Soil carbon and water quality in Rwanda
The soil carbon is important in all soil processes and both a sink for carbon sequestration and a source of carbon release. The increase of precipitations and temperatures attendant to climate and land cover changes in tropical regions can reduce the soil carbon storage through the export of dissolved organic carbon (DOC) from lands into aquatic ecosystems especially in high altitude ecosystems. The resulting DOC increase in aquatic ecosystems will potentially affect the water quality and therefore their functioning. Our study aims assessing and predicting the effect of climate and land cover changes on total organic carbon (TOC) and DOC in high altitude agricultural dominated lands and DOC export into rivers at watershed scale. The research project site is Rukarara watershed located in the southern Rwanda, upstream of Lake Victoria Basin. This watershed is characterized with Nyungwe natural forest, plantation forests and cultivated areas with annual crops (e.g. common bean, sorghum, maize, etc.) and perennial crops (e.g. tea and banana plantations, etc.). A GIS-based model, the Regional Hydro-Ecological Simulation System (RHESSys) will be adapted to quantify DOC exported into water streams through leaching and runoff.