Modelling spatial distributions of sediments fingerprinting in the Ruvu Basin of Tanzania without continuous sediment monitoring

Abstract

This study investigates various hinterlands’ contribution of sediments into the sub-basin known as Ruvu that comprises Mindu, Kibungo, Mvuha and Mindu catchments of Morogoro, Eastern Tanzania. An integrated geochemical and isotopic data were used to constrain this. Strategic sampling of basement and silty-sized sediments was conducted and the data were modelled using mass-balance computations. This approach revealed that, more than 70% of suspended sediments in the Mgeta River originate from Kigalamila, Sezima, Kingule, Mafumbo and Kibuko areas. Thus, hills north of Kisaki are major contributors of sediments with less contribution from the southern terrain. After modelling of the data from Mvuha sub-catchment, results suggest that the sediments (~50%) originate from Msuluzi area and significant erosion comes from Vihengele region. Evidence for Vihengele is also due to elevated CaCO₃ abundances in the Mvuha samples from the calcareous rocks. Sediments in the Mindu sub-catchment largely originate from Msaga and Monde areas that are dominated by granulites and gneisses based on simulated mixing calculations. Thus, the extreme southern part of the sub-catchment is more prone to erosion. Sediments of more than 47% for the Kibungo sub-catchment originate from the Mfizigo area. However, no significant erosive activities in the catchment were noted.