A Limnological Survey of Malagarasi River in Western Tanzania

Abstract

The present study surveyed the limnological functioning of the Malagarasi River in Western Tanzania during the dry season from the river delta at the Lake Tanganyika confluence point to the source of the river at the Burundi-Tanzania Border. A total of 66 samples were samples from 8 different accessible sites using standard methods to determine dissolved oxygen (DO), turbidity, temperature, electrical conductivity (EC), redox potential (Eh), pH and transparency. Nutrients such as chlorophyll a, phosphate (PO₄3^-), nitrate (NO₃^-), silica (SiO₂) and iron (Fe²⁺) and alkalinity (HCO₃^-) were determined in the laboratory. Data show sporadic variations in the abiotic parameter levels and river geomorphology amongst the sampled sites. The mean concentrations of Fe²⁺ and PO₄^3- were noted to increase with depth at some sites. These variations are attributed to processes including dissolution, diffusion, reduction, absorption, adsorption, photosynthesis, nitrification, denitrification and mixing effects. We also found that the geomorphology of the river system is strongly driven by both the geology of the area and the anthropogenic activities as shown by the measured parameters. Quantification of both climate variability and tectonic effects on the abiotic parameters of the river is highly recommended for effective evaluation of the limnological functioning of the Malagasi River System.

Keywords: Limnology, Malagarasi River, Western Tanzania, abiotic parameters, processes, anthropogenic activities.