Dutton, C., & Manyifika, M. (2020). Using sediment fingerprinting to identify erosion hotspots in a sub-catchment of Lake Kivu, Rwanda. Environmental Monitoring and Assessment, 192(12), 1-15.https://doi.org/10.1007/s10661-020-08774-5