Using sediment fingerprinting to identify erosion hotspots in a sub-catchment of Lake Kivu, Rwanda
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Using sediment fingerprinting to identify erosion hotspots in a sub-catchment of Lake Kivu, Rwanda
Providence Akayezu & Laban Musinguzi & Vianny Natugonza & Richard Ogutu-Ohwayo & Ken Mwathe & Christopher Dutton & Marc Manyifika
Received: 16 August 2019 / Accepted: 22 November 2020 # Springer Nature Switzerland AG 2020
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.
P. Akayezu (*) BirdLife International, Kigali Project Office, P.O. Box 2527, Kigali, Rwanda e-mail: [email protected]
C. Dutton Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA
L. Musinguzi : V. Natugonza : R. Ogutu-Ohwayo National Fisheries Resources Research Institute (NaFIRRI), P.O. Box 343, Jinja, Uganda
M. Manyifika Rwanda Water and Forestry Authority (RWFA), P.O. Box 7445, Kigali, Rwanda
K. Mwathe BirdLife International, Africa Partnership Secretariat, P.O. Box 3502, 00100 GPO, Westlands, Nairobi, Kenya
Keywords Sebeya River . Erosion hotspots . Sediment fingerprinting . Rwanda
Introduction Sedimentation is a challenge facing freshwater systems, with undesirable implications for aquatic ecosystem and
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human health. Sedimentation reduces water quality through enrichment with excessive nutrients and siltation, with negative impacts on key parameters such as transparency, turbidity and dissolved solids (Tundu et al. 2018). The compromise to water quality
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